DOCSLIB.ORG

Fossil Reptiles Mired in Controversy

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Fossil Reptiles Mired in Controversy NEWS NATURE|Vol 451|31 January 2008 The aetosaur, which lived more than 200 million years ago, was a reptile related to crocodiles and dinosaurs (artist’s impression). Fossil reptiles mired in controversy An ethics row has broken out among palaeon- was harmful to many young researchers.” mass produce essentially self-published and tologists over the naming of aetosaurs, a type In an e-mail response to Dzik, Lucas blamed non-peer-reviewed papers”, the letter claims. of ancient armoured reptile. the Polish researchers for not being more Lucas is known in the palaeontology com- Doctoral students in the United States and explicit about their fossil-examination rules, munity for his desire to publish a high volume Poland are accusing scientists at the Albu- but he did apologize for what he called “a mis- of papers. He acknowledges that his “tough” querque-based New Mexico Museum of understanding”. approach has brought him into conflict with Natural History and Science (NMMNHS) Another article published in the Bulletin by researchers before. “They are obviously angry,” of publishing articles that allegedly pilfered Spielmann and his bosses involves a reinterpre- he says, but the complaint “doesn’t have any their research. The allegations concern three tation of an aetosaur called Redondasuchus4. substance”. articles published in the NMMNHS Bulletin Jeff Martz, a palaeontology doctoral student The New Mexico cultural-affairs depart- by the museum’s interim director Spencer at Texas Tech University in Lubbock, says this ment, which oversees the museum, conducted Lucas, former director Adrian Hunt and their reinterpretation — involving bony spikes along a review of two of the instances last Octo- co-authors. the animal’s back — failed to properly credit his ber and concluded that the allegations were The disputed articles name and describe own similar description in a master’s thesis, an groundless. But some experts call that review different aetosaurs, and detail how the 220-mil- act akin to plagiarism. a whitewash, claiming that it failed to follow lion-year-old reptiles are related to crocodiles In a letter of complaint sent in 2007 to New accepted practices of US academic institu- and dinosaurs. In one instance, Lucas, Hunt Mexico government officials, Martz, Mathew tions faced with claims of misconduct. Now all and Justin Spielmann, the museum’s geoscience Wedel of the University of California at Merced three cases are before the Ethics Education collections manager, are accused of rushing to and Michael Taylor of the University of Port- Committee of the Society of Vertebrate Pale- publish a new name for an aetosaur (Rioarriba- smouth, UK, wrote: “It is our strong suspicion ontology, a professional organization based suchus)1 when they allegedly knew that palae- the [New Mexico Museum team members] in Northbrook, Illinois, which is awaiting ontologist William Parker of the Petrified Forest deliberately abused their editorial powers to responses from the New Mexico team before National Park in Arizona was soon to publish an take credit for observations and insights of making a ruling. article naming the species (as Heliocanthus)2. Parker and Martz.” Such actions, the letter “What we sought is a point-by-point response The International Commission on Zoologi- argues, corrupt the scientific process and harm to our allegations,” says Martz. Attorneys for cal Nomenclature says scientists must not name young researchers. Because Lucas largely edits New Mexico state blocked such a response, species if they know a competing scientist is in the Bulletin, he and his team have been able “to according to Peter Gerity, vice-chairman of the process of doing so. Lucas denies know- the museum’s advisory board who is also vice- ing of Parker’s plans. Hunt, who left the president for academic affairs at New Mexico museum last July to head the Flying Herit- Tech in Socorro. Gerity says he helped age Collection being set up by Microsoft review the 2007 letter of complaint, which co-founder Paul Allen in Everett, Washing- was rejected. Gerity told Nature he was ton, did not comment. unaware of the Polish criticism. And last July, Jerzy Dzik of the Palaeo- With Lucas now seeking to become perma- biology Institute at the University of Warsaw nent director of the New Mexico museum, the ■ B. MUELLER/MUS. TEXAS TECH B. MUELLER/MUS. sent Lucas an e-mail in complaint after Lucas publishing debate isn’t expected to go away. published an article in the Bulletin describing Rex Dalton Polish aetosaur fossils3. The article appeared shortly after Lucas had visited the War- 1. Lucas, S. G., Hunt, A. P. & Spielmann, J. A. NMMNHS Bull. saw Institute, when the fossils were close to No. 37, 581–582 (2006). 2. Parker, W. G. J. System. Palaeontol. 5, 1, 41–68 (2007). being described by scientists there. Such a 3. Lucas, S. G. et al. NMMNHS Bull. No. 41, 248–258 (2007). thing had not occurred in the past 50 years at Interlocking bony plates covered the 4. Spielmann, J. A. et al. NMMNHS Bull. No. 37, 583–587 his institute, Dzik wrote, adding: “Your action aetosaur’s body, shown one-third of actual size. (2006). 510.
Load more

Recommended publications
  • 8. Archosaur Phylogeny and the Relationships of the Crocodylia
    8. Archosaur phylogeny and the relationships of the Crocodylia MICHAEL J. BENTON Department of Geology, The Queen's University of Belfast, Belfast, UK JAMES M. CLARK* Department of Anatomy, University of Chicago, Chicago, Illinois, USA Abstract The Archosauria include the living crocodilians and birds, as well as the fossil dinosaurs, pterosaurs, and basal 'thecodontians'. Cladograms of the basal archosaurs and of the crocodylomorphs are given in this paper. There are three primitive archosaur groups, the Proterosuchidae, the Erythrosuchidae, and the Proterochampsidae, which fall outside the crown-group (crocodilian line plus bird line), and these have been defined as plesions to a restricted Archosauria by Gauthier. The Early Triassic Euparkeria may also fall outside this crown-group, or it may lie on the bird line. The crown-group of archosaurs divides into the Ornithosuchia (the 'bird line': Orn- ithosuchidae, Lagosuchidae, Pterosauria, Dinosauria) and the Croco- dylotarsi nov. (the 'crocodilian line': Phytosauridae, Crocodylo- morpha, Stagonolepididae, Rauisuchidae, and Poposauridae). The latter three families may form a clade (Pseudosuchia s.str.), or the Poposauridae may pair off with Crocodylomorpha. The Crocodylomorpha includes all crocodilians, as well as crocodi- lian-like Triassic and Jurassic terrestrial forms. The Crocodyliformes include the traditional 'Protosuchia', 'Mesosuchia', and Eusuchia, and they are defined by a large number of synapomorphies, particularly of the braincase and occipital regions. The 'protosuchians' (mainly Early *Present address: Department of Zoology, Storer Hall, University of California, Davis, Cali- fornia, USA. The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds (ed. M.J. Benton), Systematics Association Special Volume 35A . pp. 295-338. Clarendon Press, Oxford, 1988.
    [Show full text]
  • Late Triassic) Adrian P
    New Mexico Geological Society Downloaded from: http://nmgs.nmt.edu/publications/guidebooks/56 Definition and correlation of the Lamyan: A new biochronological unit for the nonmarine Late Carnian (Late Triassic) Adrian P. Hunt, Spencer G. Lucas, and Andrew B. Heckert, 2005, pp. 357-366 in: Geology of the Chama Basin, Lucas, Spencer G.; Zeigler, Kate E.; Lueth, Virgil W.; Owen, Donald E.; [eds.], New Mexico Geological Society 56th Annual Fall Field Conference Guidebook, 456 p. This is one of many related papers that were included in the 2005 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. Besides detailed road logs, the guidebooks contain many well written, edited, and peer-reviewed geoscience papers. These books have set the national standard for geologic guidebooks and are an essential geologic reference for anyone working in or around New Mexico. Free Downloads NMGS has decided to make peer-reviewed papers from our Fall Field Conference guidebooks available for free download. Non-members will have access to guidebook papers two years after publication. Members have access to all papers. This is in keeping with our mission of promoting interest, research, and cooperation regarding geology in New Mexico. However, guidebook sales represent a significant proportion of our operating budget. Therefore, only research papers are available for download. Road logs, mini-papers, maps, stratigraphic charts, and other selected content are available only in the printed guidebooks.
    [Show full text]
  • A Revision of the Upper Triassic Ornithischian Dinosaur Revueltosaurus, with a Description of a New Species
    Heckert, A.B" and Lucas, S.O., eds., 2002, Upper Triassic Stratigraphy and Paleontology. New Mexico Museum of Natural History & Science Bulletin No.2 J. 253 A REVISION OF THE UPPER TRIASSIC ORNITHISCHIAN DINOSAUR REVUELTOSAURUS, WITH A DESCRIPTION OF A NEW SPECIES ANDREW B. HECKERT New Mexico Museum of Natural History, 1801 Mountain Road NW, Albuquerque, NM 87104-1375 Abstract-Ornithischian dinosaur body fossils are extremely rare in Triassic rocks worldwide, and to date the majority of such fossils consist of isolated teeth. Revueltosaurus is the most common Upper Triassic ornithischian dinosaur and is known from Chinle Group strata in New Mexico and Arizona. Historically, all large (>1 cm tall) and many small ornithischian dinosaur teeth from the Chinle have been referred to the type species, Revueltosaurus callenderi Hunt. A careful re-examination of the type and referred material of Revueltosaurus callenderi reveals that: (1) R. callenderi is a valid taxon, in spite of cladistic arguments to the contrary; (2) many teeth previously referred to R. callenderi, particularly from the Placerias quarry, instead represent other, more basal, ornithischians; and (3) teeth from the vicinity of St. Johns, Arizona, and Lamy, New Mexico previously referred to R. callenderi pertain to a new spe­ cies, named Revueltosaurus hunti here. R. hunti is more derived than R. callenderi and is one of the most derived Triassic ornithischians. However, detailed biostratigraphy indicates that R. hunti is older (Adamanian: latest Carnian) than R. callenderi (Revueltian: early-mid Norian). Both taxa have great potential as index taxa of their respective faunachrons and support existing biochronologies based on other tetrapods, megafossil plants, palynostratigraphy, and lithostratigraphy.
    [Show full text]
  • New Insights on Prestosuchus Chiniquensis Huene
    New insights on Prestosuchus chiniquensis Huene, 1942 (Pseudosuchia, Loricata) based on new specimens from the “Tree Sanga” Outcrop, Chiniqua´ Region, Rio Grande do Sul, Brazil Marcel B. Lacerda1, Bianca M. Mastrantonio1, Daniel C. Fortier2 and Cesar L. Schultz1 1 Instituto de Geocieˆncias, Laborato´rio de Paleovertebrados, Universidade Federal do Rio Grande do Sul–UFRGS, Porto Alegre, Rio Grande do Sul, Brazil 2 CHNUFPI, Campus Amı´lcar Ferreira Sobral, Universidade Federal do Piauı´, Floriano, Piauı´, Brazil ABSTRACT The ‘rauisuchians’ are a group of Triassic pseudosuchian archosaurs that displayed a near global distribution. Their problematic taxonomic resolution comes from the fact that most taxa are represented only by a few and/or mostly incomplete specimens. In the last few decades, renewed interest in early archosaur evolution has helped to clarify some of these problems, but further studies on the taxonomic and paleobiological aspects are still needed. In the present work, we describe new material attributed to the ‘rauisuchian’ taxon Prestosuchus chiniquensis, of the Dinodontosaurus Assemblage Zone, Middle Triassic (Ladinian) of the Santa Maria Supersequence of southern Brazil, based on a comparative osteologic analysis. Additionally, we present well supported evidence that these represent juvenile forms, due to differences in osteological features (i.e., a subnarial fenestra) that when compared to previously described specimens can be attributed to ontogeny and indicate variation within a single taxon of a problematic but important
    [Show full text]
  • Aetosaurs (Archosauria: Stagonolepididae) from the Upper Triassic (Revueltian) Snyder Quarry, New Mexico
    Zeigler, K.E., Heckert, A.B., and Lucas, S.G., eds., 2003, Paleontology and Geology of the Snyder Quarry, New Mexico Museum of Natural History and Science Bulletin No. 24. 115 AETOSAURS (ARCHOSAURIA: STAGONOLEPIDIDAE) FROM THE UPPER TRIASSIC (REVUELTIAN) SNYDER QUARRY, NEW MEXICO ANDREW B. HECKERT, KATE E. ZEIGLER and SPENCER G. LUCAS New Mexico Museum of Natural History, 1801 Mountain Road NW, Albuquerque, NM 87104-1375 Abstract—Two species of aetosaurs are known from the Snyder quarry (NMMNH locality 3845): Typothorax coccinarum Cope and Desmatosuchus chamaensis Zeigler, Heckert, and Lucas. Both are represented entirely by postcrania, principally osteoderms (scutes), but also by isolated limb bones. Aetosaur fossils at the Snyder quarry are, like most of the vertebrates found there, not articulated. However, clusters of scutes, presumably each from a single carapace, are associated. Typothorax coccinarum is an index fossil of the Revueltian land- vertebrate faunachron (lvf) and its presence was expected at the Snyder quarry, as it is known from correlative strata throughout the Chama basin locally and the southwestern U.S.A. regionally. The Snyder quarry is the type locality of D. chamaensis, which is considerably less common than T. coccinarum, and presently known from only one other locality. Some specimens we tentatively assign to D. chamaensis resemble lateral scutes of Paratypothorax, but we have not found any paramedian scutes of Paratypothorax at the Snyder quarry, so we refrain from identifying them as Paratypothorax. Specimens of both Typothorax and Desmatosuchus from the Snyder quarry yield insight into the anatomy of these taxa. Desmatosuchus chamaensis is clearly a species of Desmatosuchus, but is also one of the most distinctive aetosaurs known.
    [Show full text]
  • OSTEODERMS of JUVENILES of STAGONOLEPIS (ARCHOSAURIA: AETOSAURIA) from the LOWER CHINLE Group, EAST-CENTRAL ARIZONA
    Heckert, A.B., and Lucas, S.O., eds., 2002, Upper Triassic Stratigraphy and Paleontology. New Mexico Museum of Natural History and Science Bulletin No. 21. 235 OSTEODERMS OF JUVENILES OF STAGONOLEPIS (ARCHOSAURIA: AETOSAURIA) FROM THE LOWER CHINLE GROUp, EAST-CENTRAL ARIZONA ANDREW B. HECKERT and SPENCER G. LUCAS New Mexico Museum of Natural History, 1801 Mountain Rd NW, Albuquerque, NM 87104 Abstract-We describe for the first time small «25 mm) dorsal paramedian, lateral, and appendicu­ lar /ventral scutes (osteoderms) of aetosaurs from the Blue Hills in Apache County, east-central Ari­ zona. These diminutive scutes, collected by c.L. Camp in the 1920s, preserve diagnostic features of the common Adamanian aetosaur Stagonolepis. Stagonolepis wellesi was already known from the Blue Hills, so identification of juvenile scutes of Stagonolepis simply confirms the existing biostratigraphic and paleogeographic distribution of the genus. Still, application of the same taxonomic principles used to identify larger, presumably adult, aetosaur scutes suggests that juvenile aetosaurs should provide the same level of biostratigraphic resolution obtained from adults. Keywords: Arizona, aetosaur, juvenile, Stagonolepis, Chinle, Blue Mesa Member INTRODUCTION Aetosaurs are an extinct clade of heavily armored, primar­ ily herbivorous, archosaurs known from Upper Triassic strata on all continents except Antarctica and Australia (Heckert and Lucas, 2000). The osteoderms (scutes) of aetosaurs are among the most common tetrapod fossils recovered from the Upper Triassic Chinle Group, and are typically identifiable to genus (Long and Ballew, 1985; Long and Murry, 1995; Heckert and Lucas, 2000). This in tum has facilitated development of a robust tetrapod-based bios­ tratigraphy of the Chinle Group and other Upper Triassic strata 34' Springetille co worldwide (e.g., Lucas and Hunt, 1993; Lucas and Heckert, 1996; c: o Lucas, 1997, 1998).
    [Show full text]
  • Heptasuchus Clarki, from the ?Mid-Upper Triassic, Southeastern Big Horn Mountains, Central Wyoming (USA)
    The osteology and phylogenetic position of the loricatan (Archosauria: Pseudosuchia) Heptasuchus clarki, from the ?Mid-Upper Triassic, southeastern Big Horn Mountains, Central Wyoming (USA) † Sterling J. Nesbitt1, John M. Zawiskie2,3, Robert M. Dawley4 1 Department of Geosciences, Virginia Tech, Blacksburg, VA, USA 2 Cranbrook Institute of Science, Bloomfield Hills, MI, USA 3 Department of Geology, Wayne State University, Detroit, MI, USA 4 Department of Biology, Ursinus College, Collegeville, PA, USA † Deceased author. ABSTRACT Loricatan pseudosuchians (known as “rauisuchians”) typically consist of poorly understood fragmentary remains known worldwide from the Middle Triassic to the end of the Triassic Period. Renewed interest and the discovery of more complete specimens recently revolutionized our understanding of the relationships of archosaurs, the origin of Crocodylomorpha, and the paleobiology of these animals. However, there are still few loricatans known from the Middle to early portion of the Late Triassic and the forms that occur during this time are largely known from southern Pangea or Europe. Heptasuchus clarki was the first formally recognized North American “rauisuchian” and was collected from a poorly sampled and disparately fossiliferous sequence of Triassic strata in North America. Exposed along the trend of the Casper Arch flanking the southeastern Big Horn Mountains, the type locality of Heptasuchus clarki occurs within a sequence of red beds above the Alcova Limestone and Crow Mountain formations within the Chugwater Group. The age of the type locality is poorly constrained to the Middle—early Late Triassic and is Submitted 17 June 2020 Accepted 14 September 2020 likely similar to or just older than that of the Popo Agie Formation assemblage from Published 27 October 2020 the western portion of Wyoming.
    [Show full text]
  • A Giant Phytosaur (Reptilia: Archosauria) Skull from the Redonda Formation (Upper Triassic: Apachean) of East-Central New Mexico
    New Mexico Geological Society Guidebook, 52 nd Field Conference, Geology of the LlallO Estacado, 2001 169 A GIANT PHYTOSAUR (REPTILIA: ARCHOSAURIA) SKULL FROM THE REDONDA FORMATION (UPPER TRIASSIC: APACHEAN) OF EAST-CENTRAL NEW MEXICO ANDREW B. HECKERT ', SPENCER G. LUCAS', ADRJAN P. HUNT' AND JERALD D. HARRlS' 'Department of Earth and Planetary Sciences, University of New Me~ico, Albuquerque, NM 87131- 1116; INcw Me~ico Museum of Natural History and Science, 1801 Mountain Rd NW, Albuquerque, 87104; lMesalands Dinosaur Museum, Mesa Technical Coll ege, 911 South Tenth Street, Tucumcari, NM 88401; ' Department of Earth and Environmental Sciences, University of Pennsylvania, Philadelphia, PA 19104 Abslr.cl.-In the Sum!Mr of 1994, a field party of the New Mexico Museum of Natural History and Science (NMMNH) collected a giant, incomplete phytosaur skull from a bonebed discovered by Paul Sealey in east-central New Me~ieo. This bonebed lies in a narrow channcl deposit of intrafonnational conglomerate in the Redonda Fonnation. Stratigraphically, this specimen comes from strata identical to the type Apachean land·vertebrate faunachron and thus of Apachean (latest Triassic: latc Norian·Rhaetian) age. The skull lacks most of the snout but is otherwise complete and in excellent condition. As preserved, the skull measures 780 mm long, and was probably 1200 mm or longer in life, making it nearly as large as the holotype of Ru{iodon (- lIfaehaeroprosoprls . ..Smilwlldllls) gngorii, and one of the largest published phytosallr sku ll s. The diagnostic features of Redondasall'us present in the skull include robnst squamosal bars extending posteriorly well beyond the occiput and supratemporal fenestrae that are completely concealed in dorsal view.
    [Show full text]
  • Table of Contents
    Downloaded from http://sp.lyellcollection.org/ by guest on October 1, 2021 Contents Participants from the First Symposium of Early Archosaur Evolution vii NESBITT, S. J., DESOJO,J.B.&IRMIS, R. B. Anatomy, phylogeny and palaeobiology of early 1 archosaurs and their kin EZCURRA, M. D., BUTLER,R.J.&GOWER, D. J. ‘Proterosuchia’: the origin and early history of 9 Archosauriformes SOOKIAS,R.B.&BUTLER, R. J. Euparkeriidae 35 SUES, H.-D., DESOJO,J.B.&EZCURRA, M. D. Doswelliidae: a clade of unusual armoured 49 archosauriforms from the Middle and Late Triassic TROTTEYN, M. J., ARCUCCI,A.B.&RAUGUST, T. Proterochampsia: an endemic archosauriform 59 clade from South America STOCKER,M.R.&BUTLER, R. J. Phytosauria 91 DALLA VECCHIA, F. M. Triassic pterosaurs 119 LANGER, M. C., NESBITT, S. J., BITTENCOURT,J.S.&IRMIS, R. B. Non-dinosaurian 157 Dinosauromorpha VON BACZKO,M.B.&EZCURRA, M. D. Ornithosuchidae: a group of Triassic archosaurs with a 187 unique ankle joint DESOJO, J. B., HECKERT, A. B., MARTZ, J. W., PARKER, W. G., SCHOCH, R. R., 203 SMALL,B.J.&SULEJ, T. Aetosauria: a clade of armoured pseudosuchians from the Upper Triassic continental beds NESBITT, S. J., BRUSATTE, S. L., DESOJO, J. B., LIPARINI, A., DE FRANc¸a, M. A. G., 241 WEINBAUM,J.C.&GOWER, D. J. Rauisuchia IRMIS, R. B., NESBITT,S.J.&SUES, H.-D. Early Crocodylomorpha 275 RAUGUST, T., LACERDA,M.&SCHULTZ, C. L. The first occurrence of Chanaresuchus bonapartei 303 Romer 1971 (Archosauriformes, Proterochampsia) of the Middle Triassic of Brazil from the Santacruzodon Assemblage Zone, Santa Maria Formation (Parana´ Basin) NIEDZ´ WIEDZKI, G., BRUSATTE,S.L.&BUTLER,R.J.Prorotodactylus and Rotodactylus tracks: an 319 ichnological record of dinosauromorphs from the Early–Middle Triassic of Poland LANGER,M.C.&FERIGOLO, J.
    [Show full text]
  • Paleontology at Petrified Forest National Park
    Paleontology at Petrifi ed Forest National Park TRIASSIC TUNES Do you like to sing? Learn the words and motions of this tune about the Triassic animals of Petrifi ed Forest National Park. Sing to the tune of “If You’re Happy and You Know It Clap You’re Hands.” Verse one Oh, the phytosaur (fi e-toe-sore) it was a mighty beast, Grr-owl (make growling sounds) Oh, the phytosaur it was a mighty beast, DIARY OF A PALEONTOLOGIST. Grr-owl It measured thirty feet in length In the fi eld… Weighed a ton and gulped down meat. The sun bums the back of my neck. A heavy drop of sweat rolls Oh, the phytosaur it was a mighty beast! down my nose, drops off , and plop! It just misses my pencil as I’m writing in my notebook. My fi ngernails are dirty and sand Verse two coats my skin. Yet, I am as happy as I have ever been! I brush Oh Placerias (pla-sair-e-us) was an herbivore, away more of the dirt and clay that covers more than 200 million Munch, munch, (say it loud and clap outstretched year old bone. I have only a few pieces left before the fossil arms together) comes out of its rock tomb, and I take it to the laboratory for Oh, Placerias was an herbivore, study. Munch, munch It ate leaves, plants, young “shoots”, In the laboratory... Used its tusks to dig up roots I use the same kind of tools my dentist uses when he cleans Oh, Placerias was an herbivore.
    [Show full text]
  • "Reassessment of the Aetosaur "Desmatosuchus" Chamaensis With
    Journal of Systematic Palaeontology: page 1 of 28 doi:10.1017/S1477201906001994 C The Natural History Museum Reassessment of the Aetosaur ‘DESMATOSUCHUS’ CHAMAENSIS with a reanalysis of the phylogeny of the Aetosauria (Archosauria: Pseudosuchia) ∗ William G. Parker Division of Resource Management, Petrified Forest National Park, P.O. Box 2217, Petrified Forest, AZ 86028 USA SYNOPSIS Study of aetosaurian archosaur material demonstrates that the dermal armour of Des- matosuchus chamaensis shares almost no characters with that of Desmatosuchus haplocerus.In- stead, the ornamentation and overall morphology of the lateral and paramedian armour of ‘D.’ chamaensis most closely resembles that of typothoracisine aetosaurs such as Paratypothorax. Auta- pomorphies of ‘D.’ chamaensis, for example the extension of the dorsal eminences of the paramedian plates into elongate, recurved spikes, warrant generic distinction for this taxon. This placement is also supported by a new phylogenetic hypothesis for the Aetosauria in which ‘D.’ chamaensis is a sister taxon of Paratypothorax and distinct from Desmatosuchus. Therefore, a new genus, Heliocanthus is erected for ‘D.’ chamaensis. Past phylogenetic hypotheses of the Aetosauria have been plagued by poorly supported topologies, coding errors and poor character construction. A new hypothesis places emphasis on characters of the lateral dermal armour, a character set previously under-utilised. De- tailed examination of aetosaur material suggests that the aetosaurs can be divided into three groups based on the morphology of the lateral armour. Whereas it appears that the characters relating to the ornamentation of the paramedian armour are homoplastic, those relating to the overall morphology of the lateral armour may possess a stronger phylogenetic signal.
    [Show full text]
  • Osteology of the Late Triassic Aetosaur Scutarx Deltatylus (Archosauria: Pseudosuchia)
    Osteology of the Late Triassic aetosaur Scutarx deltatylus (Archosauria: Pseudosuchia) William G. Parker1,2 1 Division of Resource Management, Petrified Forest National Park, Petrified Forest, Arizona, United States 2 Jackson School Museum of Earth History, University of Texas at Austin, Austin, Texas, United States ABSTRACT Aetosaurians are some of the most common fossils collected from the Upper Triassic Chinle Formation of Arizona, especially at the Petrified Forest National Park (PEFO). Aetosaurians collected from lower levels of the park include Desmatosuchus spurensis, Paratypothorax, Adamanasuchus eisenhardtae, Calyptosuchus wellesi, and Scutarx deltatylus. Four partial skeletons collected from the park between 2002 and 2009 represent the holotype and referred specimens of Scutarx deltatylus. These specimens include much of the carapace, as well as the vertebral column, and shoulder and pelvic girdles, and a new naming convention proposed for osteoderms descriptions better differentiates portions of the carapace and ventral armor. A partial skull from the holotype specimen represents the first aetosaur skull recovered and described from Arizona since the 1930s. The key morphological feature distinguishing Scutarx deltatylus is the presence of a prominent, triangular boss located in the posteromedial corner of the dorsal surface of the dorsal paramedian osteoderms. Scutarx deltatylus can be distinguished from closely related forms Calyptosuchus wellesi and Adamanasuchus eisenhardtae not only morphologically, but also stratigraphically.
    [Show full text]