The Braincase of Youngina Capensis (Reptilia, Diapsida): New Insights from High-Resolution CT Scanning of the Holotype

Detailed descriptions of braincase anatomy in early diapsid reptiles have been historically rare given the difficulty of accessing this deep portion of the skull, because of poor preservation of the fossils or the inability to remove the surrounding skull roof. Previous descriptions of the braincase of Youngina capensis, a derived stem-diapsid reptile from the Late Permian (250 MYA) of South Africa, have relied on only partially preserved fossils. High resolution X-ray computed tomography (HRXCT) scanning, a new advance in biomedical sciences, has allowed us to examine the reasonably complete braincase of the holotype specimen of Youngina capensis for the first time by digitally peering through the sandstone matrix that filled the skull postmortem. We present the first detailed 3D visualizations of the braincase and the vestibular system in a Permian diapsid reptile. This new anatomical description is of great comparative and phylogenetic relevance to the study of the structure, function and evolution of the reptilian head.

[1]  W. Joyce,et al.  Transitional fossils and the origin of turtles , 2010, Biology Letters.

[2]  R. Reisz,et al.  Apsisaurus witteri from the Lower Permian of Texas: Yet Another Small Varanopid Synapsid, Not a Diapsid , 2010 .

[3]  E. S. Gaffney,et al.  The cranial morphology of Kayentachelys, an Early Jurassic cryptodire, and the early history of turtles , 2009 .

[4]  G. Bever,et al.  An Archosaur-Like Laterosphenoid in Early Turtles (Reptilia: Pantestudines) , 2009 .

[5]  Johannes Müller,et al.  The enigmatic diapsid Acerosodontosaurus piveteaui (Reptilia: Neodiapsida) from the Upper Permian of Madagascar and the paraphyly of ``younginiform'' reptiles , 2009 .

[6]  L. Witmer,et al.  New Insights Into the Brain, Braincase, and Ear Region of Tyrannosaurs (Dinosauria, Theropoda), with Implications for Sensory Organization and Behavior , 2009, Anatomical record.

[7]  I. Werneburg,et al.  Timing of organogenesis support basal position of turtles in the amniote tree of life , 2009, BMC Evolutionary Biology.

[8]  Lawrence M Witmer,et al.  Inner ear anatomy is a proxy for deducing auditory capability and behaviour in reptiles and birds , 2009, Proceedings of the Royal Society B: Biological Sciences.

[9]  L. Witmer,et al.  Cranial Kinesis in Dinosaurs: Intracranial Joints, Protractor Muscles, and Their Significance for Cranial Evolution and Function in Diapsids , 2008 .

[10]  O. Rieppel,et al.  An ancestral turtle from the Late Triassic of southwestern China , 2008, Nature.

[11]  C. U. Smith.  Classification and phylogeny , 2002, The Sepsidae (Diptera) of Europe.

[12]  L. Witmer,et al.  Using CT to Peer into the Past: 3D Visualization of the Brain and Ear Regions of Birds, Crocodiles, and Nonavian Dinosaurs , 2008 .

[13]  M. John,et al.  Structure of the brain cavity and inner ear of the centrosaurine ceratopsid dinosaur Pachyrhinosaurus based on CT scanning and 3 D visualization , 2008 .

[14]  Johannes Müller,et al.  Impedance-Matching Hearing in Paleozoic Reptiles: Evidence of Advanced Sensory Perception at an Early Stage of Amniote Evolution , 2007, PloS one.

[15]  J. Maisano,et al.  The ossified braincase and cephalic osteoderms of Shinisaurus crocodilurus (Squamata, Shinisauridae) , 2005 .

[16]  Johannes Müller.  Early loss and multiple return of the lower temporal arcade in diapsid reptiles , 2003, Naturwissenschaften.

[17]  R. Reisz,et al.  AN ENIGMATIC NEW DIAPSID REPTILE FROM THE UPPER PERMIAN OF EASTERN EUROPE , 2003 .

[18]  Michael S. Y. Lee.  Molecules, morphology, and the monophyly of diapsid reptiles , 2001 .

[19]  O. Rieppel,et al.  THE ORIGIN AND EARLY EVOLUTION OF TURTLES , 1999 .

[20]  L. Poling,et al.  A molecular phylogeny of reptiles. , 1999, Science.

[21]  O. Rieppel,et al.  Turtles as diapsid reptiles , 1996, Nature.

[22]  S. Evans,et al.  New material of Youngina: Evidence of juvenile aggregation in Permian diapsid reptiles , 1996 .

[23]  O. Rieppel.  The genus Placodus : systematics, morphology, paleobiogeography, and paleobiology / Olivier Rieppel --. , 1995 .

[24]  James M. Clark,et al.  The laterosphenoid bone of early archosauriforms , 1993 .

[25]  E. S. Gaffney,et al.  The comparative osteology of the Triassic turtle Proganochelys. Bulletin of the AMNH ; no. 194 , 1990 .

[26]  S. Evans.  The early history and relationships of the Diapsida , 1988 .

[27]  S. Evans.  The braincase of Youngina capensis (Reptilia: Diapsida; Permian) , 1987 .

[28]  S. Evans.  The braincase of Prolacerta broomi (Reptilia, Triassic) , 1986, Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen.

[29]  M. Benton.  Classification and phylogeny of the diapsid reptiles , 1985 .

[30]  P. Currie.  The osteology and relationships of Tangasaurus mennelli Haughton , 1982 .

[31]  R. Carroll.  Plesiosaur Ancestors from the Upper Permian of Madagascar , 1981 .

[32]  P. Currie.  Hovasaurus boulei, an aquatic eosuchian from the Upper Permian of Madagascar , 1981 .

[33]  L. Radinsky,et al.  Vertebrate paleontology: new approaches and new insights , 1980, Paleobiology.

[34]  P. Currie.  A new younginid (Reptilia: Eosuchia) from the Upper Permian of Madagascar , 1980 .

[35]  R. Reisz.  Petrolacosaurus, the Oldest Known Diapsid Reptile , 1977, Science.

[36]  J. Harris,et al.  Kenyasaurus, a new eosuchian reptile from the early Triassic of Kenya , 1977 .

[37]  C. Gans,et al.  Ear and hearing in Sphenodon punctatus. , 1976, Proceedings of the National Academy of Sciences of the United States of America.

[38]  W. K. Gregory.  Pareiasaurs versus placodonts as near ancestors to the turtles. Bulletin of the AMNH ; v. 86, article 6 , 1946 .

[39]  E. C. Olson.  Notes on the Skull of Youngina Capensis Broom , 1936, The Journal of Geology.

[40]  J. GRAHAM KERR,et al.  The Osteology of the Reptiles , 1926, Nature.

[41]  R. Broom.  A new Thecodont Reptile , 1914 .

[42]  R W S,et al.  COMPARATIVE MORPHOLOGY. , 1886, Science.