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The Subeng tracks: stratigraphy, sedimentology and a digital archive of a historic Upper palaeosurface (lower ), Leribe, (southern Africa)

Emese M. Bordy, Miengah Abrahams & Lara Sciscio

E.M. Bordy, Department of Geological Sciences, University of Cape Town, University Avenue 13, ZA-7701 Cape Town, ; [email protected] M. Abrahams, Department of Geological Sciences, University of Cape Town, University Avenue 13, ZA-7701 Cape Town, South Africa; [email protected] L. Sciscio, Department of Geological Sciences, University of Cape Town, University Avenue 13, ZA-7701 Cape Town, South Africa; [email protected]

KEY WORDS - 3D digital model, dinosaur, cynodont, southern Africa, palaeoenvironment, trace .

ABSTRACT - Dinosaur vertebrate body and ichnofossils are relatively abundant in the Upper Triassic-Lower Elliot Formation (, ) in the main Karoo Basin in southern Africa. Herein we present the results of our sedimentological, stratigraphical and ichnological investigations at a historic ichnosite in NE Lesotho that is among the first documented vertebrate track- bearing palaeosurfaces in southern Gondwana. After decades of neglect, the Subeng ichnosite is restudied in this paper in light of the advances in ichnological methods and the formalised stratigraphy of the Stormberg Group. Documentation of this ichnosite was conducted using a mix of field-based sedimentological and ichnological methods and photogrammetry, which collectively allowed us to place the site within the lowermost Elliot Formation (Upper Triassic). Our detailed palaeoenvironmental reconstruction, based on palaeocurrent measurements and sedimentary facies analysis of the host rocks, suggests that this diverse Upper Triassic assemblage of vertebrate ichnofossils, which is an integral part of the history of life on land just before the end-Triassic mass extinction event, formed near a shallow oxbow lake or drying up watering hole on the of a meandering river system. This water source attracted numerous bipedal and quadrupedal animals as attested by the presence of tridactyl, tetradactyl and pentadactyl tracks on the palaeosurface. We have also produced a photogrammetric digital 3D model (available online) of the Subeng ichnosite to serve as a digital replica and archive for further ichnological study. This digital documentation is important not only for the preservation of this rapidly eroding palaeosurface (situated in an active streambed), but also for the provision of a visually stimulating tool for community outreach and science education in rural African communities.

RIASSUNTO - [Le impronte di vertebrati di Subeng: stratigrafia, sedimentologia ed archivio digitale di una paleosuperficie del Triassico Superiore di interesse storico (parte inferiore della Formazione di Elliot), Leribe, Lesotho (Africa meridionale)] - Resti fossili, impronte e piste di dinosauro sono relativamente abbondanti nella Formazione di Elliot (Triassico Superiore-Giurassico Inferiore; Gruppo di Stormberg, Supergruppo del Karoo; Africa meridionale). In questo studio presentiamo i risultati di ricerche sedimentologiche, stratigrafiche ed icnologiche sull’icnosito di Subeng (coordinate GPS 28°49’23.53”S, 28°4’29.82”E). Si tratta di un icnosito di fondamentale importanza situato a nordest del villaggio di Hlotse (Distretto di Leribe) in Lesotho, rappresentato da una paleosuperficie attribuibile alla parte inferiore della Formazione di Elliot. Questa superficie è esposta ed attivamente erosa dall’azione del torrente Subeng. Dal punto di vista storico, l’icnosito di Subeng rappresenta una delle prime superfici ad impronte di vertebrati ad essere state documentate in Africa meridionale. Tuttavia, dopo la prima perizia nel 1955 ed il successivo studio nei primi anni ‘70, l’icnosito ha ricevuto poca attenzione. Le revisioni icnotassonomiche delle icniti di Subeng si sono concentrate su pochi calchi realizzati a partire da materiale originale. Pertanto, era necessario rivalutare l’icnosito di Subeng, specialmente alla luce degli avanzamenti metodologici in icnologia e dell’aggiornamento della stratigrafia del Gruppo di Stormberg. Lo studio dell’icnosito di Subeng è stato realizzato combinando metodi fotogrammetrici con metodi icnologici e sedimentologici tradizionali. Sulla base della sedimentologia e dei resti fossili di vertebrati, collochiamo l’icnosito di Subeng nel Triassico Superiore. Più precisamente, collochiamo l’icnosito nella porzione superiore della parte inferiore della principale unità arenitica della Formazione di Elliot, ed a meno di 15 metri dalla Formazione di Molteno. Viene fornita anche una dettagliata ricostruzione paleoambientale del sito, coadiuvata dalla misurazione delle paleocorrenti e dall’analisi di facies. Il primo approccio indica una corrente diretta approssimativamente verso E-NE, mentre il secondo indica che la paleosuperficie si colloca al culmine di una sequenza di fining upward, tipica dei fiumi a meandri. Questo contesto sedimentologico è tipico per una superficie ad impronte. La principale caratteristica icnologica dell’icnosito di Subeng è la presenza di prominenti impronte pentadattile, tetradattile e tridattile. È importante sottolineare che tre piste sono presenti sulla superficie attualmente esposta, la più lunga delle quali è costituita da 14 grandi impronte pentadattile; queste indicano che l’autore della pista si muoveva verso sud. Due piste tetradattile indicano che due animali quadrupedi, possibilmente un esemplare adulto e uno giovane, camminavano uno a fianco all’altro verso est. Impronte tridattile di bipedi, sporadicamente distribuite sulla paleosuperficie, sono attribuite ad animali di dimensioni comparabili; queste non formano piste. Sui ripple marks asimmetrici e tra le fratture di disseccamento si osservano comunemente tracce di invertebrati, preservate come tane superficiali con parziale backfill. Sulla base delle caratteristiche sedimentologiche, osteologiche ed icnologiche, il paleoambiente viene interpretato come una lanca poco profonda oppure una pozza che fungeva da abbeveratoio, presente in un’ampia piana alluvionale di un sistema fluviale a meandri. Questa fonte d’acqua temporanea attirava numerosi animali bipedi e quadrupedi, sia erbivori (cinodonti e sauropodomorfi) che carnivori. Il modello fotogrammetrico 3D costituisce una durevole replica digitale dell’icnosito ed un archivio per futuri studi icnologici. Questa documentazione digitale è importante non solo per la preservazione della paleosuperficie (il moderno torrente Subeng la erode intensamente, causando una rapida ed inevitabile perdita di dettaglio icnologico) ma anche per fornire alle comunità rurali africane uno strumento visuale stimolante per l’educazione scientifica. In questa zona persiste una cronica mancanza di risorse per l’educazione scientifica. Questo fenomeno si traduce in un limitato accesso a risorse quali materiale educativo, economico o gratuito, e musei di scienze naturali. Ci auguriamo che il modello digitale renda la superficie di Subeng più visibile sia alla scala locale che globale, e che permetta alla comunità locale di esibire l’importanza scientifica del sito durante le loro attività geoturistiche.

ISSN 0375-7633 doi:10.4435/BSPI.2017.12 182 Bollettino della Società Paleontologica Italiana, 56 (2), 2017

INTRODUCTION sedimentary rocks suitable for the palaeoenvironmental reconstruction and stratigraphical analysis (Figs 1-3). The Subeng ichnosite in the Upper Triassic portion The Subeng ichnotaxa mentioned in the literature (e.g., of the lower Elliot Formation exposes a variety of Ellenberger, 1955, 1970, 1972; Ellenberger & Ellenberger, trace fossils of and as well as 1958) are summarized in Fig. 2 and Tab. 1. The ichnosite

Fig. 1 - Geographical and stratigraphical positions of the footprint-bearing surface. a) Geological map of the main Karoo Basin in southern Africa with an inset showing the spatial distribution of the Upper Triassic to Lower Jurassic Elliot Formation. b) Geological context of the Subeng ichnosite situated in the lowermost Elliot Formation, about 6.6 km N-NE of Hlotse, Leribe District, Lesotho (GPS 28°49’23.53”S, 28°4’29.82”E). White lines are the village tracks. c) Generalized sedimentary log of the Elliot Formation just east of the Subeng ichnosite. In the log, dots indicate and dashed lines show (clay- and siltstones). In b and c, LEF and UEF refer to the lower and upper Elliot formations, respectively. E.M. Bordy et alii - Upper Triassic vertebrate tracks and trackways at Subeng in Lesotho, southern Africa 183 is located in the Subeng (Seobeng) stream bed (GPS material that does not have the detail visible in the 28°49’23.53”S, 28° 4’29.82”E), about 6.6 km N-NE of actual specimen. Furthermore, the potential human Hlotse (Leribe District, Lesotho; Fig. 1). error associated with mislabelled or miscataloged The Subeng ichnosite is among the first documented casts and drawings (see below) introduces additional vertebrate footprint palaeosurfaces in southern Africa, complications. Furthermore, ichnological assessment having been briefly described and sketched for the first (that includes but goes beyond sound ichnotaxonomy) time by its discoverer, Paul Ellenberger in 1955 (“dalle de aimed at the understanding of a trackmaker’s behaviour, Subeng”) (Fig. 2). Subsequently, individual Subeng tracks in the palaeoenvironmental milieu, is impossible without and trackways have been documented by Ellenberger & the accurate documentation of the track- and trackway- Ellenberger (1958) and Ellenberger (1970, 1972) (Fig. bearing palaeosurfaces in their original field context. Such 2; Tab. 1), but a complete illustration of all the tracks on contextual analysis is necessary for morphometric and the surface was never produced. More recently, D’Orazi shape-difference analyses, and biomechanics. Porchetti & Nicosia (2007) described the ichnotaxonomy The aims of this paper are: 1) provide a long of some of the Subeng ichnites (e.g., based on the direct overdue palaeoenvironmental context for the Subeng examination track replicas deposited by P. Ellenberger site; 2) revise its position within the southern Africa in the Laboratoire de Paléontologie of the University of stratigraphy; 3) generate a digital 3D model of this historic Montpellier II). It is noteworthy that just like Olsen & footprint-bearing palaeosurface, from which a distinctive Galton (1984) and Lockley et al. (2006), D’Orazi Porchetti ichnotype (holotype) had been identified. The latter will & Nicosia (2007) too have only studied the Lesotho tracks aid further work related to the ichnotaxonomy of the from significant but non-primary material (i.e., only tracks and trackways, the behaviour and biomechanics drawings in the former study and plaster cast replicas in of the various trackmakers, and the Subeng community- the latter two studies). While we genuinely acknowledge driven geotourism. The community is actively and the absolute value of these ichnotaxonomic revisions, enthusiastically involved in geotouristic promotion of the in our view, their study materials are problematic for site, but not in the preservation of the palaeosurface due ichnotaxonomic work, because they rely on incomplete to lack of resources, and more specifically because it is

Fig. 2 - Outline drawings of the Subeng tracks. Six ichnotaxa were described from the site and illustrated in Ellenberger (1970, 1972); see Tab. 1 for details. a) Redrawing of the first illustration of the Subeng ichnosite (“dalle de Subeng”) published by Ellenberger in 1955. Redrawings of the first illustrations of the Subeng trackways published by Ellenberger & Ellenberger (1958) are as follows: b) Trackway E, c) Trackway D, d) Trackway I and e) Trackway H. Note that the original trackway labels of Ellenberger & Ellenberger (1958) are kept for ease of cross-reference. 184 Bollettino della Società Paleontologica Italiana, 56 (2), 2017

Ichnotaxa Primary reference (figure/plate Current Trackmaker animal Illustration Original name numbers) ichnogenera

Quadrupedal or - Fig. 52 A in Ellenberger, 1970 Pentasauropus facultative biped: ?pseudosuchian; - Trackway I in Ellenberger & Pentasauropus incredibilis (D’Orazi ?theromorph; Ellenberger, 1958 (Ellenberger, 1970) Porchetti & ?large amphibian; Nicosia, 2007) ?prosauropod; - Planche I and XIV in ?dicynodont Ellenberger, 1972

Quadrupedal: degenerate chirotherian; - Fig. 51 in Ellenberger, 1970 Invalid, ?pseudosuchian; a undertrack - small ?sauropod; - Trackway H in Ellenberger & Deuterosauropodus minor ?sauropodomorpha Ellenberger, 1958 (Ellenberger, 1970) (D’Orazi Quadrupedal: Porchetti & degenerate chirotherian; - Planche XIII in Ellenberger, Nicosia, 2007) ?pseudosuchian; a small ?sauropod; 1972 ?sauropodomorpha

Grallator Fig. 44 in Ellenberger, 1970 Deuterotrisauropus socialis Tridactyl bipedal: (Ellenberger, 1970) (Olsen & ?saurischians Planche XIII in Ellenberger, 1972 Galton, 1984)

indeterminate Mafatrisauropus errans Tridactyl bipedal: Fig. 45 in Ellenberger, 1970 (Ellenberger, 1970) (Olsen & ?saurischians Galton, 1984)

- Fig. 49 A Ellenberger, 1970 Pseudotrisauropus indeterminate subengensis (Ellenberger, Tridactyl bipedal: - Trackway E in Ellenberger & 1970) or Psilotrisauropus (Olsen & ?saurischians Ellenberger, 1958 subengensis (Ellenberger, Galton, 1984) 1972) - Planche XII in Ellenberger, 1972

- Fig. 49 B in Ellenberger, 1970 indeterminate - Trackway D in Ellenberger & Pseudotrisauropus dieterleni Tridactyl bipedal: Ellenberger, 1958 (Ellenberger, 1970) (Olsen & ?saurischians Galton, 1984) - Planche XII and XIII in Ellenber- ger, 1972

Tab. 1 - Summary of the Subeng ichnotaxa identified and depicted by Ellenberger (1970, 1972). All scale bars are equal to 5 cm. situated in an active riverbed in a subtropical, seasonally- GEOLOGICAL BACKGROUND flowing Subeng stream. We used the 3D model in this work (Supplementary data at https://dx.doi.org/10.6084/ The Subeng ichnosite is surrounded by clastic m9.figshare.4737535) to document our observations of sedimentary rocks of the Upper Triassic-Lower Jurassic the physical parametres of the tracks and trackways as Stormberg Group, which forms part of the Karoo well as their spatial relationship. The current contribution Supergroup in southern Africa and contains the Molteno, forms part of our ongoing research program dedicated to Elliot and Clarens formations (Fig. 1). The Molteno the stratigraphic revision of vertebrate track distribution Formation is a -bearing, wedge-shaped siliciclastic in the Upper Triassic-Lower Jurassic Stormberg Group unit with a maximum thickness of about 600 m in the south of southern Africa. and minimum thickness of ≤ 10 m in the north (Johnson et E.M. Bordy et alii - Upper Triassic vertebrate tracks and trackways at Subeng in Lesotho, southern Africa 185 al., 2006). occurred in broad, shallow braided (“Belesodon leribeensis”) (Kitching & Raath, 1984). rivers and extensive under cool and wet The latter taxon has been restudied by Battail (2005) palaeoclimatic conditions as suggested by its abundant who assigned it to a large traversodont cynodont, and assemblages (Anderson Scalenodontoides macrodontes (Crompton & Ellenberger, et al., 1998). While bone fossils are extremely rare (to 1957), which is exclusive to the lower Elliot Formation date, only fossil fishes have been found),Grallator -like in southern Africa. Finally, vertebrate ichnofossils are not footprints, a possible chelonian track and a tail mark only limited to the Elliot Formation near Subeng, because of unknown vertebrate have been recorded from two small tetradactyl and pentadactyl tracks and one tetradactyl localities in the Formation (Raath et al., 1990; Raath, bipedal trackway have been apparently recovered from 1996; Anderson et al., 1998). the Lower Jurassic (see tracks M and The Elliot Formation is a succession of red L and trackway G in Ellenberger & Ellenberger, 1958). and mudrock that reaches a maximum thickness of about 550 m in the south, near Elliot and thins progressively to the north, where the minimum METHODS thickness is < 50 m (Bordy et al., 2004a, b; Bordy & Eriksson, 2015). It has an unconformable lower contact Field evidence was collected in the form of with the underlying Molteno and gradual, conformable macroscopic observations of the host sedimentary contact with overlying Clarens formations (Bordy et al., rocks in the immediate vicinity as well as few kilometre 2005). Based on sedimentary and geochemical data, the radius around the Subeng ichnosite. We applied standard deposition occurred under increasing aridity, initially field techniques by recording the following: lithology, in high-energy, mixed-load meandering rivers and geometry (including thickness and lateral continuity), laterally continuous floodplains, and then in ephemeral primary and secondary sedimentary structures, grain fluvial systems with flash floods (Bordy et al., 2004a, b; size variations in vertical and lateral directions, colour, Sciscio & Bordy, 2016). Although the age of the Elliot and density and spacing of ichnofossils. Formation is generally accepted to be Upper Triassic We also obtained 15 palaeocurrent measurements to Lower Jurassic (Olsen & Galton, 1984; Lucas & from the host rock of the Subeng ichnosite, which in Hancox, 2001; Knoll, 2004), unfortunately, the absolute combination with other sedimentological observations, age dates for the Elliot Formation are lacking, and our can assist in reconstructing the mean flow direction geochronological dating of the detrital zircon samples and magnitude of the palaeocurrents (Tucker, 2011). In collected from the ichnosite are not yet available. our study, we only used the most reliable palaeocurrent The Elliot Formation therefore straddles the Triassic- indicators, namely the foresets of trough cross-bedded Jurassic boundary (Fig. 1c) and contains a rich terrestrial sandstones, because other measurements, such as crest vertebrate body and record from before and orientation of ripple marks, are known to deviate from after the end-Triassic biotic crisis (Bordy & Eriksson, the regional (and locally strongest) flow trends (Tucker, 2015; Sciscio et al., in press). 2011; Bordy et al., 2004c). The palaeocurrent data The Lower Jurassic Clarens Formation represents required no additional corrections, because the regional the last stages of in the main Karoo Basin dip of the strata ranges between 5° to 10°. The results before the outpouring the voluminous continental flood are presented in a rose diagram in Fig. 3d. basalts and intrusion of the associated subvolcanic We also generated a photogrammetric digital 3D complexes about 183±1 Ma ago (Karoo Large Igneous model of the Subeng ichnosite, largely using the Province - Duncan et al., 1997; Johnson et al., 2006). photogrammetric technique explained in Mallison & The deposition of the yellowish-brown, fine- to medium- Wings (2014). Here, we only highlight some steps that grained Clarens (previously Cave) sandstones occurred we adopted. Over 300 photographs were taken using a in a wet desert environment that was associated with Canon EOS 1200D (Focal length 28 mm, 5184 x 3456 playa lakes, sheet floods and ephemeral streams. In pixel resolution) were automatically stitched together spite of the overall arid conditions, the palaeobotanical, in the Agisoft Photoscan (standard version 1.1.4) osteological and ichnological records show that the software. We manually excluded photographs that were Clarens desert was capable of supporting a relatively of low quality or contained foreign objects (e.g., foot diverse ecosystem of , conchostracans, , of photographer) from the input data set, because these lungfish, bony fish, synapsids and dinosaurs (Kitching introduce errors and reduce the overall quality of the & Raath, 1984; Bordy, 2008). model. Agisoft provides an automatic image quality In addition to the ichnofossils (Tab. 1, Figs 1-3), filter, which examines the sharpness level of the most vertebrate fossil remains have also been found in the focused point in a photograph, and all photographs lower Elliot Formation in the Subeng (aka Leribe- with a quality less than below a certain threshold were Subeng) area, which is the type locality of Basutodon removed from further processing. Subsequently, from ferox (Huene, 1932) that has been identified from a large the photographs, a dense point cloud was generated. tooth (type specimen: NMB R.610). This tooth and its The latter is scale-less, therefore an object of known taxonomic affinities have not been well-studied, and it length (e.g., photo with a scale bar on the surface) was may possibly belong to a theropod or an archosauriform used to calibrate the model. Lastly, an “orthomosaic” (rauisuchian archosaur) taxa (Knoll, 2004). Other bone digital elevation model was applied. Three-dimensional fossils from the vicinity of the ichnosite have been model as well as all the photographs used for generating assigned to sauropodomorphs ( sp.) the model can be downloaded from https://dx.doi. (Haughton, 1924), “pseudosuchians” and cynodonts org/10.6084/m9.figshare.4737535. 186 Bollettino della Società Paleontologica Italiana, 56 (2), 2017

RESULTS which is the regional palaeoflow direction in Elliot Formation (Bordy et al., 2004c, d). The low consistency Stratigraphy and sedimentology of the ichnosite ratio of the palaeoflow data does not match that of Based on our field investigation of the local geology, meandering rivers but this discrepancy may be related to the Subeng ichnosite is located < 15 m above basal the small size of the outcrop where foreset measurements contact of the Elliot Formation, within the upper portion were obtained (< 700 m2). The orientation of sandstone of the lowermost major sandstone unit in the lower outcrops at the Subeng ichnosite did not allow the 3D Elliot Formation (Fig. 1b-c). Locally, the basal contact assessment of sandstone architecture, but nearby sites at of the Elliot Formation is about 1575-1590 m above sea a similar elevation have revealed well-developed lateral level, below which the coarse- to very coarse-grained accretion surfaces indicative of meandering rivers (see sandstones of the Molteno Formation are exposed (N of Bordy et al., 2004d, fig. 4A). In summary, the dominance the ichnosite in the Caledon River) both in Lesotho and of trough cross-bedded, medium-grained sandstones, and neighbouring South Africa (Fig. 1b). The upper contact pedogenic alteration-free, red and light purple mudstones, of the Elliot Formation is about 1710-1740 m above sea as well as the lack of diagnostic upper Elliot Formation level in the region, above which the conspicuous, beige to facies (e.g., carbonate nodule conglomerates, clast-rich white, fine to medium-grained sandstones of the Clarens sandstones; Bordy et al., 2004b, c) collectively argue Formation occur as cliff forming features (SE and E of for the Subeng ichnosite as being part of lower Elliot the ichnosite; Fig. 1b-c). The contact of the lower and Formation. upper Elliot Formation is difficult to identify here due to the lack of semi-continuous outcrops of these two, Ichnological e-archive - the digital 3D model of the sedimentologically contrasting units (Bordy et al., 2004b, Subeng ichnosite d). However, based on limited outcrop information (e.g., In our field inspection of the Subeng ichnosite in 2003, grain size, sandstone architecture, pedogenic alteration) 2012, 2015 and 2016, we repeatedly noted that the original and the position of the geomorphological break along surface as described by Ellenberger in 1955 is no longer the slopes that are underlined by the Elliot Formation, it exposed to its fullest extent (compare Fig. 4a and c with is very tentatively positioned about 1620-1630 m above Fig. 4b and d). Furthermore, we noted that the remaining sea level (Fig. 1b-c). northern part of the surface is being severely eroded by In our assessment, the coarse- to very-coarse grained, stream action (Fig. 5), which has already visibly removed tabular, sheet-like, and mostly planar cross-bedded important ichnological detail (e.g., positive epirelief of sandstones of the Molteno Formation cannot be identified traces, expulsion rims around digits, depth at the ichnosite. Conversely, the most common rocks in variation of tracks). In order to preserve the ichnological the immediate vicinity of the ichnosite are about 40-50 detail on the remaining palaeosurface, we generated a cm thick, medium-grained, strongly trough cross-bedded digital 3D model of the currently exposed surface (Figs sandstones (Fig. 3a-c) that are found in the lower part of 5-6). On the current surface, we were able to detect 33 a well-developed upward-fining and thinning succession, pes tracks, of which 16 are pentadactyl, 8 are tetradactyl which is < 10 m in thickness (Fig. 1c). Localized and 10 are tridactyl. Fourteen of pentadactyl tracks form -clast conglomerates are confined to < 50 cm the longest trackway, showing a locomotion direction wide and < 20 cm thick lenses (Fig. 3f). Towards the top towards south (Figs 5-6). A partially preserved, second of the about 4-5 m thick succession, the sandstones are pentadactyl trackway comprises two pentadactyl track medium- to fine-grained, 10-30 cm thick, massive to ripple (Figs 5-6). The tetradactyl tracks make up two trackways cross-laminated. In addition to the abundant vertebrate and show movement from west to east (Figs 5-7). The ichnites, the upper bedding planes expose abundant tridactyl tracks (Figs 5-6, 8) do not form any trackways asymmetrical ripple marks and desiccation cracks as well on the currently exposed surface (compare to Fig. 2a). as rare invertebrate traces (Fig. 3e-f). The crest orientation of the ripple marks is E-W and shows flow direction to the Subeng tracks and potential trackmakers N. The sandstones are directly overlain by red and light Pentadactyl tracks - The most spectacular track at purple mudstones (Fig. 3g) that lack pedogenic alteration the Subeng ichnosite is the pentadactyl, crescent-shaped features and appear to be unfossiliferous in the immediate Pentasauropus incredibilis (Figs 2, 4-6; Tabs 1-2), which vicinity of the ichnosite. was discovered by Ellenberger in the 1950s and named The locally measured mean palaeoflow direction is in 1970 (Ellenberger, 1970). Because it has recently been from about WSW to about ENE at the Subeng ichnosite, reviewed ichnotaxonomically by D’Orazi Porchetti &

Fig. 3 - Sedimentological context of the Subeng ichnosite. Trough cross-bedded sandstone beds (St - a, b & c) are common, especially in the lower part of the upward-fining succession, which contains the track-bearing palaeosurface (see Fig. 1c). a) Trough cross-bedded sandstone (St) in map view. b) Outline of troughs and palaeoflow direction (compare to a). c) Trough cross-bedded sandstone in mainly side view. d) Rose diagram of the trough cross-bedded, medium-grained sandstone beds indicate palaeoflow to ~ENE. Chief sedimentary characteristics of the footprint-bearing palaeosurface in the Subeng stream are listed as follows in e-f. e) Asymmetrical ripple marks (Sr - palaeoflow direction to the north) that are locally bioturbated by shallow, partially backfilled invertebrate traces. f) Desiccation cracks, which initially formed in a thin mud layer and were filled with sand subsequently. The casts of the desiccation cracks adhere to the top of massive sandstone (Sm) that is underlain by massive, mudstone-clast conglomerates (Gcm). g) Light red to purple, massive mudstone (Fm) directly overlies the track- bearing palaeosurface and are conspicuously free of pedogenic alteration features. Note the bulk of the exposure shows the light yellow-pink recent, unconsolidated sediments of the Subeng stream. E.M. Bordy et alii - Upper Triassic vertebrate tracks and trackways at Subeng in Lesotho, southern Africa 187 188 Bollettino della Società Paleontologica Italiana, 56 (2), 2017

Fig. 4 - Changes in the size and relief of the Subeng palaeosurface over 40 years in the Subeng stream. a) Photograph from Planche XIV in Ellenberger (1972), modified after Ellenberg (1972). b) Photograph taken by Fabien Knoll in 2012. The upper (southern) part of the Subeng palaeosurface as was seen in the 1970s is now completely obscured (middle area between the concrete bridge and foreground) by recent stream sediments and water. Note the difference in size and distribution of the large boulders in the streambed, which is an indication of the occasional extremely high energy levels of the Subeng stream. c-d) Photographs of the northern part of the Subeng palaeosurface taken over 40 years apart. c) Photograph from Planche I in Ellenberger (1972). d) Part of the photogrammetric image of the same part of the surface. Note the well-developed expulsion rims around the digit impressions in the Pentasauropus tracks in the pre-1972 image, which, have been planated by streambed erosion by 2016. Also see Fig. 4b. E.M. Bordy et alii - Upper Triassic vertebrate tracks and trackways at Subeng in Lesotho, southern Africa 189

Fig. 5 - Ortophoto and interpretive outline drawing of the tridactyl, tetradactyl and pentadactyl ichnites at the Subeng ichnosite. a) Detailed overview of the tracks on a single 21 m2 sandstone slab derived from the 3D digital model of the surface (see https://dx.doi.org/10.6084/ m9.figshare.4737535). b) Individual tracks, some of which make up the three trackways (labelled P, T1 and T2; see Fig. 6), are colour coded for clarity: red for pentadactyl tracks; green for tetradactyl tracks and blue for tridactyl tracks. The latter tracks do not form part of any trackway. Note the well-developed current ripple marks (palaeoflow to south) and desiccation cracks in the southwestern and northwestern part of the surface, respectively. 190 Bollettino della Società Paleontologica Italiana, 56 (2), 2017

Nicosia (2007), the full description of Pentasauropus worldwide known, with the oldest having been described will not be repeated here. It should suffice to say that at from the Lower Triassic Wiory Formation (Poland), where the Subeng ichnosite, the type locality for Pentasauropus, these ichnites were labelled as cf. Therapsipus by Klein these unique, pentadactyl tracks currently form a about & Niedzwiedzki (2012) and attributed them to therapsids. 3.7 m long trackway (compare to Fig. 2a) comprised of Other occurrences of the similar pentadactyl ichnites are 14 tracks, three of which are only partially preserved (Figs mentioned by Lockley & Hunt (1995) and Hunt-Foster 5-6; Tab. 2). The average width of the complete tracks is 37 et al. (2017) from the Late Triassic Chinle Group of Utah cm with strides ranging from 47 to 76 cm and an average (USA). D’Orazi Porchetti & Nicosia (2007) also argue pace angulation of 50° (Fig. 6; Tab. 2). Each pair of tracks that dicynodonts are the most plausible trackmakers (e.g., 2-3, 4-5; Fig. 6) is orientated in the same direction. of Pentasauropus due to the close match between the On the preservation scale of Belvedere & Farlow (2016), tracks and their skeletal autopodia. Body fossils of large Pentasauropus at Subeng would fall into the quadruped therapsids have been reported from stratigraphically grade 1 to 2 categories. equivalent strata (i.e., the Upper Triassic lower Elliot These pentadactyl, crescent-shaped, mostly Formation) in southern Africa, and from Subeng in unguligrade or digitigrade and occasionally plantigrade particular (e.g., Battail, 2005), but we prefer to be cautious tracks of manus and pes (with rounded sole if preserved) and only discuss the identity of the trackmaker after our have been attributed to a variety of trackmakers investigation of all six different Pentasauropus localities (e.g., prosauropod, pseudosuchian, theromorph, large in the lower Elliot Formation (i.e., , Seaka-Falatsa, amphibian, dicynodont - e.g., Ellenberger & Ellenberger, Morobong, Maphutseng-Majakaneng, Phuthiatsana). 1958; Ellenberger, 1972). Pentasauropus-like tracks are In particular, we wish to: 1) probe how therapsids, a

Fig. 6 - Sketches and associated measurements of the three trackways at the Subeng ichnosite. a) Trackways P comprises pentadactyl tracks (Pentasauropus incredibilis). b-c) Trackways T1 and T2 comprise tetradactyl tracks (Deuterosauropodopus minor). Stride/pace measurements are indicated in centimetres. TL: trackway length; TW: trackway width; PA: pace angulation. E.M. Bordy et alii - Upper Triassic vertebrate tracks and trackways at Subeng in Lesotho, southern Africa 191

Trackway P (pentadactyl) Trackway T1 (tetradactyl) Track # W Pace Track # FL W FL/W Pes to manus distance 1 38 1a 25 20 1.3 1a to 1b 41 2 37 2 to 5 71 1b 9 3 30 2a 28 23 1.2 2a to 2b 40 4 38 4 to 7 2b 11 5 38 3a 6 37 6 to 9 73 4a 24 21 1.1 7 29 Trackway T2 (tetradactyl) 8 34 8 to 11 70 Track # FL W FL/W Pes to manus distance 9 38 1a 33 25 1.3 1a to 1b 49 10 36 10 to 13 73 1b 13 11 30 2a 31 23 1.3 2a to 2b 45 12 39 2b 12 13 40 3a 27 24 1.1 3a to 3b 40 14 37 3b 13 Average: 35.7 4a

Tridactyl tracks Track # FL (DL III) DL II DL IV W r FL/W r/w r/FL * 100 II^IV II^III III^IV 1 24 18 16 15 8 1.6 0.5 33 46 22 24 2 23 12 14 14 8.5 1.6 0.6 37 36 19 17 3 27 17 15 13 11 2.1 0.8 41 50 4 24 12 15 14 8 1.7 0.6 33 44 23 21 5 22 12 17 15 8.4 1.5 0.6 38 46 27 19 6 22 16 1.4 7 21 13 16 15 6.5 1.4 0.4 31 62 8 22 17 22 15 8 1.5 0.5 36 60 9 19 11 10 13 11 1.5 0.8 58 56 26 30 10 9.1 9.5 3.7 1.0 0.4 41 54 Average: 21 14 16 14 8 1.5 0.6 39 50 23 22

Tab. 2 - Measurements of the pentadactyl, tetradactyl and tridactyl tracks and trackways (P, T1, T2) at the Subeng ichnosite. All distance measurements are in centimetres; angles are in degrees. Grey blocks are for measurements that could not be determined due to e.g., absence of digit impressions. Abbreviations: FL - track length; W - track width; r - length of rear of phalangeal part of foot; DL - digit length; II^III, III^IV, II^IV - interdigital divarication angles of respective digits. taxonomic group generally considered to be short-toed tetradactyl, plantigrade, asymmetrical tracks with high plantigrades, could make mostly unguligrade or (semi-) heteropody (Figs 5-7), suggesting that the impressions digitigrade tracks throughout Lesotho, especially in the were most likely made by quadrupeds. Trackway T1 (Fig. light of the documented South African therapsid tracks 6b) is about 2.5 m long and 54 cm wide and is comprised (e.g., De Beer, 1986; MacRae, 1990; De Klerk, 2002); of six tracks with an average pes track length and width 2) how the southern African Pentasauropus tracks of 26 and 21 cm, respectively, and an average manus compare to those in Poland and USA; 3) fully consider the width of 10 cm (Tab. 2). The pes tracks have a slight relatively rich osteological record of the Elliot Formation inward rotation but the manus rotation is unclear, because in search for the oversized “palaeo-Cinderella” (see generally the manus tracks are very poorly preserved. “Cinderella syndrome” of Lockley, 1998) that could fit Trackway T1 has an average stride length of about 1.5 into the gigantic Seaka footprint (formerly known as cm and a high average pace angulation of 152° (Figs Tetrasauropus gigas, Ellenberger, 1970; the humongous 5-6). Trackway T2 (Fig. 6c) is about 2.3 m long and 62 foot is about 70 cm long and about 55 cm wide). cm wide and consists of seven tracks with an average pes track length and width of 30 and 24 cm, respectively, Tetradactyl tracks - The two trackways, running and an average manus width of 13 cm (Tab. 2). The pes parallel to each other and nearly perpendicular to the and manus stride in T2 average about 1.3 m long with Pentasauropus trackway at Subeng, are made up of high average pace angulations of 139° and 157° for the 192 Bollettino della Società Paleontologica Italiana, 56 (2), 2017

Fig. 7 - Comparison of the various illustrations of the same Deuterosauropodopus minor ichnite on the Subeng palaeosurface. a) Planche XIII in Ellenberger (1972). b) Fig. d in Ellenberger (1955). c) Track in trackway H in Ellenberger & Ellenberger (1958). d) Fig. 51 in Ellenberger (1970). e) Tracing of photo in f) taken in this study (see track 1a in the T2 trackway in Figs 5-6). All scale bars are equal to 10 cm. pes and manus tracks, respectively (Figs 5-6). Tab. 2 and (Ellenberger, 1970, fig. 40),Paratetrasauropus seakensis Figs 5-6 also show that while the overall morphology of (Ellenberger, 1972, fig. 37),Pseudotetrasauropus elegans the tracks in the two tetradactyl trackways is similar, the (Ellenberger, 1970, fig. 30), P. francisci (Ellenberger, wider trackway T2 comprises larger (longer and wider) 1970, fig. 32) and P. curtus (Ellenberger, 1972, fig. pes and wider manus impressions, and therefore it is 10B). The latter three are considered nomen dubium likely that the two trackways were made at the same time by D’Orazi Porchetti & Nicosia (2007). The further in- by the same kind, but different size quadrupedal animals depth assessment of the tracks made by putative basal (i.e., an adult and a juvenile), possibly moving adjacent sauropodomorphs at Subeng is not possible before the to one another towards east. On the preservation scale of conclusion of (or at least further advance in) our ongoing Belvedere & Farlow (2016), tetradactyl tracks at Subeng ichnological research in Lesotho. In this case, it requires would fall into the quadruped grade 1 category. the assessment of the morphological resemblance among The tetradactyl tracks at the Subeng were assigned all the above listed ichnites after the full documentation to Deuterosauropodopus minor by Ellenberger (1970, of their field context. 1972). Although, he referred this ichnotaxa to a basal sauropodomorph trackmaker, D’Orazi Porchetti & Tridactyl tracks - Ongoing erosion at the Subeng Nicosia (2007), who assessed a single cast of D. minor ichnosite has most severely affected the tridactyl (specimen LES 053), concluded that D. minor is invalid bipedal tracks (Figs 2, 4-5) since their first in depth and the specimen is an undertrack of a chirotherian [cf. documentation by Ellenberger (1970, 1972; Tab. 1). Of Brachychirotherium (Beurlen, 1950)]. This is a curious the remaining tridactyl tracks, some are preserved only case, because in the explanation of D’Orazi Porchetti as digit impressions, others as connected digit traces and & Nicosia (2007, p. 221), the inventory number in the some merged with inflated proximal regions (Figs 5, 8). Ellenberger specimen labels with the abbreviation LES Quantitative analysis of the tracks (Tab. 2) suggests that (Lesotho) ought to correspond to the original number they are morphometrically similar to each other, with an in the Ellenberger (1970) ichnotaxa list. In Ellenberger average length and width of 21 and 14 cm, respectively (1970), figure 53A, B, C depicts Pentasauropus erectus, (average L/W ratio of 1.5). Anomalous to these averages and figure 53D showsParatrisauropus equester, none of is track G10 (Figs 5, 8), which is half of the average length which are similar to D. minor mentioned from Subeng and two-thirds of the average width, suggesting that is only by Ellenberger (1970, 1972) or to LES 053 specimen partially reserved track. The average of the divarication shown in D’Orazi Porchetti & Nicosia (2007, fig. 21). angles is 50° and have an average mesaxonic index of Irrespective of this confusion, we agree with Ellenberger’s 0.6 (i.e., anterior triangle L/W as in Lockley, 2009), with view that D. minor at Subeng is more probably made by digit III being the longest digit, projecting on average a basal sauropodomorph, because we note the similarity 39% relative to the tip of digits II and IV (Tab. 2, Fig. 8). of the footprint morphology and position of manus in all Track G9 is the exception projecting at 58%; the excessive Deuterosauropodopus ichnites (Ellenberger, 1970, figs projection is most likely due to the drag of the digit. The 50A-B, 51A-B) to some other Lesotho ichnites that are digits are straight, with slight divergent curvature along linked, though not exclusively, to basal sauropodomorphs. their extent, and often end in pointed tips (e.g., G1, G2, These morphologically similar ichnites are Sauropodopus G9, G10 in Fig. 8). None of the tracks preserve additional

Fig. 8 - Photographs and interpretive outlines of the individual tridactyl tracks currently exposed at the Subeng ichnosite. Tracks G1, G5 and G6 (a, b, j) were shown on the first sketch of the surface (Ellenberger, 1955) and were identified as Pseudotrisauropus dieterlini in Ellenberger (1970, 1972). Note the resemblance of tracks G2 and G10 (g, h) to P. dieterlini. Tracks G7, G8, G9 and G10 (d, e, f, h) are further to the east, outside the area documented in Ellenberger (1955). Tracks G2, G3 and G4 (g, i, c) are not shown on the first sketch of the surface. Note that tracks G4, G7, G8 and G9 (c, d, e, f) contain desiccation cracks of different sizes. For measurements of the individual tracks, see Tab. 2. All scale bars are equal to 5 cm. E.M. Bordy et alii - Upper Triassic vertebrate tracks and trackways at Subeng in Lesotho, southern Africa 193 194 Bollettino della Società Paleontologica Italiana, 56 (2), 2017 morphological features such as digital pad impressions DISCUSSION or hallux impressions. Desiccation cracks are preserved within numerous tracks (e.g., G7, G8, G9 in Fig. 8). On Stratigraphy and palaeoenvironment the preservation scale of Belvedere & Farlow (2016), Our sedimentological and lithostratigraphical tridactyl tracks at Subeng would fall into the biped grades observations show that the Subeng ichnosite is located 0 to 1 categories. about 5 m above the regional contact of the Elliot These observations are similar to diagnostic features Formation with the underlying Molteno Formation of the ichnogenus Grallator (Hitchcock, 1858), which despite initial assertion by Ellenberger et al. (1967) forms part of the continuum of Grallator-Anchisauripus- and Ellenberger (1970) that the ichnite-bearing host Eubrontes defined by Olsen et al. (1988), and which are rocks belong to the Molteno Formation (Fig. 1B). commonly attributed to theropod dinosaurs. Grallator This stratigraphic reinterpretation is in line with the ichnogenera are described as small (length < 15 cm; reassessment of the stratigraphic position of the Lesotho FL/W ratio of 2), tulip-shaped footprints, where III cynodonts from the Molteno to the lower Elliot Formation digit is the longest and shows excessive projection, by Turner (1972) and supported, among others, by Battail but never exceeding 50% of total footprint length. (2005). Discrepancies in Ellenberger’s stratigraphic Outer digit divarication angles are narrow (i.e., can be interpretation of the Stormberg Group have also been as narrow as 10-30°). Grallator is distinguished from addressed in Olsen & Galton (1984). Given that the similar looking ichnogenera Carmelopodus, which lacks accepted age of the lower Elliot Formation is Late Triassic metatarsophalangeal pads (Lockley et al., 1998) and throughout southern Africa (e.g., Olsen & Galton, 1984; Jialingpus (Zhen et al., 1983), which has an inflated Lucas & Hancox, 2001), the age of the Subeng ichnosite proximal area with digit IV metatarsophalangeal pad is most probably Late Triassic (Norian-Rhaetian), and being twice as large as in Grallator (Xing et al., 2014). thus falls into the upper part of Brachychirotherium (sensu While no pads are observed in the remaining tridactyl stricto) tetrapod footprint biochron of Klein & Lucas tracks at the Subeng ichnosite, the tracks are more (2010). This proposed age can be confirmed by refining likely to be Grallator-like, because there is no digit IV of the chronostratigraphy of the Elliot Formation and proximal enlargement in the tracks as would be expected determining the absolute age the ichnosite in particular for Jialingpus. From the osteological record of southern (work in progress by authors). Africa, there are two possible theropod trackmakers Based on the local sedimentological and ichnological of Grallator-like tracks: 1) the smaller observations, the palaeosurface at the Subeng ichnosite rhodesiensis (Raath, 1969) and 2) the larger represents a snapshot of a shallow oxbow lake in the Late regent (Yates & Raath, 2005). Given the average length Triassic. The site possibly served as a watering hole for a of the tracks being about 21 cm, the biped Coelophysis variety of bipedal, quadrupedal and potentially facultative rhodesiensis is deemed more likely as the trackmaker of bipedal vertebrates that roamed the broad fluvial floodplain the tridactyl tracks at the Subeng ichnosite. (Fig. 9). The latter was dissected by both abandoned Since their first description by Ellenberger (1970, channels and active, high-energy meandering rivers that 1972), the tridactyl ichnospecies (Tab. 1) from the Subeng migrated laterally (Bordy et al., 2004d; fig. 4A) across ichnosite have only been revised to some degree by the floodplain, and formed part of the drainage pattern Olsen & Galton (1984). The latter authors have assigned on the NE directed regional palaeoslope (Bordy et al., Deuterotrisauropus socialis to the Grallator ichnogenera, 2004c, d). At the time of track formation, the oxbow lake and grouped the Pseudotrisauropus (Psilotrisauropus) still contained some water (that was occasionally moving; subengensis; Pseudotrisauropus dieterleni and Fig. 9), however its shallow nature and shrinking surface Mafatrisauropus errans into an indeterminate category area are demonstrated by the multitude of small ripple of taxa with the remark that if “better material” would marks and desiccation cracks that cover the palaeosurface. become available, these ichnotaxa may in fact turn out to be distinct and valid ichnogenera. Of the remaining tridactyl Ichnological e-archive - the digital 3D model of the tracks, only two, G1 and G5, are marked in Ellenberger’s Subeng ichnosite (1955) depiction of the Subeng ichnosite. Ellenberger The photogrammetric digital 3D model of this classified both of these tracks as Pseudotrisauropus historic track-bearing palaeosurface at Subeng is now dieterlini (Tabs 1-2), which Olsen & Galton (1984) in the public domain (https://dx.doi.org/10.6084/ classified as intermediate ichnotaxa. Both G1 and G5 m9.figshare.4737535). Digital 3D models of ichnosites show distinct, narrow, curved digits with a “webbed” are essentially resilient, accurate replicas as well as outline as drawn by Ellenberger (1970, 1972; Tab. 1). archives of weighty palaeosurfaces, which are usually Given our aforementioned observations, we suggest that difficult to conserve for various legislative, bureaucratic, a) P. dieterlini should be synonymised with ichnogenus infrastructural, etc. reasons. Housing structures to protect Grallator, and, b) the features distinguishing P. dieterlini tracksites (e.g., Moyeni in Lesotho, Glen Rose in USA) from Grallator are simply extra-morphological resulting do not ensure their preservation and may limit scientific from variable preservational conditions, such as the work. At Glen Rose, despite the enclosure, loss of detail moisture- and clay-content of the substrate, and track- and an overall deterioration of the tracksite is observed substrate interaction, amongst others. The other tridactyl (Bates et al., 2009; Adams et al., 2010). At Moyeni, the ichnogenera that Ellenberger (1970, 1972) described at structure is robust, but the interior design is so basic that the Subeng ichnosite (Tab. 1) cannot be observed and ichnological work on the palaeosurface is rather difficult therefore their ichnological validity or synonymy with (e.g., light conditions being suboptimal for high quality other ichnogenera cannot be established here. photographs). E.M. Bordy et alii - Upper Triassic vertebrate tracks and trackways at Subeng in Lesotho, southern Africa 195

Fig. 9 - Palaeoenvironmental reconstruction of the Subeng palaeosurface. This Late Triassic snapshot captures the depositional dynamics in the fluvio-lacustrine lower Elliot Formation and the generation of tracks around oxbow lakes by moderate size (some juvenile) sauropodomorphs, small bipedal theropod dinosaurs as well as large herbivorous cynodonts (therapsids). Outlines of the theropod and traversodont cynodont adapted from Olsen (1988). Numbers refer to: 1 - pentadactyl trackways: Pentasauropus incredibilis; 2 - tetradactyl trackways: Deuterosauropodopus minor; 3 - tridactyl trackways: Deuterotrisauropus socialis; 4 - tridactyl trackways: Psilotrisauropus subengensis. See text and Tab. 1 for details regarding ichnotaxonomy. Artwork by Emese M. Bordy.

In addition to creating a durable replica, digital models no disposable income. It is our wish therefore that this 3D can be evaluated, restudied remotely or re-assessed when model and its description will contribute to the aspiration new methods and analytical techniques become available. of the local community to share the message from the past Digital 3D models of ichnosites also allow for the more with their visitors and to highlight the need to protect the quantitative analysis of measurements and comparisons of Subeng ichnosite for future generations. results (Petti et al., 2008; Bates et al., 2009). Furthermore, digital models offer an abundance of possibilities to assess the locomotor dynamics of trackmakers as well CONCLUSION as formation and preservation of tracks (Bates et al., 2009). For example, due to the dynamic nature of 3D The sedimentary properties and the close stratigraphical models that allow high magnification and examination of position of the Subeng ichnosite relative to the lower tracks from any perspective, Razzolini et al. (2014) were contact of the Elliot Formation allow its placement able to quantitatively link intra-track morphology to the into the lowermost part of the lower Elliot Formation, sedimentology of the track-bearing substrate. which is generally accepted to be Upper Triassic (Olsen It is hoped that in addition to scientific work, the & Galton, 1984; Lucas & Hancox, 2001; Knoll, 2004). digital 3D model of the Subeng ichnosite will serve as The Subeng ichnosite and associated host rocks near a visually stimulating tool for community outreach and Leribe (NW Lesotho) record the dynamics of the fluvio- science education. This is especially true where in rural lacustrine depositional environment and its biota in the African communities access to natural science museums Late Triassic, including short-term palaeoenvironmental and other educational materials is very restricted or changes (e.g., abandonment of meandering river lacking. It is noteworthy that in the past few years, the channels, wet and dry cycles resulting in desiccation local Basotho community who lives near the Subeng cracks). The 21 m2 sandstone palaeosurface is dominated ichnosite has made great effort to showcase their by the presence of several tridactyl, tetradactyl and geoscientific heritage. For example, two small African pentadactyl ichnites. The former are single tracks, and huts (Fig. 10) were built and are maintained as a tiny the others mainly make up two tetradactyl trackways visitors’ centre adjacent to the ichnosite. The huts, which and one pentadactyl trackway. Our palaeoenvironmental only contain a visitors’ book and a few fragmentary fossil reconstruction demonstrates that these tracks were made bones from the Elliot Formation, and their maintenance around an ancient oxbow lake on a broad floodplain on are a major achievement for the on-the-ground custodians which meandering rivers migrated laterally and flowed of the Subeng ichnosite, who unfortunately have little or towards east-north-east. The animals which made the 196 Bollettino della Società Paleontologica Italiana, 56 (2), 2017

showcasing the geoscientific heritage of Lesotho on a local and global scale.

SUPPLEMENTARY DATA ARCHIVING

All the Supplementary data of this work are available at the Figshare https://dx.doi.org/10.6084/ m9.figshare.4737535.

ACKNOWLEDGEMENTS

This work is a contribution to the call for papers arising from the Fourth International Congress on Ichnology “Ichnia 2016 - Ichnology for the 21st century: (palaeo)biological traces towards sustainable development”, held in Idanha-a-Nova (Portugal), 6-9 May 2016. For this call and for the excellently managed event, we are indebted to the organizers of Ichnia 2016. We thank our colleagues and friends, Dr Fabien Knoll and Dr Blair McPhee for their guidance regarding the of the Elliot Formation and their genuine interest in our work. The local community around the Subeng ichnosite is acknowledged for their hospitality, cheerful companionship, enthusiastic site cleaning efforts and interest in our work. We are also very grateful to the Editors, Carlos Neto de Carvalho and Andrea Baucon, as well as reviewers Matteo Belvedere, Martin G. Lockley and Gerard Gierlínski for their assistance in improving this manuscript. This work was supported by the National Research Foundation of South Africa Competitive Programme for Rated Researches [NRF Grant number 93544 Bordy]. LS and MA are recipients of postdoctoral and postgraduate funding, respectively, from the DST-NRF Centre of Excellence in Palaeosciences (CoE in Palaeosciences). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Opinions expressed and conclusions arrived at are those of the authors and are not necessarily to be attributed to the CoE in Palaeosciences or NRF CPRR. We receive no financial benefit from this research. Fig. 10 - The Subeng ichnosite is currently managed on a volunteer basis, with extremely limited and private resources, by the Basotho community living in the vicinity of the site. In spite of lacking of REFERENCES funds, a sign board to the ichnosite (a) was erected on the main A1 road (sadly this was totally destroyed in 2016) and two small Adams T.L., Strganac C., Polcyn M.J. & Jacobs L.L. (2010). African huts (b) were built that function as the visitors’ centre. High resolution three-dimensional laser-scanning of the type Various groups of locals (c) proudly and enthusiastically showcase specimen of Eubrontes (?) glenrosensis Shuler, 1935, from the the geoscientific heritage of the site to all visitors. Comanchean (Lower ) of Texas: Implications for digital archiving and preservation. Palaeontologia Electronica, 13: 1-12. Anderson J.M., Anderson H.M. & Cruickshank A.R.I. (1998). Late pentadactyl and tetradactyl tracks are considered to Triassic ecosystems of the Molteno/Lower Elliot biome of have been of moderate to large size based on the size Southern Africa. Palaeontology, 41: 387-421. and morphology of the tracks. Tetradactyl tracks are Bates T., Falkingham P.L., Hidgetts D., Farlow J.O., Breithaupt B.H., O’Brien M., Matthews N., Sellers W.I. & Manning P.L. (2009). most likely made by sauropodomorphs, the fossils Digital imaging and public engagement in palaeontology. remains of which dominate the osteological record in Geology Today, 25: 134-139. the lower Elliot Formation (Knoll, 2004). Previously, Battail B. (2005). Late Triassic traversodontids (Synapsida, the pentadactyl tracks have been considered to represent Cynodontia) in South Africa. Palaeontologia Africana, 41: a herbivorous dicynodont (therapsid) trackmakers. 67-80. The tridactyl tracks are most likely associated with Belvedere M. & Farlow J.O. (2016). A numerical scale for small bipedal theropod dinosaurs. The 3D digital quantifying the quality of preservation of vertebrate tracks. model of the Subeng ichnosite will allow for future In Falkingham P.L., Marty D. & Richter A. (eds), Dinosaur study and more detailed quantitative analyses of this tracks, the next steps. Indiana University Press, Bloomington, Indiana: 92-98. key ichnological palaeosurface in the Upper Triassic Beurlen K. (1950). Neue Fährtenfunde aus der Fränkischen Trias lowermost Elliot Formation. Importantly, this visual [New track discoveries in the Franconian Triassic]. Neues tool can aid the current and on-going promotion and, Jahrbuch für Geologie und Paläontologie Monatshefte, 1950: ultimately, preservation of the Subeng ichnosite while 308-320. E.M. Bordy et alii - Upper Triassic vertebrate tracks and trackways at Subeng in Lesotho, southern Africa 197

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