Karoo Palaeontology


Karoo Palaeontology

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Peecook B.R.,University of Washington | Sidor C.A.,University of Washington | Nesbitt S.J.,University of Washington | Smith R.M.H.,Karoo Palaeontology | And 2 more authors.
Journal of Vertebrate Paleontology | Year: 2013

Recent discoveries have shown that non-dinosaurian dinosauromorphs were morphologically diverse, globally distributed, and have a stratigraphic range extending into the Upper Triassic. Silesauridae, the sister group to Dinosauria, contains at least seven species. Here we describe Lutungutali sitwensis, gen. et sp. nov., the first silesaurid from the upper portion of the Ntawere Formation of the Luangwa Basin, Zambia. The upper Ntawere Formation has been correlated with subzone C of the Cynognathus Assemblage Zone of the Karoo Basin in South Africa and the Lifua Member of the Manda beds in the Ruhuhu Basin in Tanzania, both of which are considered Anisian in age and the latter has yielded the silesaurid Asilisaurus kongwe. The results of our phylogenetic analysis, including a new pelvic character, allies Lutungutali with Upper Triassic silesaurids such as Silesaurus, Sacisaurus, and Eucoelophysis rather than with the possibly coeval Asilisaurus. The Zambian silesaurid shares a laterally oriented brevis fossa on the ilium and a transversely thin ischium in cross-section with Upper Triassic forms. Silesaurids were more diverse during their early evolution in the Anisian than previously suspected. Lutungutali and Asilisaurus are the two oldest known members of the bird-line archosaurs represented by body fossils. Together they show that a subclade of bird-line archosaurs was diversifying soon after its origin, building further support for the rapid diversification of Archosauria in the wake of the Permo-Triassic extinction. SUPPLEMENTAL DATA - Supplemental materials are available for this article for free at www.tandfonline.com/UJVP © 2013 by the Society of Vertebrate Paleontology.

Smith R.M.H.,Karoo Palaeontology | Smith R.M.H.,University of Cape Town | Botha-Brink J.,Karoo Palaeontology | Botha-Brink J.,University of the Free State
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

Bone-bearing coprolites are fossilised faeces of carnivores and as such they provide important information about food webs and feeding strategies of the ancient ecosystem. With this aim we examined the morphology and composition of Late Permian bone-bearing coprolites from the Hoedemaker Member of the Teekloof Formation (Lower Beaufort Group) of the southern Karoo Basin, South Africa. Analysis of the size and shape of 150 specimens collected from this member resulted in the recognition of 5 different morphotypes. Each morphotype is matched to carnivorous taxa within the Tropidostoma Assemblage Zone fauna which biostratigraphically defines the Hoedemaker Member strata in this part of the basin. Morphotype 1 are long cylinder-shaped non-segmented faeces, or possible cololites, rounded at both ends and commonly contain complete small bones as well as bone fragments and were most likely produced by the large gorgonopsians Aelurognathus and Gorgonops torvus. Smaller, tubular Morphotype 2 coprolites are attributed to the smaller therocephalians and juvenile gorgonopsians. Rare double-pointed Morphotype 3 are similar in size and shape to scats of the modern wild cat and we attribute these to the medium-sized gorgonopsians Cyonosaurus and Lycaenops or possibly juveniles of the large gorgonopsian species. Morphotype 4 coprolites are bullet-shaped and are interpreted as disaggregated portions of compound faeces. They are the most common coprolite found in the Hoedemaker mudrocks and are also attributed to small and medium-sized therocephalians and gorgonopsians. Morphotype 5 are rare flattened disc-shaped coprolites that contain abundant fish-scales and are linked to the temnospondyl, Rhinesuchus africanus, the only known piscivore from the Tropidostoma assemblage. Analyses of the microstructure of the bone inclusions within morphotypes 1-4 revealed two distinct tissue types. Bone tissue type A consists of highly vascularised, rapidly-forming bone interpreted as being that of very young perinatal and/or early juvenile therapsids, probably dicynodonts. Judging by the relative abundance of their body fossils, the herbivorous dicynodonts were by far the most abundant tetrapods in the Tropidostoma Assemblage Zone and it is probably that their young, both embryonic and neonatal juveniles, were commonly preyed upon. Some of the larger carnivores swallowed small prey whole, or with minimal mastication, allowing complete limbs to pass through the digestive tract in articulation. Inclusions of bone tissue type B, which consists of poorly-vascularised, slow-growing bone, are interpreted to be the skeletal remains of small parareptiles. © 2011 Elsevier B.V.

Botha-Brink J.,Karoo Palaeontology | Botha-Brink J.,University of the Free State | Smith R.M.H.,Karoo Palaeontology | Smith R.M.H.,University of Cape Town
Journal of Vertebrate Paleontology | Year: 2011

The South African non-archosauriform archosauromorph Prolacerta and the archosauriforms Proterosuchus, Erythrosuchus, and Euparkeria were important constituents of the Early to early Middle Triassic Karoo ecosystem following the end-Permian mass extinction. We present new data on the osteohistology of these stem archosaurs and provide insight into their paleobiology. Bone tissues of the Early Triassic Prolacerta contain a poorly defined fibro-lamellar complex, with parallelfibered bone in some regions, whereas the contemporaneous Proterosuchus exhibits rapidly forming uninterrupted fibrolamellar bone early in its ontogeny, which becomes slow forming lamellar-zonal bone with increasing age. The early Middle Triassic Erythrosuchus deposited highly vascularized, uninterrupted fibro-lamellar bone throughout ontogeny, whereas the growth of the contemporaneous Euparkeria was relatively slow and cyclical. When our data are combined with those of previous studies, preliminary results reveal that Early and Middle Triassic non-crown group archosauromorphs generally exhibit faster growth rates than many of those of the Late Triassic. Early rapid growth and rapid attainment of sexual maturity are consistent with life history expectations for taxa living in the unpredictable conditions following the end-Permian mass extinction. Further research with larger sample sizes will be required to determine the nature of the environmental pressures on these basal archosaurs. © 2011 by the Society of Vertebrate Paleontology.

Sidor C.A.,University of Washington | Angielczyk K.D.,Field Museum | Weide D.M.,University of Washington | Weide D.M.,California State University, Long Beach | And 3 more authors.
Journal of Vertebrate Paleontology | Year: 2010

Vertebrate fossils from the Ruhuhu Basin of southern Tanzania have been known for over 75 years, but the details of their stratigraphic distribution remain imperfectly understood. Recent fleldwork in the Upper Permian Usili Formation (Songea Group) has led to the discovery of a tetrapod assemblage in a conglomeratic unit at its base. The fossils are concentrated in matrix-supported intraformational clay pebble conglomerates interpreted as mass flow deposits in wide, shallow channels in the distal reaches of an alluvial fan. Included in this new collection are fossils representing the first record of a burnetiid therapsid from Tanzania. The anatomy of the interorbital and intertemporal skull roof indicates that the Usili burnetiid most closely resembles Burnetia from the Dicynodon Assemblage Zone of South Africa's Beaufort Group. Review of the Usili Formation tetrapod fauna recognizes 29 genera, 6 of which are endemic (Katumbia, Kawingasaurus, Pachytegos, Peltobatrachus, Ruhuhucerberus, Titanogorgon, as well as a new, undescribed cryptodontian dicynodont). In addition, eight genera are shared between the basal conglomerate and rocks higher in section, which suggests that the available data fail to support the recognition of two faunal horizons within the Usili Formation, as was suggested previously. The recognition of a single (undivided) Usili tetrapod fauna calls for several therapsid genera to have unequal stratigraphic ranges (and temporal durations) in the Ruhuhu and Karoo basins. We suggest that the fine-scale biostratigraphic utility of therapsids likely diminishes between basins, especially when rates of subsidence, depositional setting, and paleoenvironment are taken into consideration. © 2010 by the Society of Vertebrate Paleontology.

Modesto S.P.,Cape Breton University | Botha-Brink J.,Karoo Palaeontology | Botha-Brink J.,University of the Free State
Journal of African Earth Sciences | Year: 2010

The best record of continental tetrapod faunas crossing the Permo-Triassic boundary (PTB) is found in the Karoo Basin of South Africa. Similar records are not known elsewhere among the former Gondwanan land masses, but it was recently proposed on the basis of palaeontological evidence that the Buena Vista Formation of Uruguay preserves a South American record of continental PTB tetrapods. The Buena Vista Formation was previously correlated to the Lower Triassic (Olenekian) Sanga do Cabral Formation of Brazil on the basis of lithostratigraphic evidence, but recent collecting in the former unit has produced a tetrapod fauna that is distinct to that documented for the latter. The unequivocal tetrapod fossils that have been described thus far from the Buena Vista Formation include indeterminate mastodonsaurid temnospondyls, a plagiosauroid temnospondyl, and a procolophonid reptile. The temnospondyls belong to Triassic groups, whereas the procolophonid is allied most closely with Early Triassic taxa from the Karoo Basin. We conclude that there is no compelling palaeontological evidence for placing any part of the Buena Vista Formation in the Permian. A precise placement of the Buena Vista Formation in the Triassic on the basis of its tetrapod fauna is not possible at this time. Accordingly, the Karoo Basin of South Africa remains the only Gondwanan basin that records a PTB tetrapod fauna. © 2009 Elsevier Ltd.

Modesto S.P.,Cape Breton University | Scott D.M.,University of Toronto | Botha-Brink J.,Karoo Palaeontology | Reisz R.R.,University of Toronto | Reisz R.R.,University of the Free State
Journal of Vertebrate Paleontology | Year: 2010

A small skull collected from the base of the Katberg Formation of South Africa represents a new Early Triassic procolophonid parareptile. Phonodus dutoitorum, gen. et sp. nov., is diagnosed by a roughly straight ventral temporal margin, prefrontals that contact each other along the dorsal midline, presence of a large posterior maxillary tooth, an edentulous pterygoid, a reduced transverse flange of the pterygoid, and other autapomorphies. A cladistic analysis identifies P. dutoitorum as a basal member of the procolophonid clade Leptopleuroninae. The presence of large maxillary teeth, their positioning ventral to strongly developed antorbital buttresses, and the loss of the ventral temporal emargination are suggestive of a durophagous diet. Phonodus dutoitorum is recognized as the oldest known leptopleuronine. Optimization of geographic distributions onto procolophonid phylogeny indicates that the presence of P. dutoitorum in the Karoo Basin of South Africa is explained most parsimoniously as the result of migration from Laurasia. Phonodus dutoitorum is the fifth procolophonoid species to be described from the Induan of the Karoo Basin, providing further support for the hypothesis that procolophonoid evolution was not greatly perturbed by the end-Permian extinction event. © 2010 by the Society of Vertebrate Paleontology.

Botha-Brink J.,Karoo Palaeontology | Botha-Brink J.,University of the Free State | Modesto S.P.,Cape Breton University
Palaeontology | Year: 2011

Abstract: We provide a redescription of the therocephalian therapsid Olivierosuchus parringtoni based on a new specimen recovered from the Lower Triassic Lystrosaurus Assemblage Zone of South Africa and discuss the biostratigraphic implications of Lower Triassic South African therocephalians. The new specimen comprises a skull and articulated anterior portion of the postcranial skeleton. Olivierosuchus parringtoni can be distinguished from its akidnognathid relatives, Promoschorhynchus and Moschorhinus, by the presence of a relatively slender snout. Features that further distinguish Olivierosuchus from Promoschorhynchus include fewer upper postcanines, an obtuse angle of the transverse process of the pterygoid and an oblique alignment of the suborbital fenestra margin of the palatine. Features that further distinguish Olivierosuchus from Moschorhinus include the presence of a sharp rather than blunt crista choanalis, a spatulate posterior portion of the ectopterygoid instead of a narrow shaft, the presence of prominent pterygoid tuberosities and a narrow, elongated tabular. A reappraisal of Lower Triassic therocephalian biostratigraphy reveals that most of these taxa are restricted to the lowermost part of the Lystrosaurus Assemblage Zone revealing a high diversity, whereafter the diversity decreases dramatically in the middle of the zone. However, despite their scarcity in the middle and upper Lystrosaurus Assemblage Zone, therocephalians in the Karoo Basin remain the most diverse therapsid clade in the lowermost Triassic, which suggests that they were able to recover relatively quickly from the end-Permian extinction event and form an important part of the postextinction earliest Triassic recovery. © The Palaeontological Association.

Botha-Brink J.,Karoo Palaeontology | Botha-Brink J.,University of the Free State | Angielczyk K.D.,The Field Museum
Zoological Journal of the Linnean Society | Year: 2010

Dicynodonts were the most diverse and abundant herbivorous therapsids of the Permo-Triassic. They include Lystrosaurus, one of the few taxa known to survive the end-Permian extinction and the most abundant tetrapod during the Early Triassic postextinction recovery. Explanations for the success of Lystrosaurus and other dicynodonts remain controversial. This study presents an assessment of dicynodont growth patterns using bone histology, with special focus on taxa associated with the end-Permian extinction event. Bone histological analysis reveals a high cortical thickness throughout the clade, perhaps reflecting a phylogenetic constraint. Growth rings are absent early in ontogeny, and combined with high vascular density, indicate rapid, sustained growth up to the subadult stage. Extraordinarily enlarged vascular channels are present in the midcortex of many dicynodonts, including adults, and may have facilitated a more efficient assimilation of nutrients and rapid bone growth compared to other therapsids. Both increased channel density and enlarged vascular channels evolved at or near the base of major radiations of dicynodonts, implying that the changes in growth and life history they represent may have been key to the success of dicynodonts. Furthermore, this exceptionally rapid growth to adulthood may have contributed to the survival of Lystrosaurus during the end-Permian extinction and its dominance during the postextinction recovery period. © 2010 The Linnean Society of London.

Modesto S.P.,Cape Breton University | Smith R.M.H.,Karoo Palaeontology | Campione N.E.,University of Toronto | Reisz R.R.,University of Toronto
Naturwissenschaften | Year: 2011

We report on a partial varanopid skull and mandible from the Pristerognathus Assemblage Zone of the Beaufort Group, in the South African Karoo Basin, which is probably latest Middle Permian (Capitanian) in age. This mycterosaurine is not only the youngest known varanopid from the Southern Hemisphere, but it is also the youngest known "pelycosaur" (i.e., non-therapsid synapsid). Like all other members of this clade of hypercarnivores, the teeth are strongly flattened, recurved, and have finely serrated cutting edges. The anterior dentary teeth form a caniniform region, and the splenial features a foramen intermandibularis oralis, the first ever to be described in a "pelycosaur." The last varanopids were the smallest carnivores of latest Middle Permian continental faunas. Occupation of the small carnivore guild appears to have allowed varanopids to achieve a nearly cosmopolitan distribution throughout the Middle Permian, between the great Early Permian radiation of basal synapsids and the spectacular diversification of therapsid synapsids in the Late Permian and Early Triassic. © 2011 Springer-Verlag.

Ruta M.,University of Lincoln | Botha-Brink J.,Karoo Palaeontology | Mitchell S.A.,University of the Free State | Benton M.J.,University of Bristol
Proceedings of the Royal Society B: Biological Sciences | Year: 2013

Cynodont therapsids diversified extensively after the Permo-Triassic mass extinction event, and gave rise to mammals in the Jurassic.We use an enlarged and revised dataset of discrete skeletal characters to build a newphylogeny for all main cynodont clades from the Late Permian to the Early Jurassic, and we analyse models of morphological diversification in the group. Basal taxa and epicynodonts are paraphyletic relative to eucynodonts, and the latter are divided into cynognathians and probainognathians, with tritylodonts and mammals forming sister groups. Disparity analyses reveal a heterogeneous distribution of cynodonts in a morphospace derived from cladistic characters. Pairwise morphological distances are weakly correlated with phylogenetic distances. Comparisons of disparity by groups and through time are nonsignificant, especially after the data are rarefied. A disparity peak occurs in the Early/Middle Triassic, after which period the mean disparity fluctuates little. Cynognathians were characterized by high evolutionary rates and high diversity early in their history, whereas probainognathian rates were low. Community structure may have been instrumental in imposing different rates on the two clades. © 2013 The Authors.

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