Triassic Temnospondyl Research Articles

3D external restorations of stegocephalian skulls using ZBrush: The renaissance of fossil amphibians

Cranial soft tissues (eyes, dermis, muscles, etc.) have never been preserved in fossil stegocephalians, and few specific studies have been done on their related osteological features (such as dermosensory canals, dermal bone ornamentation and microstructure). Consequently, the most useful tool to reconstruct stegocephalians remains the actualistic comparison with analogous living ecomorphotypes. Coupled with numerical sculpturing technologies available with the software ZBrush, it is now possible to appreciate the cranial soft tissues in 3D and to better reconstruct the external skull structures. Examples are given of the early tetrapod Acanthostega gunnari from the Devonian of Greenland and the Triassic temnospondyls Edingerella madagascariensis from Madagascar and Parotosuchus sp. from Antarctica. This palaeontological application of ZBrush is one of its first scientific uses. The obtained reconstructions are useful for scientific publication and in return they allow palaeontologists to better understand the palaeobiology of extinct organisms.

Preliminary observations on the bone microstructure, growth patterns, and life habits of some Triassic temnospondyls from India

ABSTRACT The osteohistology including bone cross-sectional geometry of skeletal elements such as the limb bones, ribs, and intercentra of three Triassic temnospondyl taxa from India were examined to reveal varied bone microstructure and differing growth patterns. The Early Triassic trematosaurid examined is characterized by a change in tissue type from a well-vascularized fibrolamellar bone early in ontogeny to peripheral lamellar bone and lines of arrested growth later in ontogeny, suggesting a fast initial growth followed by a slow and intermittent growth later in life. In contrast, the Middle Triassic paracyclotosaurid and the Late Triassic chigutisaurid examined had a cyclical, overall slow growth, as evidenced from predominance of lamellar bone in the cortex. It is hypothesized that the rapid growth of the trematosaurids was an attempt to stabilize the ecosystem after the Permo-Triassic extinction event. Fibrolamellar bone tissue is described for the first time in a Triassic temnospondyl. Bone cross-sectional geometry, low-to-average cortical porosity, and other parameters imply that the members of the Early and Middle Triassic taxa recovered from India retained a high level of terrestriality. The high cortical porosity and extensive medullary spongiosa suggest that the Late Triassic chigutisaurids had a semi-aquatic or aquatic life style. The varying cortical thickness of the limb bones in paracyclotosaurids may be attributed to different biomechanical constraints.

On the Presence of a Pustulated Temnospondyl in the Lower Triassic of Southern Brazil

The fossil record of temnospondyls in South America has been greatly expanded in the last 10 years, increasing their overall significance. They occur in Argentina, Brazil, and Uruguay, and range from the Guadalupian to the Late Triassic. The Early Triassic temnospondyl record in southern Brazil is mainly composed of fragmentary specimens, usually repre− sented by dermal skull bones from the Sanga do Cabral Formation. Some of these fragments were tentatively referred to Lydekkerinidae and Rhytidosteidae based on their characteristic ridge−grooved “spider−web” pattern of ornamentation. In this contribution we report, for the first time, a temnospondyl skull fragment with pustulated sculpturing pattern, which is tentatively ascribed to Plagiosauridae. This new record could indicate the presence of a new temnospondyl taxon for the Lower Triassic of South America. Key wor ds: Temnospondyli, Plagiosauridae, paleobiogeography, Sanga do Cabral Formation, Lower Triassic, western Gondwana.

Growth patterns of fossil vertebrates as deduced from bone microstructure: case studies from India

Bone microstructure is affected by ontogeny, phylogeny, biomechanics and environments. These aspects of life history of an extinct animal, especially its growth patterns, may be assessed as fossil bone generally maintains its histological integrity. Recent studies on the bone histology of fossil vertebrates from India encompass different types of temnospondyls and dicynodonts from different Permian and Triassic horizons. The examined taxa show that they had distinct bone histology and varied growth patterns. The Early Triassic trematosaurids had an overall fast growth, which contrasts with that of the Middle and Late Triassic temnospondyl taxa examined. The dicynodonts on the other hand, were characterized by an overall fast growth with periodic interruptions, variable growth rates dependent on ontogeny and indeterminate growth strategy. A comparative study encompassing several neotherapsid genera including the dicynodonts shows signifi cant evolutionary trends towards determinate growth strategy and reduced developmental plasticity.

A new Triassic temnospondyl from Antarctica and a review of Fremouw Formation biostratigraphy

ABSTRACT A new temnospondyl, Kryostega collinsoni, gen. et sp. nov., is described on the basis of a large snout fragment from the Triassic upper Fremouw Formation of Antarctica. K. collinsoni is characterized by greatly enlarged teeth of the transvomerine and parachoanal tooth rows, a reduced transvomerine tooth row, as well as a distinct process on the palatal surface of the premaxilla. Although key palatal and tabular features are not preserved, the shape and position of the external naris, choana, and anterior palatal vacuity suggest that K. collinsoni may be allied to the Heylerosauridae or basal Mastodonsauridae. The discovery of K. collinsoni in the upper Fremouw is surprising, given that Triassic vertebrates from Antarctica are typically considered a subset of coeval taxa from the Karoo Basin of South Africa. Based on its unique occurrence in Antarctica, K. collinsoni suggests that high latitude Triassic tetrapods had a more restricted geographic distribution than previously considered. Biostratigraphically, the fauna of the upper Fremouw Formation is best correlated with the Cynognathus Assemblage Zone of South Africa's Beaufort Group, although the lack of species—level identifications for many of the Antarctic fossils precludes a more refined correlation. A review of the Triassic fossil record identifies several tetrapods that make their first appearance in the Fremouw, with a later appearance in the Karoo Basin, suggesting that the high latitude regions of Gondwana might have served as an important area for speciation.

A new brachyopid temnospondyl from the Cynognathus Assemblage Zone, Upper Beaufort Group, South Africa

ABSTRACT A new brachyopid temnospondyl is described from the Early to Middle Triassic Cynognathus Assemblage Zone of the upper Beaufort Group, Karoo Basin of South Africa. Vanastega plurimidens, gen. et sp. nov. is the third brachyopid taxon from the South African Karoo and is distinguished from all other brachyopids mainly through a combination of primitive and derived character states. The position of the nostrils exceptionally close to and anteriorly confluent with the skull margin represents the single known autapomorphy of V. plurimidens. Incorporation of V. plurimidens into a data matrix modified from a recent PAUP-based study of brachyopoids produces a phylogeny in which V. plurimidens is the sister species to Vigilius wellesi from the Anisian of North America. In addition, the Brachyopoidea appear to be phylogenetically closer to the Dvinosauria than to other Triassic temnospondyls, with weak support for the alternative hypothesis, which places the Brachyopoidea closer to typical Triassic stereospondyls. This suggests that brachyopids are derived dvinosaurians, in agreement with earlier hypotheses of brachyopoid interrelationships. Stratigraphie calibration of this phylogeny reveals significant ghost lineages primarily within the Brachyopidae and Chigutisauridae, but also suggests a ghost lineage for the Brachyopoidea back into the Late Permian of southern Africa.

Triassic temnospondyls of the Pranhita–Godavari basin, India

The Pranhita–Godavari (P–G) basin of central India has yielded Early, Middle and Late Triassic temnospondyl families. Bracyops laticeps, the type for the family Brachyopidae was first described from the Lower Triassic ‘Mangli Beds’ of the northernmost extension of the P–G basin. In the northern and central parts of the P–G basin itself, the Middle Triassic Yerrapalli Formation has Stanocephalosaurus rajareddyi, a paracyclotosaurid, and the Upper Triassic Maleri Formation has Buettneria maleriensis, a metoposaurid and two other chigutisaurid taxa, Compsocerops cosgriffi and Kuttycephalus triangularis. A critical review of Triassic temnospondyls of the P–G basin indicates that the affinities of S. rajareddyi and K. triangularis are somewhat uncertain and discovery of further material is necessary to establish their relationships among similar temnospondyls of the world. It is also noted that B. maleriensis is displaced by the two chigutisaurid genera and species at the Carnian–Norian boundary. Thus, P–G basin is unique in having Pangaean metoposaurids and exclusively Gondwanan chigutisaurids in successive faunal zones within the same formation. Significantly, the end of Carnian is marked by the demise of metoposaurids in India as well as in Africa and Europe. In North America, their size appears to have diminished during that time.

Triassic temnospondyl biostratigraphy, biochronology and correlation of the German Buntsandstein and North American Moenkopi Formation

Triassic temnospondyl biostratigraphy, biochronology and correlation of the German Buntsandstein and North American Moenkopi Formation

Triassic temnospondyl biostratigraphy, biochronology and correlation of the German Buntsandstein and North American Moenkopi Formation

Based on temnospondyl distributions, we propose a correlation of the non-marine Lower and Middle Triassic strata of Germany and the western United States. This correlation relies principally on the presence of two genera, Nonesian (late Early Triassic) Parotosuchus and Perovkan (early Middle Triassic) Eocyclotosaurus. The distribution of Parotosuchus helgolandicus indicates that the Torrey Member of the Moenkopi Formation in Utah, USA is equivalent to the Volpriehausen Formation of the German Buntsandstein of Nonesian age. Magnetostratigraphy and the distribution of Eocyclotosaurus indicate that the Perovkan Holbrook Member of the Moenkopi Formation in Arizona corresponds to a short interval of Anisian time, as does the German Upper Buntsandstein. The Buntsandstein and Moenkopi biostratigraphic schemes agree with a recently proposed biochronology of Triassic terrestrial tetrapods.

A NEW TEMNOSPONDYL AMPHIBIAN FROM THE LATE TRIASSIC OF TEXAS

Abstract A skull representing a new genus and species of Late Triassic temnospondyl, Rileymillerus cosgriffi, is described from the Cooper Canyon Formation, upper Dockum Group of Garza County, Texas. Rileymillerus resembles Latiscopus disjunctus in size and proportions, but the very poorly preserved unique type specimen of L. disjunctus indicates that the taxon should be considered a nomen dubium. Characters of R. cosgriffi include its small size combined with relatively small laterally-facing orbits, relatively high skull, lack of lateral line canals, lateral exposure of the palatine on the skull surface, and lack of otic notch/quadrate angle. No postcranial material can be definitely associated, although we describe a partial vertebral column that might pertain to R. cosgriffi. Relationships of R. cosgriffi are uncertain. The possibilities of a close relationship to Almsauridae, Tupilakosauridae or (especially) Brachyopoidea are explicitly examined, but for the present we consider R. cosgriffi as Temnos...

A new temnospondyl amphibian from the Late Triassic of Texas

A skull representing a new genus and species of Late Triassic temnospondyl, Rileymillerus cosgriffi, is described from the Cooper Canyon Formation, upper Dockum Group of Garza County, Texas. Rileymillerus resembles Latiscopus disjunctus in size and proportions, but the very poorly preserved unique type specimen of L. disjunctus indicates that the taxon should be considered a nomen dubium. Characters of R. cosgriffi include its small size combined with relatively small laterally-facing orbits, relatively high skull, lack of lateral line canals, lateral exposure of the palatine on the skull surface, and lack of otic notch/quadrate angle. No postcranial material can be definitely associated, although we describe a partial vertebral column that might pertain to R. cosgriffi. Relationships of R. cosgriffi are uncertain. The possibilities of a close relationship to Almsauridae, Tupilakosauridae or (especially) Brachyopoidea are explicitly examined, but for the present we consider R. cosgriffi as Temnospondyl incertae sedis. Characters described in the text have been converted to the tripartite (part, feature, state) standardized format developed for the PRESERVE web site, and are presented as a 125-character data matrix in the Appendix.

Giant temnospondyl amphibians from the Early to Middle Triassic Narrabeen Group of the Sydney Basin, New South Wales, Australia

Material of giant temnospondyl amphibians is described from two localities in the Early to Middle Triassic Narrabeen Group of the Sydney Basin, Australia. The capitosaurid Bulgosuchus gargantua gen. et. sp. nov. from the Bulgo Sandstone (Scythian) at Longreef, represented by an incomplete mandible and a femur, is the largest known Early Triassic temnospondyl and the earliest occurrence of a temnospondyl in the Sydney Basin Triassic. B. gargantua is phenetically most similar to Paracyclotosaurus and to ‘P’. gunganj, but also shows affinities with Eryosuchus and Middle Triassic species of ‘Parotosuchus’. An anterior portion of a large mandible from the Terrigal Formation (late Scythian-early Anisian) at Bouddi is also described and tentatively referred to the Capitosauridae, but is generically indeterminate. The morphology of the post-glenoid area in members of the Capitosauridae is described, and derived characters of the capitosaurid mandible are provided.

The mandibles of the Triassic temnospondyl amphibians

A format is presented for describing the largely conservative mandible of the Triassic temnospondyls. It concentrates on those features which can be used to identify whole or sometimes partial mandibles to family level, and can be used to some extent to ascertain relationships between the families. The mandibular feature having the most diagnostic value is the postglenoid area. An example of the use of the format is given using previously undescribed material and the format is applied to some problematical examples.

A new rhytidosteid (Amphibia, Labyrinthodontia) from the Early Triassic Arcadia Formation of Queensland, Australia, and the relationships of Triassic temnospondyls

ABSTRACT The Early Triassic Arcadia Formation of Queensland, Australia, has yielded a second rhytidosteid labyrinthodont, the description of which allows reevaluation of the Triassic temnospondyls, which are here divided into two groups, trematosaurians and capitosaurians. Characters used in this division are discussed, and an hypothesis of relationships among the families of Triassic temnospondyls is proposed. The superfamily Rhytidosteoidea is rejected. The superfamily Trematosauroidea is increased to two families, the Trematosauridae and the Rhytidosteidae, the members of the family Indobrachyopidae being included in the Rhytidosteidae. The superfamily Brachyopoidea is included as the sister group of the Trematosauroidea within the trematosaurian group. The family Lydekkerinidae shares some trematosaurian group characters but lacks others and thus has been placed with some hesitation in the trematosaurian group. Description of the anatomy of the new rhytidosteid has led to a reexamination of certain as...