Dicynodonts (Therapsida: Anomodontia) of South America

Kammerer, Christian F.; Ordóñez, María de los Ángeles

doi:10.1016/j.jsames.2021.103171

Cited by 22 publications

(46 citation statements)

References 88 publications

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“…, Kammerer and Ordoñez 106 , and Angielczyk et al 107 , but note that other topologies for Pristerodon, Brachyprosopus, the endothiodonts, and the emydopoids have appeared in recent phylogenetic analyses 42,108,109 . Branch lengths are arbitrary.…”

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confidence: 99%

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Histology and μCT reveal the unique evolution and development of multiple tooth rows in the synapsid Endothiodon

Olroyd

LeBlanc

Araújo

et al. 2021

Sci Rep

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Several amniote lineages independently evolved multiple rows of marginal teeth in response to the challenge of processing high fiber plant matter. Multiple tooth rows develop via alterations to tooth replacement in captorhinid reptiles and ornithischian dinosaurs, but the specific changes that produce this morphology differ, reflecting differences in their modes of tooth attachment. To further understand the mechanisms by which multiple tooth rows can develop, we examined this feature in Endothiodon bathystoma, a member of the only synapsid clade (Anomodontia) to evolve a multi-rowed marginal dentition. We histologically sampled Endothiodon mandibles with and without multiple tooth rows as well as single-rowed maxillae. We also segmented functional and replacement teeth in µ-CT scanned mandibles and maxillae of Endothiodon and several other anomodonts with ‘postcanine’ teeth to characterize tooth replacement in the clade. All anomodonts in our sample displayed a space around the tooth roots for a soft tissue attachment between tooth and jaw in life. Trails of alveolar bone indicate varying degrees of labial migration of teeth through ontogeny, often altering the spatial relationships of functional and replacement teeth in the upper and lower jaws. We present a model of multiple tooth row development in E. bathystoma in which labial migration of functional teeth was extensive enough to prevent resorption and replacement by newer generations of teeth. This model represents another mechanism by which multiple tooth rows evolved in amniotes. The multiple tooth rows of E. bathystoma may have provided more extensive contact between the teeth and a triturating surface on the palatine during chewing.

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confidence: 99%

“…Cladogram illustrating changes in tooth replacement across stemward dicynodonts. Phylogeny based on Olroyd et al47 , Kammerer and Ordoñez106 , and Angielczyk et al107 , but note that other topologies for Pristerodon, Brachyprosopus, the endothiodonts, and the emydopoids have appeared in recent phylogenetic analyses42,108,109 . …”

mentioning

confidence: 99%

Histology and μCT reveal the unique evolution and development of multiple tooth rows in the synapsid Endothiodon

Olroyd

LeBlanc

Araújo

et al. 2021

Sci Rep

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“…Figure 12 depicts the phylogenetic distribution of anatomical modifications to the angular region suggested by the systematic review discussed above. The cladistic relationships used are primarily those discussed by Rubidge and Sidor (2001), with the dicynodont part of the tree based on Olroyd et al (2018) and Kammerer and Ordoñez (2021). However, it should be noted that several studies have suggested alternative arrangements, and most agree that character support for the higher-level clades is weak (Hopson and Barghusen, 1986; Rowe, 1988; Sidor and Rubidge, 2006; Kemp, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…See Table 1 for voucher specimens for each taxon. Higher level cladistic topology based on Sidor and Hopson (1998), with dicynodont topology based on Olroyd et al (2018) and Kammerer and Ordoñez (2021).…”

Section: Discussionmentioning

confidence: 99%

“…This hypothesis is supported by the fact that the shape and relative position is consistent between the therocephalian dorsal 1 for voucher specimens for each taxon. Higher level cladistic topology based on Sidor and Hopson (1998), with dicynodont topology based on Olroyd et al (2018) and Kammerer and Ordoñez (2021). Olroyd and Sidor-Reflected lamina morphology (e2101923-15) notch and the posterodorsal fossa of other therapsids (Fig.…”

Section: Evolution and Homologies Of The Angular Complexmentioning

confidence: 99%

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Nomenclature, comparative anatomy, and evolution of the reflected lamina of the angular in non-mammalian synapsids

Olroyd

Sidor

2022

Journal of Vertebrate Paleontology

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The reflected lamina of the angular has long been portrayed as a key component in understanding the evolution of the mammalian mandible and middle ear, yet the function of this structure in non-mammalian therapsids remains uncertain. We undertake a broad scale survey of two aspects of the reflected lamina that have been poorly characterized: the ridges and fossae on its lateral surface and the extent of the underlying angular cleft. These two features were visualized in a wide range of therapsids using CT data from the literature and blue light surface scanning. Most species exhibit a clade-specific pattern of surface topography, although dicynodonts are highly variable. A striking similarity in the general number and orientation of fossae and ridges is seen between the otherwise disparate therapsid clades, and we propose homologies in these surface features across Therapsida. These features may serve as useful phylogenetic characters in analyses of the relationships among the major therapsid clades. The angular cleft does not underlie all of what is often referred to as the 'reflected lamina' in the literature, and an updated definition of this term is provided. Several therapsid groups independently expanded the angular cleft to further separate the reflected lamina from the angular body. We discuss some functional consequences of our findings and note inconsistency between proposed clade-specific muscle attachment sites and the presence of homologous fossae and ridges across much of Therapsida.

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New rhadinosuchine proterochampsids from the late Middle‐early Late Triassic of southern Brazil enhance the diversity of archosauriforms

Paes‐Neto,

Lacerda,

Ezcurra

et al. 2023

The Anatomical Record

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Proterochampsidae is a clade of non‐archosaurian archosauriforms restricted to the Middle to the Late Triassic of the Ischigualasto‐Villa Unión Basin of Argentina and the Santa Maria Supersequence of Brazil. A reappraisal of proterochampsid specimens from the Brazilian Dinodontosaurus Assemblage Zone (AZ) of the Pinheiros‐Chiniquá Sequence (late Ladinian‐early Carnian) is presented here. One of the specimens was preliminary assigned to Chanaresuchus sp., whose type species comes from the Massetognathus‐Chanaresuchus AZ of the Chañares Formation of Argentina. However, our revision indicates that it differs from Chanaresuchus, being more closely related to the middle‐late Carnian Rhadinosuchus gracilis. We therefore propose the new taxon, Pinheirochampsa rodriguesi, to reallocate this specimen. Additionally, we present a revision of other putative Chanaresuchus occurrences in Brazil, including the only known specimen described for the Santacruzodon AZ (Santa Cruz do Sul Sequence; early Carnian), also proposing it as a new taxon: Kuruxuchampsa dornellesi. Both new species are characterized, among other features, by transverse expansion of the anterior end of the rostrum, similar to the condition present in Rhadinosuchus, but absent in Chanaresuchus, Gualosuchus, Pseudochampsa, and non‐rhadinosuchine proterochampsids. These two new species expand the growing knowledge of the non‐archosaurian archosauriform diversity during the Middle‐Late Triassic in South America and enhance faunal and chronological comparisons between approximately coeval geological units between Argentina and Brazil.

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Dicynodonts (Therapsida: Anomodontia) of South America

Cited by 22 publications

References 88 publications

Histology and μCT reveal the unique evolution and development of multiple tooth rows in the synapsid Endothiodon

Histology and μCT reveal the unique evolution and development of multiple tooth rows in the synapsid Endothiodon

Nomenclature, comparative anatomy, and evolution of the reflected lamina of the angular in non-mammalian synapsids

New rhadinosuchine proterochampsids from the late Middle‐early Late Triassic of southern Brazil enhance the diversity of archosauriforms

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