Cranial morphology of Dvinia prima amalitzky (Cynodontia, Theromorpha)

Ivakhnenko, M. F.

doi:10.1134/s0031030113010048

Cited by 10 publications

(15 citation statements)

References 8 publications

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“…The apparent contact seen in Fig. 8 is an artifact of deformation in AMNH FARB 2227 (as is also the case in some specimens of Procynosuchus and Dvinia ; Abdala & Allinson, ; contra Ivakhnenko, ). Here, the left palatal process of the maxilla is clearly broken off and displaced, overlapping the right one (Fig.…”

Section: Resultsmentioning

confidence: 63%

“…), but it probably originated as structural support for the snout (Thomason & Russell, ) and evolved multiple times in different therapsid lineages (Hopson & Barghusen, ; Angielczyk & Walsh, ). The earliest appearance of a secondary palate homologous with that of mammals is in Permian cynodonts such as Procynosuchus , Dvinia and Abdalodon (Tatarinov, ; Kemp, ; Hopson & Kitching, ; Ivakhnenko, ; Kammerer, ). However, these taxa do not possess a complete osseous secondary palate; the medial projections (transverse laminae) of their premaxillae, maxillae and palatines do not contact each other on the midline.…”

Section: Resultsmentioning

confidence: 99%

“…Interpterygoid vacuities are also present in small juveniles of Thrinaxodon (but absent in subadult and adult specimens; Estes, ; Fourie, ; Jasinoski et al. ) and Cynosaurus (Van den Brandt & Abdala, ) and adult specimens of Dvinia (Tatarinov, ; Ivakhnenko, ) and Platycraniellus (Abdala, ), so this structure seems to be homoplastic among early cynodonts (Jasinoski & Abdala, ). At its posterior end, the pterygoid of AMNH FARB 2227 contacts the basipterygoid articulation of the parabasisphenoid and forms the floor of the braincase anterior to the epipterygoid.…”

Section: Resultsmentioning

confidence: 99%

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Cranial anatomy of the early cynodont Galesaurus planiceps and the origin of mammalian endocranial characters

2019

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The cranial anatomy of the early non-mammalian cynodont Galesaurus planiceps from the South African Karoo Basin is redescribed on the basis of a computed tomographic reconstruction of the skull. Previously, little was known about internal skull morphology and the nervous and sensory system of this taxon. The endocranial anatomy of various cynodonts has been intensively studied in recent years to understand the origin of mammalian characters in the nasal capsule, brain and ear. However, these studies have focused on only a few taxa, the earliest of which is another Early Triassic cynodont, Thrinaxodon liorhinus. Galesaurus is phylogenetically stemward of Thrinaxodon and thus provides a useful test of whether the mammal-like features observed in Thrinaxodon were present even more basally in cynodont evolution. The cranial anatomy of G. planiceps is characterized by an intriguing mosaic of primitive and derived features within cynodonts. In contrast to the very similar internal nasal and braincase morphology of Galesaurus and Thrinaxodon, parts of the skull that seem to be fairly conservative in non-prozostrodont cynodonts, the morphology of the maxillary canal differs markedly between these taxa. Unusually, the maxillary canal of Galesaurus has relatively few ramifications, more similar to those of probainognathian cynodonts than that of Thrinaxodon. However, its caudal section is very short, a primitive feature shared with gorgonopsians and therocephalians. The otic labyrinth of Galesaurus is generally similar to that of Thrinaxodon, but differs in some notable features (e.g. proportional size of the anterior semicircular canal). An extremely large, protruding paraflocculus of the brain and a distinct medioventrally located notch on the anterior surface of the tabular, which forms the dorsal border of the large parafloccular lobe, are unique to Galesaurus among therapsids with reconstructed endocasts. These features may represent autapomorphies of Galesaurus, but additional sampling is needed at the base of Cynodontia to test this.

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Section: Resultsmentioning

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Cranial anatomy of the early cynodont Galesaurus planiceps and the origin of mammalian endocranial characters

2019

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“…SAM‐PK‐K10138 can be distinguished from Dvinia prima (based on PIN 2005/2465 and PIN 2005/2469) by most of the features that also separate it from Procynosuchus , as well as the absence of a maxillary perforation for the lower postcanine and completely different postcanine morphology (strongly labiolingually expanded with numerous cuspules in Dvinia , as is also the case for another Russian Permian cynodont, Sludica bulanovi , known only from isolated dentition) (Ivakhnenko , ). Dvinia does have a depression on the lateral surface of the maxilla, but it is dissimilar to that of SAM‐PK‐K10138 and Charassognathus , being in a higher, more posterior position and being an anteroposteriorly elongate ovoid (Ivakhnenko ) as opposed to being dorsoventrally elongate and located immediately posterior to the canine. SAM‐PK‐K10138 can also be differentiated from the purported Russian Permian ‘thrinaxodontids’ Nanocynodon seductus and Uralocynodon tverdokhlebovae (both known only from partial lower jaws, PIN 2415/1 and SGU 104 89/308): in these taxa, the lower postcanine tooth row is not inset.…”

Section: Discussionmentioning

confidence: 99%

“…Botha et al . () considered the notch in the posterior margin of the dentary (anterior to the mandibular fenestra) of Charassognathus to be a precursor of the masseteric fossa, as a similar notch is present at the base of the fossa in Dvinia and Procynosuchus (Kemp ; Ivakhnenko ). However, there is no evidence that this notch is part of a transformational series in the development of the masseteric fossa: similar mandibular openings (but never a masseteric fossa) are present independently in therocephalians, and both notch and masseteric fossa are absent in the more crownward cynodont clade Galesauridae (Kammerer pers.…”

Section: Discussionmentioning

confidence: 99%

A new taxon of cynodont from the Tropidostoma Assemblage Zone (upper Permian) of South Africa, and the early evolution of Cynodontia

Kammerer

2016

Papers in Palaeontology

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A new taxon of early cynodont, Abdalodon diastematicus gen. et sp. nov., is described. The new taxon is represented by a single skull from the upper Permian Tropidostoma Assemblage Zone (AZ) of the Beaufort Group (Karoo Basin, South Africa), which was previously referred to Procynosuchus delaharpeae. Abdalodon is distinguished from Procynosuchus by the presence of only four upper and three lower incisors, fewer postcanines, a well-developed depression on the lateral surface of the maxilla posterior to the canine root, a tall mandibular symphysis forming a distinct 'chin', a relatively short snout, and weak or absent interdigitation of sutures in the interorbital region. These features are shared with the only other Tropidostoma AZ cynodont, Charassognathus gracilis. Abdalodon is distinguished from Charassognathus by its postcanine morphology, the presence of an expanded masseteric fossa, inset postcanine tooth rows, a broader interorbital region, and proportionally shorter temporal region. Most strikingly, Abdalodon has a lengthy diastema between the canines and postcanines on both the maxilla and the dentary. Charassognathus has a short diastema between the upper canine and postcanines, but not the lowers, and diastemata are absent from the tooth rows of Procynosuchus. Phylogenetic analysis recovers Abdalodon as the sister-taxon of Charassognathus, forming a clade (Charassognathidae fam. nov.) at the base of Cynodontia. These taxa represent a previously unrecognized radiation of small-bodied Permian cynodonts. Despite their small size, the holotypes of Abdalodon and Charassognathus probably represent adults and indicate that early evolution of cynodonts may have occurred at small body size, explaining the poor Permian fossil record of the group.

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Physiological implications of the abnormal absence of the parietal foramen in a late Permian cynodont (Therapsida)

Benoît

Abdala

Brandt

et al. 2015

Sci Nat

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The third eye (pineal eye), an organ responsible for regulating exposure to sunlight in extant ectotherms, is located in an opening on the dorsal surface of the skull, the parietal foramen. The parietal foramen is absent in extant mammals but often observed in basal therapsids, the stem-group to true mammals. Here, we report the absence of the parietal foramen in a specimen of Cynosaurus suppostus, a Late Permian cynodont from South Africa (SA). Comparison with Procynosuchus delaharpeae, a contemporaneous non-mammalian cynodont from SA, demonstrates that the absence of this foramen is an abnormal condition for such a basal species. Because seasonality was marked during the Late Permian in SA, it is proposed that the third eye was functionally redundant in Cynosaurus, possibly due to the acquisition of better thermoregulation or the evolution of specialized cells in the lateral eyes to compensate for the role of the third eye.

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Cranial morphology of Dvinia prima amalitzky (Cynodontia, Theromorpha)

Cited by 10 publications

References 8 publications

Cranial anatomy of the early cynodont Galesaurus planiceps and the origin of mammalian endocranial characters

Cranial anatomy of the early cynodont Galesaurus planiceps and the origin of mammalian endocranial characters

A new taxon of cynodont from the Tropidostoma Assemblage Zone (upper Permian) of South Africa, and the early evolution of Cynodontia

Physiological implications of the abnormal absence of the parietal foramen in a late Permian cynodont (Therapsida)

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