<i>Apsisaurus witteri</i>from the Lower Permian of Texas: yet another small varanopid synapsid, not a diapsid

Reisz, Robert R.; Laurin, Michel; Marjanović, David

doi:10.1080/02724634.2010.501441

Cited by 28 publications

(111 citation statements)

References 11 publications

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“…Although similarities have hitherto been documented between varanopids and early diapsids (Reisz & Modesto ; Reisz et al . ), the present study demonstrates that the similarities are more numerous and detailed than previously recognized, calling into question the phylogenetic distinctness of varanopids from early diapsids. To explore these similarities further, we score Orovenator into an existing phylogenetic data matrix designed to recognize affinities between diapsids and varanopids.…”

contrasting

confidence: 45%

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A redescription of Orovenator mayorum (Sauropsida, Diapsida) using high‐resolution μCT, and the consequences for early amniote phylogeny

Ford

Benson

2018

Papers in Palaeontology

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The earliest known neodiapsid Orovenator mayorum from the lower Permian of Oklahoma is redescribed using high‐resolution μCT, revealing remarkable details of the skull anatomy. Our findings are relevant to both palaeoecology (suggesting burrowing and nocturnality) and phylogeny. Orovenator and other sauropsids share at least 16 character states with varanopids, many of which were not recognized by previous studies. These include a rounded subnarial shelf of the premaxilla, a posterodorsal extension of the external naris, the asymmetrical bifurcation of the anterior vomer, and a prominent dorsomedial shelf of the surangular. This exceptional degree of similarity between Orovenator and varanopids (a nominally synapsid clade) questions our current understanding of relationships among early amniotes. We test this by including Orovenator in a phylogenetic data matrix used in an earlier study to differentiate between early diapsids and synapsids, and find a monophyletic clade of Orovenator + varanopids within Diapsida. Recent phylogenetic research on early amniote evolution has focused on resolving intra‐clade affiliations rather than the interrelationships of major taxonomic groups. Nevertheless, the relative incompleteness of existing phylogenetic character lists for early amniotes can only be remedied by detailed cross‐clade assessment. We therefore suggest that early amniote relationships require further scrutiny before we can confidently accept or reject our new phylogenetic hypothesis.

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contrasting

confidence: 45%

“…Indeed, Captorhinus , along with Paleothyris , Petrolacosaurus and Youngina , is scored as possessing a septomaxilla shaped as a curled sheet in the character–taxon matrix of Reisz et al . (). This view was questioned by Modesto et al .…”

Section: Descriptionmentioning

confidence: 97%

A redescription of Orovenator mayorum (Sauropsida, Diapsida) using high‐resolution μCT, and the consequences for early amniote phylogeny

Ford

Benson

2018

Papers in Palaeontology

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“…However, Apsisaurus was recently re-interpreted as a varanopid synapsid [43]. Accordingly, we propose here that the basal neodiapsid Lanthanolania ivakhnenkoi be used to constrain the maximum divergence time of Sauria because it is the closest of the sister taxa to Sauria [75] that is unambiguously older than the earliest known saurian fossils.…”

Section: Discussionmentioning

confidence: 87%

The Origin and Early Evolution of Sauria: Reassessing the Permian Saurian Fossil Record and the Timing of the Crocodile-Lizard Divergence

2014

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Sauria is the crown-group of Diapsida and is subdivided into Lepidosauromorpha and Archosauromorpha, comprising a high percentage of the diversity of living and fossil tetrapods. The split between lepidosauromorphs and archosauromorphs (the crocodile-lizard, or bird-lizard, divergence) is considered one of the key calibration points for molecular analyses of tetrapod phylogeny. Saurians have a very rich Mesozoic and Cenozoic fossil record, but their late Paleozoic (Permian) record is problematic. Several Permian specimens have been referred to Sauria, but the phylogenetic affinity of some of these records remains questionable. We reexamine and review all of these specimens here, providing new data on early saurian evolution including osteohistology, and present a new morphological phylogenetic dataset. We support previous studies that find that no valid Permian record for Lepidosauromorpha, and we also reject some of the previous referrals of Permian specimens to Archosauromorpha. The most informative Permian archosauromorph is Protorosaurus speneri from the middle Late Permian of Western Europe. A historically problematic specimen from the Late Permian of Tanzania is redescribed and reidentified as a new genus and species of basal archosauromorph: Aenigmastropheus parringtoni. The supposed protorosaur Eorasaurus olsoni from the Late Permian of Russia is recovered among Archosauriformes and may be the oldest known member of the group but the phylogenetic support for this position is low. The assignment of Archosaurus rossicus from the latest Permian of Russia to the archosauromorph clade Proterosuchidae is supported. Our revision suggests a minimum fossil calibration date for the crocodile-lizard split of 254.7 Ma. The occurrences of basal archosauromorphs in the northern (30°N) and southern (55°S) parts of Pangea imply a wider paleobiogeographic distribution for the group during the Late Permian than previously appreciated. Early archosauromorph growth strategies appear to be more diverse than previously suggested based on new data on the osteohistology of Aenigmastropheus.

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“…In addition, Langston (1963) noted that the posterior ascending process of the dentary was identical to that figured by Romer and Price (1940) for Mycterosaurus. Mycterosaurus dentary teeth were not well known at that time, and the genus has since been re-described as a mycterosaurine varanopid (Berman and Reisz, 1982), a hypothesis that is well supported by subsequent phylogenetic analyses (Benson, 2012;Campione and Reisz, 2010;Maddin et al, 2006;Reisz et al, 2010). The dentary of mycterosaurines, and varanopids in general, is thin relative to its length, and tapers towards the symphysis; their teeth are labiolingually thin, highly recurved along the entire length of the tooth row, and the mesial-most teeth are not angled forward (Campione and Reisz, 2010;Reisz and Berman, 2001;Reisz and Dilkes, 2003).…”

Section: Systematic Palaeontologymentioning

confidence: 96%

“…Although the methodology described by the authors is more objective compared to traditional anatomical comparisons, it is unfortunately of limited use here. In particular, current character matrices that include both early reptile and synapsid OTUs (e.g., Laurin and Reisz, 1995;Reisz et al, 2010) either do not code characters that pertain to the anatomical regions described in this study or include characters that, when coded for the specimens examined here, are plesiomorphic. Similar issues occur within more exclusive clades, including Parareptilia (MacDougall and Tsuji, 2006) and non-therapsid synapsids (Benson, 2012;Sidor, 2003).…”

Section: Systematic Palaeontologymentioning

confidence: 97%

Amniote faunal revision of the Pictou Group (Permo-Carboniferous), Prince Edward Island, Canada

Brink

Campione

Hawthorn

2013

Comptes Rendus Palevol

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Apsisaurus witterifrom the Lower Permian of Texas: yet another small varanopid synapsid, not a diapsid

Cited by 28 publications

References 11 publications

A redescription of Orovenator mayorum (Sauropsida, Diapsida) using high‐resolution μCT, and the consequences for early amniote phylogeny

A redescription of Orovenator mayorum (Sauropsida, Diapsida) using high‐resolution μCT, and the consequences for early amniote phylogeny

The Origin and Early Evolution of Sauria: Reassessing the Permian Saurian Fossil Record and the Timing of the Crocodile-Lizard Divergence

Amniote faunal revision of the Pictou Group (Permo-Carboniferous), Prince Edward Island, Canada

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