Two New Cynodonts (Therapsida) from the Middle-Early Late Triassic of Brazil and Comments on South American Probainognathians

Martinelli, Agustín G.; Soares, Marina Bento; Schwanke, Cibele

doi:10.1371/journal.pone.0162945

Cited by 55 publications

(68 citation statements)

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“…In general, the postcanine morphotype of MPDC-501-117 is most similar to that of Aleodon brachyrhamphus among cynodonts ([20]; NHMUK PV R9390, UMZC T906) (Fig 4), differing considerably from that of other known taxa [3, 14, 32]. Although gomphodont cynodonts also possess transversely wide postcanines, the crown morphology in these taxa is fundamentally different: the upper postcanines have a conspicuous transverse crest, often with three discrete cusps, that divides or bounds the occlusal basin and opposes a transverse crest with two main cusps generally present on the lower postcanines (e.g., [80]).…”

Section: Resultsmentioning

confidence: 99%

The African cynodont Aleodon (Cynodontia, Probainognathia) in the Triassic of southern Brazil and its biostratigraphic significance

et al. 2017

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In this contribution we report the first occurrence of the enigmatic African probainognathian genus Aleodon in the Middle-early Late Triassic of several localities from the state of Rio Grande do Sul in southern Brazil. Aleodon is unusual among early probainognathians in having transversely-expanded postcanine teeth, similar to those of gomphodont cynognathians. This genus was previously known from the Manda Beds of Tanzania and the upper Omingonde Formation of Namibia. The Brazilian record of this genus is based upon multiple specimens representing different ontogenetic stages, including three that were previously referred to the sectorial-toothed probainognathian Chiniquodon theotonicus. We propose a new species of Aleodon (A. cromptoni sp. nov.) based on the specimens from Brazil. Additionally, we tentatively refer one specimen from the upper Omingonde Formation of Namibia to this new taxon, strengthening biostratigraphic correlations between these strata. Inclusion of A. cromptoni in a phylogenetic analysis of eucynodonts recovers it as the sister-taxon of A. brachyrhamphus within the family Chiniquodontidae. The discovery of numerous specimens of Aleodon among the supposedly monospecific Chiniquodon samples of Brazil raises concerns about chiniquodontid alpha taxonomy, particularly given the extremely broad geographic distribution of Chiniquodon. The discovery of Brazilian Aleodon and new records of the traversodontid Luangwa supports the hypothesis that at least two subzones can be recognized in the Dinodontosaurus Assemblage Zone.

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Section: Resultsmentioning

confidence: 99%

The African cynodont Aleodon (Cynodontia, Probainognathia) in the Triassic of southern Brazil and its biostratigraphic significance

et al. 2017

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“…UFSM 11579b was included in the data matrix published by Liu & Olsen () and modified by Martinelli et al . (). In addition, Therioherpeton cargnini was re‐scored for some character‐states (see Martinelli et al .…”

Section: Methodsmentioning

confidence: 97%

“…Three extremely fragmentary taxa, which are comparable with Alemoatherium , were also included: Santacruzgnathus abdalai (based on UFRGS‐PV‐1121‐T and Martinelli et al . ), Microconodon tenuirostris (based on Simpson and Sues ) and Charruodon tetracuspidatus (based on MCP‐3934 PV and Abdala & Ribeiro ). Due to the incompleteness of the taxa, we performed three different analyses: the first only including Alemoatherium huebneri , the second also including Santacruzgnathus abdalai and Microconodon tenuirostris , and the third also including Charruodon tetracuspidatus .…”

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confidence: 99%

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A new cynodont from the Santa Maria formation, south Brazil, improves Late Triassic probainognathian diversity

Martinelli

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Da-Rosa

et al. 2017

Papers in Palaeontology

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The fossil record of non-mammaliaform probainognathian cynodonts is outstanding in the Late Triassic rocks of Brazil and Argentina. Approximately 15 genera are known, providing unique insights in the study of the major skeletal transformations prior to the mammalian condition. Globally, the diversity of probainognathians is possibly under-represented, as the discovery of small-to very small-sized taxa based on relatively well-preserved specimens is rare. Several species, for example much of the Laurasian record, are based on isolated teeth and jaw fragments. Here, we describe a new probainognathian from the Late Carnian Hyperodapedon Assemblage Zone of the Santa Maria Formation, south Brazil. Alemoatherium huebneri gen. et sp. nov. is based on a left lower jaw with almost complete dentition that exhibits a combination of features not seen in any other known probainognathian. Its slender lower jaw, anterodorsally bent process of the dentary, high number of lower incisors, reduced canine, triconodont-like postcanine teeth with mesiolingual and distolingual cingular cusps are all features that support the inclusion of A. huebneri as a member of the Prozostrodontia clade. This new find highlights the conspicuous probainognathian cynodont fossil record in southern Brazil, with a plethora of forms near the mammalian origin.

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“…B, stratigraphy of the Santa Maria Supersequence, modified from Martinelli et al . () and Horn et al . ().…”

Section: Geological and Biostratigraphical Settingsmentioning

confidence: 86%

A new gomphodont cynodont (Traversodontidae) from the Middle–Late Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence, Brazil

2017

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The tetrapod faunas from the terrestrial Middle–Late Triassic basins of Africa and South America are among the richest in the world, especially in non‐mammalian cynodonts. Despite the great abundance of cynodont specimens found in these basins, there are few known taxa that exhibit interbasinal distributions. Here we describe a new species of traversodontid cynodont of the genus Scalenodon from the Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence, from the state of Rio Grande do Sul, Brazil. Scalenodon ribeiroae sp. nov. is based on a partial skull that possesses a combination of features not observed in any other South American traversodontid: ellipsoid upper postcanines with the transverse crest formed by three cusps, lacking a mesiobuccal accessory cusp, and with lingual cusp projected lingually creating a concave lingual surface on the upper postcanines; the paracanine fossa is positioned medially to the upper canine, and jugal lacks a suborbital process. A phylogenetic analysis places the new taxon in a basal position within the Family Traversodontidae, with the African Scalenodon angustifrons as sister‐taxon. The new specimen of Scalenodon represents the first record of this genus outside of the Manda Beds of Tanzania, and reinforces the biostratigraphical and biogeographical connection between Gondwanan Middle–Late Triassic tetrapod faunas. Although recent advances have been made, our current knowledge of these faunas is limited by the lack of absolute dates for most units and by uncertainties in the taxonomy and stratigraphical provenance of key fossils.

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Two New Cynodonts (Therapsida) from the Middle-Early Late Triassic of Brazil and Comments on South American Probainognathians

Cited by 55 publications

References 66 publications

The African cynodont Aleodon (Cynodontia, Probainognathia) in the Triassic of southern Brazil and its biostratigraphic significance

The African cynodont Aleodon (Cynodontia, Probainognathia) in the Triassic of southern Brazil and its biostratigraphic significance

A new cynodont from the Santa Maria formation, south Brazil, improves Late Triassic probainognathian diversity

A new gomphodont cynodont (Traversodontidae) from the Middle–Late Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence, Brazil

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