The skull of a small anomodont therapsid, from the Tapinocephalus Assemblage Zone (Abrahamskraal ... more The skull of a small anomodont therapsid, from the Tapinocephalus Assemblage Zone (Abrahamskraal Formation, Beaufort Group, Upper Permian) in Northern Cape Province, South Africa, represents a new basal dicynodont and is described in detail. Colobodectes cluveri gen. et sp. nov. is distinguished from other dicynodonts by an anteroposteriorly extensive caniniform process, parietals that were broadly overlapped posterolaterally by posterodorsal processes of the postorbitals, diverging anterior palatal ridges, and a dorsoventrally low foramen magnum. A phylogenetic analysis indicates that Colobodectes is the basalmost member of a dicynodont clade that excludes Eodicynodon. This position is not particularly strong, as two additional steps are needed to make Colobodectes and Eodicynodon oosthuizeni exchange places on the most parsimonious tree. Another discovery of the phylogenetic analysis is that there is little basis for recognizing Eodicynodon oelofseni as the closest relative of E. oosthuizeni. The former species is identi®ed as the sister taxon of a clade that includes the latter and all other dicynodonts.
We report on a large burrow cast with skeletal contents from Lower Triassic strata of the Palingk... more We report on a large burrow cast with skeletal contents from Lower Triassic strata of the Palingkloof Member of the Balfour Formation, which forms the lowermost portion of the Lystrosaurus Assemblage Zone (LAZ) of South Africa. The burrow cast is similar to large burrow casts previously ...
Proceedings. Biological sciences / The Royal Society, Jan 22, 2015
Amniotes, tetrapods that evolved the cleidoic egg and thus independence from aquatic larval stage... more Amniotes, tetrapods that evolved the cleidoic egg and thus independence from aquatic larval stages, appeared ca 314 Ma during the Coal Age. The rapid diversification of amniotes and other tetrapods over the course of the Late Carboniferous period was recently attributed to the fragmentation of coal-swamp rainforests ca 307 Ma. However, the amniote fossil record during the Carboniferous is relatively sparse, with ca 33% of the diversity represented by single specimens for each species. We describe here a new species of reptilian amniote that was collected from uppermost Carboniferous rocks of Prince Edward Island, Canada. Erpetonyx arsenaultorum gen. et sp. nov. is a new parareptile distinguished by 29 presacral vertebrae and autapomorphies of the carpus. Phylogenetic analyses of parareptiles reveal E. arsenaultorum as the closest relative of bolosaurids. Stratigraphic calibration of our results indicates that parareptiles began their evolutionary radiation before the close of the Ca...
... SEAN P. MODESTO 1,* ,; DIANE M. SCOTT 2 ,; DAVID S. BERMAN 1 ,; JOHANNES MÜLLER 2 ,; ROBERT R... more ... SEAN P. MODESTO 1,* ,; DIANE M. SCOTT 2 ,; DAVID S. BERMAN 1 ,; JOHANNES MÜLLER 2 ,; ROBERT R. REISZ 2. Article first published online: 13 FEB 2007. DOI: 10.1111/j.1096-3642.2007.00242.x. Issue. ... Correspondence: SEAN P. MODESTO,. ...
Problems of the origins and early diversification of crown-group Diapsida are highlighted by the ... more Problems of the origins and early diversification of crown-group Diapsida are highlighted by the taxonomic history of Prolacerta broomi, a small reptile from the Early Triassic of South Africa and Antarctica. Parrington (1935) erected Prolacerta broomi for a skull from the Lower Triassic Lystrosaurus Assemblage Zone of South Africa. He regarded the new reptile as intermediate between more basal diapsids (such as Youngina) and lizards, primarily because of the incomplete lower temporal bar. Despite its supposed squamate affinities, ...
Proceedings of the Royal Society B: Biological Sciences, 2001
A reptile specimen from the Lystrosaurus Assemblage Zone of the Beaufort Group, lowermost Triassi... more A reptile specimen from the Lystrosaurus Assemblage Zone of the Beaufort Group, lowermost Triassic of South Africa, represents a new procolophonoid parareptile. Sauropareion anoplus gen. et sp. nov. is identi¢ed as the sister taxon of Procolophonidae in a phylogenetic analysis of procolophonoids. Stratigraphic calibration of the most parsimonious tree reveals that four of the six procolophonoid lineages originating in the Permian Period extended into the succeeding Triassic Period. This relatively high taxic survivorship (67%) across the Permo-Triassic boundary strongly suggests that procolophonoids were little if at all a¡ected by the mass extinction event that punctuated the end of the Palaeozoic Era (ca. 251 million years ago).
Proceedings of the Royal Society B: Biological Sciences, 2007
Living species of mammals, crocodiles and most species of birds exhibit parental care, but eviden... more Living species of mammals, crocodiles and most species of birds exhibit parental care, but evidence of this behaviour is extremely rare in the fossil record. Here, we present a new specimen of varanopid 'pelycosaur' from the Middle Permian of South Africa. The specimen is an aggregation, consisting of five articulated individuals preserved in undisturbed, close, lifelike, dorsal-up, subparallel positions, indicating burial in 'life position'. Two size classes are represented. One is 50% larger than the others, is well ossified, has fused neurocentral sutures and is distinguished by a coat of dermal ossifications that covers the neck and shoulder regions. We regard this individual to be an adult. The remaining four skeletons are considered to be juveniles as they are approximately the same size, are poorly ossified, have open neurocentral sutures and lack dermal ossifications. Aggregates of juvenile amniotes are usually siblings. Extant analogues of adult and juvenile groupings suggest that the adult is one of the parents, leading us to regard the aggregation as a family group. The Late Middle Permian age of the varanopid family predates the previously known oldest fossil evidence of parental care in terrestrial vertebrates by 140 Myr.
The skeletal structure of Coletta seca, a small procolophonoid reptile from the Lower Triassic Ly... more The skeletal structure of Coletta seca, a small procolophonoid reptile from the Lower Triassic Lystrosaurus Assemblage Zone of South Africa, is reconsidered in light of descriptions of other procolophonoids. The presence of a single row of relatively large, fang-like vomerine teeth, identi®ed originally as the single autapomorphy of this taxon, is reinterpreted as two rows of parachoanal vomerine teeth that are similar in organization to those of coeval procolophonids from Russia. Coletta is distinguished from other procolophonoids by a complex tongue-and-groove suture between the anterolateral margin of the parietal and the posterolateral edge of the postfrontal, and by a transversely broad interpterygoid vacuity. The postfrontal in Coletta retains contact with the postorbital, as in basal taxa such as Owenetta, but it is restricted to the orbital margin, as in Procolophon and all other procolophonids. A phylogenetic analysis identi®es Coletta as the sister taxon of the clade Procolophonidae. This phylogenetic position suggests that Procolophonoidea originated and diversi®ed initially in Gondwana during the Permian, prior to Procolophonidae achieving a cosmopolitan distribution in the succeeding Triassic.
Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. Th... more Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your work, please use the accepted author's version for posting to your own website or your institution's repository. You may further deposit the accepted author's version on a funder's repository at a funder's request, provided it is not made publicly available until 12 months after publication.
J. 2001 12 14: A second varanopseid skull from the Upper Permian of South Africa: implications fo... more J. 2001 12 14: A second varanopseid skull from the Upper Permian of South Africa: implications for Late Permian 'pelycosaur' evolution. Lethaia, Vol. 34, pp. 249-259. Oslo. ISSN 0024-1164. Late Permian terrestrial faunas of South Africa and Russia are dominated taxonomically and ecologically by therapsid synapsids. On the basis of a single specimen from the Upper Permian of South Africa, the varanopseid Elliotsmithia longiceps is the sole basal synapsid ('pelycosaur') known from Gondwana. Recent eldwork in the Upper Permian of South Africa has produced a second varanopseid specimen that is referrable to Elliotsmithia. Data from both this specimen and the holotype suggest that Elliotsmithia forms a clade with Mycterosaurus from the Lower Permian of North America and Mesenosaurus from the Upper Permian of Eastern Europe. That postulate is supported by the three most parsimonious trees discovered in a new analysis of varanopseid phylogeny. However, the available data cannot resolve the interrelationships of these three genera. The new phylogenetic results contrast with earlier work identifying Elliotsmithia as the basal member of a clade that includes the North American taxa Aerosaurus, Varanops, and Varanodon. The new trees reduce the stratigraphic debt required by the latter scenario, and the one with the least stratigraphic debt identi es Elliotsmithia and Mesenosaurus as sister taxa. Two new taxa are erected, Mycterosaurinae and Varanodontinae, for the two varanopseid subclades. & Paleobiogeography, 'pelycosaurs', Permian, phylogeny, varanopseids. Sean Modesto* [sean.modesto@eudoramail.com] and Bruce S. Rubidge [106gar@cosmos. wits.ac.za],
ABSTRACT Several new specimens of the Triassic therocephalian Tetracynodon darti have become avai... more ABSTRACT Several new specimens of the Triassic therocephalian Tetracynodon darti have become available in recent years, allowing substantial corrections and expansions to previous descriptions. We here analyze T. darti in the context of therocephalian relationships and biology, using computed tomographic (CT) scanning to reveal details of the skull. Histological sections, as well as the degree of ossification of individual elements, both suggest that the available specimens are subadults (rather than rapidly growing neonates ...
A new specimen of the parareptile Colobomycter pholeter, from the Lower Permian Dolese Brothers Q... more A new specimen of the parareptile Colobomycter pholeter, from the Lower Permian Dolese Brothers Quarry near Fort Sill, Oklahoma, preserves previously unknown portions of the skull, including the premaxilla, elements of the palate, and the sphenethmoid. The premaxilla houses two teeth, of which the first is caniniform in size. The pattern and the morphology of the upper dentition indicates that
... Science 275:1450-1452. Gauthier, JA, A. Kluge, and T. Rowe. 1988. The early evolution of the ... more ... Science 275:1450-1452. Gauthier, JA, A. Kluge, and T. Rowe. 1988. The early evolution of the Amniota; pp. ... 2000. Acanthotoposaurus brem-neri and the origin of the Triassic archosauromorph reptile fauna of South Africa. South African Journal of Science 95:553-555. ...
... Jennifer Botha-Brink *, 1, 2 and Sean P. Modesto 3 . (2009) Anatomy and Relationships of the ... more ... Jennifer Botha-Brink *, 1, 2 and Sean P. Modesto 3 . (2009) Anatomy and Relationships of the Middle Permian Varanopid Heleosaurus scholtzi Based on a Social Aggregation from the Karoo Basin of South Africa. Journal of ...
... The ecological niche of the Vangfontein archosauriform in the LAZ is difficult to reconstruct... more ... The ecological niche of the Vangfontein archosauriform in the LAZ is difficult to reconstruct with the limited information afforded by its ... Winchester Press, New York. ... 2004. The skull of the EarlyTriassic archosauromorph reptile Prolacerta broomi and its phylogenetic significance. ...
The anatomy of individuals is described from a 'pelycosaur' aggregation preserving two age classe... more The anatomy of individuals is described from a 'pelycosaur' aggregation preserving two age classes, from the Middle Permian of the South African Karoo Basin, that have been referred to Heleosaurus scholtzi. These skeletons allow the recognition of new features for H. scholtzi, including a strong anterior inclination of the occiput, exclusion of the quadratojugal from the temporal fenestra, a maxilla-prefrontal contact, and a maxilla-quadratojugal contact. In addition to some of these features, the absence of an anterodorsal contact between the squamosal and the jugal allows us to assign H. scholtzi to the varanopid clade Mycterosaurinae. Phylogenetic analysis of Varanopidae using an augmented data matrix from the literature positions Heleosaurus as the sister taxon of Elliotsmithia within the varanopid subfamily Mycterosaurinae. Both this sister-group relationship and the monophyly of Mycterosaurinae are weak and collapse with one extra step. Many of the clades discovered in the analysis exhibit the same support level, however, indicating that further studies on varanopids are needed.
The skull of a carnivorous therapsid from the Tapinocephalus Assemblage Zone of the Beaufort Grou... more The skull of a carnivorous therapsid from the Tapinocephalus Assemblage Zone of the Beaufort Group, Middle Permian of South Africa, is described as a new burnetiamorph biarmosuchian. Pachydectes elsi n. gen. and sp. is distinguished from all other therapsids by its possession of a conspicuous pachyostotic maxillary boss that sheathes the root of the upper canine. It shares the presence of a preparietal ossification with other biarmosuchians and a pachyostotic boss below the postorbital bar with other burnetiamorphs. Pachydectes is the first burnetiamorph known from along the Ecca-Beaufort contact in the eastern part of the Karoo Basin and only the second burnetiamorph to be described from the Tapinocephalus Assemblage Zone. All other South African burnetiamorphs, save Bullacephalus jacksoni, are known from much younger biozones of the Beaufort Group. Our phylogenetic analysis links Pachydectes and Bullacephalus, which are the stratigraphically lowest-occurring taxa, with Burnetia, the burnetiamorph known from the highest position in the lower Beaufort Group. This result suggests that most of the history of biarmosuchians in South Africa is unrecorded.
The skull of a small anomodont therapsid, from the Tapinocephalus Assemblage Zone (Abrahamskraal ... more The skull of a small anomodont therapsid, from the Tapinocephalus Assemblage Zone (Abrahamskraal Formation, Beaufort Group, Upper Permian) in Northern Cape Province, South Africa, represents a new basal dicynodont and is described in detail. Colobodectes cluveri gen. et sp. nov. is distinguished from other dicynodonts by an anteroposteriorly extensive caniniform process, parietals that were broadly overlapped posterolaterally by posterodorsal processes of the postorbitals, diverging anterior palatal ridges, and a dorsoventrally low foramen magnum. A phylogenetic analysis indicates that Colobodectes is the basalmost member of a dicynodont clade that excludes Eodicynodon. This position is not particularly strong, as two additional steps are needed to make Colobodectes and Eodicynodon oosthuizeni exchange places on the most parsimonious tree. Another discovery of the phylogenetic analysis is that there is little basis for recognizing Eodicynodon oelofseni as the closest relative of E. oosthuizeni. The former species is identi®ed as the sister taxon of a clade that includes the latter and all other dicynodonts.
We report on a large burrow cast with skeletal contents from Lower Triassic strata of the Palingk... more We report on a large burrow cast with skeletal contents from Lower Triassic strata of the Palingkloof Member of the Balfour Formation, which forms the lowermost portion of the Lystrosaurus Assemblage Zone (LAZ) of South Africa. The burrow cast is similar to large burrow casts previously ...
Proceedings. Biological sciences / The Royal Society, Jan 22, 2015
Amniotes, tetrapods that evolved the cleidoic egg and thus independence from aquatic larval stage... more Amniotes, tetrapods that evolved the cleidoic egg and thus independence from aquatic larval stages, appeared ca 314 Ma during the Coal Age. The rapid diversification of amniotes and other tetrapods over the course of the Late Carboniferous period was recently attributed to the fragmentation of coal-swamp rainforests ca 307 Ma. However, the amniote fossil record during the Carboniferous is relatively sparse, with ca 33% of the diversity represented by single specimens for each species. We describe here a new species of reptilian amniote that was collected from uppermost Carboniferous rocks of Prince Edward Island, Canada. Erpetonyx arsenaultorum gen. et sp. nov. is a new parareptile distinguished by 29 presacral vertebrae and autapomorphies of the carpus. Phylogenetic analyses of parareptiles reveal E. arsenaultorum as the closest relative of bolosaurids. Stratigraphic calibration of our results indicates that parareptiles began their evolutionary radiation before the close of the Ca...
... SEAN P. MODESTO 1,* ,; DIANE M. SCOTT 2 ,; DAVID S. BERMAN 1 ,; JOHANNES MÜLLER 2 ,; ROBERT R... more ... SEAN P. MODESTO 1,* ,; DIANE M. SCOTT 2 ,; DAVID S. BERMAN 1 ,; JOHANNES MÜLLER 2 ,; ROBERT R. REISZ 2. Article first published online: 13 FEB 2007. DOI: 10.1111/j.1096-3642.2007.00242.x. Issue. ... Correspondence: SEAN P. MODESTO,. ...
Problems of the origins and early diversification of crown-group Diapsida are highlighted by the ... more Problems of the origins and early diversification of crown-group Diapsida are highlighted by the taxonomic history of Prolacerta broomi, a small reptile from the Early Triassic of South Africa and Antarctica. Parrington (1935) erected Prolacerta broomi for a skull from the Lower Triassic Lystrosaurus Assemblage Zone of South Africa. He regarded the new reptile as intermediate between more basal diapsids (such as Youngina) and lizards, primarily because of the incomplete lower temporal bar. Despite its supposed squamate affinities, ...
Proceedings of the Royal Society B: Biological Sciences, 2001
A reptile specimen from the Lystrosaurus Assemblage Zone of the Beaufort Group, lowermost Triassi... more A reptile specimen from the Lystrosaurus Assemblage Zone of the Beaufort Group, lowermost Triassic of South Africa, represents a new procolophonoid parareptile. Sauropareion anoplus gen. et sp. nov. is identi¢ed as the sister taxon of Procolophonidae in a phylogenetic analysis of procolophonoids. Stratigraphic calibration of the most parsimonious tree reveals that four of the six procolophonoid lineages originating in the Permian Period extended into the succeeding Triassic Period. This relatively high taxic survivorship (67%) across the Permo-Triassic boundary strongly suggests that procolophonoids were little if at all a¡ected by the mass extinction event that punctuated the end of the Palaeozoic Era (ca. 251 million years ago).
Proceedings of the Royal Society B: Biological Sciences, 2007
Living species of mammals, crocodiles and most species of birds exhibit parental care, but eviden... more Living species of mammals, crocodiles and most species of birds exhibit parental care, but evidence of this behaviour is extremely rare in the fossil record. Here, we present a new specimen of varanopid 'pelycosaur' from the Middle Permian of South Africa. The specimen is an aggregation, consisting of five articulated individuals preserved in undisturbed, close, lifelike, dorsal-up, subparallel positions, indicating burial in 'life position'. Two size classes are represented. One is 50% larger than the others, is well ossified, has fused neurocentral sutures and is distinguished by a coat of dermal ossifications that covers the neck and shoulder regions. We regard this individual to be an adult. The remaining four skeletons are considered to be juveniles as they are approximately the same size, are poorly ossified, have open neurocentral sutures and lack dermal ossifications. Aggregates of juvenile amniotes are usually siblings. Extant analogues of adult and juvenile groupings suggest that the adult is one of the parents, leading us to regard the aggregation as a family group. The Late Middle Permian age of the varanopid family predates the previously known oldest fossil evidence of parental care in terrestrial vertebrates by 140 Myr.
The skeletal structure of Coletta seca, a small procolophonoid reptile from the Lower Triassic Ly... more The skeletal structure of Coletta seca, a small procolophonoid reptile from the Lower Triassic Lystrosaurus Assemblage Zone of South Africa, is reconsidered in light of descriptions of other procolophonoids. The presence of a single row of relatively large, fang-like vomerine teeth, identi®ed originally as the single autapomorphy of this taxon, is reinterpreted as two rows of parachoanal vomerine teeth that are similar in organization to those of coeval procolophonids from Russia. Coletta is distinguished from other procolophonoids by a complex tongue-and-groove suture between the anterolateral margin of the parietal and the posterolateral edge of the postfrontal, and by a transversely broad interpterygoid vacuity. The postfrontal in Coletta retains contact with the postorbital, as in basal taxa such as Owenetta, but it is restricted to the orbital margin, as in Procolophon and all other procolophonids. A phylogenetic analysis identi®es Coletta as the sister taxon of the clade Procolophonidae. This phylogenetic position suggests that Procolophonoidea originated and diversi®ed initially in Gondwana during the Permian, prior to Procolophonidae achieving a cosmopolitan distribution in the succeeding Triassic.
Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. Th... more Your article is protected by copyright and all rights are held exclusively by Springer-Verlag. This e-offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your work, please use the accepted author's version for posting to your own website or your institution's repository. You may further deposit the accepted author's version on a funder's repository at a funder's request, provided it is not made publicly available until 12 months after publication.
J. 2001 12 14: A second varanopseid skull from the Upper Permian of South Africa: implications fo... more J. 2001 12 14: A second varanopseid skull from the Upper Permian of South Africa: implications for Late Permian 'pelycosaur' evolution. Lethaia, Vol. 34, pp. 249-259. Oslo. ISSN 0024-1164. Late Permian terrestrial faunas of South Africa and Russia are dominated taxonomically and ecologically by therapsid synapsids. On the basis of a single specimen from the Upper Permian of South Africa, the varanopseid Elliotsmithia longiceps is the sole basal synapsid ('pelycosaur') known from Gondwana. Recent eldwork in the Upper Permian of South Africa has produced a second varanopseid specimen that is referrable to Elliotsmithia. Data from both this specimen and the holotype suggest that Elliotsmithia forms a clade with Mycterosaurus from the Lower Permian of North America and Mesenosaurus from the Upper Permian of Eastern Europe. That postulate is supported by the three most parsimonious trees discovered in a new analysis of varanopseid phylogeny. However, the available data cannot resolve the interrelationships of these three genera. The new phylogenetic results contrast with earlier work identifying Elliotsmithia as the basal member of a clade that includes the North American taxa Aerosaurus, Varanops, and Varanodon. The new trees reduce the stratigraphic debt required by the latter scenario, and the one with the least stratigraphic debt identi es Elliotsmithia and Mesenosaurus as sister taxa. Two new taxa are erected, Mycterosaurinae and Varanodontinae, for the two varanopseid subclades. & Paleobiogeography, 'pelycosaurs', Permian, phylogeny, varanopseids. Sean Modesto* [sean.modesto@eudoramail.com] and Bruce S. Rubidge [106gar@cosmos. wits.ac.za],
ABSTRACT Several new specimens of the Triassic therocephalian Tetracynodon darti have become avai... more ABSTRACT Several new specimens of the Triassic therocephalian Tetracynodon darti have become available in recent years, allowing substantial corrections and expansions to previous descriptions. We here analyze T. darti in the context of therocephalian relationships and biology, using computed tomographic (CT) scanning to reveal details of the skull. Histological sections, as well as the degree of ossification of individual elements, both suggest that the available specimens are subadults (rather than rapidly growing neonates ...
A new specimen of the parareptile Colobomycter pholeter, from the Lower Permian Dolese Brothers Q... more A new specimen of the parareptile Colobomycter pholeter, from the Lower Permian Dolese Brothers Quarry near Fort Sill, Oklahoma, preserves previously unknown portions of the skull, including the premaxilla, elements of the palate, and the sphenethmoid. The premaxilla houses two teeth, of which the first is caniniform in size. The pattern and the morphology of the upper dentition indicates that
... Science 275:1450-1452. Gauthier, JA, A. Kluge, and T. Rowe. 1988. The early evolution of the ... more ... Science 275:1450-1452. Gauthier, JA, A. Kluge, and T. Rowe. 1988. The early evolution of the Amniota; pp. ... 2000. Acanthotoposaurus brem-neri and the origin of the Triassic archosauromorph reptile fauna of South Africa. South African Journal of Science 95:553-555. ...
... Jennifer Botha-Brink *, 1, 2 and Sean P. Modesto 3 . (2009) Anatomy and Relationships of the ... more ... Jennifer Botha-Brink *, 1, 2 and Sean P. Modesto 3 . (2009) Anatomy and Relationships of the Middle Permian Varanopid Heleosaurus scholtzi Based on a Social Aggregation from the Karoo Basin of South Africa. Journal of ...
... The ecological niche of the Vangfontein archosauriform in the LAZ is difficult to reconstruct... more ... The ecological niche of the Vangfontein archosauriform in the LAZ is difficult to reconstruct with the limited information afforded by its ... Winchester Press, New York. ... 2004. The skull of the EarlyTriassic archosauromorph reptile Prolacerta broomi and its phylogenetic significance. ...
The anatomy of individuals is described from a 'pelycosaur' aggregation preserving two age classe... more The anatomy of individuals is described from a 'pelycosaur' aggregation preserving two age classes, from the Middle Permian of the South African Karoo Basin, that have been referred to Heleosaurus scholtzi. These skeletons allow the recognition of new features for H. scholtzi, including a strong anterior inclination of the occiput, exclusion of the quadratojugal from the temporal fenestra, a maxilla-prefrontal contact, and a maxilla-quadratojugal contact. In addition to some of these features, the absence of an anterodorsal contact between the squamosal and the jugal allows us to assign H. scholtzi to the varanopid clade Mycterosaurinae. Phylogenetic analysis of Varanopidae using an augmented data matrix from the literature positions Heleosaurus as the sister taxon of Elliotsmithia within the varanopid subfamily Mycterosaurinae. Both this sister-group relationship and the monophyly of Mycterosaurinae are weak and collapse with one extra step. Many of the clades discovered in the analysis exhibit the same support level, however, indicating that further studies on varanopids are needed.
The skull of a carnivorous therapsid from the Tapinocephalus Assemblage Zone of the Beaufort Grou... more The skull of a carnivorous therapsid from the Tapinocephalus Assemblage Zone of the Beaufort Group, Middle Permian of South Africa, is described as a new burnetiamorph biarmosuchian. Pachydectes elsi n. gen. and sp. is distinguished from all other therapsids by its possession of a conspicuous pachyostotic maxillary boss that sheathes the root of the upper canine. It shares the presence of a preparietal ossification with other biarmosuchians and a pachyostotic boss below the postorbital bar with other burnetiamorphs. Pachydectes is the first burnetiamorph known from along the Ecca-Beaufort contact in the eastern part of the Karoo Basin and only the second burnetiamorph to be described from the Tapinocephalus Assemblage Zone. All other South African burnetiamorphs, save Bullacephalus jacksoni, are known from much younger biozones of the Beaufort Group. Our phylogenetic analysis links Pachydectes and Bullacephalus, which are the stratigraphically lowest-occurring taxa, with Burnetia, the burnetiamorph known from the highest position in the lower Beaufort Group. This result suggests that most of the history of biarmosuchians in South Africa is unrecorded.
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