An Ichnological Perspective on Some Major Events of Paleozoic Tetrapod Evolution

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A Bollettino della Società Paleontologica Italiana, 58 (3), 2019, 223-266. Modena L

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N N Invited Paper N An ichnological perspective on some major events of Paleozoic tetrapod evolution

Spencer G. Lucas

S.G. Lucas, New Mexico Museum of Natural History, 1801 Mountain Road NW, 87104 Albuquerque (New Mexico), USA; [email protected]

KEY WORDS - late Paleozoic, trace fossils, footprints, evolutionary history, extinction.

ABSTRACT - Tetrapod trace fossils (primarily footprints) provide signifi cant insight into some major events of the Paleozoic evolution of tetrapods. The oldest fossils of tetrapods are Middle Devonian footprints from Ireland. Bona fi de Devonian tetrapod footprints indicate lateral sequence walking by quadrupedal tetrapods with a smaller manus than pes. These trackways indicate that tetrapods other than “ichthyostegalians” remain to be discovered in the Devonian body-fossil record. Devonian tetrapod footprints are from nonmarine paleoenvironments, so they do not support a marginal marine/marine origin of tetrapods. Nevertheless, the Devonian tetrapod footprint record is too sparse to be of paleobiogeographic signifi cance and to evaluate unsubstantiated claims of Late Devonian tetrapod mass extinctions. “Romer’s gap”, a supposed paucity of Early Mississippian terrestrial fossils, has largely been fi lled by sampling and description of already known fossils. It includes the fi rst substantial assemblage of tetrapod footprints, from Blue Beach, Nova Scotia, Canada. This assemblage consists of footprints of small and large temnospondyls and reptiliomorphs, which supports the concept that the Carboniferous diversifi cation of terrestrial tetrapods had begun during (or before) Tournaisian time. No defi nite pre-Pennsylvanian amniote footprints are known, so the Early Pennsylvanian age of the oldest amniote footprints and body fossils is the same. The Kasimovian revolution was a prolonged and complex change across the Middle-Late Pennsylvanian boundary from the “coal forests” to a more xerophytic vegetation accompanied by changes and “sluggish evolution” in the marine biota and the appearance of new tetrapod taxa in the body-fossil record, notably the oldest high fi ber herbivores, the diadectomorphs and the edaphosaurid eupelycosaurs. However, the tetrapod footprint record changes little during the Kasimovian and documents much older records of diadectomorph and eupelycosaur (possible edaphosaurs) footprints in the Bashkirian, thus diminishing the extent of tetrapod originations during the Kasimovian revolution. The Permian tetrapod footprint record is much more extensive and better understood than the Carboniferous footprint record. Tetrapod footprints confi rm the body-fossil record in demonstrating no signifi cant changes in tetrapod evolution took place across the Carboniferous- Permian boundary. The late early Permian sauropsid radiation is best documented by a change in the tetrapod footprints from synapsid- and non-amniote-dominated assemblages to those dominated by the footprints of captorhinomorphs and parareptiles. Early Permian tetrapod footprints from eolian sediments demonstrate the colonisation of deserts by tetrapods. Olson’s gap is a global hiatus in the tetrapod body-fossil record during which eupelycosaur-dominated assemblages of the early Permian were replaced by therapsid-dominated assemblages of the middle-late Permian. The gap in the body fossil record corresponds to most of Kungurian time, and the tetrapod footprint record indicates an abundance of captorhinomorph footprints and very few eupelycosaur footprints just before and during Olson’s gap, suggesting that the extinction of the eupelycosaurs had already begun well before the fi rst appearance of therapsids. The substantial extinction of dinocephalian therapsids and other tetrapods at approximately the end of the middle Permian, the dinocephalian extinction event, is well documented by the tetrapod footprint record in paleoequatorial Pangea, where there is a paucity of tetrapod body fossils during this interval. The lack of an end-Permian tetrapod mass extinction fi nds support in the tetrapod footprint record because most late Permian tetrapod footprint ichnogenera continue into the Triassic. Late Permian archosauriform footprints add evidence that their diversifi cation, and the upright gait, began during the Permian. Most Paleozoic tetrapod trackways indicate quadrupedal lateral sequence walking with a sprawling gait, but relatively narrow gauge tetrapod trackways as old as Carboniferous may indicate some semi-upright to upright walking. Defi nite upright walking is demonstrated by late Permian therapsid and archosauriform footprints, and no know footprints of bipedal tetrapods are known from Paleozoic strata, although a few Permian tetrapod taxa known from skeletons may have been bipeds. Besides footprints, other Paleozoic tetrapod trace fossils (bromalites, burrows and dentalites) are too poorly known and too little studied to provide much insight into Paleozoic tetrapod evolution. Nevertheless, the tetrapod footprint record documents key events in Devonian-Permian tetrapod evolution and needs to be part of a complete understanding of Paleozoic tetrapod evolutionary history.

RIASSUNTO - [Gli eventi principali dell’evoluzione dei tetrapodi paleozoici analizzati su basi ichnologiche] - Le tracce fossili di tetrapodi (principalmente orme) forniscono una lettura importante dei maggiori eventi dell’evoluzione dei tetrapodi paleozoici. I più antichi tetrapodi fossili sono rappresentati da orme del Devoniano Medio dell’Irlanda. Le orme del Devoniano indicano locomozione in sequenza laterale di tetrapodi quadrupedi, con impronta della manus più piccola dell´impronta del pes. Queste tracce indicano che tetrapodi diversi dagli “ichthyostegaliani” non sono ancora stati rinvenuti come resti fossili nel record del Devoniano. Le orme di tetrapodi devoniani sono conservate in rocce sedimentarie di ambiente continentale, quindi non supportano l’origine marina/marina marginale dei tetrapodi. La documentazione delle orme di tetrapodi del Devoniano è purtroppo molto discontinua per permettere analisi paleobiogeografi che e per valutare una eventuale estinzione in massa di tetrapodi nel Devoniano Superiore. Il “Romer’s gap”, una ipotetica riduzione di fossili terrestri durante il Mississipiano Inferiore, è stato ampiamente colmato da nuovi rinvenimenti di fossili già precedentemente conosciuti. Tra questi è importante la prima associazione signifi cativa di orme di tetrapodi, documentata nella località di Blue Beach, Nova Scotia, Canada. Questa associazione comprende orme di temnospondili e rettilomorfi di dimensioni sia grosse che piccole, che suggeriscono che nel Carbonifero la diff erenziazione dei tetrapodi terrestri abbia avuto luogo durante (o prima) del Tournasiano. Le prime orme di amnioti sono note nel Pennsylvaniano Inferiore, e sono coeve con i primi ritrovamenti di reperti ossei di questo gruppo. La rivoluzione del Kasimoviano è consistita in un cambiamento complesso e che ha richiesto un tempo abbastanza lungo in corrispondenza del limite tra Pennsylvaniano Medio e Superiore, con il passaggio da una “coal forest” ad una vegetazione ricca in xerofi te, accompagnata

ISSN 0375-7633 doi:10.4435/BSPI.2019.20 224 Bollettino della Società Paleontologica Italiana, 58 (3), 2019 da cambiamenti nei biota marini, con la comparsa di nuovi taxa di tetrapodi documentati anche da resti scheletrici. Tra questi i più antichi erbivori in grado di assimilare piante con alto contenuto in fibre, i diadectomorfi e gli edafosauri eupelicosauri. In questo contesto, il record di orme di tetrapodi presenta pochi cambiamenti nel Kasimoviano, mentre evidenzia una comparsa più antica, nel Bashkiriano, di diadectomorfi e di eupelicosauri (forse edafosauri), che riduce l´ammontare di comparse di tetrapodi durante la rivoluzione kasimoviana. Il record permiano di orme di tetrapodi è molto più ampio e meglio conosciuto. Le orme di tetrapodi sono coerenti con il record di resti ossei nel dimostrare che al limite Carbonifero/Permiano non si sono verificati cambiamenti significativi nell’evoluzione dei tetrapodi. La radiazione dei sauropsidi della fine del Permiano inferiore è documentata molto bene da un cambiamento nelle orme di tetrapodi da associazioni dominate da sinapsidi e non-amnioti ad associazioni dominate da orme di captorinomorfi e pararettili. Nel Permiano inferiore la colonizzazione dei deserti da parte dei tetrapodi è dimostrata dal rinvenimento di orme in sedimenti eolici. L’Olson’s gap è uno hiatus globale nel record dei resti ossei dei tetrapodi, durante il quale le associazioni del Permiano inferiore, dominate da eupelicosauri, sono state sostituite da associazioni dominate da terapsidi nel Permiano medio e superiore. Il gap corrispode a parte del Kunguriano, e il record di orme di tetrapodi documenta una abbondanza di orme di captorinomorfi e pararettili, con poche orme di eupelycosauri appena prima e durante l’Olson’s gap. Questo dato a sua volta suggerisce che l’estinzione degli eupelicosauri sia avvenuta molto prima della comparsa dei terapsidi. L’evento di estinzione dei terapsidi dinocefali e di altri tetrapodi verso la fine del Permiano medio, è ben documentata dal record di orme di tetrapodi nella fascia equatoriale della Pangea, mentre il record di resti ossei è scarso. Al contrario, il record di orme di tetrapodi non evidenzia alcun evento di estinzione alla fine del Permiano, in quanto la maggior parte degli ichnogeneri di orme del Permiano superiore continuano e sono presenti nel Triassico. Le orme di arcosauriformi del Permiano superiore evidenziano che la loro diversificazione e la postura eretta di questo gruppo iniziarono nel Permiano. La maggior parte delle piste di spostamento di tetrapodi del Paleozoico indica locomozione quadrupede in sequenza laterale con postura non eretta, tuttavia a partire dal Carbonifero alcune piste relativamente strette possono provare una locomozione semi-eretta. A partire dal Permiano superiore la locomozione con postura eretta è comprovata con certezza da orme di terapsidi e arcosauriformi. Nel Paleozoico non sono mai state trovate orme di tetrapodi bipedi, sebbene alcuni scheletri di tetrapodi permiani potrebbero essere compatibili con locomozione bipede. Oltre alle orme, nel Paleozoico sono note anche altre tracce ascrivibili a tetrapodi, come bromaliti, dentaliti e tracce di scavo. Queste tracce sono però poco conosciute e non forniscono particolare supporto alla ricostruzione dell’evoluzione paleozoica dei tetrapodi. Il record di orme di tetrapodi è invece ricco e ben conosciuto e fornisce elementi molto importanti per identificare gli eventi chiave dell’evoluzione devoniana-permiana dei tetrapodi. Questo record merita quindi di essere considerato a tutti gli effetti per la ricostruzione dell’evoluzione paleozoica dei tetrapodi.

INTRODUCTION ICHNOTAXONOMY OF TETRAPOD TRACE FOSSILS Fossils of tetrapods (amphibians and amniotes, the latter include reptiles, synapsids, birds and mammals) There are two approaches to ichnology (and to first appear in Devonian strata. What their subsequent ichnotaxonomy). Invertebrate trace fossils (ichnofossils) Paleozoic fossil record documents is a complex history are primarily used to interpret behavior and of originations, extinctions, ecological expansion and paleoenvironments (e.g., Bromley, 1996; Buatois & behavioral innovation. This history is culminated by Mángano, 2011). This is because many invertebrate a prolonged turnover of the tetrapod biota from late trace fossils are homeomorphic (i.e., the same trace fossil Paleozoic temnospondyl- and synapsid-dominated morphology is made by different tracemakers). As a good assemblages to early Mesozoic assemblages dominated example, consider Cruziana, classically the Paleozoic by archosaurs, that also include the oldest lissamphibians, trackway/trail made by a trilobite and the moniker of turtles, lizards and mammals. What we know about the one of Seilacher’s (1964, 1967) archetypal invertebrate Paleozoic evolutionary history of tetrapods is primarily ichnofacies. However, traces assigned to Cruziana are based on their body-fossil record of bones, teeth and known from post-Paleozoic strata, long after the Permian skeletons. The Paleozoic trace-fossil (ichnofossil) extinction of trilobites (and sometimes assigned to the record, which is mostly of footprints, though long synonymous ichnogenus Isopodichnus, see Bromley known and locally and periodically extensive, has been & Asgaard, 1972, 1979; Keighley & Pickerill, 1996). utilised much less to interpret the Paleozoic history of These post-trilobite Cruziana must have been made by tetrapods. My purpose here is to review the Paleozoic another tracemaker such as branchiopod crustaceans, trace-fossil record of tetrapods and to use it to inform notably notostracans (Minter et al., 2007). Nevertheless, our understanding of some major aspects of Paleozoic the trace made by two different makers is of such similar tetrapod evolution. morphology that it is assigned to a single ichnogenus. The This article has at its core a review of the trace- morphology of the invertebrate trace is thus seen to signify fossil record of Paleozoic tetrapods. It uses that record a behavior more than a particular tracemaker, in this case to analyse: 1) the timing, location and paleoecology of a particular mode of locomotion. Lucas (2005; Hunt & tetrapod origins; 2) supposed Late Devonian tetrapod Lucas, 2005, 2007) referred to this as the ethological mass extinctions; 3) Devonian tetrapod locomotion tradition in (approach to) ichnology. and evolutionary relationships; 4) Romer’s gap; 5) In contrast to invertebrate ichnology, the ichnotaxonomy amniote origins; 6) the Kasimovian revolution; 7) the of vertebrate trace fossils proceeds from different Coyotean chronofauna; 8) the sauropsid radiation; 9) premises. The morphology of vertebrate trace fossils tetrapod colonisation of deserts; 10) Olson’s gap; 11) the also indicates behavior, but the taxonomic identity of the dinocephalian extinction event; 12) the supposed end- tracemaker plays an important role in the generation of Permian tetrapod mass extinction; and 13) the Paleozoic the morphology useful for ichnotaxonomic identification evolution of tetrapod terrestrial locomotion. Lucas (2005; Hunt & Lucas, 2005, 2007) called this the S.G. Lucas - Ichnology and Paleozoic tetrapods 225

Fig. 1 - Reconstruction of a large temnospondyl trackmaker of Palaeosauropus walking on a Mississippian, ripple-marked floodplain surface in eastern Pennsylvania, USA (from Fillmore et al., 2012). The footprints shown are optimal footprints that very accurately reflect the morphology of the trackmaker’s feet. Artwork by Matt Celeskey. biotaxonomic tradition in (approach to) ichnology. Most morphology that matches the anatomical structure of the vertebrate trace fossils are tetrapod footprints, so this trackmaker’s foot. Footprints that accurately preserve approach to ichnology can be readily understood in its these anatomical features are regarded as well preserved application to footprints. or of optimal morphological preservation (Fig. 1). They Thus, tetrapod footprints are assigned to ichnotaxa provide a basis for identifying the actual trackmaker based primarily on their anatomy-consistent morphology by matching known foot structure to the optimally- (e.g., Marchetti et al., 2019d). This is the footprint preserved footprint. Factors that influence the morphology 226 Bollettino della Società Paleontologica Italiana, 58 (3), 2019 of tetrapod footprints so that they are not of optimal preservation are those that produce extramorphology, an extremely important concept in the study of tetrapod footprints (Peabody, 1948). Such extramorphological features are not anatomy consistent due to alteration of the optimal footprint morphology during and after footprint registration in the sediment. Factors that create extramorphology include the nature of the substratum walked on and the speed of the trackmaker, undertracking and many other aspects of the locomotory process and taphonomy. Many tetrapod footprint ichnotaxa have been based on such extramorphological features. Haubold (1996) referred to such ichnotaxa as phantom taxa, and Lucas (2001) coined the term taphotaxon to encompass many such ichnotaxa. As Pickerill (1994), Bromley (1996) and many others have stressed, ichnogenera and ichnospecies do not necessarily correspond to genera and species based on body fossils. And, as several authors have pointed out, ichnogenera of tetrapod footprints almost always correspond to much broader taxonomic categories than do genera based on body fossils because of a certain degree of homeomorphy in the tetrapod footprints (e.g., Baird, 1980; Haubold et al., 1995; Haubold, 1996; Carrano & Wilson, 2001; Lucas, 2007). For example, Batrachichnus is the footprint ichnogenus made by relatively small temnospondyls (Fig. 2) and has a stratigraphic range of Carboniferous-Triassic (Fillmore et al., 2012; Schneider et al., 2020). During that timespan numerous genera and species of small temnospondyls (e.g., Milner, 1990; Schoch, 2014) left footprints that are assigned to Batrachichnus. Thus, this tetrapod footprint ichnogenus refers to a large subset of the biotaxon Temnospondyli. In a few cases, a specific footprint ichnogenus can be connected directly to a relatively low-ranked biotaxon such as a family or a genus (e.g., Voigt et al., 2007; Marchetti et al., 2017), but such connections are rare. More often, footprint ichnogenera correspond to orders or sub orders (e.g., Marchetti et al., 2019c). Fig. 2 - Artist’s reconstruction of a small temnospondyl walking This means that ichnogenera must have much on an actual Batrachichnus trackway from the lower Permian slower apparent evolutionary turnover rates than do of New Mexico, USA (from Lucas, 2014). Note the range of body-fossil genera, so an ichnogenus will have a much extramorphology in the footprints, from nearly optimal footprints longer stratigraphic range than does a body-fossil genus. behind the trackmaker’s right hind foot to digit scratch marks to the Therefore, a priori, any biostratigraphy or biochronology left of the trackmaker’s tail. Artwork by Matt Celeskey. based on tetrapod footprint ichnogenera will be less precise than one based on body-fossil genera. Nevertheless, footprint ichnogenera are generally more common and paleoecological and paleobiogeographic analysis. Most widely-distributed than tetrapod body-fossil genera, which striking is when the trace fossils provide a datum not suffer from very scattered and often localised records known from body fossils. A good example of this is (e.g., Lucas, 2006, 2018). The slower turnover rates of Devonian tetrapod footprints, which establish the oldest tetrapod ichnogenera also means that they do not shed record of tetrapods as Middle Devonian, whereas their light on many of the features of tetrapod evolution that body fossils are no older than Late Devonian (see below). took place over relatively short timespans. Tetrapod footprints are present in facies that rarely if ever yield tetrapod-body fossils. This is particularly true of eolian deposits, and, in the Permian, tetrapod ichnofossils SIGNIFICANCE OF TETRAPOD provide the first definitive record of the colonisation TRACE FOSSILS and habitation of deserts by tetrapods, as discussed below. Also, as reviewed later, lower-middle Permian The biotaxonomic approach to tetrapod ichnotaxonomy tetrapod footprints from the equatorial paleolatitudes creates ichnotaxa that are proxies of biological taxa based of Pangea are the most extensive tetrapod fossil records on body fossils. Thus, tetrapod ichnotaxa can be used to in this region, so they are important to documenting the establish the distribution of tetrapod taxa in time and space, paleobiogeographic distribution of some tetrapod taxa so the trace fossils are of some value to biostratigraphic, (Marchetti et al., 2019b). S.G. Lucas - Ichnology and Paleozoic tetrapods 227

Tetrapod footprints also provide prima facie evidence biostratigraphy (based on fishes and miospores) of the of tetrapod behavior. In terms of the evolution of tetrapod footprint-bearing stratigraphic interval is less precise locomotion and other kinds of behavior, such as burrowing and indicates a mid-Devonian through Fammenian age and scavenging, the best evidence with which to infer (Stössel, 1995). Stössel (1995) provided few data on the behavior is the tetrapod trace-fossil record. environment of deposition of the footprint-bearing strata, merely stating that it was a nonchannelised sheetflood deposit of alluvial (nonmarine) origin, and he doubted that DEVONIAN the footprints were made subaqueously. A more detailed sedimentological analysis by Stössel et al. (2016) shows Devonian tetrapod footprint record that the Valentia Island trackways were made along river Lucas (2015) provided a recent and comprehensive margins in a freshwater setting. review of the Devonian tetrapod footprint record (Fig. At the Valentia Island tracksite, there are multiple 3), obviating the need for a detailed review here. He trackways. Most impressive is a trackway of 150 footprints concluded that only three published records of Devonian without median drag marks across a long, meandering “tetrapod footprints” can be verified as produced by a path that extends for a course of about 10 meters (Fig. tetrapod trackmaker: Valentia Island, Ireland; Genoa 4). This trackway shows both size differentiation of River, Australia; and Easter Ross, Scotland. The supposed manus and pes footprints and an alternating trackway tetrapod footprints from the Middle Devonian of the pattern of a quadruped with an estimated gleno-acetabular Zachełmie quarry, Poland, fail the criteria for identification length of 38 cm and a coupling value (coupling value = as Devonian tetrapod footprints. Instead, Lucas (2015) gleno-acetabular distance/length of forelimb + length reinterpreted them as fish nests/feeding traces (ichnogenus of hind limb: Peabody, 1959) of 1.2-1.4 (Stössel, 1995; Piscichnus). Other reports of supposed Devonian tetrapod Stössel et al., 2016). No details of footprint morphology footprints, from Australia (Grampians Range), Brazil, are preserved because of cleavage of the sediments, but Greenland and Scotland (Orkney Islands) are clearly not Stössel drew attention to the footprints being wider than tetrapod footprints; some are invertebrate trace fossils long, and suggested this indicated a polydactyl trackmaker (Lucas, 2015). (it also infers forward-oriented digits). Clack (1997) and Lucas (2015) accepted the Valentia Island trackway(s) as Middle Devonian, Ireland - Stössel (1995) reported having been made by tetrapods. a trackway from the Devonian Valentia Slate Formation on Valentia Island in southwestern Ireland, and Stössel et Genoa River, Australia - Warren & Wakefield al. (2016) provided much more detailed data on multiple (1972) published tetrapod trackways from Upper trackways from this location. Williams et al. (1997) Devonian strata on the Genoa River in New South Wales, published a U-Pb age of ~ 385 Ma for an air-fall tuff Australia. These are from nonmarine strata of fluvial origin that is ~ 230 m stratigraphically above the trackway. On of the Combyingbar Formation of Frasnian age (Young, the current ICS timecale, 385 Ma is a Givetian age, so 2006). Here, three trackways show differentiation of this makes the trackway Middle Devonian, though the manus and pes sizes, alternating trackway patterns and,

Fig. 3 - Devonian continental configuration showing Devonian tetrapod footprint localities. Abbreviations are Ar = Arabia, B = Baltica, K = Kazakstan, Lu = Laurentia, NC = North China, SC = South China, Sib = Siberia, Ta = Tarim. Localities are: 1) Valentia Island, Ireland; 2) Easter Ross, Scotland; 3) Genoa River, Australia. Artwork of Tulerpeton by Arthur Escher. 228 Bollettino della Società Paleontologica Italiana, 58 (3), 2019 S.G. Lucas - Ichnology and Paleozoic tetrapods 229

Fig. 4 - The oldest tetrapod fossils, Middle Devonian trackways from Valentia Island, Ireland. a) Overview of trackway DO1, scale bar = 50 cm. b) Western part of trackway surface showing trackways DO1-6, scale bar = 25 cm. c) Trackway DO3, which is curved with a median groove, scale bar = 20 cm. Modified from Stössel et al. (2016) from images provided by Iwan Stössel.

in some imprints, evident digit impressions (Fig. 5). One trackway has a clear median drag, whereas the other lacks a median impression. The estimated gleno-acetabular length of the trackmaker is 22 cm. Both trackways (Fig. 5) show an alternating pattern and differentiation (by size) of the manus (smaller) and pes (larger) (Fig. 5). The trackway without a median drag impression preserves overstepped, broad and short manus impressions smaller than pes impressions that are longer than wide. Some of the manus and pes impressions have at least five, short and blunt, laterally-directed digit imprints. The other trackway shows a definite median drag mark and well-separated manus and pes impressions that lack definition. Lucas (2015) concluded that these are tetrapod trackways made subaerially in a nonmarine setting.

Northern Scotland - Rogers (1990) documented what he interpreted as a tetrapod trackway from the Upper Old Red Sandstone of Easter Ross in northern Scotland. However, the Devonian age of this tracksite is not certain. According to Rogers (1990) it is ~ 900 m stratigraphically above a marine fossiliferous bed of Givetian age, and could range in age from Givetian to Tournaisian. Clack (1997) also stressed that this tracksite could be early Carboniferous in age. Very recently, Marshall et al. (2018) raised the possibility that the Easter Ross footprints could be of Permian age. However, no biostratigraphic data tightly constrain the age of these footprints (Marshall et al., 2018), so I continue to tentatively consider them to be of Late Devonian age (Lucas, 2015). According to Rogers, the footprint-bearing stratum is part of an eolian sabkha deposit in a sandstone bed with wind ripple and planar laminations, so the footprints were impressed subaerially. The footprints form an alternating trackway of three steps in which inferred manus and pes imprints can be differentiated on the basis of size (manus much smaller than pes). Rogers described the manus and pes as of similar size, but on the left side of the trackway the inferred manus impressions are clearly smaller than the pes impressions. The estimated glenoacetabular length of the tetrapod trackmaker is ~ 29 cm. Both Clack (1997) and Lucas (2015) accepted this as a tetrapod trackway, though its Devonian age remains uncertain.

“Tetrapod footprints” from the Zachełmie quarry, Poland - Niedźwiedzki et al. (2010) reported putative tetrapod trackways from Middle Devonian (lower-middle Eifelian), shallow marine strata at the Zachełmie quarry in Poland (Fig. 6). Acceptance of the structures from the Zachełmie quarry as the oldest tetrapod footprints, ergo the oldest record of tetrapods, has been Fig. 5 - The Late Devonian tetrapod trackways from the Genoa widespread among students of early tetrapod evolution River in eastern Australia. Note the two parallel trackways, one with (e.g., Janvier & Clément, 2010; Clack, 2012; Steyer, distinct manus impressions overstepped by pes impressions (on the left), the other with linear, scratch-like footprints and a sinusoidal 2012; Ahlberg, 2018). Indeed, the Devonian “trackways” median drag mark of the tail/body (the inset drawing scales [scale from Zachełmie even appeared in a recent edition of a bar = 10 cm] and interprets parts of the trackways; m = manus, p prominent American historical geology textbook (Stanley = pes). This trackway remains in the field. Photograph courtesy of & Luczaj, 2014, fig. 14.21). John Warren, inset drawing from Lucas (2015). 230 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

The oldest record of tetrapods based on the Zachełmie quarry “footprints” forces a re-evaluation of the current phylogeny of tetrapod origins and the recognition of numerous lengthy ghost lineages (Niedźwiedzki et al., 2010; Clack, 2012; Ahlberg, 2018). Furthermore, the Zachełmie quarry “footprints” indicate much larger tetrapods than do other Devonian tetrapod trackways and the tetrapod-body-fossil record. As Clack (2012) noted, they indicate a trackmaker with a total length of as much as 2.5 m, whereas known body fossils of Devonian tetrapods and their close relatives among “fishes” are much shorter animals. Indeed, extremely large structures at the Zachełmie quarry, as much as 50 cm long, have been interpreted as tetrapod undertracks (Niedźwiedzki et al., 2010, supplementary information, fig. 18B), although no known Paleozoic tetrapod footprint is remotely near that size. If we accept the Zachełmie quarry structures as tetrapod footprints, Clack (2012, p. 126) wrote that “we may well have to rethink the whole question of timing, sequence and circumstances of the origin of tetrapods” (also see Ahlberg, 2018). However, Lucas (2015) argued that what needs a rethink is the identity of the structures in the Zachełmie quarry (Fig. 6). He stressed that no convincing case has been made that they are tetrapod footprints, and he made a very strong argument that they are fish feeding traces/nests. The “footprints” from the Zachełmie quarry are in a 3.2-3.8 m thick interval of thin-bedded dolomicrites, interpreted on diverse evidence as shallow marine/ Fig. 6 - Photographs of the shallow, dish-like structures from lagoonal sediments (Niedźwiedzki et al., 2010). However, the Middle Devonian strata at the Zachełmie quarry, Poland, recently Qvarnström et al. (2018) re-interpreted the identified by Niedzwiedski et al. (2010) as tetrapod footprints, but re-identified by Lucas (2015) as fish nests. Photographs courtesy Zachełmie deposit as a series of ephemeral freshwater of Joerg Schneider. lakes. Given that the deposit is a succession of dolomites with invertebrate trace fossils and microbially-induced sedimentary structures characteristic of shallow marine trackways are known to provide a reliable basis for settings (e.g., Niedźwiedzki et al., 2014), I find the re- paleobiogeographic interpretation. interpretation of Qvanström et al. (2018) questionable. For more than a century, the paleoenvironment of However, if the Zachełmie deposit is freshwater, then tetrapod origins has been debated-marine or nonmarine, it provides no support for a marine origin of tetrapods dry or wet (e.g., Clack, 2000, 2012; George & Blieck, for those who believe the circular depressions there are 2011; Retallack, 2011; Schultze, 2013). Bona fide tetrapod footprints. Nevertheless, no evidence has been Devonian tetrapod footprints are from nonmarine presented that these circular depressions, which do not facies, so they do not support a marginal marine origin form clear trackways, are footprints, so they are irrelevant of tetrapods. They indicate lateral sequence walking to the Devonian tetrapod fossil record (Lucas, 2015). and pelvic-limb-propelled, fully terrestrial (subaerial) locomotion in freshwater environments (mostly subaerial) Timing, location and paleoenvironment of tetrapod origins by at least some Devonian tetrapods. The tetrapod trackways from Valentia Island in Ireland are likely no younger than Givetian, so this is the Late Devonian tetrapod mass extinctions oldest record of tetrapods. The oldest Devonian tetrapod Few have made a case for Devonian tetrapod mass trackways thus provide an important datum that places extinctions as part of the Late Devonian extinctions at the tetrapod origins during the Middle Devonian, or earlier. Frasnian-Fammenian boundary (“Kellwasser event”) and/ Clack & Milner (2015) provided a useful review of or at the end of the Devonian, the Fammenian-Tournaisian diverse ideas about Devonian tetrapod paleobiogeography, boundary (“Hangenberg event”). Indeed, McGhee (2013) most of which advocate tetrapod origins in Euramerica may represent the only extensive published argument (Laurussia). Middle Devonian tetrapod footprints for such tetrapod extinctions, basing it largely on the are known from Ireland, and Late Devonian tetrapod biostratigraphic compilation of the Devonian body-fossil footprints are known from Scotland and Australia (Fig. record of tetrapods by Blieck et al. (2010). However, this 3). The Irish record is the oldest tetrapod record, so on compilation identified only three or four Frasnian tetrapod face value it could indicate an origin of tetrapods in genera and eight or nine Fammenian genera, most of Euramerica. However, given how sparse the Devonian which are known from single localities based on one or a tetrapod footprint record is, this conclusion should be few specimens, for example the records of Elginerpeton, viewed with great caution. Too few Devonian tetrapod Obruchevichthys, Tulerpeton and Ventastega, among S.G. Lucas - Ichnology and Paleozoic tetrapods 231 others. Of course, the Devonian tetrapod body-fossil bridged by the Middle Devonian, because the tracks from record has been augmented since the Blieck et al. (2010) Ireland already show propulsion driven by the hind limbs. compilation, but most of the new records continue to be The transition from fins to limbs is widely regarded of a single taxon from a single locality known from one to have taken place in the aquatic realm. In other words, or a few specimens (e.g., Clack & Milner, 2015; Olive et Devonian tetrapods are regarded as primarily aquatic al., 2016). Indeed, of the Devonian tetrapod body-fossil (e.g., Coates & Ruta, 2007; Clack, 2012). Indeed, Coates taxa, only two are known from substantial numbers of & Clack (1995) argued that the limbs of Ichthyostega and specimens, Ichthyostega and Acanthostega (e.g., Coates, Acanthostega (Fig. 7) were relatively inflexible paddles 1996; Jarvik, 1996; Blom, 2005; Marzola et al., 2018). that were unlikely to have left the kinds of Devonian The Devonian tetrapod body-fossil record thus is trackways attributed to tetrapods. This may in part explain sparse and lacks the stratigraphic density with which to the rarity of Devonian tetrapod footprints-most Devonian evaluate Late Devonian diversity dynamics (Kaiser et al., tetrapods spent little or no time walking on land. 2016; Lucas, 2018b). The Devonian tetrapod footprint Bona fide Devonian tetrapod footprints indicate an record is so poor and disconnected from the body fossil alternating pattern of limb-supported locomotion by a record that it does not improve this situation. tetrapod with a larger hind foot than forefoot (Fig. 8). This The analysis of Late Devonian vertebrate extinctions is the characteristic pattern of quadrupedal locomotion of by Sallan & Coates (2010) identified no dramatic post-Devonian tetrapods. The Devonian tetrapod footprint Devonian tetrapod extinction events. However, they did record thus indicates such locomotion was possible at argue that the paucity of early Carboniferous tetrapods, least some of the time by some Devonian tetrapods. Body part of the phenomenon referred to as “Romer’s gap” (see fossils of these Devonian tetrapods await discovery. below), was part of a “post-extinction trough” after the Hangenberg event. But, as noted below, “Romer’s gap” was an artifact of sampling that has steadily been filled. CARBONIFEROUS It now has even produced “ichthyostegalian” body fossils (Anderson et al., 2015) that indicate that the stem tetrapods Carboniferous tetrapod footprint record survived the end of the Devonian. Therefore, no case for Carboniferous tetrapod footprints have an almost Late Devonian tetrapod mass extinctions can be made strictly Euramerican distribution (Fig. 9), and currently based on current tetrapod body-fossil or footprint data. suffer from a confused and confusing ichnotaxonomy. Matthew (1903a) last attempted a comprehensive revision, Early tetrapod locomotion and evolution though Haubold (1970, 1971), Sundberg et al. (1990), The tetrapodomorph fishes, the sister taxon to Haubold et al. (2005), Lucas et al. (2010a) and Fillmore tetrapods, such as Panderichthys and Tiktaalik, have et al. (2012), among a few others, have clarified some of robust pectoral fins, much larger than their hind fins, the ichnotaxonomy. The need for vast ichnotaxonomic quite different from the larger pelvic limbs of tetrapods revision is obvious (Cotton et al., 1995; Hunt et al., 1995; (Shubin et al., 2004; Swartz, 2012). There is thus a marked Lucas, 2004, 2007). Nevertheless, to revise Carboniferous disconnect between the locomotory apparatus of fully tetrapod footprint ichnotaxonomy is beyond my scope terrestrial tetrapods, driven by hind limb propulsion, here, though I am working on such a revision together with and that of their nearest relatives, driven by forelimb J. Calder, B. Hebert, A. Hunt, C. Mansky and M. Stimson. propulsion (e.g., Boisvert, 2005; Boisvert et al., 2008; Cotton et al. (1995), Hunt et al. (1995) and Lucas Pierce et al., 2013). The Devonian tetrapod footprint (2003, 2007) provided useful reviews of the distribution of record suggests this evolutionary gap had already been Carboniferous footprints (Fig. 9). One of the most extensive

Fig. 7 - Reconstruction of the Devonian “ichthyostegalian” Acanthostega by Arthur Escher. Note the paddle-like limbs, thought to be characteristic of “ichthyostegalians” and indicating that they were incapable of extensive terrestrial locomotion. 232 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fig. 8 - Interpretation of Middle Devonian trackways on Valentia Island, Ireland, showing lateral sequence walking by a tetrapod with a larger pes than manus. Modified from Stössel et al. (2016) with images courtesy of Iwan Stössel.

Carboniferous footprint records comes from Nova Scotia age are known: Tournaisian Blue Beach and Hurd Creek (Canada). Paleozoic tetrapod footprints were discovered members of the Horton Bluff Formation in Nova Scotia, in Nova Scotia in 1841, Lyell (1843) published this record, Canada, and late Visean Mauch Chunk Formation in and although originally considered to have been made by eastern Pennsylvania, USA (Fig. 10). Other Mississippian- a reptilian trackmaker, they were later shown to be those age footprint records are few and mostly single trackways: of an amphibian. Extensive work by Dawson (1844, 1845, 1) Paleosauropus from the Tar Springs Formation 1863a, b, 1868, 1872, 1882, 1894, 1895), Matthew (1903a, in Indiana (Colbert & Schaeffer, 1947); 2) footprints b, c, 1904, 1905) and Sternberg (1933) followed, and the originally assigned to Dromopus, but later reassigned Nova Scotian footprint record represents the most complete by Haubold (1971) to “Asperipes,” from the Hinton single stratigraphic succession of Carboniferous footprints Formation in Virginia (Branson, 1910); 3) indeterminate (Lucas, 2007). It encompasses footprint assemblages that footprints from the Pocono Formation (Dunkle, 1948), and range in age from Early Mississippian to early Permian Hylopus from the Bluefield Formation (Sundberg et al., and should be the global standard for understanding the 1990) in West Virginia; and (4) large amphibian footprints temporal succession of Carboniferous tetrapod footprint from England (Barkas, 1873; Sarjeant, 1974; Scarboro ichnotaxa (Lucas, 2003, 2007). & Tucker, 1995; Bird et al., 2019). The Mississippian footprints represent the Hylopus biochron of Fillmore et Mississippian tetrapod footprints - Only two al. (2012), dominated by amphibian and reptiliomorph substantial tetrapod footprint assemblages of Mississippian footprints but lacking the amniote footprint Notalacerta.

Fig. 9 - Carboniferous continental configuration showing tetrapod footprint localities. Abbreviations are: B = Baltica, K = Kazakstan, NC = North China, SC = South China, Sib = Siberia, Su = Subumasu, Ta = Tarim. Localities are: 1) Western USA; 2) Eastern USA; 3) Nova Scotia, Canada; 4) east Greenland; 5) Europe; 6) Chile; 7) Morocco; 8) Shanxi, China. S.G. Lucas - Ichnology and Paleozoic tetrapods 233

Fig. 10 - The two localities that yield extensive Mississippian tetrapod-footprint assemblages. a) The Horton Bluff Formation at Blue Beach, Nova Scotia, Canada. b) The Mauch Chunk Formation at Tumbling Run Reservoir in Pennsylvania, USA.

In Nova Scotia, Mississippian footprints are principally deposited within a restricted marine bay, and is associated from the Horton Bluff Formation and have been with an invertebrate ichnofossil assemblage dominated assigned recently to the ichnogenera Batrachichnus, by arthropod walking and resting traces (Mansky & Palaeosauropus, Hylopus, Pseudobradypus and Lucas, 2013). Bones of tetrapods are also present in the Attenosaurus (Lucas et al., 2010c; Mansky & Lucas, Horton Bluff Formation, and some of these belong to 2013). These are the footprints of small and large “ichthyostegalians” (Anderson et al., 2015). Yet, there temnospondyls (Batrachichnus, Palaeosauropus) and of are no polydactyl footprints or trackways indicative of reptiliomorphs (Fig. 11). The Horton Bluff assemblage “ichthyostegalians” in the Horton Bluff tetrapod-footprint is from brackish to freshwater lake-margin sediments assemblage.

Fig. 11 - Some characteristic tetrapod footprints from the Horton Bluff Formation at Blue Beach, Nova Scotia, Canada. a-b)Palaeosauropus . c) Batrachichnus. d) Pseudobradypus. Tracks are in the collection of the Blue Beach Museum, Nova Scotia, Canada. Scale bars in mm and cm. 234 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fig. 12 - Some characteristic tetrapod footprints from the Mauch Chunk Formation in eastern Pennsylvania, USA. a) Lea’s (1853) drawing of the holotype of Palaeosauropus primaevus. b) The holotype of Palaeosauropus primaevus. c) Palaeosauropus. d) Hylopus. e) Batrachichnus. Tracks are in the collection of the Reading Public Museum, Pennsylvania, USA. Scale bars in mm and cm.

The Mauch Chunk tetrapod footprint assemblage Large Mississippian temnospondyl footprints from in Pennsylvania, is from fluvial red beds that yield an both the Horton Bluff and the Mauch Chunk formations invertebrate ichnoassemblage dominated by backfilled indicate the presence of Mississippian temnospondyls burrows of deposit feeders (Fillmore et al., 2010, 2012). The much larger than any known from the coeval body-fossil tetrapod ichnogenera present are Batrachichnus, Hylopus, record. The Horton Bluff and Mauch Chunk tetrapod Matthewichnus, Palaeosauropus and Pseudobradypus footprint assemblages indicate fully terrestrial tetrapods (Fig. 12). These are dominantly the footprints of various with pentadactyl/tetradactyl feet walking in an alternating temnospondyls and a few reptiliomorph footprints gait by Tournaisian time (cf. Schaeffer, 1941). They also (Hylopus, Pseudobradypus). A particularly unusual lack unambiguous amniote footprints, which supports a trace fossil from the Mauch Chunk Formation consists post-Visean origin of amniotes. of temnospondyl-body resting traces (Temnocorpichnus of Lucas et al., 2010b) associated with the footprint Pennsylvanian tetrapod footprints - Cotton et ichnogenus Batrachichnus (Fig. 13). al. (1995), Hunt et al. (1995) and Lucas (2003, 2007) Despite the striking facies differences, the Horton Bluff reviewed the Pennsylvanian record of tetrapod footprints. and Mauch Chunk tetrapod footprint assemblages share Most of that record is of scattered occurrences in eastern key features: 1) low ichnodiversity (four-five ichnogenera); and western North America and in western Europe, 2) amphibian footprints (Palaeosauropus and subordinate and there are only a handful of sites in other parts of Batrachichnus) are most common; 3) other footprint the world (Fig. 9). Lucas (2007) identified a footprint ichnogenera (Hylopus, Matthewichnus, Attenosarus) biochron of ~ Early-Middle Pennsylvanian age that are rare; and 4) both well represent the Batrachichnus was originally called the Pseudobradypus biochron, but ichnofacies of Hunt & Lucas (2007). One difference is renamed the Notalacerta biochron by Fillmore et al. common Pseudobradypus in the Horton Bluff assemblage, (2012). Footprint assemblages of the Notalacerta biochron whereas this ichnotaxon is rare in the Mauch Chunk show a mixture of amphibian (e.g., Batrachichnus, assemblage. Pseudobradypus has been claimed to represent Limnopus, Matthewichnus), reptiliomorph (Hylopus, the oldest amniote footprint in the Lower Pennsylvanian Pseudobradypus, Ichniotherium) and amniote (e.g., of New Brunswick, Canada (see below). However, the Dimetropus, Notalacerta) footprints. Lucas (2007) also Horton Bluff records are much older and are more likely to named the succeeding footprint biochron, which begins have been made by basal tetrapods such as anthracosaurs during the Late Pennsylvanian, the Dromopus biochron that have foot structures homeomorphic with those of later (see below). amniotes. Furthermore, Mauch Chunk redbeds represent There are three extensive tetrapod footprint assemblages relatively “dry” fluvial paleoenvironments yet lack amniote of Pennsylvanian age: Joggins, Nova Scotia, Canada; the footprints, although this is the kind of paleoenvironment Union Chapel Mine (UCM), Alabama, USA; and Keota, that some have posited as the likely paleoenvironment of Oklahoma, USA (Fig. 14). The Joggins and UCM records aminote origins (Falcon-Lang et al., 2007, 2010) are Early Pennsylvanian, whereas the Keota record is of S.G. Lucas - Ichnology and Paleozoic tetrapods 235

Fig. 13 - Temnocorpichnus isaacleai, resting traces of temnospondyl amphibians associated with Batrachichnus footprints from the Mississippian Mauch Chuink Formation, Pennsylvania, USA. a) Photograph of holotype specimen. b) Line drawing outlining the resting traces. Three resting traces are labeled A through C. Note the overlap of the posterior region of A with the head of B. c) Restoration of Temnocorpichnus isaacleai by Matt Celeskey showing speculative courtship ritual. The trace fossil is in the collection of the Reading Public Museum, Pennsylvania, USA.

Middle Pennsylvanian age, so these are assemblages of Other Pennsylvanian footprint records in the eastern the Notalacerta biochron (Fig. 15). United States are scattered, less extensive (often single In Nova Scotia, the principal Pennsylvanian footprint- records) and come from the states of Massachusetts, bearing strata are an ~ 20-m-thick interval of the early Rhode Island, Pennsylvania, Ohio, Indiana, Virginia, West Westphalian Joggins Formation at Joggins (cf. Stimson et Virginia, Kentucky, Tennessee and Georgia (e.g., King, al., 2012, fig. 2; Fig. 14). Many ichnogeneric names have 1845; Moore, 1873; Cox, 1874; Leidy, 1879; Woodworth, been applied to these footprints (e.g., Matthew, 1903a; 1900; Branson, 1910; Lull, 1920; Carman, 1927;Willard Sternberg, 1933; Sarjeant & Mossman, 1978; Mossman & Cleaves, 1930; Mitchell, 1931, 1933; Baird, 1952, & Grantham, 1996, 2000), but most of these names 1965; Haubold, 1971; Patterson, 1971; Jake & Blake, are invalid. The most common valid ichnogenera are 1982; Schneck & Fritz, 1985; McClelland, 1988; Lane Batrachichnus, Limnopus, Matthewichnus, Notalacerta & Maples, 1990; Martino, 1991; Chestnut et al., 1994; and Pseudobradypus, so these are the footprints of diverse Kohl & Bryan, 1994; Cotton et al., 1995; Monks, 2002; temnospondyls and reptiliomorphs and rare amniotes Lucas & Dalman, 2013; Fillmore et al., 2015; Getty et al., (Fig. 16). 2017). Many ichnogeneric names have been applied to In Alabama, Aldrich (in Aldrich & Jones, 1930), these footprints, but they mostly pertain to the ichnogenera originally described some endemic ichnogenera, Batrachichnus, Limnopus, Hylopus, Matthewichnus, including Cincosaurus and Attenosaurus, from the Lower Dromopus, Notalacerta and Pseudobradypus, though Pennsylvanian Pottsville Formation (also see Jones, note that the Notalacerta and Pseudobradypus records all 1930). An extensive footprint assemblage (Fig. 16), now appear to be older than the Dromopus records. Many of assigned to Batrachichnus (= Nanopus), Matthewichnus, the footprint assemblages are imprecisely dated, but the Attenosaurus (= Alabamasauripus) and Notalacerta (= older records (pre-Gzhelian/Virgilian) are assemblages of Cincosaurus) comes from the Union Chapel Mine (UCM) the Notalacerta biochron, whereas the younger records (Hunt et al., 2004, 2005; Haubold et al., 2005). A similar, represent the Dromopus biochron. and perhaps equally prolific footprint assemblage, is also Scattered occurrences of tetrapod footprints are known known from the Crescent Valley Mine in Alabama (Buta from the Carboniferous strata of the western United States et al., 2013). (Wyoming, Colorado, Oklahoma, Kansas and Missouri) The Keota locality in eastern Oklahoma (Fig. 14) is and are mostly assignable to Batrachichnus, Limnopus the only substantial Moscovian age footprint assemblage. and Notalacerta (e.g., Jillison, 1917; Henderson, 1924; In the upper part of the McAlester Formation, it is Branson & Mehl, 1932; Toepelman & Roedeck, 1936; assigned an early Desmoinesian age based on conodont Houck & Lockley, 1986; Reisz, 1990; Lockley & Hunt, biostratigraphy (Schneider et al., 2020). The locality 1995). An important ichnoassemblage from the Gzhelian produces a prolific but low ichnodiversity assemblage (Virgilian) Wescogame Formation in the Grand Canyon (Fig. 16) dominated by Batrachichnus and Notalacerta of Arizona that includes Batrachichnus, cf. Limnopus, with rare cf. Amphisauropus (Lucas et al., 2001; Lerner cf. Amphisauropus and Varanopus (Gilmore, 1927; et al., 2002). Haubold, 1971; Marchetti et al., in press) may be one 236 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Turek, 1989; Milner, 1994; Voigt & Ganzelweski, 2010). These tracksites contain many of the same ichnogenera as their North American correlatives (e.g., Batrachichnus, Limnopus, Paleosauropus, Pseudobradypus) and thus show a mixture of amphibian footprints and reptiliomorph footprints. They also include the significant, oldest records of the ichnogenera Dimetropus and Ichniotherium (Voigt & Ganzelewski, 2010) discussed below. Younger, Stephanian (approximately Late Pennsylvanian) tracksites are in Germany, France, Italy, England and Spain (e.g., Haubold & Sarjeant, 1973; Gand, 1975; Sotty, 1975a, b, 1976, 1977; Langiaux, 1979, 1980, 1981; Langiaux & Mietto et al., 1985; Blieck et al., 1997; Soler-Gijón & Moratalla, 2001; Marchetti et al., 2018). These are broadly similar to the Westphalian assemblages, and are mostly records of Batrachichnus, Limnopus, Dromopus and Dimetropus, ichnotaxa characteristic of the Dromopus biochron. Outside of Euramerica, there are only a few records of Pennsylvanian tetrapod footprints; 1) northern Chile, temnospondyl footprints (Bell & Boyd, 1986); 2) incomplete footprints identified as aff. Dimetropus from Shanxi, China (Lucas & Ataabadi, 2010); 3) Limnopus from the Vig Formation in Greenland (Milàn et al., 2016); and 4) an ichnoassemblage from the Souss basin of south- central Morocco consisting of footprints identified as Batrachichnus, Limnopus, Dimetropus and Ichniotherium (Lagnaoui et al., 2017).

Romer’s Gap The Late Devonian tetrapods known from body fossils were aquatic (Coates & Clack, 1995), and appeared long before the oldest clearly terrestrial tetrapod faunas of the Carboniferous. The interval between the Late Devonian aquatic tetrapods and the “terrestrial” tetrapods was long perceived of as much of the Early Mississippian (the entire Tournaisian and first half of the Visean stages), at least 20 million years (Romer, 1941, 1956; Clack, 2002). This interval was named Romer’s gap (Fig. 15), and thought to conceal the poorly known/undocumented transition from stem tetrapods that were not fully terrestrial to terrestrial Fig. 14 - Outcrops at the three Pennsylvanian localities that yield tetrapods in crown-group lineages (Coates & Clack, 1995). extensive tetrapod-footprint assemblages. a) Early Pennsylvanian However, it is now clear that Romer’s gap was mostly Joggins Formation at Joggins, Nova Scotia, Canada. b) The abandoned coal strip mine in the Lower Pennsylvanian Pottsville an artifact of the available fossil sample that has been filled Formation, the Union Chapel Mine (UCM) in Alabama, USA. c) The by discovery and description of already known fossils Middle Pennsylvanian McAlester Formation at the Keota locality (Rygel et al., 2006; Smithson et al., 2012; Mansky & in eastern Oklahoma. Lucas, 2013; Anderson et al., 2015; Kearsey et al., 2016; Chen et al., 2018; Clack et al., 2019a, b). Significantly, body fossils deemed “consistent” with ichthyostegids, of the oldest tetrapod footprint assemblages from eolian acanthostegids and Tulerpeton are now documented from strata (see later discussion). Footprints from the Virgilian Romer’s gap in the Horton Bluff Formation at Blue Beach, Howard Limestone in Kansas include the type material Nova Scotia, so these characteristic Devonian tetrapods of Limnopus and Dromopus (Mudge, 1874; Marsh, 1894; are now known from the lower Carboniferous (Anderson Baird, 1952; Schoewe, 1956). et al., 2015). In Europe, Pennsylvanian tetrapod footprints come Nevertheless, as shown by body fossils, there was a principally from Germany, France and Great Britain, substantial diversification of early tetrapods during the but there are also some records in Spain, Italy and the Carboniferous, amounting to nearly 40 families, most Czech Republic. Westphalian (approximately Early- of which began during early Carboniferous time (e.g., Middle Pennsylvanian) tracksites are more common Ruta et al., 2003; Coates et al., 2008; Schoch, 2013; and are found in Germany (especially in the Ruhr basin Schoch & Milner, 2014; Benton, 2015). The Blue Beach and in Sachsen), France and the Czech Republic (e.g., tetrapod footprint assemblage is consistent with that Wolansky, 1952; Schmidt, 1956, 1959, 1963; Müller, diversification, as it contains footprints of temnospondyls 1962; Dollé et al., 1970; Haubold, 1970; Fichter, 1982; and of reptiliomorphs early in Visean time. S.G. Lucas - Ichnology and Paleozoic tetrapods 237

Fig. 15 - Carboniferous tetrapod footprint biochronology (after Fillmore et al., 2012). Abbreviations are: FAD = first appearance datum; SGCS = standard global chronostratigraphic scale. Artwork of Balanerpeton and Hylonomus by Arthur Escher.

Amniote origins Recognising this, Falcon-Lang et al. (2007) compiled The oldest amniote fossils have long been considered metric data on 14 genera of reptiliomorphs and early to be those of Hylonomus and Paleothyris from the Lower amniotes to establish criteria that they claimed distinguish Pennsylvanian (middle Langsettian) at Joggins, Nova the feet (and footprints) of amniotes from those of more Scotia (e.g., Dawson, 1895; Carroll, 1969, 1970, 1982; primitive reptiliomorphs. Falcon-Lang et al. (2007) Carroll & Baird, 1972; Clack, 2002; Steyer, 2012; Benton, concluded that the footprint ichnogenus Pseudobradypus, 2015; Fig. 15). Hylonomus is known from essentially notable among Carboniferous footprints for the relatively complete skeletal material that reveals it to have been a long and slender manus and pes imprints (Fig. 11), is the small (up to 20 cm long) lightly-built predator (Fig. 17). footprint of an amniote. Indeed, Hylonomus is typically restored as a lizard-like Nevertheless, Keighley et al. (2008) critiqued the predator (e.g., Steyer, 2012). conclusions of Falcon-Lang et al. (2007), pointing out Falcon-Lang et al. (2007) claimed to have found first that the Grande Anse Formation footprints are not older evidence of amniotes in the form of footprints definitely older than the Joggins Formation footprint and they identified as Pseudobradypus from the Grande bone record, which includes definite amniote body fossils Anse Formation in New Brunswick, Canada. However, and footprints. Keighley et al. (2008) also noted that there Pseudobradypus does not necessarily indicate an is a fair degree of overlap in the degree of digital splay amniote trackmaker, and Marchetti et al. (2019d) between reptiliomorphs and amniotes, so there is no clear argued that the footprints Falcon Lang et al. (2007) separation of the two groups based on the ratio of foot assigned to Pseudobradypus more likely belong to the length and width. reptiliomorph ichnogenus Hylopus. This, despite the Fillmore et al. (2012) and Marchetti et al. (2019d) fact that Pseudobradypus has been associated by some reinforced the conclusions of Keighley et al. (2008). workers with an amniote trackmaker (largely because Although in reply to Keighley et al. (2008), Falcon-Lang of its pentadactyl manus), either a captorhinoromph & Benton (in Keighley et al., 2008) conceded their major or a eupelycosaur (Haubold, 1971; Milner, 1994). points, the entire discussion of Pseudopbradypus as an However, there are a variety of reptiliomorphs, sensu amniote footprint, including the table of metrics found in Ruta et al. (2003) (anthracosaurs, seymouriamorphs and Falcon-Lang et al. (2007), was repeated subsequently by diadectomorphs) that have a pentadactyl manus (Fig. 17). Falcon-Lang et al. (2010). 238 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fig. 16 - Some characteristic tetrapod footprints of the Notalacerta bichron. a-b) Batrachichnus, from the Union Chapel Mine (UCM) (a) and Keota (b). c) Matthewichnus from the UCM. d) Attenosaurus from the UCM. e) Notalacerta (“Cincosaurus”) from the UCM. f) Pseudobradypus from Joggins. Tracks from the UCM are in the collection of the Alabama Museum of Natural History, Tuscaloosa, Alabama, USA; tracks from Keota are in the New Mexico Museum of Natural History, Albuquerque, New Mexico, USA. Scale bars in mm and cm. S.G. Lucas - Ichnology and Paleozoic tetrapods 239

Pseudobradypus has definite Mississippian records (especially anthracosaurs) and by early amniotes, and, (Fig. 15), both in the Mauch Chunk Formation and in given the similarity in overall foot structure, there is no the older, Lower Mississippian Horton Bluff Formation obvious way to distinguish the trackmaker. footprint assemblage from Nova Scotia (Lucas et al., Nevertheless, Anderson et al. (2015) noted that there 2010c). If Falcon-Lang et al. (2007, 2010) are correct may be some evidence of amniote origins before the that Pseudobradypus is an amniote footprint, then this Carboniferous. Thus, some molecular evidence (e.g., means the footprint record indicates amniotes as old as Zhang et al., 2005; Roelants et al., 2007; San Mauro, the Early Mississippian. This is a clear problem of the 2010; but see Zheng et al., 2011) supports a Devonian homeomorphy of the footprints of early amniotes and of divergence of amphibians and amniotes. The suggestions some reptiliomorphs (Fig. 17). The footprint ichnogenus that Late Devonian Tulerpeton is an embolomere and Pseudobradypus was made by both reptiliomorphs that embolomeres are stem-group amniotes (Panchen &

Fig. 17 - Comparison of the foot skeletons of reptiliomorphs (a, an anthracosaur) and one of the oldest amniotes, Hylonomus (b, not to scale). a) The reptiliomorph skeleton is the anthracosaur Proterogyrinus, as is the manus; the pes is from Archeria. b) The amniote skeleton and feet skeleton are of Hylonomus. Modified from images in Romer (1957), Carroll (1969, 1982) and Holmes (1984). 240 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Smithson, 1988; Lebedev & Coates, 1995) also support a Kasimovian-Gzhelian transition (Fillmore et al., 2012; possible Devonian amniote origins. However, at present Voigt & Lucas, 2018; Schneider et al., 2020; Fig. 15), the oldest definite amniote body fossils and footprints are though it could be older, within the Kasimovian. Thus, of Early Pennsylvanian age. note that there are two possible Kasimovian records of Dromopus, in Morocco and in England (Hmich et al., 2006; Kasimovian revolution Meade et al., 2016). Gzhelian (Virgilian) occurrences of The beginning of the Late Pennsylvanian (the Dromopus include its type material from the Howard beginning of the Kasimovian and Missourian ages) was Limestone (Wabaunsee Group) in Kansas (Marsh, 1894) a time of substantial climatic and biotic changes. In the and the Thuringian Forest basin in Germany (Voigt, marine realm, important evolutionary turnover in many 2005, 2012). The Dromopus biochron extends through taxa took place, notably fusulinids, brachiopods, sponges, a large part of the early Permian (Voigt & Lucas, 2018), ammonoids and conodonts, and there were slow rates of and Gzhelian records include other characteristic early origination and extinction, so-called “sluggish evolution” Permian tetrapod footprint ichnogenera, including (e.g., Boardman et al., 1998; Stanley & Powell, 2003; Batrachichnus, Dimetropus, Ichniotherium and Limnopus Powell, 2005). On land, a profound transformation took (Fig. 18) place in the vegetation, the so-called “Carboniferous However, other than Dromopus, most of the tetrapod rainforest collapse,” when the tropical rainforest biome ichnogenera of the Dromopus biochron have older (popularly referred to as the “Coal Forests”) gave way Pennsylvanian (and, in some cases, Mississippian) to much more xerophytic vegetation (e.g., Phillips et records (see above). There are also much older records al., 1974; Pfefferkorn & Thomson, 1982; DiMichele of diadectomorph footprints (ichnogenus Ichniotherium) & Phillips, 1996; Kosanke & Cecil, 1996; Peppers, and of eupelycosaur footprints (ichnogenus Dimetropus) 1996, 1997; Sahney et al., 2010; McGhee, 2018). These from the Bashkirian of Germany (Voigt & Ganzelewski, changes in the marine realm and in the vegetation were 2010). These records substantially predate the oldest body- not, however, a single event, having begun during the fossil records of their inferred trackmakers, which are no Moscovian and extending through the Kasimovian, older than Kasimovian. The Bashkirian Ichniotherium taking place at different times in different parts of Pangea are particularly interesting as possibly representing the (e.g., DiMichele et al., 2011). The original claim that this oldest fossils of a tetrapod high-fiber herbivore. These caused a substantial tetrapod extinction and drove tetrapod Bashkirian footprint records thus diminish the extent of the endemism has not withstood subsequent analysis (Dunne Kasimovian revolution in tetrapod evolutionary history by et al., 2018). But, there still were important changes in pushing back the record of two significant tetrapod groups the tetrapod biota during the Middle-Late Pennsylvanian (diadectomorphs and eupelycosaurs minus varanopids) transition. thought to have first appeared during the Kasimovian. The changes in the biota that took place across A much more extensive tetrapod footprint record from the Moscovian-Kasimovian boundary were not mass Bashkirian and Moscovian strata may push back the extinctions but instead a complex and prolonged supposed Kasimovian or Gzhelian first appearances of evolutionary turnover that I refer to as the Kasimovian other tetrapod taxa. The tetrapod footprint record thus revolution. This was a major step on land toward seems to diminish the apparent evolutionary turnover of terrestrialisation of both the flora and the fauna. tetrapods during the Kasimovian revolution indicated by For tetrapods, it was the end of what Milner (1987) their body-fossil record. termed the “Westphalian chronofauna,” characterised by loxommatoids, colosteids, aistopods, nectrideans, temnospondyls, anthracosaurs, microsaurs and primitive PERMIAN amniotes. During the Late Pennsylvanian (~ Stephanian), body fossils of several important new tetrapod taxa Permian tetrapod footprints appeared, including the Eryopidae, Cochleosauridae, Voigt & Lucas (2018) provided a recent review of the Dissorophidae, Discosauriscidae?, Trimerorhachidae, Permian tetrapod footprint record, obviating the need for Diadectidae, Petrolacosauridae, Varanopidae, a detailed review here (also see Cotton et al., 1995; Hunt Sphenacodontidae and Edaphosauridae (e.g., Reisz, et al., 1995; Voigt, 2005, 2012; Gand & Durand, 2006; 1986; Milner, 1987; Berman et al., 1997; Lucas, 2004; Hunt & Lucas, 2006; Lucas & Hunt, 2006; Lucas, 2007; Carroll, 2009; Lucas et al., 2018; Schneider et al., 2020). Marchetti et al., 2019a, b, c, in press). Tetrapod footprints Before the Late Pennsylvanian, tetrapod-body fossils are common fossils in some nonmarine Permian strata indicate no direct consumption of high fiber plant foods and have a much more extensive and global record than by tetrapods. Then, during the Late Pennsylvanian, the do Carboniferous tetrapod footprints (Fig. 19). Like first obligate high-fiber herbivores appear in the tetrapod Carboniferous footprints, Permian footprints have a body-fossil record, the diadectomorphs, bolosaurids, long history of study; indeed, they were among the first caseasaurs and edaphosaurid eupelycosaurs (e.g., Hotton published vertebrate ichnofossils (Anonymous, 1828; et al., 1997; Sues & Reisz, 1998; Reisz & Sues, 2000; Pemberton et al., 1996; Lockley & Meyer, 2000). Reisz & Fröbisch, 2014; Modesto et al., 2015; Spindler Carboniferous tetrapod footprints have an almost et al., 2016; Lucas et al., 2018). exclusively Euramerican distribution, but Permian The change in the tetrapod footprint record that may footprints have been found Pangea-wide (Fig. 19). The represent part of the Kasimovian revolution is reflected North American record is the most extensive, coming in the Notolacerta-Dromopus tetrapod footprint biochron primarily from the American Southwest (New Mexico, boundary. This has been thought to coincide with the Arizona, Colorado and Texas), and there are also a few S.G. Lucas - Ichnology and Paleozoic tetrapods 241

Fig. 18 - Three characteristic ichnotaxa of the Dromopus biochron and their trackmakers (not to scale). Left: Batrachichnus made by a small temnospondyl amphibian. Middle: Dromopus made by a neodiapsid. Right: Dimetropus made by a eupelycosaur. From Lucas (2014), artwork by Matt Celeskey. localities in the eastern USA and eastern Canada (e.g., 1998; Haubold & Lucas, 2001, 2003; Calder et al., 2004; Lull, 1918; Gilmore, 1926, 1927, 1928; Baird, 1952, Lucas & Hunt, 2005; Van Allen et al., 2005; Lucas et al., 1965, 1980; Mossman & Place, 1989; Haubold et al., 2011, 2016; Voigt & Lucas, 2012, 2013, 2015a, b, 2017; 1995; Hunt et al., 1995; Lucas & Heckert, 1995; Calder, Francischini et al., 2019; Marchetti et al., 2019b). 242 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fig. 19 - Permian continental configuration showing tetrapod footprint localities. Abbreviations are: B = Baltica, K = Kazakstan, NC = North China, SC = South China, Sib = Siberia, Su = Subumasu, Ta = Tarim. Localities are: 1) Western USA; 2) eastern Canada; 3) Europe, including western Russia; 4) Argentina; 5) Brazil; 6) Morocco; 7) Niger; 8) South Africa; 9) Australia.

All North American Permian footprints are of early 2014; Voigt & Marchetti, 2014; Voigt & Haubold, 2015; Permian age and mostly from waterlaid sediments, mainly Mujal et al., 2015a, 2016a, b; Marchetti et al., 2015a, 2017, siliciclastic red beds. However, some of the footprints 2019b). Unlike the North American Permian footprint are from eolian sediments, most notably the extensive record, the European record spans most of Permian time tetrapod-footprint assemblage from the Coconino (Lucas & Hunt, 2006; Gand & Durand, 2006; Voigt & Sandstone in Arizona (e.g., Gilmore, 1926, 1927; Lucas, 2018). The German Rotliegend and correlative Spamer, 1984; Francischini et al., 2019; Marchetti et al., strata in France, Italy, Austria, the Czech Republic, Poland 2019a, in press). The characteristic ichnogenera include and Russia contain footprints of the Dromopus biochron, Batrachichnus, Limnopus, Dromopus, Ichniotherium, whereas footprints of the Erpetopus biochron are known Amphisauropus, Dimetropus, Hyloidichnus, Erpetopus from younger, early Permian strata in Spain, France and and Varanopus. Lucas (2007) assigned all of these Italy (Marchetti et al., 2015a, b; Mujal et al., 2016a; Voigt assemblages to the Dromopus biochron, but subsequent & Lucas, 2018). work has shown that there is a substantial change in the The German Zechstein strata and correlatives tetrapod footprint assemblages close to the base of the (primarily of Wuchiapingian age) in Spain, Italy, Poland Leonardian (~ base of upper Artinskian). This is marked and Russia contain distinctive footprint assemblages by the lowest occurrence of Erpetopus and dominance marked by the first appearance of the ichnogenus of the footprint assemblages by captorhinomorph and Paradoxichnium (Gubin et al., 2003; Surkov et al., parareptile footprints (e.g., Marchetti et al., 2019a). This 2007; Voigt, 2012; Marchetti et al., 2017; Mujal et al., is the beginning of the Erpetopus biochron of Voigt & 2017). These are assemblages of the Paradoxichnium Lucas (2017, 2018) and marks the sauropsid radiation biochron of Voigt & Lucas (2018) and are dominated discussed below (Fig. 20). by the footprints of pareiasaurs (Pachypes), parareptiles Europe also has an extensive record of Permian (Erpetopus, Procolophonichnium) and captorhinomorphs tetrapod footprints from Great Britain, France, Spain, (Hyloidichnus), and also include footprints of neodiapsids Germany, Austria, Italy, the Czech Republic, Hungary, (Rhynchosauroides, Paradoxichnium) and therapsids Serbia, Poland and Russia (e. g., Geinitz, 1861; Pabst, (Capitosauroides, Dicynodontipus, Dolomitipes). The 1908; Czyzewska, 1955; Kaszap, 1968; Haubold, 1971, European late Permian footprint record also encompasses 1984; Haubold & Sarjeant, 1973, 1974; Barabas-Stuhl, assemblages from eolian strata in Germany and Scotland 1975; Conti et al., 1977; Haubold & Katzung, 1978; (McKeever & Haubold, 1996; Marchetti et al., 2019b). Niedermayr & Scheriau-Niedrmayr, 1980; Holub & In Africa, Permian tetrapod footprints are known from Kozur, 1981; Boy & Fichter, 1988; Ceoloni et al., 1988; Morocco, Tunisia, Niger and South Africa (e.g., Newell Gand, 1988; Schneider et al., 1992; Gand et al., 1997, et al., 1976; De Beer, 1986; Smith, 1993; De Klerk, 2000; Tverdokhlebov et al., 1997; Lucas et al., 1999; 2002; Voigt et al., 2010, 2011a, b; Hminna et al., 2012; Avanzini et al., 2001; Haas, 2001; Gubin et al., 2003; Smith et al., 2015; Contessi et al., 2018; Marchetti et al., Voigt, 2005, 2012; Gand & Durand, 2006; Surkov et al., 2019c). Other Permian tetrapod footprint records are more 2007; Jovanovic, 2012, 2013; Voigt et al., 2012; Marchetti, scattered: Turkey (Gand et al., 2011), Argentina (Melchor S.G. Lucas - Ichnology and Paleozoic tetrapods 243

Fig. 20 - Stratigraphic distribution of Permian terrestrial tetrapod taxa and related footprint ichnotaxa. Based on Voigt & Lucas (2018), updated by Marchetti et al. (2019c). Image courtesy of Lorenzo Marchetti.

& Sarjeant, 2004; Krapovickas et al., 2015), Brazil (Costa Coyotean chronofauna da Silva et al., 2012) and Australia (Warren, 1997). As earlier workers noted (e.g., Romer, 1935; Olson, Based on the stratigraphic distribution of the 13 best 1975), no substantial turnover in tetrapods took place known Permian tetrapod ichnotaxa, Voigt & Lucas (2018) across the Carboniferous-Permian boundary (Lucas, 2004, recognised three Permian footprint biochrons: 1) Dromopus: 2006, 2017, 2018). As this encompasses the Coyotean latest Carboniferous (~Kasimovian? or Gzhelian) to late land-vertebrate faunachron (“age”) of Lucas (2006), he early Permian (~ middle Artinskian), ichnoassemblages referred to it as the Coyotean chronofauna (Lucas, 2006, dominated by footprints of temnospondyls, reptiliomorphs, 2017, 2018a). This is a long-lasting succession of tetrapod eupelycosaurs and early diapsids; 2) Erpetopus: body-fossil assemblages dominated by lepospondyl late early Permian (~late Artinskian) to late middle and temnospondyl amphibians, diadectomorphs, Permian (~Capitanian), ichnoassemblages dominated seymouriamorphs and amniotes (notably, eupelycosaurs) by footprints of captorhinomorphs and parareptiles; that appeared during the Late Pennsylvanian and persisted and 3) Paradoxichnium: late Permian (Wuchiapingian- through much of the early Permian. Changhsingian), ichnoassemblages dominated by As already noted, the oldest Permian tetrapod footprint footprints of medium- and large-size parareptiles, non- assemblages are a continuation of those of the Late diapsid eureptiles and early saurians (Fig. 20). Pennsylvanian. These are footprint assemblages of the 244 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fig. 21 - Tetrapod footprint biochronology of the middle-late early and middle Permian (slightly modified from Marchetti et al., 2019a). Gray bars are ichnogenera occurrences in non-eolian strata, green bars are ichnogenera occurrences in eolian strata. Trackmakers are: 1) temnospondyl amphibians; 2) reptiliomorphs; 3) eupelycosaur-grade synapsids; 4) therapsid synapsids; 5) parareptiles; 6) captorhinid eureptiles; 7) diapsid eureptiles/parareptiles. Image courtesy of Lorenzo Marchetti.

Dromopus biochron (time interval) of Lucas (2007) that radiation of sauropsids in North America (e.g., Tsuji et are characterised by the footprints of temnospondyls, al., 2010, 2012; MacDougall & Reisz, 2014; Modesto seymouriamorphs, diadectomorphs, eupelycosaurs and et al., 2014) mirrored by the co-eval sauropsid radiation small parareptiles or early eureptiles. Of Kasimovian? or based on the footprint record in North America, North Gzhelian-middle Artinskian age, this footprint biochron Africa and Europe (Voigt et al., 2011a; Marchetti et al., parallels the Coyotean tetrapod chronofauna (assemblage 2013, 2015a, b, 2019a, in press; Voigt & Lucas 2015a, of long duration) based on body fossils in showing that no b, 2017, 2018; Marchetti, 2016; Mujal et al., 2016a). substantial change of the tetrapod fauna took place across Marchetti et al. (2019a) argued that the first appearances the Carboniferous-Permian boundary. of the ichnogenera Hyloidichnus and Erpetopus define a two-phase faunal transition (I and II) during the late early Sauropsid radiation Permian. The pre-transition footprint assemblages have Most early Permian tetrapod-body fossil and footprint a relative abundance of 0-40% of sauropsid footprints. assemblages are dominated by non-amniote and synapsid During the early Artinskian phase I this increases to fossils (e.g., Lucas, 2004, 2006, 2017, 2018a; Voigt 25-44%, with the appearance of Hyloidichnus. During & Lucas, 2018). Abundant footprints of sauropsids the middle Artinskian phase II, with the appearance of (captorhinomorphs and parareptiles) have long been Erpetopus, this value increases to 25-66%. During the known from some early Permian localities but were Kungurian, the turnover was complete, and the footprint considered facies controlled and therefore of no broad assemblages were dominated by sauropsid footprints biostratigraphic or evolutionary significance (e.g., (50-100%). Haubold & Lucas, 2001, 2003; Gand & Durand, 2006; This two-phase sauropsid radiation is facies crossing, Hunt & Lucas, 2006, 2007; Lucas, 2007). However, recent as it is documented by the footprint record of fluvial- discoveries and analysis have provided definite evidence lacustrine and eolian inland to marginal marine facies from tetrapod footprint assemblages of a diversification (Haubold & Lucas, 2003; Marchetti et al., 2015a, b, in of captorhinomorphs and parareptiles during the late press; Voigt & Lucas, 2017, 2018). It represents a tetrapod early Permian (e.g., Marchetti et al., 2015a, b; Voigt & faunal transition from the amphibian- and synapsid- Lucas, 2015a, 2017). This is the beginning of the footprint dominated early early Permian ichnoassemblages assemblages of the Erpetopus biochron of late Artinskian- (Dromopus footprint biochron) to the sauropsid-dominated Guadalupian age (Voigt & Lucas, 2017) and encompass late early Permian ichnoassemblages (Erpetopus footprint abundant footprints of parareptiles and eureptiles, less biochron) in all paleoenvironments across Pangea. abundant seymouriamorph and eupelycosaur footprints and rare temnospondyl footprints. Marchetti et al. (2019a) Tetrapod colonisation of deserts referred to this as the sauropsid radiation, an important The Paleozoic conquest of terrestrial environments evolutionary event best documented by the tetrapod by metazoan animals began during Ordovician time but footprint record (Fig. 21). was not complete until all of the terrestrial environments Recent discoveries and revisions of the tetrapod body- had been colonised. The terrestrial ichnofossil record fossil record also indicate an evident late early Permian indicates that invertebrate animals had colonised all S.G. Lucas - Ichnology and Paleozoic tetrapods 245 of the major terrestrial environments no later than the deposits (e.g., Blakey, 1990), so the presence of a desert is Devonian (Buatois et al., 1998; Minter et al., 2016; Buatois uncertain. However, the preservation of the Wescogame & Mángano, 2018). In particular, what many regard as footprints and their matrix are not obviously of eolian the most difficult terrestrial environment to colonise, the origin, so this may not be an eolian ichnoassemblage. eolian (desert) system, was inhabited by arthropods at Direct examination in the field of the Wescogame about the Silurian-Devonian boundary (e.g., Trewin & tracksites will be needed to determine this. McNamara, 1995). Among tetrapods, this did not take The older Manakacha Formation (Middle place until possibly the Pennsylvanian, and definitely Pennsylvanian, Atokan) in the Grand Canyon has during the early Permian, when the colonisation of eolian supposedly produced a trackway from eolian strata systems is well documented by footprints in the absence (Rowland, 2017; Rowland & Caputo, 2018), but this of a relevant body-fossil record. remains to be fully documented. In the Grand Canyon, The oldest tetrapod footprint assemblage from strata the Permian Coconino Sandstone (Fig. 22) has the oldest of possible eolian (desert) origin is from the Upper extensive ichnoassemblage of tetrapod footprints from Pennsylvanian (Virgilian) Wescogame Formation of eolian strata. Arizona (Gilmore, 1927, 1928; Haubold, 1971; Marchetti Lull (1918) first reported Coconino Sandstone et al., in press). Marchetti et al. (in press) have revised footprints from the Grand Canyon, and Gilmore (1926, the ichnotaxonomy of the Wescogame footprints to assign 1927) monographed extensive material collected along the them to Batrachichnus, cf. Limnopus, cf. Amphisauropus Hermit Trail. He assigned the footprints to 10 ichnogenera and cf. Varanops, which are the footprints of temnospondyl and 16 ichnospecies that he inferred represented a diverse amphibians, seymouriamorphs and reptiles. An important array of amphibian and amniote trackmakers. However, in point is that there are eolian sediments in the Wescogame the 1990s, German ichnologist Hartmut Haubold reduced Formation but it also includes fluvial and shallow marine Coconino (and other Permian eolianite) tetrapod footprint

Fig. 22 - Permian stratigraphy of the Grand Canyon. Panoramic view looking west at the wall of Hermit Canyon showing the track-bearing Permian units, the Hermit Formation and eolian Coconino Sandstone. 246 Bollettino della Società Paleontologica Italiana, 58 (3), 2019 ichnodiversity to one ichnogenus (Chelichnus) with three Olson’s gap ichnospecies (McKeever & Haubold, 1996; Haubold, The Permian tetrapod body-fossil record demonstrates 2000). Haubold inferred that only synapsid (likely caseid) that the transition from the early to the middle Permian trackmakers made the Permian eolianite footprints, so is characterised by a worldwide change in the global this implied a very low diversity of tetrapod trackmakers assemblages of tetrapod vertebrates, with the extinction living in the Permian deserts. of the eupelycosaur-grade synapsids during the early Marchetti et al. (2019a) recently revised the Coconino middle Permian, overlapping the onset of the radiation tetrapod footprint ichnotaxonomy. Critical to that revision of the therapsid synapsids, a change also evident in the was actualistic work that allowed a more nuanced tetrapod footprint record (e.g., Lucas, 2004, 2017, 2018a; understanding of the extramorphology of footprints Voigt & Lucas, 2018; Marchetti et al., 2019b, c; Schneider and trackways made in eolian sand showing upslope et al., 2020). In evaluating the timing of this change, and downslope progression, with a possible transverse Lucas (2004) recognised a global gap or hiatus (named component. This indicated that most of the previous “Olson’s gap”) between the youngest early Permian ichnotaxonomy had incorrectly interpreted digit drag marks eupelycosaur-dominated tetrapod assemblages (which as actual digit impressions. This underlay Gilmore’s (1926, are in North America) and the oldest middle Permian 1927) overestimation of Coconino footprint ichnodiversity therapsid-dominated tetrapod assemblages (which are and Haubold’s (2000; McKeever & Haubold, 1996) in Russia) (Fig. 24). Originally thought to primarily underestimation. Thus, Marchetti et al. (2019a) recognised encompass Roadian time (Lucas, 2004), the age of the gap the following ichnotaxa in the Coconino Sandstone: cf. has been more accurately determined as Kungurian based Amphisauropus, cf. Dromopus, Erpetopus, Ichniotherium, on advances in marine biostratigraphy, particularly of the cf. Tambachichnium and Varanopus (Fig. 21). Francischini Russian section (Lucas & Golubev, 2019). et al. (2019) described newly recognised diadectomorph Equating Olson’s gap to the Roadian, Lucas (2004) footprints of Ichniotherium from the Coconino Sandstone suggested it was 2-4 million years long. However, its of the Grand Canyon (Fig. 23). The slightly older DeChelly equivalence to much of the Kungurian suggests it may erg in the American Four Corners region has a similar be as much as 4-6 million years long. Nevertheless, there set of ichnogenera: Amphisauropus, cf. Dromopus, are no reliable numerical constraints tied to useful marine Erpetopus, Ichniotherium and cf. Varanopus (Marchetti et biostratigraphy within the Kungurian, and the beginning al., 2019a). These are footprints made by diadectomorphs, of Kungurian time has only been indirectly estimated at seymouriamorphs, parareptiles, captorhinomorphs, about 283.5 + 0.5 Ma (Henderson et al., 2012; Ramezani & varanopid synapsids and diapsids. Bowring, 2018). The age of the beginning of the Roadian Thus, the DeChelly and the Coconino Sandstone is under discussion, with estimates ranging from ~ 272 to ~ footprint ichnoassemblages are very similar to the 277 Ma (Wu et al., 2017; Davydov et al., 2018). Depending contemporary non-eolian tetrapod footprint assemblages on which date is chosen, the Kungurian is either ~12 or of the Erpetopus footprint biochron (Marchetti et al., ~6 million years long. Olson’s gap represents most of 2015a, b, 2019a, in press). They indicate a diversity of Kungurian time (Fig. 24), so it is at least 4 million years tetrapod trackmakers in the DeChelly and Coconino long, perhaps twice that. However, better numerical age deserts, and thus a substantial colonisation of deserts by control will be needed to provide a more accurate estimate tetrapods during late early Permian (Leonardian) time, of the duration of Olson’s gap in millions of years. an important paleoecological event for which no tetrapod The only tetrapod body-fossil assemblage known body-fossil record exists. Furthermore, the presence of that is within Olson’s gap is the Inta assemblage in non-amniotes in these Permian deserts raises questions Russia, of Ufimian age (Fig. 24). It is an assemblage about how those tetrapods reproduced and thus the timing of limited numbers of fossils and of low diversity and phylogenetic context of the origin of the amniotic egg. consisting of eryopid (Clamorosaurus) and intasuchid These are questions that cannot be answered with current (Intasuchus, Syndyosuchus) temnospondyls; eogyrinid data from trace or body fossils (Francischini et al., 2019). (Aversor) and enosuchid (Nyctiboetus) anthracosaurs; a Baird (1965) first drew attention to differences in captorhinid (Riabininus); and bolosaurids (Bolosaurus Permian tetrapod footprint assemblages from water- and Gnorhimosuchus) (Ivakhnenko et al., 1997). It is of deposited red beds and eolianites. He suggested that these early Permian aspect in that it lacks therapsids, but its differences reflect different facies, and Lockley et al. (1994) precise age within the Ufimian regional stage is not clear named a Laoporus ichnofacies to single out what they (Lozovsky et al., 2009). perceived to be the unique nature of the Permian eolian Recognition of Olson’s gap does not preclude the footprint ichnoassemblages. Hunt & Lucas (2007) renamed possibility of an extinction at the early-middle Permian this the Chelichnus ichnofacies and applied it to tetrapod boundary (“Olson’s extinction” of Sahney & Benton, 2008) footprint ichnoassemblages in eolian deposits of any age, or during the Kungurian ( Brocklehurst et al., 2017, 2018; contrasting it with the Batrachichnus ichnofacies of red Brocklehurst, 2018). However, the gap makes it impossible beds of Permian and other ages. However, re-evaluation to establish the magnitude, precise timing and structure of of the ichnotaxonomy of Permian eolian footprints the extinctions that must have taken place across Olson’s reveals them to belong to many of the ichnotaxa found gap. Despite this, Sahney & Benton (2008) identified a in Permian red beds, thus reducing the dichotomy first single major crash of tetrapod diversity at the Cisuralian- identified by Baird (Francischini et al., 2019; Marchetti Guadalupian (Kungurian-Roadian) boundary, which they et al., 2019a, b, in press). Therefore, the “Chelichnus call “Olson’s extinction.” To achieve this result, Sahney ichnofacies” may better be recognised as a “taphofacies” of & Benton (2008) compressed all the extinctions of the the Batrachichnus ichnofacies (Marchetti et al., in press). Kungurian-Roadian into one event (also see Benton, 2012). S.G. Lucas - Ichnology and Paleozoic tetrapods 247

Fig. 23 - Ichniotherium from the eolian Coconino Sandstone. a-c) Huge, fallen boulder (in the field) of Coconino Sandstone with trackways of Ichniotherium located on the south rim of the Grand Canyon Arizona, USA, overview (a), false color depth map (b) and closeup of part of one trackway (c). d) Trackway of Ichniotherium from near Williams, Arizona (collection of New Mexico Muiseum of Natural History, Albuquerque, New Mexico, USA). Modified from Francischini et al. (2019).

Contrary to previous conclusions (Lucas, 2004, 2017), body-fossil record. Thus, the Erpetopus biochron is well the tetrapod footprint record does fill Olson’s gap to some documented by tetrapod-footprint assemblages from extent and reinforces the record of changes in the tetrapod the southwestern USA, Italy and France that, for many 248 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fig. 24 - Olson’s gap is shown here as the hiatus between the youngest early Permian eupelycosaur-dominated tetrapod assemblages of Texas- Oklahoma, USA, and the oldest Russian Permian therapsid-dominated tetrapod assemblages. From Lucas & Golubev (2019). reasons, are clearly no younger than Kungurian (Voigt event by Lucas (2009a, b). This was a more substantial & Lucas, 2018; Schneider et al., 2020). They contain no tetrapod extinction than the one that took place close therapsid footprints and suggest that Olson’s gap was the to the end of the Permian (Lucas, 2017). In the Karoo time of captorhinomorph and parareptile diversification basin, this middle Permian extinction is marked by the referred to here as the sauropsid radiation (see above). total disappearance of the dinocephalians (Fig. 25), which Guadalupian tetrapod footprint assemblages are were the first significant evolutionary diversification of almost exclusively known from France (e.g., Gand & the therapsids, a group of carnivores and herbivores that Durand, 2006) and South Africa (Marchetti et al., 2019c) included some very large and specialised forms (Day et and contain the oldest therapsid footprints, though none al., 2015). Furthermore, eupelycosaurs also disappeared of these assemblages are as old as Roadian. There could at (or just before) this extinction (Modesto et al., 2011), thus be said to be a gap in the global tetrapod footprint large drops in the diversity of gorgonopsians and record slightly younger than Olson’s gap based on body therocephalians took place, and these latter groups did fossils. The tetrapod footprint gap is of early Guadalupian not recover diversity till substantially later in the Permian age, whereas the body fossil gap is of late Kungurian (Lucas, 2017). Post-extinction tetrapod assemblages age. The two records indicate that the major turnover lack dinocephalians and are initially characterised in the in the global tetrapod assemblage from eupelycosaur Karoo basin by a low diversity assemblage numerically dominated to therapsid dominated is, as Lucas (2004) dominated (~ 85% of all specimens) by the dicynodont first argued, very close to the early-middle Permian Diictodon. Indeed, the dinocephalian extinction event (Cisuralian-Guadalupian) boundary. But, the timing of the sets the stage for the dicynodont takeover of much of the extinctions and orginations that produced these turnovers Permian tetrapod herbivore niche (Lucas, 2017). needs to be much improved and certainly needs facies This extinction is well documented in the tetrapod consistent (isotaphonomic) records across the Cisuralian- body-fossil record of the Karoo basin in South Africa and Guadalupian boundary to be more completely evaluated. the Ural foreland basin in Russia (Lucas, 2017; Sennikov & Golubev, 2017). The extinction of dinocephalians Dinocephalian extinction event and related tetrapod extinctions are consistent with less There was a profound extinction of tetrapods during extensive and less precisely dated tetrapod-body fossil the middle Permian, termed the dinocephalian extinction assemblages from Brazil, China, Zambia and Tanzania S.G. Lucas - Ichnology and Paleozoic tetrapods 249

province in southwestern China, at about 260 Ma (Huang et al., 2016). As noted above, middle Permian footprints are little known outside of France (Lucas & Hunt, 2006). These French footprint assemblages have been interpreted to be dominated by the footprints of therapsids (e.g., Gand & Durand, 2006), though more analysis is needed to establish the ichnotaxonomy and the trackmakers with certainty. Because of that, Voigt & Lucas (2018) included the French footprint assemblages in the latter part of the Erpetopus biochron. However, I suspect such analysis will indicate that the French Guadalupian footprint assemblages should be assigned to a footprint biochron distinct from and between the Erpetopus and Paradoxichnium biochrons (essentially the “Brontopus sub-biochron” of Marchetti et al., 2019c; Fig. 20).

End-Permian extinctions Fig. 25 - Reconstruction of the dinocephalian Struthiocephalus by Matt Celeskey. Dinocephalians and many other tetrapods suffered an Lucas (2009b, 2017) argued that the tetrapod-body apparent mass extinction at about the end of middle Permian time, an fossil record does not document a mass extinction of extinction seen in both the tetrapod body-fossil and footprint records. tetrapods across the Permo-Triassic boundary (PTB). The tetrapod fooprint record is consistent with that conclusion. As already noted, late Permian tetrapod footprint (Lucas, 2017). But, no dinocephalian body fossils from assemblages contain definite pareiasaur and therapsid Guadalupian strata are known from low paleolatitudes of footprints, as well as captorhinomorph, eureptilian and Pangea (Lucas, 2006, 2017), and the earliest Lopingian early saurian footprints. These are footprints of the (mid-Wuchiapingian) tetrapod body-fossil assemblages Paradoxichnium biochron of Voigt & Lucas (2018). of low paleolatitudes (in Germany and England) do not The most extensive tetrapod footprint assemblage of include therapsid fossils (e. g., Haubold & Schaumberg, the Paradoxichnium biochron is from the late Permian 1985; Evans & King, 1993; Gottmann-Quesada & (Wuchiapingian) Val Gardena Sandstone of northern Sander, 2009). So, the end-Guadalupian extinction is Italy. Recently revised by Marchetti et al. (2017), it not readily identifiable with tetrapod-body fossils at includes the footprints of small temnospondyls (cf. low paleolatitudes of Pangea but it is identifiable with Batrachichnus), therocephalians (Capitosauroides), footprints (Marchetti et al., 2019b) (Fig. 20). cynodonts (Dicynodontipus), dicynodonts (Dolomitipes), The middle-late Permian footprint record from neodiapsids (cf. Dromopus, Rhynchosauroides), both non-eolian and eolian settings of Pangean low parareptiles (Pachypes, Procolophonichum) and paleolatitudes is much more abundant and complete archosauriforms (Protochirotherium). Most of these than the body-fossil record (Marchetti et al., 2019b). ichnogenera (Batrachichnus, Capitosauroides, Guadalupian tetrapod assemblages that constrain the Dicynodontipus, Dolomitipes, Procolophonichnium, extinction include dinocephalian footprints (ichnogenera Protochirotherium and Rhynchosauroides) are known Brontopus and Planipes), and are known from southern from Triassic strata (Fig. 20), so the Val Gardena footprint France (Heyler & Lessertisseur, 1963; Gand et al., 1995, assemblage has a “clear Triassic affinity,” as stressed by 2000) (Fig. 20). Based on diverse evidence, the age of Marchetti et al. (2017). these strata is Guadalupian (Gand & Durand, 2006; Furthermore, the presence of the archosauriform Michel et al., 2015; Schneider et al., 2020), in agreement ichnogenus Protochirotherium in the Wuchiapingian Val with the presence of dinocephalian footprints. de Gardena Sandstone (Fig. 26) reinforces body-fossil data The Lopingian low-paleolatitude tetrapod footprint that indicate that archosauriforms had already diversified assemblages are consistent with the body-fossil record in substantially by the late Permian (Conti et al., 1977; showing a substantial turnover of the tetrapod fauna. Thus, Bernardi et al., 2015). These Permian archosauriform they lack dinocephalian footprints and have new records footprints thus further undermine the old idea that the of cynodont, dicynodont and neodiapsid footprints, which change from therapsid-dominated to archosaur-dominated characterise the Paradoxichnium biochron (Marchetti et tetrapod assemblages characterised the PTB. al., 2017, 2019b, c; Voigt & Lucas, 2018) (Fig. 20). This, Marchetti et al. (2019c) recently documented what is together with the abundant occurrence of dinocephalian now the best tetrapod footprint record across the PTB, footprints in the low-paleolatitude Guadalupian of which is in the Karoo basin of South Africa (which France, is consistent with a global tetrapod extinction also contains the best PTB boundary tetrapod body- event at the end of the Guadalupian at all paleolatitudes fossil record). Here, too, many of the latest Permian of Pangea (Retallack et al., 2006; Lucas, 2009b, 2017). footprint ichnogenera also known from the earliest Furthermore, as demonstrated by Marchetti et al. (2019c), Triassic within the Lystrosaurus-bearing interval of the the footprint record in the South African Karoo basin Balfour Formation: Dolomitipes, cf. Dicynodontipus, also records the dinocephalian extinction event near the Procolophonichnium and Rhynchosauroides (Fig. 20). end of Guadalupian time. This extinction was probably Some workers consider these strata to be latest Permian triggered by the eruption of the Emeishan large igneous rather than Early Triassic (Gastaldo et al., 2015, 2017, 250 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fig. 26 - Footprints of an archosauriform, Protochorotherium, from the late Permian Val Gardena Sandstone in northern Italy. Scale bars = 5 cm. Footprint on left in the collection of the Museo Paleontologico of Sapienza Università di Roma, Italia . Footprint on right in collection of Museo di Scienze Naturali dell’Alto Adige/Naturmuseum Südtirol, Bolzano/Bozen, Italy. Modified from Marchetti et al. (2017), photographs courtesy of Hendrik Klein.

2018), although the most conspicuous faunal change gait. Furthermore, almost of the Paleozoic tetrapods possibly related to the PTB is at the base of Lystrosaurus employed the sprawling gait in which the proximal limb AZ and this is very close to the PTB (Marchetti et al., bones (humerus and femur) are held nearly horizontal to 2019e). Thus, the best records (though all of the South the substrate so that the feet hit the substrate well lateral African footprints may be Permian) show the continuity of the body midline (Figs 1-2, 18). Little explored is of most late Permian tetrapod footprint ichnogenera from the variation among Paleozoic tetrapods in their use of the late Permian into the Early Triassic, and thus do not the sprawling gait (e.g., Sukhanov, 1968; Bernardi & support the concept of a tetrapod mass extinction at the Avanzini, 2011). Much analysis needs to be done here to PTB. better understand variation in late Paleozoic sprawling However, it should be noted that Early Triassic gaits based on differences in body size, coupling value, footprint assemblages before the Olenekian are rare and foot and tail structure and speed of progression. usually limited to a few therapsid or neodiapsid footprints One unresolved issue with Paleozoic tetrapod (Klein & Lucas, 2010; Marchetti et al., 2019c). No locomotion is based on the presence of relatively narrow pareiasaur footprints are known from the Early Triassic, gauge trackways as early as Carboniferous that suggest the and several other footprint ichnogenera also end during trackmakers employed a semi-upright gait (e.g., Hunt & the Paradoxichnium biochron (Fig. 20). This is consistent Lucas, 1998; Voigt et al., 2007). Particularly striking in this with what is known of evolutionary turnover/tetrapod regard are long, narrow gauge trackways of eupelycosaurs extinctions across the PTB based on their body-fossil (ichnogenus Dimetropus) from the lower Permian of New record. Nevertheless, although the footprint record lacks Mexico, USA (Fig. 27). Three ideas have been proposed stratigraphic density across the PTB, it provides no support to explain such narrow gauge trackways made by late for a supposed end-Permian tetrapod mass extinction. Paleozoic tetrapods: 1) that they do indicate semi-upright walking, at least over short distances (Hunt & Lucas, Paleozoic tetrapod locomotion 1998; Abbott et al., 2017); 2) that the trackmaker used Tetrapod trackways indicate that Paleozoic tetrapods considerable lateral bending of the trunk (axial bending) were habitual quadrupeds that walked with the alternating to produce such trackways (Hopson, 2012, 2015); or S.G. Lucas - Ichnology and Paleozoic tetrapods 251

Eudibamus from the lower Permian of Germany (Berman et al., 2000), Aphelosaurus from the lower Permian of France (Falconnet & Steyer, 2007; Steyer, 2012) and Lacertulus from the upper Permian of South Africa (Carroll & Thomson, 1982). These three animals are small, lizard-like tetrapods that may have been wholly or largely arboreal, which means they were unlikely to leave any or many footprints. Nevertheless, bipedal tetrapod footprints remain to be discovered in Paleozoic strata to better document the origin of bipedality in tetrapods.

OTHER PALEOZOIC TETRAPOD TRACE FOSSILS

Bromalites The Paleozoic fossil record of vertebrate bromalites (coprolites, consumulites, regurgitalites; see Hunt & Lucas, 2012 for terminology) is extensive, beginning definitely during the Late Ordovician, and was mostly made by fishes (Hunt et al., 2012). Nevertheless, although prolific assemblages of Carboniferous and Permian coprolites are dominantly those of fishes, some do include likely tetrapod coprolites (e.g., Harris et al., 2017). However, these likely tetrapod coprolites are not readily tied to specific producers, which is the fundamental challenge facing all use of coprolites (and other bromalites) in analysis. These putative Paleozoic tetrapod coprolites are non-spiral forms generally attributed to fish-eating amphibians (Harris et al., 2017). A few documented Paleozoic tetrapod consumulites (fossilised ingested food material in the body cavity: Hunt & Lucas, 2012) provide direct evidence of the consumer’s “last meal” (e.g., Romer & Price, 1940; Eaton, 1964; Reisz, 1986; Werneburg, 1986, 1988, 1989; Munk & Sues, 1993; Werneburg et al., 2013). They are thus important to identifying the diet of Paleozoic tetrapods and Fig. 27 - Long, narrow gauge trackways of Dimetropus from the establishing some specific behaviors, including predator- lower Permian of the Robledo Mountains, New Mexico, USA. Scale prey interactions. They can also be used to analyse the bars = 1 meter. Modified from Hunt & Lucas (1998). paleoecology of Paleozoic tetrapods. A good example of this comes from the Kinney Brick Quarry in New Mexico, USA, a lagoonal deposit 3) that the trackmaker swung the limbs far forward of Kasimovian age that is a Lagerstätte for fossil plants, over a horizontal arc to plant them facing forward near invertebrates and vertebrates, including a handful of the trackway midline where limb retraction took place amphibian body fossils (e.g., Lucas et al., 2011). The (Berman & Henrici, 2003). Clearly, more analysis is few specimens of Kinney amphibians are of small, needed to resolve these disparate explanations. “branchiosaur-like” forms that were long assumed The shift from the sprawling gait to the upright gait to be freshwater animals that were washed into the has long been considered to have taken place during the Kinney lagoon. However, Schultze (2013), developing Triassic (e. g., Kubo & Benton, 2009). However, it is now the idea that many early tetrapods living in marginal clear that late Permian archosauriform footprints could marine or marine habitats, suggested that the Kinney indicate that the shift from sprawling to upright gaits had amphibians were marine animals. Nevertheless, one of taken place well in advance of the end of the Permian these amphibians, the holotype of Milnerpeton huberi, (Bernardi et al., 2015). The same is true for newly- contains a consumulite packed with what are inferred described cynodont and gorgonopsid therapsid footprints to be freshwater ostracods, so it was likely a freshwater (Marchetti et al., 2019b, c). Depending on how one views animal (Werneburg et al., 2013). the older, narrow gauge trackways just discussed, the Clearly, the Paleozoic fossil record of tetrapod capability of at least short term use of semi-upright gaits bromalites is neither extensive nor well studied. A much by tetrapods may go back to the Carboniferous. better record of Paleozoic tetrapod bromalites needs to Finally, there are no Paleozoic footprints of bipedal be collected and analysed so that these traces can further tetrapods. Yet, a few Permian tetrapods have been inferred inform us about the evolution of tetrapod consumption to be bipedal based mostly on limb proportions, including and excretion during the Paleozoic. 252 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fig. 28 - Large amphibian burrow from the Mississippian Mauch Ckunk Formation in Pennsylvania, USA. a) View of burrow with structural dip rotated out of the strata to approximate the original orientation, meter stick for scale. b) Interpretive drawing of the burrow. Modified from Storm et al. (2010).

Burrows 2002). Similar, Carboniferous-age burrows have also Some modern tetrapods construct burrows, and some been attributed to lungfish estivation (Carroll, 1965; of these burrows are the living chambers of fossorial Benton, 1988). Indeed, most Paleozoic vertebrate burrows tetrapods. Tetrapod burrowing behavior and the fossorial are likely the estivation burrows of fishes or tetrapods mode of life are relatively complex adaptations, the history (Hembree, 2010). of which remains to be fully documented (Voorhies, 1975; The oldest tetrapod burrow is a large burrow from the Zug et al., 2001; Hasiotis et al., 2007). Mississippian of Pennsylvania. This burrow (Fig. 28), The Paleozoic fossil record of vertebrate burrowing from fluvial strata of the Visean Mauch Chunk Formation, begins in Late Devonian strata at several localities consists of a tunnel with a 15-20 cm diameter and a (O’Sullivan et al., 1986; Benton, 1988; McAllister, 1992; terminal chamber with a diameter of 50-60 cm. Storm et Hasotis, 2002; Hasiotis et al., 2007). These Devonian al. (2010) argued that it is too large to have been made burrows have been attributed to the estivation behavior of by any known Misissippian arthropod, so, by default, lungfish and have long been interpreted as a response to the burrow maker was likely an amphibian. Given the seasonal droughts (e. g., Romer & Olson, 1954; Haisotis, sedimentological evidence for seasonal aridity on the S.G. Lucas - Ichnology and Paleozoic tetrapods 253

Mauch Chunk floodplains, it likely was an estivation record of Permian dentalites is well documented (Reisz burrow or at least a burrow designed to allow the & Tsuji, 2006). Most of the published documentation of amphibian protection from drought (Storm et al., 2010). dentalites is of Jurassic-Cretaceous dinosaurs. The Permian record of tetrapod burrowing encompasses Dentalites have the potential to document a wide more diverse and complex burrows (Olson & Bolles, range of behaviors (e.g., Binford, 1981; Hunt et al., 1994; 1975; Smith, 1987, 1993; Hembree et al., 2004, 2005; Drumheller-Horton, 2012; Lucas, 2016), including: 1) Hasiotis et al., 2007). For example, the Permian of predation; 2) bite method and force; 3) dietary selection; 4) Kansas contains nearly vertical, downward tapering feeding; 5) scavenging; 6) bone accumulation; 7) trophic burrows (Torridorefugium) from ephemeral pond patterns; 8) intraspecific (agonistic) interactions; 9) tooth deposits associated with periods of drought; these have sharpening; and 10) bone and rock utilisation for other been interpreted as the estivation burrows of lysorophid purposes, including mineral extraction. They are thus of amphibians (Hembree et al., 2004, 2005). diverse paleoethological significance. Nevertheless, a major innovation in tetrapod burrowing Indeed, Reisz & Tsuji (2006) claimed that the tooth behavior took place by late Permian time. Thus, in the marks they documented on the bones of an early Permian upper Permian strata in the Karoo basin of South Africa, eupelycosaur are the oldest evidence of vertebrate helical burrows produced by dicynodont therapsids scavenging (though the Devonian bone with dentalites have been recovered (Smith, 1987, 1993). In some of documented by Shubin et al., 2004, may hold that honor). these, skeletal remains are preserved within the burrow Nevertheless, the Paleozoic record of dentalites is meager, structures, directly linking the maker to the structure. and I suspect such traces are largely under-reported and Helical burrows are much more difficult to dig than are certainly understudied. Much more needs to be done to straight burrows, and they limit air circulation in and out develop an informative understanding of the Paleozoic of the deeper reaches of the burrow (Meyer, 1999). Smith record of vertebrate dentalites. (1987, 1993) noted that the South African Permian helical burrows were excavated into floodplain sediments to a depth near that of the water table. He thus argued that MAJOR EVENTS IN PALEOZOIC TETRAPOD they were likely dug to maintain a cool and most climate EVOLUTION - THE ICHNOLOGICAL in the burrow during estivation or hibernation. PERSPECTIVE Complex burrow structures made by colonial burrowers, and the burrows of completely fossorial Paleozoic tetrapod trace fossils are footprints, tetrapods, are not known before the Mesozoic. Thus, bromalites, burrows and dentalites. Only the Paleozoic during the Triassic-Jurassic, the diversity and complexity tetrapod footprint record is extensive enough and of burrowing increased (e.g., Groenewald et al., 2001; sufficiently studied to provide insight into some of the Miller et al., 2001; Damiani et al., 2003; Hasiotis et al., major events of Paleozoic tetrapod evolution (Fig. 29). 2004, 2007; Lucas et al., 2006; Tanner & Lucas, 2009), and These are: the skeletons of definitely fossorial tetrapods are known 1. The oldest tetrapod fossils are Middle Devonian (e.g., Luo & Wible, 2005). footprints. Devonian tetrapod footprints indicate lateral The classic discovery of tetrapod-body fossils in tree sequence walking by quadrupedal tetrapods with a trunks of the Pennsylvanian strata at Joggins, Nova Scotia, smaller manus than pes. Thus, tetrapods other than created the idea that these tetrapods fell into hollowed “ichthyostegalians” remain to be discovered in the stumps and were trapped there to die. This pitfall theory Devonian body-fossil record. Devonian tetrapod footprints has been repeated, even in books (e.g., Carroll, 2009, fig. are from nonmarine paleoenvironments, so they provide 7.10; Benton, 2015, fig. 5.3). However, recent research no support for a marginal marine/marine origin of suggests that at least some of these hollow stumps had a tetrapods. ground level entrance, so they may have functioned as 2. “Romer’s gap,” a supposed paucity of Early dens in which the animals lived (Calder, 2012; Stimson Mississippian terrestrial fossils, has largely been filled et al., 2013). This recent analysis has not been fully by sampling and description of already known fossils. published, but has an ichnological aspect in terms of to It includes the first substantial assemblage of tetrapod what extent the tetrapods may have fashioned these dens footprints, which are the footprints of small and large through digging, scraping and scratching activities. temnospondyls and reptiliomorphs. This footprint assemblage supports the concept that the Carboniferous Dentalites diversification of terrestrial tetrapods had begun during Hunt et al. (2018, p. 500) introduced the term dentalite (or before) Tournaisian time. “to encompass all traces produced on a substrate … by the 3. No definite pre-Pennsylvanian amniote footprints teeth or oral cavity of a vertebrate.” The substrate is most are known, so the Early Pennsylvanian age of the oldest commonly bone (Binford, 1981; Fernández & Andrews, amniote footprints and body fossils is the same. 2016) but can be vegetation (Lucas, 2016), invertebrate 4. The Kasimovian revolution was a prolonged and hard parts (Kauffman & Sawdo, 2013) or even coprolites complex change across the Middle-Late Pennsylvanian (Godfrey & Smith 2010; Godfrey & Palmer, 2015). The boundary that encompasses the appearance of new tetrapod study of vertebrate dentalites dates back almost 200 years taxa in the body-fossil record, notably the oldest high fiber (Buckland, 1822, 1824), and there are many examples herbivores, the diadectomorphs and the edaphosaurid throughout the fossil record (Lucas, 2016; Hunt et al., eupelycosaurs. However, the tetrapod footprint record 2018). Some of the oldest tetrapod bones, of Late Devonian documents much older records of diadectomorphs and age, bear putative dentalites (Shubin et al., 2004), and one eupelycosaurs (possible edaphosaurs) in the Bashkirian, 254 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fig. 29 - Summary of some major events of the Paleozoic evolutionary history of tetrapods as understood from the tetrapod footprint record. Artwork by Arthur Escher. thus diminishing the extent of tetrapod originations during 6. Tetrapod footprints indicate tetrapod colonisation the Kasimovian revolution. of deserts during the late Paleozoic, definitely during 5. There is no substantial change in tetrapod footprint the early Permian and perhaps earlier, during the assemblages across the Carboniferous-Peremian boundary, Pennsylvanian. in agreement with the lack of substantial changes indicated 7. The sauropsid radiation is best documented by by the body-fossil record across that boundary. a change in the tetrapod footprint assemblages during S.G. Lucas - Ichnology and Paleozoic tetrapods 255 the late early Permian from non-amniote and synapsid Marco Balini provided helpful reviews that improved the content dominated to assemblages dominated by the footprints and clarity of this manuscript. of captorhinimorphs and parareptiles. 8. Olson’s gap is a global hiatus in the tetrapod REFERENCES body-fossil record during which eupelycosaur-dominated assemblages of the early Permian were replaced by Abbott C.P., Sues H.-D. & Lockwood R. (2017). The therapsid-dominated assemblages of the middle-late Dimetrodon dilemma: Reassessing posture in sphenacodonts. Permian. The tetrapod footprint record indicates an Geological Society of America Abstracts with Programs, 49. abundance of captorhinomorph tracks and very few DOI 10.1130/abs/2017AM-307190 eupelycosaur footprints during Olson’s gap, suggesting Ahlberg P.E. (2018). Follow the footprints and mind the gaps: A that the extinction of the eupelycosaurs had already begun new look at the origin of tetrapods. Earth and Environmental well before the first appearance of therapsids. Transactions of the Royal Society of Edinburgh, 2018: 1-23. Aldrich T.H. & Jones W.B. (1930). Footprints from the Coal 9. The substantial extinction of dinocephalian Measures of Alabama. Alabama Museum of Natural History therapsids and other tetrapods at approximately the end of Museum Paper, 9: 1-64. the middle Permian, the dinocephalian extinction event, Anderson J.S., Smithson T., Mansky C.F., Meyer T. & Clack J. is well recorded by the tetrapod footprint record, which (2015). A diverse tetrapod fauna at the base of ‘Romer’s gap.’ documents this extinction in paleoequatorial Pangea, PlosOne, 10: e0125446. where there is a lack of tetrapod-body fossils in this region Anonymous (1828). Notice about Dumfriesshire footprints. London during this interval. and Paris Observer, 141 (February 10, 1828): 93-94. 10. The lack of an end-Permian tetrapod mass Avanzini M., Ceoloni P., Conti M.A., Leonardi G., Manni R., extinction finds support in the tetrapod footprint record Mariotti N., Mietto P., Muraro C., Nicosia U., Sacchi E., Santi G. & Spezzamonte M. (2001). Permian and Triassic tetrapod because most late Permian tetrapod footprint ichnogenera ichnofaunal units of northern Italy: Their potential contribution continue into the Triassic. Late Permian archosauriform to continental biochronology. Natura Bresciana, 25: 89-107. footprints add evidence that the diversification of Baird D. (1952). Revision of the Pennsylvanian and Permian archosauriforms began during the Permian. footprints Limnopus, Allopus, and Baropus. Journal of 11. Paleozoic tetrapod footprints mostly indicating Paleontology, 25: 832-840. quadrupedal lateral sequence walking with a sprawling Baird D. (1965). Footprints from the Cutler Formation. U. S. gait, but narrow gauge tetrapod trackways as old as Geological Survey Professional Paper, 503C: 47-50. Carboniferous may indicate some semi-upright walking. Baird D. (1980). A prosauropod dinosaur trackway from the Definite upright walking is demonstrated by late Permian Navajo Sandstone (Lower Jurassic) of Arizona. In Jacobs L.L. (ed.), Aspects of Vertebrate History: Essays in Honor of archosauriform and therapsid footprints, and no footprints Edwin Harris Colbert. Flagstaff, Museum of Northern Arizona of bipedal tetrapods are known from Paleozoic strata, Press: 219-230. although a few Permian tetrapod taxa known from Barabás-Stuhl Á. (1975). Adatok a dunántúli újpaleozóos skeletons may have been bipeds. képződmények biosztratigráfiájához [Contribution to the Besides footprints, other Paleozoic tetrapod trace biostratigraphy of the Upper Paleozoic in Transdanubia]. fossils (bromalites, burrows and dentalites) are too Földtani közlöny, 105: 320-334. poorly known and too little studied to provide much Barkas T.P. (1873). Illustrated Guide to the Fish, Amphibian, Reptilian insight into Paleozoic tetrapod evolution. Nevertheless, and Supposed Mammalian Remains of the Northumberland the tetrapod footprint record documents key events in Carboniferous Strata. 117 pp. Hutchings, London. Bell C.M. & Boyd M.J. (1986). A tetrapod trackway from the Devonian-Permian tetrapod evolution and needs to be Carboniferous of northern Chile. Palaeontology, 29: 519-526. part of a complete understanding of Paleozoic tetrapod Benton M.J. (1988). Burrowing by vertebrates. Nature, 331: 17-18. evolutionary history. Benton M.J. (2012). No gap in the middle Permian record of terrestrial vertebrates. Geology, 40: 339-342. Benton M.J. (2015). Vertebrate Palaeontology. Fourth Edition. 472 ACKNOWLEDGMENTS pp. John Wiley & Sons, New York. Berman D.S. & Henrici A.C. (2003). Homology of the astragalus During my last 25 years of studying tetrapod trace fossils, I and structure and function of the tarsus of Diadectidae. Journal have been fortunate to collaborate with truly gifted ichnologists of Paleontology, 77: 172-188. who have taught me much. I owe them great thanks: David Berman D.S, Reisz R.R., Scott D., Henrici A.C., Sumida S.S. & Fillmore (Bethlehem, Pennsylvania), Heitor Francischini (Porto Martens T. (2000). Early Permian bipedal reptile. Science, Alegre, Brazil), Hartmut Haubold (Halle, Germany), Adrian 290: 969-972. Hunt (Everett, Washington, USA), Eric Kappus (El Paso, Texas, Berman D.S, Sumida S.S. & Lombard R.E. (1997). Biogeography USA), Olivia King (Halifax, Nova Scotia, Canada), Hendrik of primitive amniotes. In Sumida S.S. & Martin K.L.M. (eds), Klein (Neumarkt, Germany) , Martin Lockley (Denver, Colorado, Amniote Origins. Academic Press, San Diego: 85-139. USA), Chris Mansky (Blue Beach, Nova Scotia, Canada), Lorenzo Bernardi M. & Avanzini M. (2011). Locomotor behavior in early Marchetti (Milan, Italy), Matt Stimson (Halifax, Nova Scotia, reptiles: Insights from an unusual Erpetopus trackway. Journal Canada) and Sebastian Voigt (Thallichtenberg, Germany) . Klein, of Paleontology, 85: 925-929. Marchetti, Joerg Schneider (Freiberg, Germany) and Iwan Stössel Bernardi M., Klein H., Petti F.M. & Ezcurra M.D. (2015). The (Schaffhausen, Switzerland) generously provided me with images origin and early radiation of archosauriformes: Integrating the they had previously published to modify and use in this article. skeletal and footprint record. Plos One. DOI: 10.1377/journal. Matt Celeskey (Albuquerque, New Mexico, USA) and Arthur pone.0128449. Escher (Lausanne, Switzerland) similarly shared some of their Binford L.R. (1981). Bones: Ancient Men and Modern Myths. 320 fabulous artwork with me so it could be used in this article. Many pp. Academic Press, New York. funders, collection managers and other research collaborators also Bird H.C., Milner A.C., Shillito A.P. & Butler R.J. (2019). A lower contributed to making this article possible. Lorenzo Marchetti and Carboniferous (Visean) tetrapod trackway represents the earliest 256 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

record of an edopoid amphibian from the UK. Journal of the the continent. Philosophical Transactions of the Royal Society Geological Society. doi.org/10.1144/jgs2019-149. of London, 112: 171-236. Blakey R.C. (1990). Supai Group and Hermit Formation. In Beus Buckland W. (1824). Reliquiae Diluvianae; Or, Observations on the S.S. & Morales M. (eds), Grand Canyon Geology. New York, Organic Remains Contained in Caves, Fissures, and Diluvial Oxford University Press: 147-182. Gravel, and on Other Geological Phenomena, Attesting The Blieck A., Clement G. & Streel M. (2010). The biostratigraphical Action of an Universal Deluge. 303 pp. J. Murray, London. distribution of earliest tetrapods (Late Devonian): A revised Buta R.J., Pashin J.C., Minter N.J. & Kopaska-Merklel D.C. version with comments on biodiversification. Geological (2013). Ichnology and stratigraphy of the Crescent Valley Mine: Society, London, Special Publications, 339: 129-138. Evidence for a Carboniferous megatracksite in Walker County, Blieck A., Conti M.A., Dalla Vecchia F.M., Flügel H.W., Gand G., Alabama. New Mexico Museum of Natural History and Science Hubmann B., Lelièvre H., Mariotti N., Nicosia U., Poplin C., Bulletin, 60: 42-56. Schneider J. & Werneburg R. (1997). Palaeozoic vertebrates Calder J.H. (1998). The Carboniferous evolution of Nova Scotia. of the Alps: A review. Bulletin de al Societe Géologique de Geological Society, London, Special Publications, 143: 261-302. France, 168: 343-350. Calder J.H. (2012). The Joggins Fossil Cliffs: Coal Age Galapagos. Blom H. (2005). Taxonomic revision of the Late Devonian tetrapod 86 pp. Nova Scotia Department of Natural Resources, Halifax. Ichthyostega from East Greenland. Palaeontology, 48: 111-134. Calder J.H., Baird D. & Urdang E.B. (2004). On the discovery Boardman D.R.II, Barrick J.E., Heckel P.H. & Nestell M. (1998). of tetrapod trackways from Permo-Carboniferous redbeds of Pennsylvanian chronostratigraphic subdivisions of the North Prince Edward Island and their biostratigraphic significance. American Midcontinent. Texas Tech University Studies in Atlantic Geology, 40: 217-226. Geology, 2: 1-16. Carman J.E. (1927). Fossil footprints from the Pennsylvanian Boisvert C.A. (2005). The pelvic fin and girdle of Panderichthys System in Ohio. Geological Society of America Bulletin, 38: and the origin of tetrapod locomotion. Nature, 438: 1145-1147. 385-396. Boisvert C.A., Mark-Kurik E. & Ahlberg P.E. (2008). The pectoral Carrano M.T. & Wilson J.A. (2001). Taxon distributions and the fin of Panderichthys and the origin of digits. Nature, 456: tetrapod track record. Paleobiology, 27: 564. 636-638. Carroll R.L. (1965). Lungfish burrows from the Michigan coal basin. Boy J. & Fichter J. (1988). Zur Stratigraphie des höheren Rotliegend Science, 148: 963-964. im Saar-Nahe-Becken (Unter-Perm; SW-Deutschland) und Carroll R.L. (1969). A Middle Pennsylvanian captorhinomorph seiner Korrelation mit anderen Gebieten. Neues Jahrbuch für and the interrelationships of primitive reptiles. Journal of Geologie und Paläontologie Abhandlungen, 176: 331-394. Paleontology, 43: 151-170. Branson E.B. (1910). Amphibian footprints from the Mississippian Carroll R.L. (1970). The earliest known reptiles. Yale Scientific of Virginia. Journal of Geology, 18: 356-358. Magazine, October 1978: 16-23. Branson E.B. & Mehl M.G. (1932). Footprint records from the Carroll R.L. (1982). Early evolution of reptiles. Annual Review of Paleozoic and Mesozoic of Missouri, Kansas and Wyoming: Ecology and Systematics, 13: 87-109. Geological Society of America Bulletin, 43: 383-398. Carroll R.L. (2009). The Rise of Amphibians: 365 Million Years of Brocklehurst N. (2018). An examination of the impact of Evolution. 360 pp. Baltimore, The Johns Hopkins University Olson’s extinction on tetrapods from Texas: PeerJ, 6:e4767. Press. DOI 10.7717/peerj.4767. Carroll R.L. & Baird D. (1972). Carboniferous stem-reptiles of the Brocklehurst N., Ruta M., Müller J. & Fröbisch J. (2015). Elevated Family Romeriidae. Bulletin of the Museum of Comparative extinction rates as a trigger for diversification rate shifts: Zoology, 143: 321-364. early amniotes as a case study: Scientific Reports, 5:17104. Carroll R.L. & Thompson P. (1982). A bipedal lizardlike reptile from DOI 10.1038/srep17104. the Karroo. Journal of Paleontology, 56: 1-10. Brocklehurst N., Day M.O., Rubidge B.S. & Fröbisch J. (2017). Ceoloni P., Conti M.A., Mariotti N., Mietto P. & Nicosia U. (1988). Olson’s extinction and the latitudinal biodiversity gradient of New late Permian tetrapod footprints from Southern Alps. tetrapods in the Permian. Proceedings of the Royal Society B, Memorie della Società Geologica Italiana, 34: 45-65. 284: 20170231. DOI 10.1098/rspb.2017.0231. Chen D., Alavi Y., Brazeau M.D., Blom H., Millward D. & Ahlberg Bromley R.G. (1996). Trace Fossils: Biology and Taphonomy. P.E. (2018). A partial lower jaw of a tetrapod from “Romer’s Second edition. 361 pp. Unwin Hyman, London. gap.” Earth and Environmental Science Transactions of the Bromley R.G. & Asgaard U. (1972). Notes on Greenland trace Royal Society of Edinburgh, 108: 55-65. fossils: Freshwater Cruziana from the Upper Triassic of Chestnut D.R. Jr., Baird D., Smith J.H. & Lewis R.Q. aq Jameson Land, east Greenland. Grønlands Geologiske (1994). Reptile trackway from the Lee Formation (Lower Undersøgelse, Rapport 49, 7-13. Pennsylvanian) of south-central Kentucky. Journal of Bromley R.G. & Asgaard U. (1979). Triassic freshwater Paleontology, 68: 154-158. ichnocoenoses from Carlsberg Fjord, east Greenland. Clack J.A. (1997). Devonian tetrapod trackways and trackmakers; Palaeogeography, Palaeoclimatology, Palaeoecology, 28: a review of the fossils and footprints. Palaeogeography, 39-80. Palaeoclimatology, Palaeoecology, 130: 277-250. Buatois L.A. & Mángano M.G. (2011). Ichnology: Organism- Clack J.A. (2000). The origin of tetrapods. In Heatwole, H. Substrate Interactions in Time. 358 pp. Cambridge, Cambridge & Carroll, R. L. (eds), Amphibian Biology Volume 4 University Press. Palaeontology. Surrey, Beatty & Sons: 980-1029. Buatois L.A. & Mángano M.G. (2018). The other biodiversity record: Clack J.A. (2002). Gaining Ground: The Origin and Evolution of Innovations in animal-substrate interactions through geological Tetrapods. First Edition. 369 pp. Indiana, Indiana University time. GSA Today, 28. doi.org/10.1130/GSATG371A.1. Press, Bloomfield. Buatois L.A., Mángano M.G., Genise J.F. & Taylor T.N. (1998). Clack J.A. (2012). Gaining Ground: The Origin and Evolution of The ichnologic record of the continental invertebrate invasion: Tetrapods. Second Edition. 523 pp. Indiana University Press, Evolutionary trends in environmental expansion, ecospace Bloomfield, Indiana. utilization, and behavioral complexity. Palaios, 13: 217-240. Clack J.A., Bennett C.E., Davies S.J., Scott A.C., Sherwin J.E. & Buckland W. (1822). Account of an assemblage of fossil teeth and Smithson, T. R. (2019a). A Tournaisian (earliest Carboniferous) bones of elephant, rhinoceros, hippopotamus, bear, tiger and conglomerate-preserved non-marine faunal assemblage and its hyaena, and sixteen other animals; discovered in a cave at environmental and sedimentological context. PeerJ, 6:e5972. Kirkdale, Yorkshire, in the year 1821; with a comparative view Clack J.A. & Milner A.R. (2015). Basal Tetrapoda. Handbook of of five similar caverns in various parts of England, and others on Palaeoherpetology, 3A1: 1-92. S.G. Lucas - Ichnology and Paleozoic tetrapods 257

Clack J.A., Ruta M., Milner A.R., Marshall J.A.E., Smithson T. Day M.O., Ramezani J., Bowring S.A., Sadler P.M., Erwin D. R. & Smithson K.Z. (2019b). Acherontiscus caledoniae: The H., Abdala F. & Rubidge B.S. (2015). When and how did earliest heterodont and durophagous tetrapod. Royal Society the terrestrial mid-Permian mass extinction occur? Evidence Open Science, 6: 182087. from the tetrapod record of the Karoo basin, South Africa. Coates M.I. (1996). The Devonian tetrapod Acanthostega gunnari Proceedings of the Royal Society B, 282: 20150834. Jarvik: Postcranial anatomy, basal tetrapod interrelationships De Beer C.H. (1986). Surface markings, reptilian footprints and and patterns of skeletal evolution. Transactions of the Royal trace fossils on a palaeosurface in the Beaufort Group near Society of Edinburgh, Earth Sciences, 87: 363-421. Fraserburg, C. P. Annale van die Geologiese Opname Republiek Coates M.I. & Clack J.A. (1995). Romer’s gap: Tetrapod origins van Suid-Afrika, 20: 129-140. and terrestriality. Bulletin Museum National Histoire Naturelle De Klerk W.J. (2002). A dicynodont trackway from the Cistecephalus Paris 17: 373-388. assemblage zone in the Karoo, east of Graaff-Reinet, South Coates M.I. & Ruta M. (2007). Skeletal changes in the transition Africa. Palaeontologia Africana, 38: 73-91. from fins to limbs.In Hall B.K. (ed.), Fins into Limbs: Evolution, DiMichele W.A., Cecil C.B., Chaney D.S., Elrick S.D., Lucas S.G., Development, and Transformation. Chicago, University of Lupia R., Nelson W.J. & Tabor N.J. (2011). Pennsylvanian- Chicago Press: 15-37. Permian vegetational changes in tropical Euramerica. In Coates M.I., Ruta M. & Friedman M. (2008). Ever since Owen: Harper J.A. (ed.), Geology of the Pennsylvanian-Permian in Changing perspectives on the early evolution of tetrapods. the Dunkard Basin. Guidebook 76th Annual Field Conference Annual Review of Ecology & Systematics, 39: 571-592. of Pennsylvania Geologists, Washington, PA: 60-102. Colbert E.H. & Schaeffer B. (1947). Some Mississippian footprints DiMichele W.A. & Phillips T.L. (1996). Climate change, plant from Indiana. American Journal of Science, 245: 614-623. extinctions and vegetational recovery during the Middle-Late Contessi M., Voigt S. & Bibonne R. (2018). Permian tetrapod Pennsylvanian transition: The case of tropical peat-forming footprints from Tunisia. Ichnos, 25: 119-127. environments in North America. Geological Society, London, Conti M.A., Leonardi G., Mariotti N. & Nicosia U. (1977). Tetrapod Special Publications, 102: 201-221. footprints of the Val Gardena Sandstone (North Italy). Their Dollé P., de Lapparent A.F. & Montenat C. (1970). Sur une dale paleontological, stratigraphic and paleoenvironmental meaning. à empreintes de pas lacertoides du houllier du basin du Nord- Palaeontographia Italica, 70: 1-91. Pas-de-Calais. Annales Société Géologique du Nord, 90: 63-68. Costa da Silva R., Sedor F.A. & Fernandes A.C.S. (2012). Fossil Drumheller-Horton S.K. (2012). An Actualistic and Phylogenetic footprints from the late Permian of Brazil: An example of Approach to Identifying and Interpreting Crocodylian Bite hidden biodiversity. Journal of South American Earth Sciences, Marks. 170 pp. Ph. D. Dissertation, University of Iowa, Iowa 38: 31-43. City. Cotton W.D., Hunt A.P. & Cotton J.E. (1995). Paleozoic vertebrate Dunkle D.H. (1948). An interesting occurrence of fossil tracks in tracksites in eastern North America: New Mexico Museum of West Virginia. Journal of the Washington Academy of Science, Natural History and Science Bulletin, 6: 189-211. 38: 130-132. Cox E.T. (1874). Colletosaurus indianaensis Cox. Geological Dunne E.M., Close R.A., Button D.J., Brocklehurst N., Cashmore Survey of Indiana, Fifth Annual Report: 247-248. D.D., Lloyd G.T. & Butler R.J. (2018). Diversity change during Czyzewska T. (1955). Tropy gadów permskich z Wambierzyc (Dolny the rise of tetrapods and the impact of the ‘Carboniferous Śląsk) [Reptile trackways from the Permian of Wambierzyce rainforest collapse.’ Proceedings of the Royal Society B, 205: (Lower Silesia)]. Acta Geologica Polonica, 5: 131-160. 20172730. Damiani R., Modesto S., Yates A. & Neveling J. (2003). Earliest Eaton T.H. Jr. (1964). A captorhinomorph predator and its prey evidence of cynodont burrowing. Proceedings of the Royal (Cotylosauria). American Museum Novitates, 2169: 1-3. Society London B, 270: 1747-1751. Evans S.E. & King M.S. (1993). A new specimen of Protorosaurus Davydov V.I., Biakov A.S., Schmitz M.D. & Silantiev V.V. (2018). (Reptilia: Diapsida) from the Marl Slate (late Permian) of Radioisotopic calibration of the Guadalupian (middle Permian) Britain. Proceedings of the Yorkshire Geological Society, 49: series: Review and updates. Earth-Science Reviews, 176: 222-240. 229-234. Dawson J.W. (1844). On the Lower Carboniferous rocks, or Falcon-Lang H.J., Benton M.J. & Stimson M. (2007). Ecology of Gypsiferous Formation of Nova Scotia. Proceedings of the earliest reptiles inferred from basal Pennsylvanian trackways. Geological Society of London, 1843: 272-281. Journal of the Geological Society of London, 164: 1113-1118. Dawson J.W. (1845). On the newer Coal Formation of the eastern Falcon-Lang H.J., Gibling M.R., Benton M.J., Miller R.F. & part of Nova Scotia: Proceedings of the Geological Society of Bashforth A.R. (2010). Diverse tetrapod trackways in the London, 1845: 504-512. Lower Pennsylvanian Tynemouth Creek Formation, near St. Dawson J.W. (1863a). Air Breathers of the Coal Period. 81 pp. Martin, southern New Brunswick, Canada: Palaeogeography, New York, Balliere. Palaeoclimatology, Palaeoecology, 296: 1-13. Dawson J.W. (1863b). Note on the footprints of a reptile from the Falconnet J. & Steyer S. (2007). Revision, osteology, and locomotion Coal Formation of Cape Breton. Canadian Naturalist and of Aphelosaurus, an enigmatic reptile from the lower Permian Geologist, 8: 430-431. of France. Journal of Morphology, 268: 1071-1072. Dawson J.W. (1868). Acadian Geology: An Account of the Fernandez-Jalvo Y. & Andrews P. (2016). Atlas of Taphonomic Geological Structure and Mineral Resources of Nova Scotia Identifications: 1001+ Images of Fossil and Recent Mammal and Portions of the Neighbouring Provinces of British America. Bone Modification. 359 pp. Springer, New York. Third Edition. 694 pp. Oliver and Boyd, Edinburgh. Fichter J. (1982). Tetrapodenfährten aus dem Oberkarbon Dawson J.W. (1872). Note on footprints from the Carboniferous (Westfalium A und C) west-und Südwestdeutschlands. Mainzer of Nova Scotia in the collection of the Geological Survey of Geowissenschaft Mitteilungen, 11: 33-37. Canada: Geological Magazine, 9: 251-253. Fillmore D.L., Lucas S.G. & Simpson E.L. (2010). Invertebrate trace Dawson J.W. (1882). On the footprints of batrachians observed in fossils in semi-arid to arid braided-ephemeral-river deposits the Carboniferous rocks of Nova Scotia. Transactions of the of the Mississippian middle member of the Mauch Chunk Royal Society of London, 173: 651-654. Formation, eastern Pennsylvania, USA: Palaeogeography, Dawson J.W. (1894). Some Salient Points in the Science of the Palaeoclimatology, Palaeoecology, 292: 222-244. Earth. 499 pp. Harper & Brothers, New York. Fillmore D.L., Lucas S.G. & Simpson E.L. (2012). Ichnology of the Dawson J.W. (1895). Synopsis of the air-breathing animals of the Mississippian Mauch Chunk Formation, eastern Pennsylvania: Paleozoic in Canada, up to 1894. Transactions of the Royal New Mexico Museum of Natural History and Science Bulletin, Society of Canada, 12: 71-88. 54: 1-136. 258 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Fillmore D.L., Lucas S.G. & Simpson E.L. (2015). Vertebrate Godfrey S.J. & Smith J.B. (2010). Shark-bitten vertebrate coprolites ichnofossils from coal mine tailings of the Pennsylvanian from the Miocene of Maryland. Naturwissenschaften, 97: Llewellyn Formation, eastern Pennsylvania. New Mexico 461-467. Museum of Natural History and Science Bulletin, 67: 33-42. Gottmann-Quesada A. & Sander P.M. (2009). A redescription of Francischini H., Lucas S.G., Voigt S., Marchetti L., Santucci V. the early archosauromorph Protorosaurus speneri Meyer, L., Knight C.L., Wood J.R., Dentzien-Dias P. & Schultz C. 1832 and its phylogenetic relationships. Palaeontographica L. (2019). On the presence of Ichniotherium in the Coconino A, 287: 123-220. Sandstone (Cisuralian) of Grand Canyon and remarks on the Groenewald G.H., Welman J. & MacEachern J.A. (2001). Vertebrate occupation of deserts by non-amniote tetrapods. PalZ. doi: burrow complexes from from the Early Triassic Cynognathus 10.1007/s12542-019-00450-5. zone (Driekoppen Formation, Beaufort Group) of the Karoo Gand G. (1975). Sur quelques empreintes de pas de vertébrés basin, South Africa. Palaios, 16: 148-160. récoltées dans le Stéphanien moyen de Montceau-les-Mines Gubin Y.M., Golubev V.K., Bulanov V.V. & Petuchov S.V. (2003). (Saône-et-Loire-France). Bulletin de la Société d’Historie Pareiasaurian tracks from the Upper Permian of Eastern Europe. Naturelle d’Autun 74: 9-31. Paleontological Journal, 37: 514-523. Gand G. (1988). Les Traces de Vertébrés Tétrapodes du Permien Haas J. (2001). Geology of Hungary. 317 pp. Eötvös University Français. 341 pp. Ph.D. Thesis, Université de Bourgogne Edition Press, Budapest. Centre des Sciences de la Terre, Dijon. Harland W.B., Armstrong R.L., Cox A.V., Craig L.E., Smith A.G. Gand G., Demathieu G. & Ballestra F. (1995). La palichnofaune & Smith D.G. (1990). A Geologic Time Scale 1989. 188 pp. de vertébrés tétrapodes du Permien supérieur de l’Esterel Cambridge University Press, Cambridge. (Provence, France). Palaeontographica, A235: 97-139. Harris S.K., Lucas S.G. & Lueth V.W. (2017). Lacustrine coprofauna Gand G. & Durand M. (2006). Tetrapod footprint ichno-associations from the Upper Pennsylvanian (Missourian) Tinajas Member of the from French Permian basins. Comparisons with other Atrasado Formation, Socorro County, New Mexico. New Mexico Euramerican ichnofaunas. Geological Society London, Special Museum of Natural History and Science Bulletin, 77: 113-132. Publications, 265: 157-177. Hasiotis S.T. (2002). Continental trace fossils. SEPM Short Course Gand G., Garric J., Demathieu G. & Ellenberger P. (2000). La Notes, 51: 1-132. palichnofaune de vertébrés tétrapodes du Permien supérieur Hasiotis S.T., Platt B.F., Hembree D.I. & Everhart M.J. (2007). du bassin de Lodève (Languedoc-France). Palaeovertebrata, The trace-fossil record of vertebrates. In Miller W. III, (ed.), 29: 1-82. Trace Fossils: Concepts, Problems, Prospects. Elsevier, New Gand G., Kerp H., Parsons C. & Martínez-García E. (1997). York: 196-218. Palaeoenvironnemental and stratigraphic aspects of animal Hasiotis S.T., Wellner R.W., Martin A.J. & Demko T.M. traces and plant remains in Spanish Permian red beds (Peña (2004). Vertebrate burrows from Triassic and Jurassic Sagra, Cantabrian Mountains, Spain). Geobios, 30: 295-318. continental deposits of North America and Antarctica: Their Gand G., Tüysüz O., Steyer J.S., Allain R., Sakinç M., Sanchez S., paleoenvironmental and paleoecological significance. Ichnos, Sengör A.M.C. & Sen S. (2011). New Permian tetrapod footprints 11: 103-124. and macroflora from Turkey (Çakraz Formation, northwestern Haubold H. (1970). Versuch einer Revision der Amphibien-Fährten Anatolia): Biostratigraphic and palaeonenvironmental des Karbon und Perm. Freiberger Forschungshefte Reihe C, implications. Comptes Rendus Palevol, 10: 617-625. 260: 83-117. Gastaldo R.A., Kamo S.L., Neveling J., Geissman J.N., Bamford M. Haubold H. (1971). Ichnia amphibiorum et reptiliorum fossilium. & Looy C.V. (2015). Is the vertebrate defined Permian-Triassic Encyclopedia of Paleoherpetology, 18: 1-124. boundary in the Karoo basin, South Africa, the terrestrial Haubold, H. (1984). Saurierfährten. 205 pp. A. Ziemsen Verlag, expression of the end-Permian marine event? Geology, 43: Wittenberg Lutherstadt. 939-942. Haubold H. (1996). Ichnotaxonomie und Klassifikation von Gastaldo R.A., Neveling J., Geissman J.W., Kamo S.L. (2018). Tetrapodenfährten aus dem Perm. Hallesches Jahrbuch für A lithostratigraphic and magnetostratigraphic framework in Geowissenschaften B, 18: 23-88. a geochronologic context for a purported Permian-Triassic Haubold H. (2000). Tetrapodenfahrten aus dem Perm-Kenntnisstand boundary section at Old (West) Lootsberg Pass, Karoo Basin, und Progress 2000. Hallesches Jahrbuch fur Geowissenschaften South Africa. GSA Bulletin, 130: 1411-1438. B, 22: 1-16. Gastaldo R.A., Neveling J., Looy C.V., Bamford M.K., Kamo Haubold H., Allen A., Atkinson T.P., Buta R.J., Lacefield J.A., S.L., Geissman J.W. (2017). Paleontology of the Blaauwater Minkin S.C. & Relihan B.A. (2005). Interpretation of the 67 and 65 Farms, South Africa: Testing the Daptocephalus/ tetrapod footprints from the Early Pennsylvanian of Alabama. Lystrosaurus biozone boundary in a stratigraphic framework. Alabama Paleontological Society Monograph, 1: 75-111. Palaios, 32: 349-366. Haubold H., Hunt A.P., Lucas S.G. & Lockley M.G. (1995). Geinitz H.B. (1861). Dyas oder die Zechsteinformation und das Wolfcampian (early Permian) vertebrate tracks from Arizona Rothliegende (Permische Formation zum Theil). 130 pp. W. and New Mexico. New Mexico Museum of Natural History and Engelmann, Leipzig. Science Bulletin, 6: 135-165. George D. & Blieck A. (2011). Rise of the earliest tetrapods: An Haubold H. & Katzung G. (1978). Paleoecology and Early Devonian origin from a marine environment. PLoS ONE, paleoenvironments of tetrapod footprints from the Rotliegend 6: e22136. (Lower Permian) of Central Europe. Palaeogeography, Getty P.R., Sproule R., Stimson M.R. & Lyons P.C. (2017). Palaeoclimatology, Palaeoecology, 23: 307-323. Invertebrate trace fossils from the Pennsylvanian Rhode Haubold H. & Lucas S.G. (2001). Die Tetrapodenfährten der Island Formation of Massachusetts, USA. Atlantic Geology, Choza Formation (Texas) und das Artinsk-Alter der Redbed- 53: 185-206. Ichnofaunen des Unteren Perm. Hallesches Jahrbuch für Gilmore G.W. (1926). Fossil footprints from the Grand Canyon I. Geowissenschaften, B23: 79-108. Smithsonian Miscellaneous Collections, 77: 1-41. Haubold H. & Lucas S.G. (2003). Tetrapod footprints of the Lower Gilmore C.W. (1927). Fossil footprints from the Grand Canyon II. Permian Choza Formation. Paläontologische Zeitschrift, 77: Smithsonian Miscellaneous Collections, 80: 1-78. 247-261. Gilmore G.W. (1928). Fossil footprints from the Grand Canyon III. Haubold H. & Sarjeant W.A.S. (1973). Tetrapodenfährten aus dem Smithsonian Miscellaneous Collections, 80: 1-16. Keele und Enville Groups (Permokarbon) von Shropshire Godfrey S.J. & Palmer B.T. (2015). Gar-bitten coprolite from South und South Staffordshire, Grossbrittannien. Zeitschrift der Carolina, USA. Ichnos, 22: 103-108. Geologische Wissenschaften Berlin, 1: 895-933. S.G. Lucas - Ichnology and Paleozoic tetrapods 259

Haubold H. & Sarjeant W.A.S. (1974). Fossil vertebrate footprints Hunt A.P. & Lucas S.G. (2006). Permian tetrapod ichnofacies. and the stratigraphical correlation of the Keele and Enville Beds Geological Society, London, Special Publications, 265: 137-156. of the Birmingham Region. Proceedings of the Birmingham Hunt A.P. & Lucas S.G. (2007). Tetrapod ichnofacies: a new Natural History Society, 22: 257-268. paradigm. Ichnos, 14: 59-68. Haubold H. & Schaumberg G. (1985). Die Fossilien des Hunt A.P. & Lucas S.G. (2012). Classification of vertebrate Kupferschiefer: Pflanzen-und Tierwelt zu Beginn des coprolites and related trace fossils. New Mexico Museum of Zechsteins; eine Erzlagerstatte und ihre Palaontologie. 76 pp. Natural History and Science Bulletin, 57: 137-146. Wittenberg Lutherstadt, A. Ziemsen Verlag. Hunt A.P., Lucas S.G., Calder J.H., Van Allen H.E.K., George E., Hembree D.I. (2010). Aestivation in the fossil record: Evidence from Gibling M.R., Hebert B.L., Mansky C. & Reid D.R. (2004). ichnology. In Navas C.A. & Carvalho J.E. (eds), Aestivation: Tetrapod footprints from Nova Scotia: The Rosetta Stone Molecular and Physiological Aspects. Berlin, Springer-Verelag: for Carboniferous tetrapod ichnology. Geological Society of 245-262. America Abstracts with Programs, 36: 66. Hembree D.I., Hasiotis S.T. & Martin L.D. (2005). Torridorefugium Hunt A.P., Lucas S.G. & Klein H. (2018). Late Triassic nonmarine eskridgensis (new ichnogenus and ichnospecies): Amphibian vertebrate and invertebrate trace fossils and the pattern of the aestivation burrows from the lower Permian Speiser Shale of Phanerozoic record of vertebrate trace fossils. In Tanner L.H. Kansas. Journal of Paleontology, 79: 583-593. (ed.), The Late Triassic World. New York, Springer Verlag, Hembree D.I., Martin L.D. & Hasiotis S.T. (2004). Amphibian Topics in Geobiology, 46: 447-543. burrows in ephemeral ponds of the lower Permian Speiser Hunt A.P., Lucas S.G. & Lockley M.G. (1995). Paleozoic tracksites Shalem, Kansas: Evidence for seasonality in the mid-continent. of the western United States. New Mexico Museum of Natural Palaeogeography, Palaeoclimatology, Palaeoecology, 203: History and Science Bulletin, 6: 213-217. 127-152. Hunt A.P., Lucas S.G., Milan J. & Spielmann J.A. (2012). Vertebrate Henderson C.M., Davydov V.I. & Wardlaw B.R. (2012). The coprolite studies: Status and prospectus. New Mexico Museum Permian Period. In Gradstein F.M., Ogg J.G., Schmitz M.D. of Natural History and Science Bulletin, 57: 5-24. & Ogg G.M. (eds), The Geologic Time Scale 2012. Volume 2. Hunt A.P., Lucas S.G. & Pyenson N.D. (2005). The significance Amsterdam, Elsevier: 653-679. of the Union Chapel Mine site: A Lower Pennsylvanian Henderson J. (1924). Footprints in Pennsylvanian sandstones of (Westphalian A) ichnological Konzentrat-Lagerstätte, Alabama, Colorado. Journal of Geology, 32: 226-229. USA. Alabama Paleontological Society Monograph, 1: 3-114. Heyler D. & Lessertisseur J. (1963). Pistes de tetrapodes permiens Hunt A.P., Meyer C.A., Lockley M.G. & Lucas S.G. (1994). dans la region de Lodeve (Herault). Memoire du Museum Archaeology, toothmarks and sauropod taphonomy. Gaia, 10: National d’Histoire Naturelle, 11: 125-221. 225-232. Hmich D., Schneider J.W., Saber H., Voigt S. & El Wartiti M. Ivakhnenko M.F., Golubyev V.K., Gubin Yu. M., Kalandadze N.N., (2006). New continental Carboniferous and Permian faunas of Novikov I.V., Sennikov A.G. & Rautian A.S. (1997). Permskiye Morocco - implications for biostratigraphy, palaeobiogeography i Triasovyye Tetrapody Vostochnoi Evropy [Permian and and palaeoclimate. Geological Society, London, Special Triassic Tetrapods of eastern Europe]. 216 pp. GEOS, Moscow. Publications, 265: 297-324. Jake T.R. & Blake B.M. Jr. (1982). 300 million year old footprints Hminna A., Voigt S., Saber H., Schneider J.W. & Hmich D. found in Tucker County: Mountain State Geology (West Virginia (2012). On a moderately diverse continental ichnofauna from Geological and Economic Survey): 23-25. the Permian Ikakern Formation (Argana Basin, Western High Janvier P. & Clément G. (2010). Muddy tetrapod origins. Nature, Atlas, Morocco). Journal of African Earth Sciences, 68: 15-32. 463: 40-41. Holmes R.B. (1984). The Carboniferous amphibian Proterogyrinus Jarvik E. (1996). The Devonian tetrapod Ichthyostega. Fossils and scheelei Romer, and the early evolution of tetrapods. Strata, 40: 1-213. Philosophical Transactions of the Royal Society of London B, Jillison W.R. (1917). Preliminary note on the occurrence of 306: 431-527. vertebrate footprints in the Pennsylvanian of Oklahoma. Holub V. & Kozur H. (1981). Revision einiger Tetrapodenfährten American Journal of Science, 194: 56-58. des Rotliegenden und biostratigraphische Auswertung der Jones W.B. (1930). Footprints found in Alabama mine. Coal Age, Tetrapodenfährten des obersten Karbon und Perm. Geologisch- 35: 92. Paläontologische Mitteilungen Innsbruck, 11: 149-193. Jovanovic M. (2012). The first record of tetrapod tracks in Permian Hopson J.A. (2012). The role of foraging mode in the origin alevrolites of vicinity of Donji Milanovac (Eastern Serbia). of therapsids: Implications for the origin of mammalian Permophiles, 56: 44-46. endothermy. Fieldiana: Life and Earth Sciences, 5: 126-148. Jovanovic M. (2013). Amphibia and Reptilia of Permian red Hopson J.A. (2015). Fossils, trackways, and transitions in sandstones (red-beds) from Glavica hill near Donji Milanovac locomotion: A case study of Dimetrodon. In Dial K.P., Shubin (Eastern Serbia). Permophiles, 57: 20-22. N. & Brainerd E.L. (eds), Great Transformations in Vertebrate Kaiser S.I., Aretz M. & Becker R.T. (2016). The global Hangenberg Evolution. The University of Chicago Press, Chicago: 125-141. crisis (Devonian-Carboniferous transition): Review of a first- Hotton N.H.III, Olson E.C. & Beerbower R. (1997). Amniote origins order mass extinction. Geological Society, London, Special and the discovery of herbivory. In Sumida S.S. & Martin K.L.M. Publications, 423: 387-437. (eds), Amniote Origins: Completing the Transition to Land. San Kaszap A. (1968). Korynichnium sphaerodactylum (Pabst) in the Diego, Academic Press: 207-264. Permian of Balatonrendes. Földtani Közlöny, 98: 429-433. Houck K. & Lockley M.G. (1986). Pennsylvanian biofacies of Kauffman E.G. & Sawdo J.K. (2013). Mosasaur predation on a central Colorado. University of Colorado at Denver, Geology nautiloid from the Maastrichtian Pierre Shale, Central Colorado, Department Magazine, Special Issue 2: 1-64. Western Interior Basin, United States. Lethaia, 46: 180-187. Huang H., Cawood P.A., Hou M., Yang J., Ni S., Du Y., Yan Z., Kearsey T.I., Bennett C.E., Millward D., Davies S.J., Gowing Wang J. (2016). Silicic ash beds bracket Emeishan large igneous C.J.B., Kemp S.J., Leng M.J., Marshall J.E.A. & Browne province to 1 m. y. at ~260 Ma. Lithos, 264: 17-27. M.A.E. (2016). The terrestrial landscapes of tetrapod evolution Hunt A.P. & Lucas S.G. (1998). Vertebrate tracks and the myth of the in earliest Carboniferous seasonal wetlands of SE Scotland. belly-dragging, tail-dragging tetrapods of the late Paleozoic: New Palaeogeography, Palaeoclimatology, Palaeoecology, 457: 52-69. Mexico Museum of Natural History and Science Bulletin, 12: 67-69. Keighley D.G., Calder J.H., Park A.F., Pickerill R.K., Waldron J.W., Hunt A.P. & Lucas S.G. (2005). Tetrapod ichnofacies and their Falcon-Lang H.J. & Benton M.J. (2008). Discussion on ecology utility in the Paleozoic. Alabama Paleontological Society of earliest reptiles inferred from basal Pennsylvanian trackways. Monograph, 1: 113-119. Journal of the Geological Society, 165: 983-987. 260 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Keighley D.G. & Pickerill R.K. (1996). Small Cruziana, Lockley M.G. & Meyer C.A. (2000). Dinosaur Tracks and Other Rusophycus, and related ichnotaxa from eastern Canada: The Fossil Footprints of Europe. 323 pp. Columbia University nomenclatural debate and systematic ichnology. Ichnos, 4: Press, New York. 261-285. Lozovsky V.R., Minikh M.G., Grunt T.A., Kukhtinov D.A., King A.T. (1845). Description of fossil footmarks found in the Ponomarenko A.G. & Sukacheva I.D. (2009). The Ufimian Carboniferous series in Weszmoreland County, Pa. American Stage of the East European scale: Status, validity, and correlation Journal of Science, 48: 343-352. potential. Stratigraphy and Geological Correlation, 17: 602- Klein H. & Lucas S.G. (2010). Tetrapod footprints-their use in 614. biostratigraphy and biochronology of the Triassic. Geological Lucas S.G. (2001). Taphotaxon: Lethaia, 34: 30. Society, London, Special Publications, 334: 419-446. Lucas S.G. (2003). Carboniferous tetrapod footprint biostratigraphy Kohl M.S. & Bryan J.R. (1994). A new Middle Pennsylvanian and biochronology. Newsletter on Carboniferous Stratigraphy, (Westphalian) amphibian trackway from the Cross Mountain 21: 36-41. Formation, east Tennessee Cumberlands. Journal of Lucas S.G. (2004). A global hiatus in the Middle Permian tetrapod Paleontology, 68: 655-663. fossil record. Stratigraphy, 1: 47-64. Kosanke R.M. & Cecil C.B. (1996). Late Pennsylvanian climate Lucas S.G. (2005). Tetrapod ichnofacies and ichnotaxonomy: Quo changes and palynomorph extinctions. Review of Palaeobotany vadis? Ichnos, 12: 157-162. and Palynology, 90: 113-140. Lucas S.G. (2006). Global Permian tetrapod biostratigraphy Krapovickas V., Marsicano C.A., Mancuso A.C., de la Fuente M.S. and biochronology. Geological Society, London, Special & Ottone E.G. (2015). Tetrapod and invertebrate trace fossils Publication, 265: 65-93. from aeolian deposits of the lower Permian of central western Lucas S.G. (2007). Tetrapod footprint biostratigraphy and Argentina. Historical Biology, 27: 827-842. biochronology. Ichnos, 14: 5-38. Kubo T. & Benton M.J. (2009). Tetrapod postural shift estimated Lucas S.G. (2009a). Global middle Permian reptile mass extinction: from Permian and Triassic trackways. Palaeontology, 52: The dinocephalian extinction event. Geological Society of 1029-1037. America Abstracts with Programs, 41: 360. Lagnaoui A., Voigt S., Belahmira A., Saber H., Klein H., Hminna A. Lucas S.G. (2009b). Timing and magnitude of tetrapod extinctions & Schneider J.W. (2017). Late Carboniferous tetrapod footprints across the Permo-Triassic boundary. Journal of Asian Earth from the Souss basin, Western High Atlas Mountains, Morocco. Sciences, 36: 491-502. Ichnos. DOI 10.1080/10420942.2017.1320284. Lucas S.G. (2014). Traces of a Permian Seacoast: Prehistoric Lane N. & Maples C.G. (1990). Fossil footprints from Indiana. Trackways National Monument. 48 pp. Albuquerque, New Journal of Vertebrate Paleontology, 9: 32A. Mexico Museum of Natural History and Science. Langiaux J. (1979). Ichnologie: 5. Baropezia polymorpha n. sp. Lucas S.G. (2015). Thinopus and a critical review of Devonian (Stéphanien terminal de Blanzy-Montceau). Revue Periodique tetrapod footprints. Ichnos, 22: 136-154. de “La Physiophile,” 90: 69-75. Lucas S.G. (2016). Two new, substrate-controlled nonmarine Langiaux J. (1980). Premières observations a Morteru (Stéphanien ichnofacies. Ichnos, 23: 248-261. de Blanzy-Montceau) ichnites, fauna, flore. Revue Periodique Lucas S.G. (2017). Permian tetrapod extinction events: Earth- de “La Physiophile,” 93: 77- 88. Science Reviews, 170: 31-60. Langiaux J. (1981). Ichnologie, 6, Deux pistes nouvelles a Morteru. Lucas S.G. (2018a). Permian tetrapod biochronology, correlation Revue Periodique de “La Physiophile,” 94: 65-74. and evolutionary events. Geological Society, London, Special Langiaux J. & Sotty D. (1975a). Ichnologie, pistes de tetrapodes Publications, 450: 405-444. fossiles dans le bassin de houllier de Blanzy-Montceau. Revue Lucas S.G. (2018b). Review of When the Invasion of Land Failed: Periodique de “La Physiophile,” 82: 46-58. The Legacy of the Devonian Extinctions by George R. McGhee Langiaux J. & Sotty D. (1975b). Ichnologie, 2, pistes de tetrapodes Jr. Fossil News: The Journal of Avocational Paleontology, 21: fossiles dans bassin houiller de Blanzy-Montceau. Revue 47-48. Periodique de “La Physiophile,” 83: 57-68. Lucas S.G., Allen B.D., Krainer K., Barrick J., Vachard D., Langiaux J. & Sotty D. (1976). Ichnologie, 3, trois nouvelles pistes Schneider J.W., DiMichele W.A. & Bashforth A.R. (2011). de tétrapodes dans le Stéphanien de Blanzy-Montceau. Revue Precise age and biostratigraphic significance of the Kinney Periodique de “La Physiophile,” 84: 46-54. Brick Quarry Lagerstätte, Pennsylvanian of New Mexico, USA. Langiaux J. & Sotty D. (1977). Ichnologie, 4, pistes et empreintes Stratigraphy, 8: 7-27. dans le Stéphanien de Blanzy-Montceau. Revue Periodique de Lucas S.G. & Ataabadi M.M. (2010). Tetrapod footprints from the “La Physiophile,” 86: 74-92. upper Carboniferous of China. Ichnos, 17: 163-165. Lea I. (1853). On the fossil foot-marks in the Red Sandstones of Lucas S.G. & Dalman S.G. (2013). Alfred King’s Pennsylvanian Pottsville, Schuylkill County, Pennsylvania. Transactions of tetrapod footprints from western Pennsylvania. New Mexico the American Philosophical Society, 10 (new series): 307-315. Museum of Natural History and Science Bulletin, 60: 233-239. Lebedev O.A. & Coates M.I. (1995). The postcranial skeleton of Lucas S.G., Fillmore D.L. & Simpson E.L. (2010a). The the Devonian tetrapod Tulerpeton curtum Lebedev. Zoological Mississippian tetrapod footprint ichnogenus Palaeosauropus: Journal of the Linnean Society, 114: 307-348. Extramorphological variation and ichnotaxonomy. Ichnos, 17: Leidy J. (1879). Fossil footracks of the anthracite coal measures. 177-186. Proceedings of the Academy of Natural Sciences of Philadelphia, Lucas S.G., Fillmore D.L. & Simpson E.L. (2010b). Amphibian 1879: 164-165. body impressions from the Mississippian of Pennsylvania, Lerner A., Lucas S.G., Bruner M. & Shipman P. (2002). A tetrapod USA. Ichnos, 17: 172-176. ichnofauna from the Middle Pennsylvanian (Desmoinesian) Lucas S.G., Gobetz K.E., Odier G.P., McCormick T. & Egan C. McAlester Formation (Krebs Group), Haskell Co., Oklahoma. (2006). Tetrapod burrows from the Lower Jurassic Navajo Journal of Vertebrate Paleontology, 22: 78A. Sandstone, southeastern Utah. New Mexico Museum of Natural Lockley M.G. & Hunt A.P. (1995). Dinosaur Tracks and Other History and Science Bulletin, 37: 147-154. Fossil Footprints of the Western United States. 338 pp. New Lucas S.G. & Golubev V.K. (2019). Age and duration of Olson’s York: Columbia University Press. gap, a global hiatus in the Permian tetrapod fossil record: Lockley M.G., Hunt A.P. & Meyer C. (1994). Vertebrate tracks and Permophiles, 67: 20-23. the ichnofacies concept: Implications for paleopecology and Lucas S.G. & Heckert A.B., eds (1995). Early Permian footprints palichnostratigraphy. In Donovan S. (ed.), The Paleobiology and facies. New Mexico Museum of Natural History and Science of Trace Fossils. Chichester, John Wiley & Sons: 241-268. Bulletin, 6: 1-301. S.G. Lucas - Ichnology and Paleozoic tetrapods 261

Lucas S.G. & Hunt A.P. (2005). Permian tetrapod tracks from producers and biostratigraphy through two major faunal crises. Texas. New Mexico Museum of Natural History and Science Gondwana Research, 72: 139-168. Bulletin, 30: 202-206. Marchetti L., Klein H., Buchwitz M., Ronchi A., Smith R.M., De Lucas S.G. & Hunt A.P. (2006). Permian tetrapod footprints: Klerk W.J., Sciscio L. & Groenewald G.H. (2019e). Reply to Biostratigraphy and biochronology. Geological Society, London, discussion of “Permian-Triassic vertebrate footprints from Special Publication, 265: 179-200. South Africa: Ichnotaxonomy, producers and biostratigraphy Lucas S.G., Kollar A.D., Berman D.S & Henrici A.C. (2016). through two major faunal crises” by Marchetti L., Klein H., Pelycosaurian-grade (Amniota: Synapsida) footprints from Buchwitz M., Ronchi A., Smith R.M.H., DeKlerk W.J., Sciscio the lower Permian Dunkard Group of Pennsylvania and west L. & Groenewald G.H. (2019). Gondwana Research. DOI Virginia. Annals of Carnegie Museum, 83: 287-294. 10.1016/j.gr.2019.08.002. Lucas S.G., Lozovsky V.R. & Shishkin M.A. (1999). Tetrapod Marchetti L., Mujal E. & Bernardi M. (2017). An unusual footprints from early Permian redbeds of the Northern Caucasus, Amphisauropus trackway and its implication for understanding Russia. Ichnos, 6: 277-281. seymouriamorph locomotion. Lethaia, 50: 162-174. Lucas S.G., Lerner A.J., Bruner M. & Shipman P. (2001). Middle Marchetti L., Petti F.M., Zoboli D. & Pillola G.L. (2018). Vertebrate Pennsylvanian ichnofauna from eastern Oklahoma, USA. and invertebrate trace fossils in the Late Pennsylvanian Ichnos, 11: 45-55. (Carboniferous) fluvio-lacustrine San Giorgio Basin (South-West Lucas S.G., Mansky C., Fillmore D.L., Calder J. & Simspon E.L. Sardinia): Remarks on the oldest continental ichnoassociation (2010c). Mississippian tetrapod footprint assemblages from of Italy. Ichnos, 25: 94-105. Pennsylvania and Nova Scotia and the oldest record of amniotes. Marchetti L., Ronchi A., Santi G. & Voigt S. (2015a). The Geological Society of America, Abstracts with Programs, 45: Gerola Valley site (Orobic Basin, Northern Italy): A key 641-642. for understanding late Early Permian tetrapod ichnofaunas. Lucas S.G., Rinehart L.F. & Celeskey M.D. (2018). The oldest Palaeogeography, Palaeoclimatology, Palaeoecology, 439: specialized tetrapod herbivore: A new eupelycosaur from the 97-116. Permian of New Mexico, USA. Palaeontologia Electronica, Marchetti L., Ronchi A., Santi G., Schirolli P. & Conti M.A. (2015b). 21.3.39A: 1-42. Revision of a classic site for Permian tetrapod ichnology Lull R.S. (1918). Fossil footprints from the Grand Canyon of the (Collio Formation, Trompia and Caffaro valleys, N. Italy), Colorado. American Journal of Science, 269: 337-346. new evidences for the radiation of captorhinomorph footprints. Lull R.S. (1920). An upper Carboniferous footprint from Attleboro, Palaeogeography, Palaeoclimatology, Palaeoecology, 433: Massachusetts. American Journal of Science, 50: 234-236. 140-155. Luo Z. & Wible J.M. (2005). A Late Jurassic digging mammal and Marchetti L., Voigt S. & Klein H. (2017). Revision of the late Permian early mammal diversification.Science , 308: 103-107. tetrapod tracks from the Dolomites (Trentino-Alto Adige, Italy). Lyell C. (1843). On the Coal Formation of Nova Scotia and on the Historical Biology. DOI 10.1080/08912963.2017.1391806. age and relative position of the gypsum and accompanying Marchetti L., Voigt S. & Lucas S.G. (2019b). An anatomy- marine limestone. Proceedings of the Geological Society of consistent study of the Lopingian eolian tracks of Germany London, 4: 184-186. and Scotland reveals the first evidence of the end-Guadalupian MacDougall M.J. & Reisz R.R. (2014). The first record of a mass extinction at low paleolatitudes of Pangea. Gondwana nyctiphruretid parareptile from the early Permian of North Research, 73: 32-53. America, with a discussion of parareptilian temporal fenestra. Marchetti L., Voigt S., Lucas S.G., Francischini H., Dentzien-Dias Zoological Journal of the Linnean Society, 172: 616-630. P., Sacchi R., Mangiacotti M., Scali S., Gazzola A., Ronchi A. Mansky C.F. & Lucas S.G. (2013). Romer’s gap revisited: & Millhouse A. (2019a). Tetrapod ichnotaxonomy in eolian Continental assemblages and ichno-assemblages from the basal paleoenvironments (Coconino and DeChelly formations, Carboniferous of Blue Beach, Nova Scotia, Canada. New Mexico Arizona) and late Cisuralian (Permian) sauropsid radiation. Museum of Natural History and Science Bulletin, 60: 244-273. Earth-Science Reviews, 190: 148-170. Marchetti L. (2014). Early Permian Vertebrate Ichnofauna from Marsh O.C. (1894). Footprints of vertebrates in the Coal Measures South Alpine Region (Northern Italy): Ichnosystematics, of Kansas. American Journal of Science, 348: 81-84. Paleoecology and Stratigraphic Meaning. Unpublished Ph.D. Marshall J.A.E., Glennie K.W., Astin T.R. & Hewitt A.J. (2018). thesis. 128 pp. Università degli Studi di Padova, Dipartimento The Old Red Group (Devonian)-Rotliegend Group (Permian) di Geoscienze Padova. unconformity in the Inner Moray Firth. Geological Society of Marchetti L. (2016). New occurrences of tetrapod ichnotaxa from the London Special Publications, 471: 237-252. Permian Orobic Basin (Northern Italy) and critical discussion Martino R.L. (1991). Limnopus trackways from the Conemaugh of the age of the ichnoassociation. Papers in Palaeontology, Group (Late Pennsylvanian), southern West Virginia. Journal 2: 363-386. of Paleontology, 65: 957-972. Marchetti L., Avanzini M. & Conti M.A. (2013). Hyloidichnus Marzola M., Mateus O., Milan J. & Clemmensen L.B. (2018). A bifurcatus Gilmore, 1927 Limnopus heterodactylus (King, 1845) review of Palaeozoic and Mesozoic tetrapods from Greenland. from the early Permian of the Southern Alps (N Italy): A new Bulletin of the Geological Society of Denmark, 66: 21-46. equilibrium in the ichnofauna. Ichnos, 20: 202-217. Matthew G.F. (1903a). An attempt to classify Paleozoic batrachian Marchetti L., Belvedere M., Voigt S., Klein H., Castanera D., footprints. Transactions of the Royal Society of Canada, 9: Díaz-Martínez I., Marty D., Xing L., Feola S., Melchor R.N. 109-121. & Farlow J.O. (2019d). Defining the morphological quality of Matthew G.F. (1903b). On batrachian and other footprints from the fossil footprints. Problems and principles of preservation in Coal Measures of Joggins, N.S. Bulletin of the Natural History tetrapod ichnology with examples from the Palaeozoic to the Society of New Brunswick, 5: 103-108. present. Earth-Science Reviews, 193: 109-145. Matthew G.F. (1903c). New genera of batrachian footprints from Marchetti L., Francischini H., Lucas S.G., Voigt S., Hunt A.P. & the Carboniferous system in eastern Canada. Canadian Record Santucci V.L. (in press). Paleozoic vertebrate ichnology of of Science, 9: 99-111. Grand Canyon. In Santucci V. L. (ed.), Grand Canyon National Matthew G.F. (1904). Note on the genus Hylopus of Dawson. Park Paleontological Resource Inventory. National Park Service Bulletin of the Natural History Society of New Brunswick, 5: Nature Resource Technical Report, Washington, D.C. 247-252. Marchetti L., Klein H., Buchwitz M. Ronchi A., Smith R.M.H., De Matthew G.F. (1905). New species and a new genus of batrachian Klerk W.J., Sciscio L. & Groenwald G.H. (2019c). Permian- footprints of the Carboniferous System in eastern Canada. Triassic vertebrate footprints from South Africa: Ichnotaxonomy Transactions of the Royal Society of Canada, 10: 77-122. 262 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

McAllister J.A. (1992). Gnathorhiza (Dipnoi): Life aspects, and diversification of parareptiles.Proceedings of the Royal Society lungfish burrows. In Mark-Kurik E. (ed.), Fossil Fishes as B, 282: 20121912. Living Animals. Academy of Sciences of Estonia, Institute of Modesto S.P., Smith R.M.H., Campione N.E. & Reisz R.R. Geology, Tallinn. (2011). The last “pelycosaur:” A varanopid synapsid from the McClelland S. (1988). Fossil footprints unearthed in eastern Pristerognathus assemblage zone, middle Permian of South panhandle. Mountain State Geology (West Virginia Geological Africa. Naturwissenschaften, 98: 1027-1034. and Economic Survey): 14-17. Monks J. (2002). A new occurrence of the reptile trackway McGhee G.R. Jr. (2013). When the Invasion of Land Failed: Notalacerta missouriensis from western Indiana. Journal of The Legacy of the Devonian Extinctions. 317 pp. Columbia Vertebrate Paleontology, 22: 89A. University Press, New York. Moore W.D. (1873). On footprints in the Carboniferous rocks of McGhee G.R. Jr. (2018). Carboniferous Giants and Mass Extinction: western Pennsylvania. American Journal of Science, 5: 292-293. The Late Paleozoic Ice Age World. 304 pp. Columbia University Mossman D.J. & Grantham R.G. (1996). A recently discovered Press, New York. amphibian trackway (Dromillopus quadrifidus) at Joggins, McKeever P.J. & Haubold H. (1996). Reclassification of vertebrate Nova Scotia. Canadian Journal of Earth Sciences, 33: 710-714. trackways from the Permian of Scotland and related forms from Mossman D.J. & Grantham R.G. (2000). Vertebrate trackways Arizona and Germany. Journal of Paleontology, 70: 1011-1022. in the Parrsboro Formation (upper Carboniferous) at Rams Meade L.E., Jones A.S. & Butler R.J. (2016). A revision of tetrapod Head, Cumberland County, Nova Scotia. Atlantic Geology, footprints from the late Carboniferous of the West Midlands, 35: 186-196. UK. PeerJ, 4: e2718. Mossman D.J. & Place C.H. (1989). Early Permian fossil vertebrate Melchor R.N. & Sarjeant W.A.S. (2004). Small amphibian and footprints and their stratigraphic setting in megacyclic sequence reptile footprints from the Permian Carapacha Basin, Argentina. II red beds, Prim Point, Prince Edward Island. Canadian Journal Ichnos, 11: 1-22. of Earth Sciences, 26: 591-605. Meyer R.C. (1999). Helical burrows as a paleoclimate Mudge B.F. (1874). Recent discoveries of fossil footprints in Kansas. response: Daemonelix by Palaeocastor. Palaeogeography, Kansas Academy of Science Transactions, 2: 7-9. Palaeoclimatology, Palaeoecology, 147: 291-298. Mujal E., Fortuny J., Oms O., Bolet A., Galobart À. & Anadón P. Michel L.A., Tabor N.J., Montañez I.P., Schmitz M.D. & Davydov (2016a). Palaeoenvironmental reconstruction and early Permian V.I. (2015). Chronostratigraphy and paleoclimatology of ichnoassemblage from the NE Iberian Peninsula (Pyrenean the Lodève Basin, France: Evidence for a pan-tropical Basin). Geological Magazine, 153: 578-600. aridification event across the Carboniferous-Permian boundary. Mujal E., Fortuny J., Pérez-Cano J., Dinarès-Turell J., Ibáñez-Insa J., Palaeogeography, Palaeoclimatology, Palaeoecology, 430: Oms O., Vila I., Bolet A. & Anadón P. (2017). Integrated multi- 118-131. stratigraphic study of the Coll de Terrers late Permian-Early Mietto P., Muscio G. and Venturini C. (1985). Impronte di tetrapodi Triassic continental succession from the Catalan Pyrenees (NE nei terreni Carboniferi delle Alpi Carniche. Gortania, 7: 59-74. Iberian Peninsula): A geologic reference record for equatorial Milan J., Klein H., Voigt S. & Stemmerik L. (2016). First record Pangaea. Global and Planetary Change, 159: 46-60. of tetrapod footprints from the Carboniferous Mesters Vig Mujal E., Gretter N., Ronchi A., López-Gómez J., Falconnet J., Diez Formation in East Greenland. Bulletin of the Geological Society J.B., De la Horra R., Bolet A., Oms O., Arche A., Barrenechea of Denmark, 64: 69-76. J.F., Steyer J-S. & Fortuny J. (2016b). Constraining the Permian/ Miller M.F., Hasiotis S.T., Babcock L.E., Isbell J.L. & Collinson Triassic transition in continental environments: Stratigraphic J.W. (2001). Tetrapod and large burrows of uncertain origin and paleontological record from the Catalan Pyrenees (NE in Triassic high paleolatitude floodplain deposits, Antarctica. Iberian Peninsula). Palaeogeography, Palaeoclimatology, Palaios, 16: 218-232. Palaeoecology, 445: 18-37. Milner A.C. (1994). A Carboniferous reptile footprint from the Müller A.H. (1962). Zur Ichnologie, Taxiologie und Ökologie Somerset Coalfield.Proceedings of the Geologists’ Association, fossiler Tiere, Teil I. Freiberger Forschungs-Hefte C, 151: 5-30. 105: 313-315. Munk W. & Sues H.D. (1993). Gut contents of Parasaurus Milner A.R. (1987). The Westphalian tetrapod fauna; some aspects (Pareiasauria) and Protorosaurus (Archosauromorpha) from of its geography and ecology. Journal of the Geological Society the Kupferschiefer (Upper Permian) of Hessen, Germany. of London, 144: 495-506. Paläontologische Zeitschrift, 67: 169-176. Milner A.R. (1990). The radiations of temnospondyl amphibians. Newell N.D., Rigby J.K., Driggs A., Boyd D.W. & Stehli F.G. In Taylor P.D. & Larwood G.P. (eds), Major Evolutionary (1976). Permian reef complex, Tunisia. Geology Studies, 23: Radiations. Systematics Association Special Volume 42: 321- 75-112. 349. Niedermayr G. & Scheriau-Niedermayr E. (1980). Eine Minter N.J., Buatois L.A., Mángano M.G., Davies N.S., Gibling Tetrapodenfährte aus dem Unter-Rotliegend von Kötschach in M.R. & Labandeira C. (2016). The establishment of continental den westlichen Gailtaler Alpen, Kärnten – Österreich. Annalen ecosystems. In Mángano M.G. & Buatois L.A. (eds), The des Naturhistorischen Museums Wien, 83: 259-264. Trace-Fossil Record of Major Evolutionary Events. New York, Niedźwiedzki G., Narkiewicz M. & Szrek P. (2014). Middle Springer Verlag, Topics in Geobiology, 39: 205-324. Devonian invertebrate trace trace fossils from the marginal Minter N.J., Krainer K., Lucas S.G., Braddy S.J. & Hunt A.P. marine carbonates of the Zachełmie tetrapod tracksite, Holy (2007). Palaeoecology of an early Permian playa lake trace fossil Cross Mountains, Poland. Bulletin of Geosciences, 89: 593-606. assemblage from Castle Peak, Texas, USA. Palaeogeography, Niedźwiedzki G., Szrek P., Narkiewicz K., Narkiewicz M. & Palaeoclimatology, Palaeoecology, 246: 390-423. Ahlberg P. E. (2010). Tetrapod trackways from the early Middle Mitchell H.R. (1931). Fossil footprints from the Pennsylvanian of Devonian period of Poland. Nature, 463: 43-48. Ohio. Ohio Journal of Science, 31: 500-504. Olive S., Ahlberg P.E., Pernegre V.N., Poty E., Steurbart É. & Mitchell H.R. (1933). Notes on another Pennsylvanian footprint Clément G. (2016). New discoveries of tetrapods (ichthyostegid- from Ohio. Ohio Journal of Science, 33: 48-49. like and whatcheeriid-like) in the Fammenian of Strud and Modesto S.P., Lamb A.J. & Reisz R.R. (2014). The captorhinid Becco (Belgium). Palaeontology, 2016: 1-14. reptile Captorhinikos valensis from the lower Permian Vale Olson E.C. (1975). Vertebrates and some problems of Permo- Formation of Texas, and the evolution of herbivory in eureptiles. Carboniferous geochronology. In Cys J.M. & Toomey D.F Journal of Vertebrate Paleontology, 34: 291-302. (eds), Permian Exploration, Boundaries, and Stratigraphy. West Modesto S.P., Scott D.M., MacDougall M.J., Sues H-D., Evans Texas Geological Society and Permian Basin Section SEPM D.C. & Reisz R.R. (2015). The oldest parareptile and the Publication, 75-65: 98-103. S.G. Lucas - Ichnology and Paleozoic tetrapods 263

Olson E. & Bolles K. (1975). Permo-Carboniferous fresh water scavenging among terrestrial vertebrates. Journal of Vertebrate burrows. Fieldiana Geology, 33: 271-290. Paleontology, 26:1021-1023. O’Sullivan M.J., Cooper M.A., MacCarthy I.A.J. & Forbes W.H. Retallack G.J. (2011). Woodland hypothesis for Devonian tetrapod (1986). The paleoenviroment and deformation of Beaconites- evolution. Journal of Geology, 119: 235-258. like burrows in the Old Red Sandstone at Gortabinna, SW Retallack G.J., Metzger C.A., Greaver T., Jahren A.H., Smith Ireland. Journal of the Geological Society of London, 143: R.M.H. & Sheldon N.D. (2006). Middle-late Permian mass 897-906. extinction on land. Geological Society of America Bulletin, Pabst W. (1908). Die Tierfährten in dem Rotliegenden ‘Deutschlands’. 118: 1398-1411. Nova Acta Leopoldina, 89: 316-481. Roelants K., Gower D.J., Wilkinson M.L., Loader S.P. & Biju Panchen A.L. & Smithson T.R. (1988). The relationships of the S.D. (2007). Global patterns of diversification in the history of earliest tetrapods. In Benton M.J. (ed.), The Phylogeny And modern amphibians. Proceedings of the National Academy of Classification Of The Tetrapods Volume 1: Amphibians, Sciences, 104: 887-892. Reptiles, Birds. Oxford, Clarendon Press: 1-32. Rogers D.A. (1990). Probable tetrapod tracks rediscovered in the Patterson R.P. (1971). Fossil trackways from the Upper Pennsylvanian Devonian of N Scotland. Journal of the Geological Society of Monogahela Formation in southeastern Ohio. Earth Science, London, 147: 746-748. 24: 181-185. Romer A.S. (1935). Early history of Texas redbeds vertebrates. Peabody F.E. (1948). Reptile and amphibian trackways from Geological Society of America Bulletin, 46: 1597-1658. the Moenkopi Formation of Arizona and Utah. University Romer A.S. (1941). Earliest land vertebrates of this continent. of California Publications Bulletins of the Department of Science, 94: 279. Geological Sciences, 27: 295-468. Romer A.S. (1956). The early evolution of land vertebrates. Peabody F.E. (1959). Trackways of living and fossil salamanders. Proceedings of the American Philosophical Society, 100: 157-167. University of California Publications in Zoology, 63: 1-72. Romer A.S. (1957). The appendicular skeleton of the Permian Pemberton S.G., Sarjeant W.A.S. & Torrens H.S. (1996). Footsteps embolomerous amphibian Archeria. Contributions of the before the Flood: The first scientific report of vertebrate Museum of Geology of the University of Michigan, 13: 103-159. footprints. Ichnos, 4: 321-323. Romer A.S. & Olson E.C. (1954). Aestivation by Permian lungfish. Peppers R.A. (1996). Palynological correlation of major Brevoria, 30: 1-8. Pennsylvanian (middle and upper Carboniferous) Romer A.S. & Price L.I. (1940). Review of the Pelycosauria. chronostratigraphic boundaries in the Illinois and other coal Geological Society of America Special Paper, 28: 1-538. basins. Geological Society of America Memoir, 188: 1-111. Rowland S.M. (2017). Trackway of a sideways-walking basal Peppers R.A. (1997). Palynology of the Lost Branch Formation of tetrapod in the Pennsylvanian Manakacha Formation in Grand Kansas-new insights on the major floral transition at the Middle- Canyon National Park. Geological Society of America, Abstracts Upper Pennsylvanian boundary. Review of Palaeobotany and with Programs, 49: 6. Palynology, 98: 223-246. Rowland S.M. & Caputo M.V. (2018). Trackway of a sideways- Pfefferkorn H.W. & Thomson M.C. (1982). Changes in dominance walking basal tetrapod in the Pennsylvanian Manakacha patterns in Upper Carboniferous plant-fossil assemblages. Formation of Grand Canyon National Park. Society of Vertebrate Geology, 10: 641-644. Paleontology, Abstracts of the 78th Annual Meeting: 206. Phillips T.L., Peppers R.A., Avcin M.J. & Laughnan P.F. (1974). Ruta M., Coates M.I. & Quicke D.L.J. (2003). Early tetrapod Fossil plants and coal: Patterns of change in Pennsylvanian relationships revisited. Biological Reviews, 78: 251-345. coal swamps of the Illinois Basin. Science, 184: 1367-1369. Rygel M.C., Calder J.H., Gibling M.R., Gingras M.L. & Melrose Pickerill R.K. (1994). Nomenclature and taxonomy of invertebrate C.S. (2006). Tournaisian forested wetlands in the Horton Group trace fossils. In Donovan S.K. (ed.), The Palaeobiology of Trace of Atlantic Canada. Geological Society of America Special Fossils. The Johns Hopkins University Press, Baltimore: 3-42. Paper, 399: 103-106. Pierce S.E., Hutchinson J.R. & Clack J.A. (2013). Historical Sahney S. & Benton M.J. (2008). Recovery from the most profound perspectives on the evolution of tetrapodomorph movement. mass extinction of all time. Proceedings of the Royal Society Integrative and Comparative Biology, 53: 209-223. B, 275: 759-765. Powell M.G. (2005). Climatic basis for sluggish macroevolution Sahney S., Benton M.J. & Falcon-Lang H.J. (2010). Rainforest during the late Paleozoic. Geology, 33: 381-384. collapse triggered Carboniferous tetrapod diversification in Qvarnström M., Szrek P., Ahlberg P.E. & Niedźwiedzki G. (2018). Euramerica. Geology, 38: 1079-1082. Non-marine palaeoenvironment associated to the earliest Sallan L.C. & Coates M.I. (2010). End-Devonian extinction and a tetrapod tracks. Nature Scientific Reports, 8: 1074. bottleneck in the early evolution of modern jawed vertebrates. Ramezani J. & Bowring S.A. (2018). Advances in numerical Proceedings of the National Academy of Science, 107: 10131- calibration of the Permian timescale based on radioisotopic 10135. geochronology. Geological Society, London, Special San Mauro D. (2010). A multilocus timescale for the origin of Publications, 450: 51-60. extant amphibians. Molecular and Phylogenetic Evolution, Reisz R.R. (1986). Pelycosauria. Encyclopedia of Paleoherpetology, 2010: 554-561. 17A: 1-102. Sarjeant W.A.S. (1974). A history and bibliography of the study of Reisz R.R. (1990). Geology and paleontology of the Garnett fossil vertebrate footprints in the British Isles. Palaeogeography, quarry. In Cunningham C. & Maples C.G. (eds), 1990 Society Palaeoclimatology, Palaecology, 16: 265-375. of Vertebrate Paleontology Upper Paleozoic of Eastern Kansas Sarjeant W.A.S. & Mossman D.J. (1978). Vertebrate footprints from Excursion Guidebook. Kansas Geological Survey Open-file the Carboniferous sediments of Nova Scotia: A historical review Report, 90-24: 43-48. and description of newly discovered forms. Palaeogeography, Reisz R.R. & Fröbisch J. (2014). The oldest caseid synapsid from the Paleoclimatology, Palaeoecology, 23: 279-306. Late Pennsylvanian of Kansas, and the evolution of herbivory Scarboro D.D. & Tucker M.E. (1995). Amphibian footprints in terrestrial vertebrates. PLoS ONE, 9: e94518. from the mid-Carboniferous of Northumberland, England: Reisz R.R. & Sues H.-D. (2000). Herbivory in late Paleozoic and Sedimentological context, preservation and significance. Triassic terrestrial vertebrates. In Sues H-D. (ed.), Evolution Palaeogeography, Palaeoclimatology, Palaeoecology, 113: of Herbivory in Terrestrial Vertebrates: Perspectives From the 335-349. Fossil Record. Cambridge University Press, Cambridge: 9-41. Schaeffer B. (1941). The morphological and functional evolution of Reisz R.R. & Tsuji L.A. (2006). An articulated skeleton of the tarsus in amphibians and reptiles. Bulletin of the American Varanops with bite marks: The oldest known evidence of Museum of Natural History, 78: 395-472. 264 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Schmidt H. (1956). Die grosse Bochumer Oberkarbon-Fährte. caseasaurian synapsids from Europe. Acta Palaeontologica Paläontologische Zeitschrift, 30: 199-206. Polonica, 61: 597-616. Schmidt H. (1959). Die Cornberger Fährten im Rahmen der Stanley S.D. & Luczaj J.A. (2014). Earth System History. Fourth Vierfüßler-Entwicklung. Abhandlungen des Hessischen edition. 587 pp. W.H. Freeman, New York. Landesamtes für Bodenforschung, 28: 1-137. Stanley S.M. & Powell M.G. (2003). Depressed rates of origination Schmidt H. (1963). Herpetichnus erneri n. sp., eine Reptilfährte aus and extinction during the late Paleozoic ice age: A new state for dem westfälischen Oberkarbon. Paläontologische Zeitschrift, the global marine ecosystem. Geology, 31: 877-880. 37: 179-184. Sternberg C.M. (1933). Carboniferous tracks from Nova Scotia. Schneck W.M. & Fritz W.J. (1985). An amphibian trackway Geological Society of America Bulletin, 44: 951-964. (Cincosaurus cobbi) from the Lower Pennsylvanian Steyer S. (2012). Earth Before Dinosaurs. 182 pp. Indiana University (“Pottsville”) of Lookout Mountain, Georgia: A first occurrence. Press, Bloomington and Indianapolis. Journal of Paleontology, 59: 1243-1250. Stimson M., Calder J., MacRae A., Hebert B., Hanley J., Owen V. Schneider J.W., Lucas S.G., Scholze F., Voigt S., Marchetti L., & Reid D. (2013). New discoveries of tetrapod-bearing fossil Klein H., Opluštil S., Werneburg R., Golubev V.K., Barrick J.E., forests at Joggins, Nova Scotia: Implications for tetrapod Nemyrovska T., Ronchi A., Day M. O., Silantiev V.V., Rößler entombment and ecological persistence. New Mexico Museum R., Saber H., Linnemann U., Zharinov V. & Shen S. (2020). Late of Natural History and Science Bulletin, 60: 425. Paleozoic-early Mesozoic continental biostratigraphy - links to Stimson M., Lucas S.G. & Melanson G. (2012). The smallest known the Standard Global Chronostratigraphic Scale. Paleoworld. tetrapod footprints: Batrachichnus salamandroides from the doi.org/10.1016/j.palwor.2019.09.001. Carboniferous of Joggins, Nova Scotia, Canada. Ichnos, 19: Schneider J., Schamaev M. I. & Walter H. (1992). Paläobiogeographie 127-140. und Stratigraphie von Tetrapoden- und Arthropoden-Fährten aus Storm L., Needle M.D., Smith C.J., Fillmore D.L., Szajna M., dem paralischen Oberkarbon und Perm (Gzhel/Assel) des Donez Simpson E.L. & Lucas S.G. (2010). Large vertebrate burrow Bassins. Freiberger Forschungshefte, C445: 104-121. from the Upper Mississippian Mauch Chunk Formation, eastern Schoch R.R. (2013). The evolution of major temnospondyl clades: Pennsylvania, USA. Palaeogeography, Palaeoclimatology, An inclusive phylogenetic analysis. Journal of Systematic Palaeoecology, 298: 341-347. Palaeontology, 11: 673-705. Stössel I. (1995). The discovery of a new Devonian tetrapod Schoch R.R. (2014). Amphibian Evolution: The Life of Early Land trackway in SW Ireland. Journal of the Geological Society of Vertebrates. 276 pp. Wiley Blackwell, Chichester. London, 152: 407-413. Schoch R.R. & Milner A.R. (2014). Temnospondyli I. Handbook Stössel I., Williams E.A. & Higgs K.T. (2016). Ichnology and of Paleoherpetology, 3A2: 1-150. depositional environments of the Middle Devonian Valentia Schoewe W.H. (1956). Geographic locations and stratigraphic Island tetrapod trackways, south-west Ireland. Palaeogeography, horizon of Pennsylvanian fossil footprints discovered in Palaeoclimatology, Palaeoecology, 462: 16-40. Osage County, Kansas by B. F. Mudge in 1873. Journal of Sues H-D. & Reisz R.R. (1998). Origins and early evolution of Paleontology, 30: 389-405. herbivory in tetrapods. Tree, 13: 141-145. Schultze H-P. (2013). The paleoenvironment at the transition from Sukhanov V.B. (1968). Symmetrical locomotion of terrestrial piscine to tetrapod sarcopterygians. New Mexico Museum of vertebrates and some features of movement of lower tetrapods. Natural History and Science Bulletin, 60: 373-397. 186 pp. Nauka, Leningrad. Seilacher A. (1964). Biogenic sedimentary structures. In Imbrie J. Sundberg F.A., Bennington J.B., Wizevich M.C. & Bambach R.K. & Newell N. (eds), Approaches to Paleoecology. Wiley, New (1990). Upper Carboniferous (Namurian) amphibian trackways York: 296-316. from the Bluefield Formation, West Virginia, USA. Ichnos, 1: Seilacher A. (1967). Bathymetry of trace fossils. Marine Geology, 111-124. 5: 413-428. Surkov M.V., Benton M.J., Twitchett R.J., Tverdokhlebov V.P. Sennikov A.G. & Golubev V.K. (2017). Sequence of Permian & Newell A.J. (2007). First occurrence of footprints of large tetrapod faunas of Eastern Europe and the Permian-Triassic therapsids from the upper Permian of European Russia. ecological crisis. Paleontological Journal, 51: 600-611. Palaeontology, 50: 641-652. Shubin N.H., Daeschler E.B. & Coates M.I. (2004). The early Swartz B. (2012). A marine stem-tetrapod from the Devonian of evolution of the tetrapod humerus. Science, 304: 90-93. western North America. PLoS ONE, 7: e33683. Smith R.M.H. (1987). Helical burrow casts of therapsid origin from Tanner L.H. & Lucas S.G. (2009). Tetrapod trace fossils from the Beaufort Group (Permian) of South Africa. Paleogeography, lowermost Jurassic strata of the Moenave Formation, northern Palaeoclimatology, Palaeoecology, 60: 155-170. Arizona, USA. Volumina Jurassica, 6: 133-141. Smith R.M.H. (1993). Sedimentology and ichnology of floodplain Toepelman W.C. & Rodeck H.G. (1936). Footprints in late Paleozoic red paleosurfaces in the Beaufort Group (late Permian), Karoo beds near Boulder, Colorado. Journal of Paleontology, 10: 660-662. sequence, South Africa. Palaios, 8: 339-357. Trewin N.H. & McNamara K.J. (1995). Arthropods invade the Smith R.M.H., Sidor C.A., Tabor N.J. & Steyer J.S. (2015). land: Trace fossils and palaeoenvironments of the Tumblagooda Sedimentology and vertebrate taphonomy of the Moradi Sandstone (?late Silurian) of Kalbarri, western Australia. Formation of northern Niger: A Permian wet desert in the Transactions of the Royal Society of Edinburgh Earth Science, tropics of Pangaea. Palaeogeography, Palaeoclimatology, 85: 177-210. Palaeoecology, 440: 128-141. Tsuji L.A., Müller J. & Reisz R.R. (2010). Microleter mckinzieorum Smithson T.R., Wood S.P., Marshall J.E.A. & Clack J.A. (2012). gen. et sp,. nov. from the lower Permian of Oklahoma: The Earliest Carboniferous tetrapod and arthropod faunas from, basalmost parareptile from Laurasia. Journal of Systematic Scotland populate Romer’s gap. Proceedings of the National Palaeontology, 8: 245-255. Academy of Science, 109: 4532-4537. Tsuji L.A., Müller J. & Reisz R.R. (2012). Anatomy of Emeroleter Soler-Gijón R. & Moratalla J.J. (2001). Fish and tetrapod trace levis and the phylogeny of the nycteroleter parareptiles. Journal fossils from the Upper Carboniferous of Puertollano, Spain. of Vertebrate Paleontology, 32: 45-67. Palaeogeography, Palaeoclimatology, Palaeoecology, 171: 1-28. Turek V. (1989). Fish and amphibian trace fossils from Westphalian Spamer E.E. (1984). Paleontology in the Grand Canyon of Arizona: sediments of Bohemia. Palaeontology, 32: 623-643. 125 years of lessons and enigmas from the Late Precambrian Tverdokhlebov V.P., Tverdokhlebova G.I., Benton M.J. & to the present. The Mosasaur, 2: 45-128. Storrs G.W. (1997). First record of footprints of terrestrial Spindler F., Falconnet J. & Fröbisch J. (2016). Callibrachion and vertebrates from the Upper Permian of the Cis-Urals, Russia. Datheosaurus, two historical and previously mistaken basal Palaeontology, 40: 157-166. S.G. Lucas - Ichnology and Paleozoic tetrapods 265

Van Allen H.E.K., Calder J.H. & Hunt A.P. (2005). The trackway Warren A.W. & Wakefield N.A. (1972). Trackways of tetrapod record of a tetrapod community in a walchian conifer forest vertebrates from the Upper Devonian of Victoria, Australia. from the Permo-Carboniferous of Nova Scotia. New Mexico Nature, 238: 469-470. Museum of Natural History and Science Bulletin, 30: 322-332. Werneburg R. (1986). Die Stegocephalen (Amphibia) der Voigt S. (2005). Die Tetrapodenichnofauna des kontinentalen Goldlauterer Schichten (Unterrotliegendes, Perm) des Oberkarbon und Perm im Thüringer Wald - Ichnotaxonomie, Thüringer Waldes, Teil I: Apateon flagrifer (Whitt.). Freiberger Paläoökologie und Biostratigraphie. 305 pp. Cuvillier Verlag, Forschungshefte C, 410: 88-101. Göttingen. Werneburg R. (1988). Die Stegocephalen der Goldlauterer Schichten Voigt S. (2012). Tetrapodenfährten. Schriftenreihe der Deutschen (Unterrotliegendes, Unterperm), Teil II: Apateon kontheri n. sp., Gesellschaft für Geowissenschaften, 61: 92-106. Melanerpeton eisfeldi n. sp. des Thüringer Waldes und andere. Voigt S., Berman D.S & Henrici A.C. (2007). First well-established Freiberger Forschungshefte C, 427: 7-23. track-trackmaker association of Paleozoic tetrapods based on Werneburg R. (1989). Die Amphibienfauna der Manebacher Ichniotherium trackways and diadectid skeletons from the lower Schichten (Unterrotliegendes, Unterperm) des Thüringer Permian of Germany. Journal of Vertebrate Paleontology, 27: Waldes. Veröffentlichungen des Naturhistorischen Museums 553-570. Schleusingen, 4: 55-68. Voigt S. & Ganzelewski M. (2010). Toward the origin of amniotes: Werneburg R., Schneider J.W. & Lucas S.G. (2013). The Diadectomorph and synapsid footprints from the early late dissorophoid Milnererpeton huberi (Temnospondyli) from Carboniferous of Germany. Acta Palaeontologica Polonica, the Late Pennsylvanian Kinney Brick Quarry in New Mexico 55: 57-72. restudied - paleontology, paleoenvironment, and age. New Voigt S. & Haubold H. (2015). Permian tetrapod footprints from Mexico Museum of Natural History and Science Bulletin, 59: the Spanish Pyrenees. Palaeogeography, Palaeoclimatology, 349-370. Palaeoecology, 417: 112-120. Willard B. & Cleaves A.B. (1930). Amphibian footprints from the Voigt S., Hminna A., Saber H., Schneider J. W. & Klein H. (2010). Pennsylvanian of the Narrangasett basin. Geological Society of Tetrapod footprints from the uppermost level of the Permian America Bulletin, 41: 321-327. Ikakern Formation (Argana Basin, Western High Atlas, Williams E.A., Sergeev S.A., Stössel I. & Ford M. (1997). An Morocco). Journal of African Earth Sciences, 57: 470-478. Eifelian U-Pb zircon date for the Enagh Tuff Bed from the Voigt S., Lagnaoui A., Hminna A., Saber H. & Schneider J.W. Old Red Sandstone of the Munster Basin in NW Iveragh, SW (2011a). Revisional notes on the Permian tetrapod ichnofauna Ireland. Journal of the Geological Society of London, 154: from the Tiddas Basin, central Morocco. Palaeogeography, 189-193. Palaeoclimatology, Palaeoecology, 302: 474-483. Wolansky D. (1952). Ein neuer Fährtenfund im Karbon des Voigt S. & Lucas S.G. (2012). Late Paleozoic Diadectidae Ruhrbezirks. Paläontologische Zeitschrift, 30: 199-206. (Cotylosauria: Diadectomorpha) of New Mexico and their Woodworth J.B. (1900). Vertebrate footprints on Carboniferous potential preference for inland habitats. Geological Society of shales of Plainville, Masachusetts. Geological Society of America, Abstracts with Programs, 44: 90. America Bulletin, 11: 449-454. Voigt S. & Lucas S.G. (2013). Carboniferous-Permian tetrapod Wu Q., Ramezani J., Zhang H., Wang T., Yuan D., Mu L., Zhang footprint biochronozonation. New Mexico Museum of Natural Y., Li X. & Shen S. (2017). Calibrating the Guadalupian History and Science Bulletin, 60: 444. Series (middle Permian) of south China. Palaeogeography, Voigt S. & Lucas S.G. (2015a). Permian tetrapod ichnodiversity of Palaeoclimatology, Palaeoecology, 466: 361-372. the Prehistoric Trackways National Monument (south-central Young G.C. (2006). Biostratigraphic and biogeographic context New Mexico, U.S.A.). New Mexico Museum of Natural History for tetrapod origins during the Devonian: Australian evidence. and Science Bulletin, 65: 153-167. Alcheringa Special Issue, 1: 409-428. Voigt S. & Lucas S.G. (2015b). On a diverse tetrapod ichnofauna Zhang P., Zhou H., Chen Y., Liu Y. & Qu L. (2005). Mitogenomic from early Permian red beds in San Miguel County, north- perspectives on the origin and phylogeny of living amphibians. central New Mexico. New Mexico Geological Society Systematic Biology, 54: 391-400. Guidebook, 2015: 241-252. Zheng Y., Peng R., Kuro-o M. & Zeng X. (2011). Exploring Voigt S. & Lucas S.G. (2017). Early Permian tetrapod footprints patterns and extent of bias in estimating divergence time from from central New Mexico. New Mexico Museum of Natural mitochondrial DNA sequence data in a particular lineage: A case History and Science Bulletin, 77: 333-352. study of salamanders (Order Caudata). Molecular Biology and Voigt S. & Lucas S.G. (2018). Outline of a Permian tetrapod Evolution, 28: 2521-2535. footprint ichnostratigraphy. Geological Society, London, Special Zug G.R., Vitt L.J. & Caldwell L.J. (2001). Herpetology. 630 pp. Publications, 450. DOI 10.1144/SP450.10. Academic Press, San Diego. Voigt S. & Marchetti L. (2014). Über eine neue Fundstelle mit Tetrapodenfährten im Perm von Kötschach-Mauthen (Gailtaler Alpen, Kärnten). Berichte der Geologischen Bundesanstalt, 105: 27-29. Voigt S., Niedźwiedzki G., Raczyński P., Mastalerz K. & Ptaszyński T. (2012). Early Permian tetrapod ichnofauna from the Intra-Sudetic Basin, SW Poland. Palaeogeography, Palaeoclimatology, Palaeoecology, 313-314: 173-180. Voigt S., Saber H., Schneider J.W., Hmich D. & Hminna A. (2011b). Late Carboniferous - Early Permian tetrapod ichnofauna from the Khenifra Basin, central Morocco. Geobios, 44: 399-407. Voorhies M.R. (1975). Vertebrate burrows. In Frey R.W. (ed.), The Study of Trace Fossils: A Synthesis of Principles, Problems, and Manuscript received 19 October 2019 Procedures in Ichnology. Springer Verlag, New York: 325-350. Revised manuscript accepted 21 December 2019 Warren A. (1997). A tetrapod fauna from the Permian of the Sydney Published online 30 December 2019 Basin. Records of the Australian Museum, 49: 25-33. Editor Marco Balini 266 Bollettino della Società Paleontologica Italiana, 58 (3), 2019

Spencer G. Lucas is a stratigrapher and paleontologist who has been Curator of Geology and Paleontology at the New Mexico Museum of Natural History and Science (Albuquerque, New Mexico, USA) since 1988. He received a B. A. degree from the University of New Mexico (1976) and M. S. (1979) and Ph.D. (1984) degrees from Yale University. Lucas’s research has focused on biostratigraphic problems of the late Paleozoic, Mesozoic and early Cenozoic. Since 1992, he has been a major contributor to refinement of the Triassic timescale as a Voting Member of the IUGS Subcommission on Triassic Stratigraphy. He is also currently a voting member of the Permian Subcommission and the Carboniferous Subcommission. He has undertaken extensive field research in the American West, Kazakstan, China, Mexico, Nicaragua and Costa Rica. Lucas has published 7 books and edited or co-edited more than 70 volumes. He has published more than 1000 scientific articles. In the mid-1990s, Lucas began to study tetrapod footprints and other vertebrate trace fossils, particularly of late Paleozoic and Triassic age.