A Possible Ctenosauriscid Archosaur from the Middle Triassic Manda Beds of Tanzania

ABSTRACT The Lifua Member of the Manda Beds of Tanzania (Middle Triassic: ?latest Anisian) has yielded an exceptionally important assemblage of early archosaurs, including numerous well-preserved specimens. However, the majority of this material has not been described formally, frustrating attempts to incorporate it into studies on early archosaur diversity and evolution. We describe an anterior dorsal vertebra from the Lifua Member as the holotype of a new taxon, Hypselorhachis mirabilis. Hypselorhachis is characterised by the possession of an elongate neural spine that is at least 5.5 times the height of the centrum, and can be diagnosed on the basis of a single autapomorphy relating to the morphology of the prezygapophysis. Hypselorhachis is similar to other early Middle Triassic archosaurs with elongate neural spines, including Arizonasaurus, Ctenosauriscus, and Lotosaurus. It is possible that these taxa form a clade, Ctenosauriscidae, but further anatomical and phylogenetic work is required before this can be confirmed.

[1]  C. Brochu Closure of neurocentral sutures during crocodilian ontogeny: Implications for maturity assessment in fossil archosaurs , 1996 .

[2]  K. Sen A new rauisuchian archosaur from the Middle Triassic of India , 2005 .

[3]  Xiaochuan Pan,et al.  Partial volume and aliasing artefacts in helical cone-beam CT. , 2004, Physics in medicine and biology.

[4]  B. Britt Pneumatic postcranial bones in dinosaurs and other archosaurs , 1993 .

[5]  R. Irmis,et al.  A critical re‐evaluation of the Late Triassic dinosaur taxa of North America , 2007 .

[6]  Robert L. Carroll,et al.  Vertebrate Paleontology and Evolution , 1988 .

[7]  R. Irmis AXIAL SKELETON ONTOGENY IN THE PARASUCHIA (ARCHOSAURIA: PSEUDOSUCHIA) AND ITS IMPLICATIONS FOR ONTOGENETIC DETERMINATION IN ARCHOSAURS , 2007 .

[8]  P. Semkiwa,et al.  Early Diagenetic Laumontite in the Lower Triassic Manda Beds of the Ruhuhu Basin, Southern Tanzania , 1991 .

[9]  S. Majumdar,et al.  Impact of spatial resolution on the prediction of trabecular architecture parameters. , 1998, Bone.

[10]  M. Benton,et al.  Paleontological evidence to date the tree of life. , 2006, Molecular biology and evolution.

[11]  S. Nesbitt Osteology of the Middle Triassic pseudosuchian archosaur Arizonasaurus babbitti , 2005 .

[12]  Octavian Catuneanu,et al.  The Karoo basins of south-central Africa , 2005 .

[13]  D. Guillery RW THE LAMINAR,et al.  a new interpretation. , 1970, The Journal of comparative neurology.

[14]  K. Angielczyk,et al.  Diictodon Feliceps (Owen, 1876), A Dicynodont (Therapsida, Anomodontia) Species with a Pangaean Distribution , 2008 .

[15]  A. Hungerbühler,et al.  A revision ofPoposaurus gracilis (Archosauria: Suchia) based on two new specimens from the Late Triassic of the southwestern U.S.A. , 2007 .

[16]  M. Gurnis Depressed continental hypsometry behind oceanic trenches: A clue to subduction controls on sea-level change , 1993 .

[17]  P. Christiansen,et al.  The detailed anatomy of Rhamphorhynchus: axial pneumaticity and its implications , 2003, Geological Society, London, Special Publications.

[18]  S. H. Haughton On a Collection of Karroo Vertebrates from Tanganyika Territory , 1932, Quarterly Journal of the Geological Society of London.

[19]  B. Gardiner,et al.  Vertebrates from the Middle Triassic Otter Sandstone Formation of Devon , 1990 .

[20]  F. V. Huene,et al.  Paläontologie und Phylogenie der Niederen Tetrapoden , 1957 .

[21]  S. Nesbitt Arizonasaurus and its implications for archosaur divergence , 2003, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[22]  E. Cope Synopsis of the Extinct Batrachia, Reptilia and Aves of North America , 2011 .

[23]  A. Cruickshank A new dicynodont genus from the Manda Formation of Tanzania (Tanganyika) , 2009 .

[24]  M. Wedel Origin of postcranial skeletal pneumaticity in dinosaurs. , 2006, Integrative zoology.

[25]  F. Abdala,et al.  A new traversodontid cynodont from the Santa Maria Formation (Ladinian-Carnian) of southern Brazil, with a phylogenetic analysis of Gondwanan traversodontids , 2003 .

[26]  Leon P A M Claessens,et al.  Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs , 2005, Nature.

[27]  N. Giannini,et al.  Chiniquodontid cynodonts: systematic and morphometric considerations , 2002 .

[28]  P. O’Connor Postcranial pneumaticity: An evaluation of soft‐tissue influences on the postcranial skeleton and the reconstruction of pulmonary anatomy in archosaurs , 2006, Journal of morphology.

[29]  Postcranial anatomy of the rauisuchian archosaur Batrachotomus kupferzellensis , 2009 .

[30]  M. Wedel Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs , 2003, Paleobiology.

[31]  S. Chatterjee,et al.  Postosuchus, a New Thecodontian Reptile from the Triassic of Texas and the Origin of Tyrannosaurs , 1985 .

[32]  M. Benton,et al.  Richard owen's giant Triassic frogs: archosaurs from the Middle Triassic of England , 1997 .

[33]  JEFFREY A. Wilson A nomenclature for vertebral laminae in sauropods and other saurischian dinosaurs , 1999 .

[34]  A. Cruickshank Biostratigraphy of the Permian tetrapod faunas from the Ruhuhu Valley, Tanzania , 1999 .

[35]  S. Nesbitt THE ANATOMY OF EFFIGIA OKEEFFEAE (ARCHOSAURIA, SUCHIA), THEROPOD-LIKE CONVERGENCE, AND THE DISTRIBUTION OF RELATED TAXA , 2007 .

[36]  M. Wedel WHAT PNEUMATICITY TELLS US ABOUT ‘PROSAUROPODS’, AND VICE VERSA , 2007 .

[37]  David L. Dilcher,et al.  The fossil record , 1992 .

[38]  Diana H. Wall,et al.  Non‐invasive techniques for investigating and modelling root‐feeding insects in managed and natural systems , 2007 .

[39]  P. O’Connor THE POSTCRANIAL AXIAL SKELETON OF MAJUNGASAURUS CRENATISSIMUS (THEROPODA: ABELISAURIDAE) FROM THE LATE CRETACEOUS OF MADAGASCAR , 2007 .

[40]  L. D. Boonstra A report on a collection of fossil reptilian bones from Tanganyika Territory , 1953 .

[41]  D. Gower Possible postcranial pneumaticity in the last common ancestor of birds and crocodilians: evidence from Erythrosuchus and other Mesozoic archosaurs , 2001, Naturwissenschaften.

[42]  G. M. Stockley The Geology of the Ruhuhu Coalfields, Tanganyika Territory , 1932, Quarterly Journal of the Geological Society of London.

[43]  E. Rayfield,et al.  Utility and Validity of Middle and Late Triassic ‘Land Vertebrate Faunachrons’ , 2009 .

[44]  H. W. Ball,et al.  The British Museum (Natural History) — University of London Joint Palæontological Expedition to Northern Rhodesia and Tanganyika, 1963 , 1964, Nature.

[45]  J. G. Carter,et al.  A New Suchian Archosaur From The Upper Triassic Of North Carolina , 2008 .

[46]  A. W. Cromptok,et al.  On some Triassic cynodonts from Tanganyika , 2009 .

[47]  M. Benton,et al.  Fossil Reptiles of Great Britain , 1995, Springer Netherlands.

[48]  R. Estes,et al.  Studies on fossil phyllodont fishes a new species of phyllodus elopiformes albuloidea from the late cretaceous of montana usa , 1978 .

[49]  P. Galton,et al.  Bromsgroveia from the Middle Triassic of England, the earliest record of a poposaurid thecodontian reptile (Archosauria: Rauisuchia) , 1996 .

[50]  C. Cox,et al.  A new genus of Triassic dicynodont from East Africa and its classification , 1983 .

[51]  R. Damiani A systematic revision and phylogenetic analysis of Triassic mastodonsauroids (Temnospondyli: Stereospondyli) , 2001 .

[52]  J. Hopson Late Triassic traversodont cynodonts from Nova Scotia and southern Africa , 1984 .

[53]  J. Gauthier Saurischian monophyly and the origin of birds , 1986 .

[54]  M. Wedel THE EVOLUTION OF VERTEBRAL PNEUMATICITY IN SAUROPOD DINOSAURS , 2003 .

[55]  P. Barrett,et al.  Postcranial skeletal pneumaticity and air-sacs in the earliest pterosaurs , 2009, Biology Letters.

[56]  R. McDonnell,et al.  A Geographical Information System (GIS) study of Triassic vertebrate biochronology , 2005, Geological Magazine.

[57]  J. Neveling,et al.  CYNODONTS FROM THE UPPERMOST BURGERSDORP FORMATION, SOUTH AFRICA, AND THEIR BEARING ON THE BIOSTRATIGRAPHY AND CORRELATION OF THE TRIASSIC CYNOGNATHUS ASSEMBLAGE ZONE , 2005 .

[58]  C. Sidor,et al.  A New Triassic Temnospondyl from Antarctica and a Review of Fremouw Formation Biostratigraphy , 2008 .