Browsing by Author "Abdala, Fernando"

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    Cranial morphology and phylogenetic analysis of Cynosaurus suppostus (Therapsida, Cynodontia) from the upper Permian of the Karoo Basin, South Africa
    (Evolutionary Studies Institute, 2018-03) van den Brandt, Marc; Abdala, Fernando
    Non-mammaliaform cynodonts are an important fossil lineage which include the ancestors of mammals and which illustrate the gradual evolution of mammalian characteristics. The earliest cynodonts (‘basal cynodonts’) are known from the late Permian. Cynosaurus suppostus is the second most abundant basal cynodont from the late Permian of the Karoo Basin of SouthAfrica, but is poorly studied, with the most recent description of this taxon being 50 years old. Since then, several important new specimens of this species have been collected, meriting a thorough description of its cranial anatomy and exploration of its interspecific variation. Here we present a comprehensive description of the cranial morphology of Cynosaurus suppostus, producing an updated diagnosis for the species and comparisons amongst basal cynodonts. Cynosaurus is identified by three autapomorphies amongst basal cynodonts: a subvertical mentum on the anterior lower jaw; a robust mandible with a relatively high horizontal ramus; and the broadest snout across the canine region, representing up to 31.74% of basal skull length. One of the new specimens described here preserves orbital scleral ossicles, structures rarely preserved in non-mammaliaform cynodonts. Cynosaurus is now only the third cynodont in which scleral ossicles have been reported.Anupdated phylogenetic analysis of basal cynodont interrelationships recovered Cynosaurus suppostus as a member of the Galesauridae in only two of 16 most parsimonious trees, providing poor support for its inclusion in that family. The majority of known Cynosaurus specimens were collected in a geographically restricted area approximately 150 kilometres in diameter. Most specimens have been recovered from the latest Permian Daptocephalus Assemblage Zone, with only two specimens known from the older Cistecephalus Assemblage Zone.
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    Cranial morphology and taxonomy of South African Tapinocephalidae (Therapsida: Dinocephalia): the case of Avenantia and Riebeeckosaurus
    (Evolutionary Studies Institute, University of the Witwatersrand, 2013-12-18) Guven, Saniye; Rubidge, Bruce S.; Abdala, Fernando
    Tapinocephalid dinocephalians comprise a large component of Middle Permian herbivorous tetrapod biodiversity and are significantly abundant in the Karoo rocks of SouthAfrica. In order to understand the effect of the alleged Middle Permian extinction in the terrestrial record of amniotes a clear understanding of the taxonomic diversity of this group is essential. The tapinocephalids Avenantia kruisvleiensis and Riebeeckosaurus longirostris have in the past been distinguished by a set of characters, including differences in the snout length which was previously interpreted as a key diagnostic character. Further preparation of the material attributed to these species shows that the purported distinguishing characters, such as snout length, low intertemporal crest, and surface thickening of the parietal represent postmortem deformation (including distortion and weathering) or can be interpreted as individual or ontogenetic variation. Accordingly A. kruisvleiensis is synonimized with R. longirostris.
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    Cranial morphology of Jonkeria truculenta (Therapsida, Dinocephalia) and a taxonomic reassessment of the family Titanosuchidae
    (The Evolutionary Studies Institute, 2024-06) Jirah, Sifelani; Rubide, Bruce S; Abdala, Fernando
    Titanosuchidae are a group of herbivorous, long-snouted dinocephalians with definitive records known only from the middle Permian Tapinocephalus Assemblage Zone of the Beaufort Group (Karoo Supergroup) of South Africa. Here, the taxonomy of this family is revised; of the nine species currently recognized, only two are found to be valid: Titanosuchus ferox and Jonkeria truculenta, which can be distinguished on the basis of appendicular proportions. Jonkeria boonstrai, J. haughtoni, J. ingens, J. parva, J. rossouwi, and J. vanderbyli are synonymized with Jonkeria truculenta, and J. koupensis is considered a nomen dubium (Titanosuchidae indet.). Several new cranial features are described for J. truculenta, such as pachyostosis of the prefrontals, postorbitals and parietals, and an ontogenetic series for the species is presented.
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    Cranial morphology of Jonkeria truculenta (Titanosuchidae, Therapsida, Dinocephalia) and a taxonomic reassessment of the family
    (Evolutionary Studies Institute, 2023) Jirah, Sifelani; Rubidge, Bruce S; Abdala, Fernando
    Titanosuchidae are a group of derived herbivorous long snouted dinocephalians currently only known from the South African Karoo. Taxonomic revision of the Titanosuchids, for the first time accompanied by detailed anatomical descriptions and illustrations of representative cranial material, enabled recognition of only two species out of the nine previously recognized. These are Titanosuchus ferox and Jonkeria truculenta. Jonkeria vanderbyli, Jonkeria ingens, Jonkeria haughtoni, Jonkeria parva, Jonkeria rossouwi and Jonkeria boonstrai are here, synonymized with Jonkeria truculenta. The species Jonkeria koupensis is a nomen dubium only identified as Titanosuchid indet. Cranial characters, which modify during ontogenetic development, were, recognized for Jonkeria truculenta, and for the first time an ontogenetic growth series is, presented for this species.
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    Early development of the mammalian superficial masseter muscle in cynodonts
    (Bernard Price Institute for Palaeontological Research, 2004-12) Abdala, Fernando; Damiani, Ross
    The masseter muscle is a hallmark of the jaw-closing mechanism of modern mammals, acting in concert with other mandibular adductor muscles to fine-tune oral food processing. The model explaining the origin of this muscle within non-mammalian therapsids involves the differentiation of a masseter-like muscle from a primitive external adductor, a downward migration of the masseter insertion on the mandible, and a division and distribution of the muscle to a condition that is similar to that in living mammals. The presence of a suborbital process of the jugal, which is interpreted as the site of origin for the superficial masseter, has been previously regarded as the earliest putative morphological evidence used to infer masseteric division. The suborbital process is first recorded in late Early Triassic (c. 245 Ma) cynognathian cynodonts. Here it is shown that primitive galesaurid cynodonts of earliest Triassic age (c. 251 Ma) display a distinct angulation of the zygomatic arch below the orbit, indicating the presence of a divided masseter amongst more basal cynodonts. This alters the timing of masseter muscle evolution by showing that the downward migration and division of the masseter occurred simultaneously, prior to the evolution of advanced cynodonts (=eucynodonts).
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    Early development of the mammalian superficial masseter muscle in cynodonts
    (BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 2004) Abdala, Fernando; Damiani, Ross
    The masseter muscle is a hallmark of the jaw-closing mechanism of modern mammals, acting in concert with other mandibular adductor muscles to fine-tune oral food processing. The model explaining the origin of this muscle within non-mammalian therapsids involves the differentiation of a masseter-like muscle from a primitive external adductor, a downward migration of the masseter insertion on the mandible, and a division and distribution of the muscle to a condition that is similar to that in living mammals. The presence of a suborbital process of the jugal, which is interpreted as the site of origin for the superficial masseter, has been previously regarded as the earliest putative morphological evidence used to infer masseteric division. The suborbital process is first recorded in late Early Triassic (c. 245 Ma) cynognathian cynodonts. Here it is shown that primitive galesaurid cynodonts of earliest Triassic age (c. 251 Ma) display a distinct angulation of the zygomatic arch below the orbit, indicating the presence of a divided masseter amongst more basal cynodonts. This alters the timing of masseter muscle evolution by showing that the downward migration and division of the masseter occurred simultaneously, prior to the evolution of advanced cynodonts (=eucynodonts).
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    First record of non-mammalian cynodonts (Therapsida) in the Sanga do Cabral Formation (Early Triassic) of southern Brazil
    (2002) Abdala, Fernando; Dias-de-Silva, Sergio; Cisneros, Juan C
    New material from the Sanga do Cabral Formation in southern Brazil is described, including one distal and three proximal portions of femora, and a distal portion of a humerus. Comparative studies indicate affinities of the proximal femora and the distal humerus with non-mammalian cynodonts, whereas the distal femur cannot be attributed with certainty to this group. These postcranial elements are the first record of non-mammalian cynodonts for the Sang a do Cabral Formation and demonstrate the presence of small- to medium-sized representatives of this group in the Early Triassic fauna of Brazil.
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    Late Permian terrestrial faunal connections invigorated: the first whaitsioid therocephalian from China
    (2023-07) Liu, Jun; Abdala, Fernando
    The record of therocephalian therapsids from the late Permian of China has recently been greatly expanded by the discovery of several new taxa of Akidnognathidae, a group previously known principally from South Africa and Russia. Continuing this string of discoveries, we present here the first Chinese record of a whaitsiid therocephalian. This is also the first record published of a tetrapod from Jingtai, Gansu, a late Permian locality that also yields remains of other groups such as dicynodonts, captorhinids, and chroniosuchians. This is the third taxon of whaitsiid therocephalian recognized in North Pangea. The new therocephalian is similar to the Russian Moschowhaitsia vjuschkovi in overall appearance, and although they are only recovered as sister-taxa in 6 out of 30 most parsimonious trees in our phylogenetic analysis, it is tentatively referred to Moschowhaitsia as a new species,M. lidaqingi. The phylogeny obtained is largely similar to previous hypotheses, recovering three main lineages of Eutherocephalia: Akidnognathidae, Whaitsioidea and Baurioidea. However, it differs from previous analyses in finding Chthonosauridae (comprising the Russian Chthonosaurus and Zambian Ichibengops) to be deeply nested within Whaitsioidea. Therocephalians were among the largest carnivores in the late Permian of North China, and may have represented the top predators in some faunas.
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    A non-mammaliaform cynodont from the Upper Triassic of South Africa: a therapsid Lazarus taxon?
    (BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 2007) Abdala, Fernando; Damiani, Ross; Yates, Adam; Neveling, Johann
    The tetrapod record of the ‘Stormberg Group’, including the Lower Elliot Formation, in the South African Karoo is widely dominated by archosaurian reptiles, contrasting with the therapsid dominion of the subjacent Beaufort Group. The only therapsids represented by skeletal remains in the Upper Triassic Lower Elliot Formation are the large traversodontid cynodont Scalenodontoides macrodontes and the recently described tritheledontid cynodont Elliotherium kersteni. Here we present a fragmentary lower jaw that provides evidence of a third type of cynodont for the Upper Triassic of South Africa. The fossil is tentatively assigned to the Diademodontidae. The latter representative of this family is known from the Late Anisian, and its tentative record in the Norian Lower Elliot Formation, if confirmed, will represent a case of Lazarus taxon. Thus, Diademodontidae apparently disappeared from the fossil record by the end of the Anisian and then reappeared in the Norian of South Africa, a stratigraphic interval of some 21 million years. This new cynodont record, together with the recently described Tritheledontidae, show that cynodonts are now the second most diverse tetrapod group in the Lower Elliot fauna.
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    Postcranial morphology of the South African middle Permian pareiasaurs from the Karoo Basin of South Africa
    (Evolutionary Studies Institute, 2021-05-28) van den Brandt, Marc J.; Benoit, Julien; Abdala, Fernando; Rubidge, Bruce S.
    Pareiasaurs were relatively abundant and globally distributed herbivorous parareptiles of the middle to late Permian. The basal-most pareiasaurs, the Bradysauria, are restricted to the middle Permian of South Africa and went extinct at the end of the Guadalupian (Capitanian) at the top of the Tapinocephalus Assemblage Zone. Currently, three genera are recognized in this group: Bradysaurus, Embrithosaurus and Nochelesaurus, but their postcrania are poorly known, and consequently poorly understood. In this paper, our third contribution designed to improve understanding of the Bradysauria, we present a detailed comparative postcranial description and updated diagnoses for Bradysaurus baini, Embrithosaurus schwarzi and Nochelesaurus alexanderi. Bradysaurus baini has one postcranial autapomorphy: anterior dorsal osteoderms smooth and strongly convex, with an incipient central boss, and very light ornamentation. Three pelvic autopomorphies of Embrithosaurus schwarzi are confirmed: anterior portion of the iliac blades flat and vertical (not everted or upturned); iIiac blades diverge anteriorly, oriented at 45–60° off the sagittal plane; and a very thick pelvic symphysis. For Nochelesaurus alexanderi we remove all three of the postcranial autapomorphies previously proposed. To the diagnoses of each species, we have added several new distinguishing postcranial features, within the local group of middle Permian pareiasaurs. The results reinforce our previous cranial studies concluding that three valid species of pareiasaurs are represented in the South African middle Permian.
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    The taxonomic status of Parathrinaxodon proops (Therapsida: Cynodontia), with comments on the morphology of the palate in basal cynodonts
    (BERNARD PRICE INSTITUTE FOR PALAEONTOLOGICAL RESEARCH, 2005) Abdala, Fernando; Allinson, Matthew
    The holotype and only specimen of Parathrinaxodon proops, a cynodont from the Upper Permian Kawinga Formation, Tanzania, is redescribed. Upper postcanines from the middle of the tooth row are ovoid in outline, presenting a large main cusp and tiny anterior and posterior accessory cusps on the sectorial margin. Anterior and posterior lingual cusps on the crown indicate the presence of a lingual cingulum. The overall postcanine morphology is remarkably similar to that of Procynosuchus delaharpeae, a Late Permian cynodont particularly common in the lower Beaufort Group of South Africa. The presence of a complete osseous palate and a medial palatal opening between the maxillae (=vomerine fossa) in Parathrinaxodon proops remain the main differences previously reported between this species and Procynosuchus delaharpeae. Restudy of the palate of Parathrinaxodon proops indicates that there exists some degree of deformation, particularly notable in the broken and distorted vomer. The supposed presence of the complete secondary palate and of the medial palatal opening in Parathrinaxodon proops are interpreted as resulting from a slight horizontal displacement of the long, and originally free, palatal processes of the maxilla and palatine. It is concluded that Parathrinaxodon proops is synonymous with Procynosuchus delaharpeae. This synonymy is problematic because Parathrinaxodon proops Parrington 1936 would have priority over Procynosuchus delaharpeae Broom 1937, but the latter is the best known Late Permian cynodont. Consequently, we propose to conserve Procynosuchus delaharpeae as the valid name for this cynodont based on article 23, section 9 (Reversal of precedence) of the International Code of Zoological Nomenclature. An analysis of the Kawinga fauna, using genus as the taxonomic unit for comparison, indicates strong similarity (67%) with faunas from theTropidostoma, Cistecephalus and Dicynodon assemblage zones from the SouthAfrican Karoo.
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    The pre-eminence of the Karoo Basin in the knowledge of the Permo-Jurassic cynodonts: a historical synthesis and taxonomical quantification
    (Evolutionary Studies Institute, 2023) Abdala, Fernando; Hendrickx, Christophe; Jasinoski, Sandra C; Gaetano, Leandro C; Liu, Jun
    The search for the ancestors of mammals is historically connected with the extensive Karoo Basin of South Africa. This is because the Karoo features some of the largest exposures of Permo-Jurassic terrestrial deposits in the world and fossil discoveries were made here early in the history of palaeontology. Among the mammal-like lineages that are well-represented in Karoo fossil assemblages are the cynodonts. Originally conceived as a group exclusively containing fossil taxa, Cynodontia was subsequently redefined to include living mammals, and its Permian and early Mesozoic members are now referred to as non-mammaliaform cynodonts. Here we present a historical account of the research programme on non-mammaliaform cynodonts in the Karoo Basin, which represent the most important record of this group in the world. It covers a time spanning from the first named species in 1859 until the present day, which we arbitrarily divided into three periods: the Early Period extending from 1859 until 1932, the Second Period from 1933 to 1982, and the Current Period from 1983 until now. In the context of the global record of named species, we present quantitative analyses documenting the total number of nominal non-mammaliaform cynodont species from the Karoo (including junior synonyms and homonyms) as well as numerical comparison with taxa currently considered valid. Lastly, we compare the record of non-mammaliaform cynodont species from South Africa with other places in the world, such as Argentina and Brazil, which also have a diverse record of this group.