David Dilkes | University of Wisconsin Oshkosh (original) (raw)

Papers by David Dilkes

Palaeontology, 2012

Abstract: Restudy of skulls and available postcrania of the proterochampsian archosauriform Prot... more Abstract: Restudy of skulls and available postcrania of the proterochampsian archosauriform Proterochampsa barrionuevoi from the Ischigualasto Formation (Upper Triassic, Carnian) in the San Juan Province, Argentina, confirms that the genus is diagnosed by autapomorphies that include dermal sculpturing consisting of prominent ridges and nodular protuberances, a large hook‐like lateral projection on the quadratojugal, an antorbital fossa restricted to a depression along the maxilla, lateral expansion of the premaxilla anterior to the premaxilla–maxilla contact, absence of a supratemporal fossa, exclusion of jugal from suborbital fenestra, basal tubera of parabasisphenoid facing ventrally and reaching laterally beyond the basipterygoid process, and a ventral lamina on the angular. Proterochampsa nodosa is a valid species distinguished from P. barrionuevoi by fewer cranial ridges with larger protuberances, relatively smaller supratemporal fenestrae and width of frontals between orbits less than that of the nasals. A phylogenetic analysis supports the monophyly of Proterochampsia consisting of Proterochampsa, Chanaresuchus bonapartei, Gualosuchus reigi, Tropidosuchus romeri and Cerritosaurus binsfeldi. A temporal separation between the two basal proterochampsians with earliest records in the Late Triassic (Proterochampsa and Cerritosaurus) and Chanaresuchus, Gualosuchus and Tropidosuchus in the Middle Triassic indicates hidden proterochampsian diversity in the Middle Triassic.

palaeontology.palass-pubs.org

Page 1. THE RHYNCHOSAUR HOWES!A BROWNI FROM THE LOWER TRIASSIC OF SOUTH AFRICA by DAVID W. DILKES... more Page 1. THE RHYNCHOSAUR HOWES!A BROWNI FROM THE LOWER TRIASSIC OF SOUTH AFRICA by DAVID W. DILKES Abstract. Howesia browni is a rhynchosaur (Reptilia : Archosauromorpha) known from a single locality ...

The Complete Dinosaur, Jun 27, 2012

Whenever one attempts to flesh out the skeleton of a dinosaur, some or most ofthe muscles must be... more Whenever one attempts to flesh out the skeleton of a dinosaur, some or most ofthe muscles must be reconstructed. However, evidence ofmuscular tissue is only rarely preserved in the fossil record (Kellner 1996; Briggs et al. 1997; Dal Sasso and Signore 1998). Why is the exercise of reconstructing muscles important when it seems to have so little actual evidential support? Perhaps more so than any other aspect of its soft anatomy, the addition of muscles helps to breathe life into a dinosaur and transform it from a collection of bones into a ...

Palaeontology, 1993

Page 1. BIOLOGY AND EVOLUTION OF THE NASAL REGION IN TREMATOPID AMPHIBIANS by DAVID W. DILKES Abs... more Page 1. BIOLOGY AND EVOLUTION OF THE NASAL REGION IN TREMATOPID AMPHIBIANS by DAVID W. DILKES Abstract. Postmetamorphic ontogeny of the nasal region in trematopid amphibians (Temnospondyli : Dissorophoidea ...

Palaeontology, 1993

Royal Society Open Science

Archosauria (birds, crocodilians and their extinct relatives) form a major part of terrestrial ec... more Archosauria (birds, crocodilians and their extinct relatives) form a major part of terrestrial ecosystems today, with over 10 000 living species, and came to dominate the land for most of the Mesozoic (over 150 Myr) after radiating following the Permian–Triassic extinction. The archosaur skull has been essential to this diversification, itself diversified into myriad forms. The archosauriform Euparkeria capensis from the Middle Triassic (Anisian) of South Africa has been of great interest since its initial description in 1913, because its anatomy shed light on the origins and early evolution of crown Archosauria and potentially approached that of the archosaur common ancestor. Euparkeria has been widely used as an outgroup in phylogenetic analyses and when investigating patterns of trait evolution among archosaurs. Although described monographically in 1965, subsequent years have seen great advances in the understanding of early archosaurs and in imaging techniques. Here, the craniu...

Http Dx Doi Org 10 1080 02724634 1990 10011809, Aug 24, 2010

Vertebrate Anatomy Morphology Palaeontology, 2015

The carpus of Eryops megacephalus and tarsus of Acheloma cumminsi known from complete and articul... more The carpus of Eryops megacephalus and tarsus of Acheloma cumminsi known from complete and articulated individuals have provided the standard anatomy of these skeletal regions for temnospondyls. Restudy of the carpus of Eryops confirms the presence of only four digits, but refutes evidence for a prepollex, postminimus, and distal carpal 5. The supposed contact surface on centrale 1 for a prepollex is reinterpreted as part of the articulation for metacarpal 1 that includes distal carpal 1. Contrary to previous interpretations, a notch on the intermedium does not fit against the lateral corner of the radius. An articular surface on the distal end of the ulna thought previously to contact an absent postminimus fits against the ulnare. Preparation of the tarsus of the type specimen of Trematops milleri (junior synonym of Acheloma cumminsi) and a previously undescribed crus and pes of Eryops finds no evidence for a pretarsale in either genus. Centrale 4 of the tarsus shares a similar rect...

… -ROYAL SOCIETY OF …, 1999

Canadian Journal of Earth Sciences, 2003

Page 1. Can. J. Earth Sci. 40: 667678 (2003) doi: 10.1139/E02-063 © 2003 NRC Canada 667 Archaeov... more Page 1. Can. J. Earth Sci. 40: 667678 (2003) doi: 10.1139/E02-063 © 2003 NRC Canada 667 Archaeovenator hamiltonensis, a new varanopid (Synapsida: Eupelycosauria) from the Upper Carboniferous of Kansas Robert R. Reisz and David W. Dilkes ...

Journal of Vertebrate Paleontology, 1995

Two series of osteoderms associated with the anterior three-quarters of the presacral vertebral c... more Two series of osteoderms associated with the anterior three-quarters of the presacral vertebral column of the Early Permian temnospondylous amphibian Cacops aspidephorus have important implications for biomechanics of the axial skeleton. An internal series consists of an osteoderm fused to the distal tip of each neural spine. Lying dorsal to the internal series and overlapping each internal osteoderm is a second external series. The orientation of the zygapophyseal facets implies modest lateral flexion with limited coupled axial rotation of the column. However, the osteoderms restricted any possible lateral flexion through their inverted V-shape, strongly angled overlap between each external osteoderm and its neighbouring internal osteoderms, and the presence of a midsagittal flange on the ventral surface of each external osteoderm that fits into grooves on the anterior and posterior edges of the neighbouring internal osteoderms. This configuration allowed vertical flexion of the vertebral column with little lateral flexion. The rodlike nature of osteoderms with the anterior three-quarters of the presacral vertebrae suggests a restricted form of forward movement for Cacops unlike that of other early tetrapods.

Restudy of skulls and available postcrania of the proterochampsian archosauriform Proterochampsa ... more Restudy of skulls and available postcrania of the proterochampsian archosauriform Proterochampsa barrionuevoi from the Ischigualasto Formation (Upper Triassic, Carnian) in the San Juan Province, Argentina, confirms that the genus is diagnosed by autapomorphies that include dermal sculpturing consisting of prominent ridges and nodular protuberances, a large hook-like lateral projection on the quadratojugal, an antorbital fossa restricted to a depression along the maxilla, lateral expansion of the premaxilla anterior to the premaxilla-maxilla contact, absence of a supratemporal fossa, exclusion of jugal from suborbital fenestra, basal tubera of parabasisphenoid facing ventrally and reaching laterally beyond the basipterygoid process, and a ventral lamina on the angular. Proterochampsa nodosa is a valid species distinguished from P. barrionuevoi by fewer cranial ridges with larger protuberances, relatively smaller supratemporal fenestrae and width of frontals between orbits less than that of the nasals. A phylogenetic analysis supports the monophyly of Proterochampsia consisting of Proterochampsa, Chanaresuchus bonapartei, Gualosuchus reigi, Tropidosuchus romeri and Cerritosaurus binsfeldi. A temporal separation between the two basal proterochampsians with earliest records in the Late Triassic (Proterochampsa and Cerritosaurus) and Chanaresuchus, Gualosuchus and Tropidosuchus in the Middle Triassic indicates hidden proterochampsian diversity in the Middle Triassic.

The Early Permian temnospondyl amphibians Acheloma cumminsi Cope, 1882 and Trematops milleri Will... more The Early Permian temnospondyl amphibians Acheloma cumminsi Cope, 1882 and Trematops milleri Williston, 1909 of the family Trematopsidae prove, upon reexamination ofthe holotypes, to be indistinguishable. Since the former name has priority, Trematops milleri is declared to be a subjective junior synonym of Acheloma cumminsi. The family name Trematopsidae is retained.

… Transactions of the Royal Society of …, Jan 1, 1998

Restudy of the unique diapsid reptile Mesosuchus browni Watson, from the Cynognathus Assemblage Z... more Restudy of the unique diapsid reptile Mesosuchus browni Watson, from the Cynognathus Assemblage Zone (late Early Triassic to early Middle Triassic) of the Burgersdorp Formation (Tarkastad Subgroup; Beaufort Group) of South Africa, confirms that it is the most plesiomorphic known member of the Rhynchosauria. A new phylogenetic analysis of basal taxa of Archosauromorpha indicates that Choristodera falls outside of the Sauria, Prolacertiformes is a paraphyletic taxon with Prolacerta sharing a more recent common ancestor with Archosauriformes than with any other clade, Megalancosaurus and Drepanosaurus are sister taxa in the clade Drepanosauridae within Archosauromorpha, and are the sister group to the clade Tanystropheidae composed of Tanystropheus, Macrocnemus, and Langobardisaurus. Combination of the phylogenetic relationships of basal archosauromorphs and their known stratigraphic ranges reveals significant gaps in the fossil records of Late Permian and Triassic diapsids. Extensions of the temporal ranges of several lineages of diapsids into the Late Permian suggests that more groups of terrestrial reptiles survived the end-Permian mass extinction than thought previously.