Middle Permian Dicynodont Chelydontops altidentalis is a Junior Synonym of Brachyprosopus broomi

A reevaluation of Brachyprosopus broomi and Chelydontops altidentalis, dicynodonts (Therapsida, Anomodontia) from the middle Permian Tapinocephalus Assemblage Zone of the Karoo Basin, South Africa

Authors:

Angielczyk et al

Abstract:

Brachyprosopus broomi was described in 1937 based on a specimen from the Tapinocephalus Assemblage Zone (Karoo Basin, South Africa), but it was largely overlooked by subsequent workers. We have identified several new specimens that show that Brachyprosopus is a valid taxon. An autapomorphy for the taxon is a curled lateral edge of the squamosal that forms a lateral wall of the external adductor fossa. Other important characters are absence of anterior median palatal ridges; maxillary tooth rows bounded laterally by a shelf; unfused vomers; raised margins of the interpterygoid vacuity; broad intertemporal region; pineal boss; dentary tables; and a long, wide posterior dentary sulcus that extends posterior to the dentary teeth. Chelydontops altidentalis is a junior synonym of B. broomi. A phylogenetic analysis places Brachyprosopus among basal dicynodonts, not as a close relative of Endothiodon. It is noteworthy that some characters, such as well-developed medial maxillary tooth rows and the shape of the palatines, are shared by Brachyprosopus, Pristerodon, Endothiodon, and Niassodon, hinting that a final resolution of relationships among toothed dicynodonts remains to be achieved. Most Brachyprosopus specimens are from the upper Abrahamskraal Formation (Moordenaars and Karelskraal members). One specimen is from low in the Koonap Formation, just above the lowermost maroon mudrocks of the Beaufort Group, and an exact correlation between this level and the strata of the Abrahamskraal Formation is uncertain. Therefore, it is likely that the stratigraphic range of Brachyprosopus extends throughout the Tapinocephalus zone and possibly down into the Eodicynodon Assemblage Zone.

Late Permian Tuskless Geikiid Cryptodont Dicynodont Pelanomodon Redescribed, Shows Sexual Dimorphism

Redescription of the geikiid Pelanomodon (Therapsida, Dicynodontia), with a reconsideration of ‘Propelanomodon’

Authors:

Kammerer et al

Abstract:

Cryptodont dicynodonts are some of the most abundant therapsid taxa in the upper Permian fossil record. Despite extensive taxonomic study of these families, the species diversity of geikiid cryptodonts remains problematic, particularly for the set of edentulous taxa in the genera Pelanomodon, Propelanomodon, and Geikia. Here, all known specimens of tuskless geikiid dicynodonts from the upper Permian Karoo Basin of South Africa are reevaluated. The genus Pelanomodon is redescribed based on a series of skulls representing a range of sizes. All tuskless geikiids from the Karoo Basin are considered to represent a single species (Pelanomodon moschops) that exhibited cranial dimorphism as adults. The nominal species Pe. moschops and Pe. rubidgei differ only in degree of facial boss development and are most parsimoniously interpreted as sexual dimorphs. Propelanomodon is considered to represent the juvenile morphotype of Pelanomodon moschops, as indicated by the geographic and stratigraphic overlap of the two taxa, the lack of any small skulls of the Pelanomodon morphotype in well-sampled localities, and the presence of specimens of intermediate size and morphology. ‘Propelanomodon’ specimens are distinctive among juvenile dicynodonts in having a significantly narrower intertemporal region than adults. Analysis of intertemporal width relative to total skull size in Pelanomodon and the abundant cryptodont taxa Aulacephalodon, Oudenodon, and Tropidostoma suggests that Pelanomodon had a unique growth trajectory. Based on available stratigraphic data, Pelanomodon was restricted to the uppermost Permian Daptocephalus Assemblage Zone of the South African Beaufort Group and was a victim of the end-Permian mass extinction.

A new Emydopoid Dicynodont From Upper Permian Tanzania

Distinctive emydopoid dicynodont (Therapsida, Anomodontia) mandibles from the Permian Ruhuhu and Usili formations (Songea Group), Ruhuhu Basin, Tanzania

Authors:

Angielczyk et al

Abstract:

Dicynodont therapsids were discovered in the Permian Usili Formation (Ruhuhu Basin, Tanzania) in the 1930s and in the Permian Ruhuhu Formation in the 1960s, with further collections being made in 2007, 2008, and 2012. Here we describe two fragmentary mandibles that represent a new morphotype of emydopoid dicynodont. One specimen was collected in the middle fossiliferous horizon of the Ruhuhu Formation, and the other originated in the overlying Usili Formation. Three synapomorphies support the placement of these specimens in the emydopoid subclade Kingoriidae: mandibular fenestra occluded by the dentary; curved ridge that follows the profile of the symphysis present on the edge between the anterior and lateral surfaces of the dentary; and posterior dentary sulcus absent. The specimens may represent a new dicynodont species, a previously known species for which mandibular material was unknown, or an intraspecific variant of Dicynodontoides nowacki. Regardless of which of these options is correct, the specimens constitute the first taxon with a stratigraphic range extending from the likely middle Permian middle fossiliferous horizon of the Ruhuhu Formation into the late Permian Usili Formation. They also improve our understanding of the middle Ruhuhu tetrapod fauna, which previously consisted only of Endothiodon tolani.

Endothiodon tolani: a new Endothiodont Dicynodont From Middle Permian Tanzania

A new endothiodont dicynodont (Therapsida, Anomodontia) from the Permian Ruhuhu Formation (Songea Group) of Tanzania and its feeding system

Athors:

Cox et al

Abstract:

Cranial material of the dicynodont Endothiodon from the middle fossiliferous horizon of the Permian Ruhuhu Formation (Ruhuhu Basin, Tanzania) is described as a new species, E. tolani. Endothiodon tolani is distinguished from other Endothiodon species by the absence of a pineal boss and the presence of tusks in most specimens. Although some parts of the Ruhuhu Formation probably correlate with the Eodicynodon or Tapinocephalus assemblage zones of the South African Karoo Basin, it is uncertain whether E. tolani is older than E. bathystoma or E. mahalanobisi. There is less evidence for extensive anteroposterior translation of the mandible in E. tolani than in other dicynodonts. The jaw joint is specialized for allowing some medial-lateral motion. Mastication involved unilateral chewing. Flexure of the postdentary bones relative to the fused dentaries permitted the posterolaterally directed rows of teeth on one side of the skull and mandible to move past one another. The long tooth rows and prominent horn-covered ridges and grooves on the palate and mandible of Endothiodon are unique among dicynodonts. Comparisons with other taxa suggest that its feeding system may have been specialized for cutting three-dimensional objects such as stems or rhizomes. The dicynodont feeding system is very stereotyped throughout the clade's history, but Endothiodon escaped the constraints that affected other dicynodonts, allowing it to evolve a unique skull morphology. This evolutionary flexibility did not translate into high taxonomic richness (we recognize only three species of Endothiodon), but Endothiodon was able to achieve high levels of relative abundance in some basins.

Emydopoid Dicynodont Digalodon rubidgei Redescribed

Redescription of Digalodon rubidgei, an emydopoid dicynodont (Therapsida, Anomodontia) from the Late Permian of South Africa. (pdf)

Authors:

Fröbisch et al

Abstract:

The Late Permian dicynodont Digalodon rubidgei Broom and Robinson, 1948, is redescribed based on reanalysis of the holotype and newly recognized referable specimens. Digalodon can be diagnosed by the presence of a long “beak” sharply demarcated from the caniniform process; an extremely tall zygomatic ramus of the squamosal, with a thickened, “folded-over” dorsal margin; raised parietal “lips” along the lateral edges of the pineal foramen; and a broad posterolateral expansion of the parietal, excluding the postorbital from the back of the skull roof. Inclusion of Digalodon in a recent analysis of anomodont phylogeny recovers it as a kistecephalian emydopoid, specifically as the sister taxon to the clade containing the remaining kistecephalians. Four definite specimens of Digalodon are known, but several additional specimens lacking tusks, the swollen pineal “lips”, and a thickened zygoma may represent sexually dimorphic females or juveniles. Specimens of Digalodon are restricted to the central portion of the Karoo Basin, in the area around Graaff-Reinet, and are part of a characteristic fauna probably representing a limited time span.

New Kannemeyeriiforme Dicynodonts From Middle Triassic China

New discoveries from the Sinokannemeyeria-Shansisuchus Assemblage Zone: 1. Kannemeyeriiformes from Shanxi, China

Author:

Jun

Abstract:

Recently, some new tetrapod fossils were collected along the Yellow River in Shanxi Province. From the Member I of the Tongchuan Formation at Baidaoyu in Linxian County, at least one species of Parakannemeyeria, and one new species of Sinokannemeyeria, S. baidaoyuensis, are identified. The new species is characterized by prefrontal anterior extension level to posterior margin of postnarial excavation. From the Ermaying Formation in Liulin County, a third kannemeyeriid genus is identified for the Sinokannemeyeria-Shansisuchus Assemblage. The new findings increase the content and time extension of the Sinokannemeyeria-Shansisuchus Assemblage.

Abajudon kaayai & Endothiodon oosthuizeni: Two New Wordian/Capitanian Permian Dicynodonts From Tanzania

New dicynodonts (Therapsida, Anomodontia) and updated tetrapod stratigraphy of the Permian Ruhuhu Formation (Songea Group, Ruhuhu Basin) of southern Tanzania

Authors:

Angielczyk et al

Abstract:

Permian tetrapod fossils were discovered in the Tanzanian Ruhuhu Formation in 1963, but they have received far less attention than the tetrapods of the overlying Usili (formerly Kawinga) Formation. Here, we describe two dicynodonts collected in the Ruhuhu Formation in 2008. Abajudon kaayai, gen. et sp. nov., is represented by a partial skull and mandible and is characterized by autapomorphic upper teeth that are triangular in cross-section, have procurved tips, and bear a deep groove on the mesial surface. Although it shows similarities to taxa such as Endothiodon and Chelydontops, the exact relationships between A. kaayai and other dicynodonts are uncertain. The second specimen also consists of a partial skull and mandible. We refer it to cf. Endothiodontia based on the medial placement of the long maxillary tooth rows, the presence of depressions on the palatine pad, a long posterior dentary sulcus, and similarities of the mandibular dentition. Tetrapods occur in three fossiliferous horizons in the Ruhuhu Formation. The likely Middle Permian lower horizon includes dinocephalians, temnospondyls, and the dicynodonts described here. The middle horizon includes a new, tusked species of Endothiodon and at least one other dicynodont. The upper horizon appears to sample an assemblage similar to that of the Usili Formation and therefore may be of Late Permian age. The discovery of Middle Permian fossils in Tanzania and Zambia provides the opportunity to test whether southern Gondwana was characterized by a cosmopolitan tetrapod fauna for an extended period of time before the biogeographic restructuring caused by the end-Permian mass extinction.

How Well Late Permian, Burrowing Anomodont Kawingasaurus Felt Vibrations and Sounds

Bone-conduction hearing and seismic sensitivity of the late permian anomodont Kawingasaurus fossilis

Author:

Laaß

Abstract:

An investigation of the internal cranial anatomy of the anomodont Kawingasaurus from the Upper Permian Usili Formation in Tanzania by means of neutron tomography revealed an unusual inner and middle ear anatomy such as extraordinarily inflated vestibules, lateroventrally orientated stapes with large footplates, and a small angle between the planes of the anterior and lateral semicircular canals. The vestibule has a volume, which is about 25 times larger than the human vestibule, although Kawingasaurus has only a skull length of approximately 40 mm. Vestibule inflation and enlarged stapes footplates are thought to be functionally correlated with bone-conduction hearing; both morphologies have been observed in fossorial vertebrates using seismic signals for communication. The firmly fused triangular head with spatulate snout was probably used for digging and preadapted to seismic signal detection. The quadrate-quadratojugal complex was able to transmit sound from the articular to the stapes by small vibrations of the quadrate process, which formed a ball and socket joint with the squamosal. Mechanical considerations suggest that the ventrolaterally orientated stapes of Kawingasaurus was mechanically better suited to transmit seismic sound from the ground to the fenestra vestibuli than a horizontal orientated stapes. The low sound pressure level transformer ratio of 2–3 in Kawingasaurus points to a seismic sensitivity of the middle ear and a vestigial or reduced sensitivity to airborne sound. Three hypothetical pathways of bone conduction in Kawingasaurus are discussed: 1) sound transmission via the spatulate snout and skull roof to the otic capsules, 2) relative movements resulting from the inertia of the mandible if sound is percepted with the skull, and 3) bone conduction from the substrate via mandible, jaw articulation, and stapes to the inner ear.

Tetrapods from Middle Triassic Antarctica

New Middle Triassic tetrapods from the upper Fremouw Formation of Antarctica and their depositional setting

Authors:

Sidor et al

Abstract:

Renewed field work in the Beardmore Glacier region of Antarctica has led to a new collection of tetrapod fossils from the upper member of the Fremouw Formation near Fremouw Peak. This locality records a sedimentary environment remarkably similar to that preserved at Gordon Valley, the only other locality known to preserve Cynognathus Assemblage Zone–equivalent taxa from Antarctica. Fossil bones are generally disarticulated and mixed with logs and reworked mudrock clasts, forming an intraformational channel-lag conglomerate. To date, very few bones of small-bodied taxa have been recovered from the upper Fremouw conglomerates, suggesting that they did not survive the reworking process. We use an apomorphy-based approach to record three previously unrecognized taxa from the upper Fremouw Formation: the dicynodont Angonisaurus, an indeterminate therocephalian therapsid, and an indeterminate crown-group archosaur. Combined with previous data, our work demonstrates that 10 distinct taxa can be recognized from the upper Fremouw, including two endemic temnospondyl species. Our recognition of Angonisaurus in the upper Fremouw Formation provides a new piece of evidence in favor of a correlation with the Cynognathus C subzone (uppermost Burgersdorp Formation) of South Africa and the Lifua Member of the Manda beds of Tanzania.

Dicynodont Coprolites From Norian/Rhaetian Triassic Poland

Putative dicynodont coprolites from the Upper Triassic of Poland

Authors:

Bajdek et al

Abstract:

A significant number (more than 100) of brown to dark and silty, carbonate or pyrite-mineralized, in part organic carbon-rich, spherical or oval-shaped structures have been collected from the Upper Triassic (uppermost Norian-lower Rhaetian) sediments of the Lipie Śląskie clay-pit at Lisowice near Lubliniec town, Poland. Their geological context, morphology, content, geochemistry and association with skeletal remains suggest they are faecal masses of a sizable herbivorous tetrapod. The only large herbivore known from the site is a giant 5 metre-long dicynodont (Synapsida: Anomodontia), represented by numerous bones and also by large, oval-shaped footprints. The putative dicynodont coprolites were collected from mudstone and siltstone with numerous organic remains that were deposited in anoxic conditions. In addition, REEs and other trace element concentrations suggest that the burial environment and diagenesis of these coprolites were under anoxic conditions. SEM and thin section images of the coprolite matrix show numerous nests with pyrite (probably bacterial in origin) and large amount of mineral particles.. The putative dicynodont coprolites contain also amorphous, dark organic matter, poorly preserved palynomorphs, small fragments of plant cuticle. Detailed characteristic of these coprolites reveals possible implications for the ecology and physiology of the source animal species. The delta 13C values of the gymnosperm cuticle and dark organic matter measured in three coprolites is − 23.4‰, − 21.2 ‰ and − 20.3 ‰, all average. The evidence from these coprolites suggests that dicynodonts processed plant soft elements into very small pieces, but wood fragments were found also in a mass accumulation in two coprolites.

Sungeodon kimkraemerae: a Kannemeyeriiform Dicynodont From Earliest Triassic China

Sungeodon kimkraemerae n. gen. n. sp., the oldest kannemeyeriiform (Therapsida, Dicynodontia) and its implications for the early diversification of large herbivores after the P/T boundary

Authors:

Maisch et al

Abstract:

The dicynodont Sungeodon kimkraemerae n. gen. n. sp. is described on the basis of a skull from the Lower Triassic Jiucaiyuan Formation of Dalongkou (Junggar Basin, Xinjiang Uygur Autonomous Region, People's Republic of China). It is the first representative of Kannemeyeriiformes from the earliest Triassic. Kannemeyeriiforms were the predominant clade of Triassic dicynodonts, which constituted a major component of terrestrial Triassic ecosystems. The new taxon helps closing one of the most significant gaps in the fossil record of dicynodonts, since stem-kannemeyeriiforms are known from the Late Permian, whereas the first true kannemeyeriiforms previously known are late Early Triassic in age. After a phylogenetic analysis Sungeodon belongs to the family Stahleckeriidae. Therefore, the Stahleckeriidae may not have had its origin in Africa as previously assumed, but in Central Asia. More importantly, Sungeodon also suggests that the major radiation of kannemeyeriiform dicynodonts, including the emergence of all relevant subgroups of this clade, occurred not later than in the Early Triassic, soon after the end-Permian extinction. To date, only few dicynodont taxa are known from the earliest Triassic, none of which are kannemeyeriiforms. The addition of Sungeodon confirms previous predictions that our knowledge of Early Triassic dicynodont diversity and evolution is far from being complete, and that new discoveries from historically low-sampled geographic regions may fill this gap. A rapid post-extinction diversification of kannemeyeriiforms also fits with the emerging picture from other clades, such as archosaurs, of a rapid recovery from the end-Permian event in the terrestrial realm.

Tetrapod (Dicynodont?) Burrows From the Middle/Upper Permian of China

Large Tetrapod Burrows from the Permian Naobaogou Formation of the Daqingshan Area, Nei Mongol, China

Authors:

LIU Jun & LI Lu

Abstract:

Two new tetrapod burrow casts from the Naobaogou Formation (Middle or Late Permian) of Nei Mongol, China are described. It marks the first pre-Cenozoic tetrapod burrow from China, and one of the earliest records of tetrapod burrows. Comparison to other Permian and Triassic burrows suggests that these burrows were created by tetrapod slightly smaller than Lystrosaurus. Deduced from the morphology and sizes of two burrows and known tetrapods of the Naobaogou Formation, the burrow should be the production of a therapsid, most likely a dicynodon. These burrows indicate a seasonal climate and this area was semiarid or arid during that time.

Niassodon mfumukasi: a new Dicynodont With Teeth From Wuchiapingian Permian Mozambique

Bringing Dicynodonts Back to Life: Paleobiology and Anatomy of a New Emydopoid Genus from the Upper Permian of Mozambique

Authors:

Castanhinha et al

Abstract:

Dicynodontia represent the most diverse tetrapod group during the Late Permian. They survived the Permo-Triassic extinction and are central to understanding Permo-Triassic terrestrial ecosystems. Although extensively studied, several aspects of dicynodont paleobiology such as, neuroanatomy, inner ear morphology and internal cranial anatomy remain obscure. Here we describe a new dicynodont (Therapsida, Anomodontia) from northern Mozambique: Niassodon mfumukasi gen. et sp. nov. The holotype ML1620 was collected from the Late Permian K5 formation, Metangula Graben, Niassa Province northern Mozambique, an almost completely unexplored basin and country for vertebrate paleontology. Synchrotron radiation based micro-computed tomography (SRµCT), combined with a phylogenetic analysis, demonstrates a set of characters shared with Emydopoidea. All individual bones were digitally segmented allowing a 3D visualization of each element. In addition, we reconstructed the osseous labyrinth, endocast, cranial nerves and vasculature. The brain is narrow and the cerebellum is broader than the forebrain, resembling the conservative, “reptilian-grade” morphology of other non-mammalian therapsids, but the enlarged paraflocculi occupy the same relative volume as in birds. The orientation of the horizontal semicircular canals indicates a slightly more dorsally tilted head posture than previously assumed in other dicynodonts. In addition, synchrotron data shows a secondary center of ossification in the femur. Thus ML1620 represents, to our knowledge, the oldest fossil evidence of a secondary center of ossification, pushing back the evolutionary origins of this feature. The fact that the specimen represents a new species indicates that the Late Permian tetrapod fauna of east Africa is still incompletely known.

Ladinian/Carnian Triassic Dicynodont (Dinodontosaurus?) Communal Latrine Found in Argentina

The oldest known communal latrines provide evidence of gregarism in Triassic megaherbivores

Authors:

Fiorelli et al

Abstract:

Defecation in communal latrines is a common behaviour of extant mammals widely distributed among megaherbivores. This behaviour has key social functions with important biological and ecological implications. Herbivore communal latrines are only documented among mammals and their fossil record is exceptionally restricted to the late Cenozoic. Here we report the discovery of several massive coprolite associations in the Middle-Late Triassic of the Chañares Formation, Argentina, which represent fossil communal latrines based on a high areal density, small areal extension and taphonomic attributes. Several lines of evidence (size, morphology, abundance and coprofabrics) and their association with kannemeyeriiform dicynodonts indicate that these large synapsids produced the communal latrines and had a gregarious behaviour comparable to that of extant megaherbivores. This is the first evidence of megaherbivore communal latrines in non-mammal vertebrates, indicating that this mammal-type behaviour was present in distant relatives of mammals, and predates its previous oldest record by 220 Mya.

 

Very Complete Juvenile Dinodontosaurus (dicynodont) From Carnian (?) Triassic Brazil Found?

link.

Lystrosaurus Subadults Were Trying to Keep Warm When They Died Creating Bonebeds in Induan (?) Triassic South Africa

Origin and palaeoenvironmental significance of Lystrosaurus bonebeds in the earliest Triassic Karoo Basin, South Africa

Authors:

Pia A. Viglietti, Roger M.H. Smith, and John S. Compton

Affiliations:

Earth experienced its most devastating extinction event at the end of the Permian period 251 million years ago (Ma). Despite an estimated 75 to 90% loss of species globally in both marine and terrestrial realms across the Permian–Triassic Boundary (PTB), around 20% of the terrestrial tetrapod genera in southwestern Gondwana survived and were immediately joined by a number of immigrant taxa to occupy most of the vacant niches of the earliest Triassic. Preserved in the Karoo Basin of South Africa is an almost continuous stratigraphic record of terrestrial sedimentation through the PTB that hosts a fossil record of ecosystem collapse, survivorship and recovery. The adaptation of the mammal like reptiles (therapsids) of the Lystrosaurus Assemblage Zone to a highly seasonal, potentially drought prone semi-arid earliest Triassic Karoo Basin is associated with changes in modes of fossilisation. Isolated dicynodont skulls and postcranial elements are commonly found in the latest Permian. However, in the earliest Triassic the dicynodonts occur as articulated, curled-up skeletons and multi-individual monotaxic bonebeds. Lack of epiphyses and relatively small skull length confirm that the bonebeds comprise several subadult Lystrosaurus declivis (L. declivis) carcasses. No significant evidence for hydraulic bone concentration along with clusters of ribs in life position points to complete carcasses being present at the site of death, and suggests that animals behaviourally congregated before perishing together. The bonebeds are hosted by an 8 m thick horizon of floodplain mudrocks in the lower Katberg Formation named the Lystrosaurus abundant zone. The bonebed horizon is overlain by sand-filled mud cracks capped by coarse sediments indicative of rapid deposition during waning floods. Stable isotope analyses of pedogenic and early diagenetic calcite nodules in association with the bonebeds yield average δ13C values ranging from − 9.5 to − 5‰ and δ18O values of 13.5 to 16‰, respectively. These isotope values support a seasonally cold, semi-arid climate at high latitude (~ 55°S). The presence of vertebrate burrow casts on bonebed horizons and evidence of shelter sharing suggests that tetrapods were attempting to escape extreme climatic conditions. Aggregation behaviour of subadult Lystrosaurus during unusual cold snaps may best explain the origin of bonebed assemblages.

PT Extinction Surviving Dicynodont Lineage Was Too Morphologically Conservative to Exploit New Niches

Ancient mammal relatives cast light on recovery after mass extinction

The study's findings are surprising as much research so far suggests that the survivors of mass extinctions are often presented with new ecological opportunities because the loss of many species in their communities allows them to evolve new lifestyles and new anatomical features as they fill the roles vacated by the victims. However, it turns out that not all survivors respond in the same way, and some may not be able to exploit fully the new opportunities arising after a mass extinction.

Dr Marcello Ruta of the University of Lincoln, with colleagues from the Field Museum of Natural History in Chicago, the Museum für Naturkunde in Berlin and the University of Bristol, studied how anomodonts responded in the aftermath of the end-Permian mass extinction, about 252 million years ago, when as many as 90 per cent of marine organisms and 70 per cent of terrestrial species became extinct.

Near the end of the Permian, a large number of anomodont species existed with a wide range of body sizes and ecological adaptations, including terrestrial plant eaters, amphibious hippo-like species, specialized burrowers, and even tree-dwelling forms. The most successful group of anomodonts, with canine-like tusks in their upper jaws and turtle-like beaks, were the most important terrestrial herbivores of their time.

Dr Ruta said: "The number of anomodont species increased during the Permian, sharply dropped during the end-Permian extinction event, and then rebounded in the Middle Triassic Period (about 240 million years ago) before the final extinction of the group at the end of the Triassic.

"However, the variety of different anatomical features found in anomodonts – that is, their anatomical diversity – declined steadily over their history. Even in the aftermath of the mass extinction, when there should have been a lot of empty ecological space, anomodonts did not evolve any fundamentally new features. Rather than allowing them to move to a new evolutionary trajectory, the genetic bottleneck they passed through constrained their future evolution."

Analyzing the response of animals and plants to this catastrophe helps scientists understand models of diversification and patterns of ecosystem reconstruction following large-scale biological crises.

Obviously Benton et al do not believe the fossil recovered from Australia is a Cretaceous dicynodont.

Open access paper link.

Dicynodonts More Diverse In Norian Triassic North America

On the Validity and Phylogenetic Position of Eubrachiosaurus browni, a Kannemeyeriiform Dicynodont (Anomodontia) from Triassic North America

Authors:

1. Christian F. Kammerer (a)
2. Jörg Fröbisch (a)
3. Kenneth D. Angielczyk (b)

Affiliations:

a. Museum für Naturkunde, Leibniz Institute for Research on Evolution and Biodiversity, Berlin, Germany

b. Department of Geology, Field Museum of Natural History, Chicago, Illinois, United States of America

Abstract:

The large dicynodont Eubrachiosaurus browni from the Upper Triassic Popo Agie Formation of Wyoming is redescribed. Eubrachiosaurus is a valid taxon that differs from Placerias hesternus, with which it was previously synonymized, by greater anteroposterior expansion of the scapula dorsally and a very large, nearly rectangular humeral ectepicondyle with a broad supinator process. Inclusion of Eubrachiosaurus in a revised phylogenetic analysis of anomodont therapsids indicates that it is a stahleckeriid closely related to the South American genera Ischigualastia and Jachaleria. The recognition of Eubrachiosaurus as a distinct lineage of North American dicynodonts, combined with other recent discoveries in the eastern USA and Europe, alters our perception of Late Triassic dicynodont diversity in the northern hemisphere. Rather than being isolated relicts in previously therapsid-dominated regions, Late Triassic stahleckeriid dicynodonts were continuing to disperse and diversify, even in areas like western North America that were otherwise uninhabited by coeval therapsids (i.e., cynodonts).

Angonisaurus and Shansiodon: Dicynodonts From the Middle Triassic

Angonisaurus and Shansiodon, dicynodonts (Therapsida, Anomodontia) from subzone C of the Cynognathus Assemblage Zone (Middle Triassic) of South Africa

Authors:

1. P. John Hancox (a)
2. Kenneth D. Angielczyka (b)
3. Bruce S. Rubidge (a)

Affiliations:

a. Bernard Price Institute for Palaeontological Research, School for Geosciences , University of the Witwatersrand , PO Wits , 2050 , South Africa

b. Department of Geology , Field Museum of Natural History , 1400 South Lake Shore Drive, Chicago , Illinois , 60605 , U.S.A.

Abstract:

Dicynodonts are the most abundant therapsids from the Beaufort Group (Karoo Basin, South Africa), and they have been used as index fossils to define most of the Beaufort biozones. Although speciose during the Late Permian, dicynodont diversity was greatly reduced by the end-Permian mass extinction. The Cynognathus Assemblage Zone, the uppermost biozone of the Beaufort Group, is traditionally known to host only the dicynodonts Kannemeyeria simocephalus and Kombuisia frerensis. Recent biostratigraphic research in this biozone has revealed the presence of two more poorly known dicynodont genera, Angonisaurus and Shansiodon, which are biostratigraphically constrained to the uppermost Cynognathus Assemblage Zone (subzone C). Although these taxa have been reported from subzone C of the Cynognathus Assemblage Zone previously, we provide the first detailed description of the material in question and justifications for the taxonomic identifications. The presence of Angonisaurus in the Cynognathus subzone C allows a direct correlation between this assemblage and that of the Lifua Member of the Manda beds in Tanzania. A correlation with the Antarctic upper Fremouw Formation also may be possible, but is less certain. The presence of Shansiodon allows a direct correlation with the upper Ermaying Formation of China, but we reject the previously proposed global ‘Shansiodon biochron’ because Shansiodon sensu stricto only occurs in China and South Africa. Biogeographically, Angonisaurus appears to have been widespread but rare in southern Gondwana, and the unusual distribution of Shansiodon mirrors that of Diictodon feliceps in the Permian. Southern African dicynodont assemblages display increased provinciality in the Middle Triassic.

Cistecephalus: One Fascinating Little Dicynodont

New insights into the biology of the Permian genus Cistecephalus (Therapsida, Dicynodontia)

Authors:

1. Tobias Nasterlack (a)
2. Aurore Canoville (a)
3. Anusuya Chinsamy (a)

Affiliations:

a. Department of Zoology, University of Cape Town, Private Bag X3, Rhodes Gift 7700, South Africa

Abstract:

The taxonomy and paleobiology of the Upper Permian dicynodont Cistecephalus have been much debated over the last century. Fossils of Cistecephalus have been identified as belonging either to one species or up to six species and hypotheses concerning their lifestyle range from aquatic to arboreal and fossorial. Earlier studies of Cistecephalus focused mainly on macroanatomical characteristics, whereas the current assessment examines a combination of anatomical features, as well as bone histology and microanatomy to unravel its biology. The allometries of a skull growth series that were examined in the present study imply that all Cistecephalus specimens belong to a single species. Furthermore, our data suggest that the variability in the occurrence of supraorbital ridges, which are raised in some specimens and leveled in others, is a feature of sexual dimorphism. Histological thin-sections of a humerus, an ulna, a femur, and ribs from two Cistecephalus specimens were studied to evaluate life history traits of this taxon. The comparison of ribs from a subadult and a fully grown specimen allows an estimation that sexual maturity was attained when the skull length was between 5.9 and 6.5 cm. The compact microstructure of the sampled Cistecephalus bones implies aquatic and/or fossorial adaptations, refuting an arboreal lifestyle. We propose that the high degree of binocular vision evident in Cistecephalus developed in response to predatory (insectivory) and/or nocturnal habits and that it is unrelated to a scansorial lifestyle.

Potentially omnivorous and fossorial.  Weird, awesome little thing.

I meant to post this before and forgot...too many things going on.  Good and bad.