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An indented, unsequenced classification of the Lepidosauromorpha.
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... is composed of Archosauromorpha, which includes Archosauria, and Lepidosauromorpha, which includes Lepidosauria. Bearing the recommendations and qualifications discussed above in mind, we offer an indented but unsequenced taxonomy (Table 1), which emphasizes the relation- ships within Lepidosauromorpha in the context of their phylogenetic position within amniotes. ...
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... Colbert (1970) suggested that, although kuehneosaurids were part of Lepidosauria, the Draco-like anatomy in kuehneosaurids is convergent with that of Draco. Phylogenetic analyses of later authors (e.g., Evans, 2009;Gauthier et al., 1988;Jones et al., 2013) recovered kuehneosaurids as non-lepidosaur lepidosauromorphs (stemlepidosaurs), or as the sister group to Drepanosauromorpha and outside Sauria (Müller, 2004), or as archosauromorphs (e.g., Benton, 1985;Evans, 1988;Pritchard & Nesbitt, 2017;Pritchard & Sues, 2019;Sobral et al., 2020). Although their relationships are contentious, most recent analyses with robust sampling across Lepidosauromorpha, Archosauromorpha, Drepanosauromorpha and other Triassic reptile clades recover kuehneosaurids as archosauromorphs. ...
... Their disparity also manifested in their body size variation, which ranged over one order of magnitude [7]. Most of this disparity is contained within Sphenodontia (= "Sphenodontida" sensu [18] and as applied in [19], all rhynchocephalians more closely related to Sphenodon punctatus than Gephyrosaurus bridensis). Although they were a dominant component of the Mesozoic fauna, Laurasian sphenodontian diversity and abundance rapidly decreased during the Early Cretaceous [10,20], possibly due to the changing climate during the fragmentation of Pangea in this period [16]. ...
... The preserved portions of the vomers extend from the posterior processes of the premaxillae to the centre of the nasals. Generally, rhynchocephalians possess fully toothed palates [18], but the vomers in Parvosaurus harudensis bear no visible teeth (Fig. 14). The position of the choana could not be determined due to the poor preservation. ...
... 1E and 16). It is likely that the palate had an extensive tooth cover similar to those in other rhynchocephalians [18]. ...
The Arnstadt Formation of Saxony-Anhalt, Germany has yielded some of Germany’s most substantial finds of Late Triassic tetrapods, including the sauropodomorph Plateosaurus and the stem-turtle Proganochelys quenstedti. Here, we describe an almost complete skull of a new sphenodontian taxon from this formation (Norian, 227–208 Ma), making it the oldest known articulated sphenodontian skull from Europe and one of the oldest in the world. The material is represented by the dermal skull roof and by the complete maxilla and temporal region, as well as parts of the palate, braincase, and lower jaw. A phylogenetic assessment recovers it as a basal sphenodontian closely related to Planocephalosaurus robinsonae and to Eusphenodontia, making it the earliest-diverging sphenodontian known with an articulated skull. Its cranial anatomy is generally similar to the well-known Diphydontosaurus avonis from the Rhaetian of England, showing that this successful phenotype was already established in the clade around 10 myr earlier than assumed. An analysis of evolutionary change rates recovers high rates of evolution in basal sphenodontians, with decreasing rates throughout the evolution of the group. However, contrary to previous studies, reversals in this trend were identified, indicating additional peaks of evolutionary change. These results improve our understanding of the early sphenodontian diversity in Europe, providing critical information on evolutionary trends throughout the history of the clade and sparking renewed interest in its evolution.
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The online version contains supplementary material available at 10.1186/s12862-024-02218-1.
... One specimen is a partially articulated skeleton of Kuehneosaurus latus, NHMUK PV R8172 (Fig. 3A). Kuehneosaurus and the Kuehneosauridae were initially interpreted as lizards (e.g., Robinson, 1962Robinson, , 1967Colbert, 1970), and then as members of the wider clade Lepidosauromorpha (e.g., Gauthier et al., 1988;Evans, 2009). In other phylogenetic analyses, Benton (1985) and Evans (1988) found evidence that Kuehneosauridae were members of Archosauromorpha, since confirmed by Pritchard and Nesbitt (2017), Sobral et al. (2020),a n d Pritchard et al. (2021). ...
... The most diverse clade of extant saurian reptiles, Lepidosauria, comprises Squamata (lizards and snakes) and Rhynchocephalia (Gauthier et al., 1988). The former is an enormously diverse clade with over 10,000 extant species recorded to date whereas the latter has only a single present-day representative, the tuatara (Sphenodon punctatus) from New Zealand (Cree, 2014). ...
... Fraser and Shelton (1988) and Whiteside and Duffin (2017) observed that there appears to be a continuum between definitely pleurodont and definitely acrodont tooth implantation in rhynchocephalians, making this difference perhaps phylogenetically less important. Gauthier et al. (1988) defined Rhynchocephalia as comprising Gephyrosaurus bridensis and Sphenodontia (as Sphenodontida). Some recent analyses have recovered Gephyrosaurus bridensis well outside Rhynchocephalia (e.g., Simões et al., 2020). ...
Skeletal remains of a small lepidosaurian reptile from the Middle Triassic (Ladinian: Longobardian) Erfurt Formation, exposed in a commercial limestone quarry near Vellberg (Germany), represent the oldest rhynchocephalian known to date. The new taxon, Wirtembergia hauboldae , is diagnosed by the following combination of features: Premaxilla with four teeth, first being largest and decreasing in size from first to fourth. Jugal with tiny, spur‐like posterior process. Lateral surface of dentary strongly convex dorsoventrally for much of length of bone, bearing distinct longitudinal ridge and sculpturing in large specimens. Coronoid eminence of dentary low, subrectangular, and with dorsoventrally concave lateral surface in larger specimens. Dentition with pleurodont anterior and acrodont posterior teeth. Posterior (=additional) teeth with (in side view) triangular, at mid‐crown level labiolingually somewhat flattened crowns, and with oval bases. Phylogenetic analysis recovered the new rhynchocephalian as the earliest‐diverging member of its clade known to date.
... This latter subclade is divided into 2 groups: (a) Phrynosoma and (b) Callisaurus, Cophosaurus, Holbrookia, and Uma. All lizard fossils described here are members of Lepidosauria based on the presence of pleurodont tooth implantation(Gauthier et al. 1988, Scarpetta 2021). REFERRED MATERIAL.-Haystack: ...
... Rhynchocephalia are a monophyletic group of small-to largesized lizard-like diapsid reptiles (Daugherty et al., 1990;Evans et al., 2001;Evans & Jones, 2010;Fraser, 1988;Romo-de-Vivar-Martínez & Soares, 2015), represented today by a solitary genus Sphenodon with only one living species, S. punctatus (the tuatara of New Zealand sensu Jones & Cree, 2012;Simões et al., 2022). Rhynchocephalia consists of two groups, the basally branching Gephyrosaurus displaying pleurodont tooth implantation, and the more derived Sphenodontia (Gauthier et al., 1988) with acrodont and fully ankylosed teeth (Chambi-Trowell et al., 2021;Evans, 1980;Säilä, 2005;Sues & Schoch, 2021), which together with Squamata form the clade Lepidosauria (Gauthier et al., 1988). The crown-group Squamata has an almost worldwide distribution at present (∼11,000 extant species; Burbrink et al., 2020) and a rich and diverse fossil record dating back to the Middle Jurassic (Evans, 1998). ...
... Rhynchocephalia are a monophyletic group of small-to largesized lizard-like diapsid reptiles (Daugherty et al., 1990;Evans et al., 2001;Evans & Jones, 2010;Fraser, 1988;Romo-de-Vivar-Martínez & Soares, 2015), represented today by a solitary genus Sphenodon with only one living species, S. punctatus (the tuatara of New Zealand sensu Jones & Cree, 2012;Simões et al., 2022). Rhynchocephalia consists of two groups, the basally branching Gephyrosaurus displaying pleurodont tooth implantation, and the more derived Sphenodontia (Gauthier et al., 1988) with acrodont and fully ankylosed teeth (Chambi-Trowell et al., 2021;Evans, 1980;Säilä, 2005;Sues & Schoch, 2021), which together with Squamata form the clade Lepidosauria (Gauthier et al., 1988). The crown-group Squamata has an almost worldwide distribution at present (∼11,000 extant species; Burbrink et al., 2020) and a rich and diverse fossil record dating back to the Middle Jurassic (Evans, 1998). ...
A new clevosaurid rhynchocephalian is described from the Upper Triassic Tiki Formation of the Rewa Gondwana Basin of India. The material is based on several partial craniomandibular elements containing acrodont and fully ankylosed tooth implantations and on the basis of multiple diagnostic features is assigned to a new taxon, Clevosaurus nicholasi. Phylogenetic analysis nests the Tiki rhynchocephalian within the clade Clevosauridae, where it is recovered as an early-diverging taxon basal to the other clevosaurs except for a clade comprising C. convallis + Sigmala sigmala. The autapomorphic characters of Clevosaurus nicholasi include a very robust dentary with an obliquely angled narrow lip of the secondary bone at the symphysis, anteriorly bifurcated Meckelian canal, a sub-dental shelf on the dentary, acrodont marginal anterior teeth, and absence of or smooth lateral and medial wear facets on the marginal dentary and maxillary teeth, respectively. The Late Triassic rhynchocephalian record of the Gondwana is relatively sparse in comparison with that of the Laurasian regions, and the new clevosaur represents the first Late Triassic record from India. Based on the paleobiogeographic distribution, a possible Gondwanan origin for Clevosauridae is hypothesized.
... analyses of reptiles (Gauthier et al., 1988), and its phylogenetic position has not been considered in more recent studies. Despite this, Palacrodon is an important biostratigraphic marker for the South African Cynognathus Assemblage Zone , and its 35-million-year stratigraphic range spanning both hemispheres (Kligman et al., 2018) makes it an important global index taxon that biostratigraphically links the northern and southern continents. ...
The rapid radiation and dispersal of crown reptiles following the end-Permian
mass extinction characterizes the earliest phase of the Mesozoic. Phylogenetically, this early radiation is difficult to interpret, with polytomies near the crown node, long ghost lineages, and enigmatic origins for crown group clades. Better understanding of poorly known taxa from this time can aid in our understanding of this radiation and Permo-Triassic
ecology. Here, we describe an Early Triassic specimen of the diapsid Palacrodon from the Fremouw Formation of Antarctica. While Palacrodon is known throughout the Triassic and exhibits a cosmopolitan geographic range, little is known of its evolutionary relationships. We recover Palacrodon outside of crown reptiles (Sauria) but more crownward than Youngina capensis and other late Permian diapsids. Furthermore, Palacrodon possesses anatomical features that add clarity to the evolution of the stapes within the reptilian lineage, as well as incipient adaptations for arboreality and herbivory during the earliest phases of the Permo–Triassic recovery.
... Rhynchocephalia are a clade of lizard-like reptiles that together with their sister taxon Squamata form crown-group Lepidosauria (Gauthier et al., 1988;de Queiroz and Gauthier, 2020). Whereas Squamata today comprise over 11,000 species globally (Uetz et al., 2022), Rhynchocephalia include only the tuatara (Sphenodon punctatus), which is restricted to New Zealand (Cree, 2014). ...
... The Meckelian groove opens medially and trends slightly anteroventrally, such that its ventral margin approaches the ventral lip of the dentary anteriorly. No splenial facets are apparent along the preserved portions of the upper and lower margins of the Meckelian groove, which likely indicates the absence of that bone (a synapomorphy of Rhynchocephalia; Gauthier et al., 1988). Similarly, no angular facet is present on the ventral lip of the dentary, which indicates that the jaw was broken anterior to the angular articulation with the dentary. ...
Rhynchocephalia, a once diverse clade of lizard-like reptiles, had a nearly global distribution during much of the Mesozoic. By the Late Cretaceous rhynchocephalians underwent a marked reduction in their diversity and biogeographic range, with sparse records of only deeply nested taxa (e.g., Sphenodontinae) found in the Upper Cretaceous–Paleocene of Patagonia and the Miocene–Recent of New Zealand. Here we describe a partial dentary with teeth of a rhynchocephalian from the Naskal locality, an intertrappean deposit within the Deccan Traps Volcanic Province in peninsular India. This discovery represents the first Cretaceous–Paleogene (K–Pg) record of a rhynchocephalian outside of Patagonia and: (i) demonstrates the clade had a broader Gondwanan distribution during the Cretaceous than previously appreciated and (ii) reinforces the emerging pattern that Rhynchocephalia were confined to Gondwana after the Early Cretaceous. This further extends the rhynchocephalian record in India, which now spans most of the Mesozoic (Late Triassic to ca. K–Pg boundary). The Naskal rhynchocephalian is a member of Acrosphenodontia based on its regionalized, acrodont marginal dentition. Its hatchling teeth appear to be unique (e.g., crowns mesially tipped, distinct break in slope along distal margin) and most similar in morphology to those of Godavarisaurus lateefi from the Lower–Middle Jurassic of India. Although the Naskal intertrappean most likely was deposited during the latest Maastrichtian, additional fossil sampling across the K–Pg boundary in India is needed to determine whether the Naskal rhynchocephalian was a victim or survivor of the end-Cretaceous mass extinction.
... The reptilian clade Rhynchocephalia is the sister taxon to Squamata (lizards, snakes and amphisbaenians) within Lepidosauria (Evans 1984(Evans , 2003Gauthier et al. 1988;Zardoya & Meyer 1998;Jones et al. 2013;Chambi-Trowell et al. 2021; see clade definitions below). Whereas Squamata is represented by more than 11,000 globally distributed species today (Uetz et al. 2022), Rhynchocephalia includes only a single extant species restricted to New Zealand (Hay et al. 2010;Cree 2014;Gemmell et al. 2020;Lamar et al. 2021). ...
... Among these are the holotype of the new taxon described herein (found by Peter Kroehler on 10 July 2010) and the referred partial skull and isolated lower jaw (found in 2003). Lepidosauria Haeckel, 1866(sensu Evans 1984 Rhynchocephalia G€ unther, 1867 (sensu Gauthier et al. 1988 Type and only species. Opisthiamimus gregori sp. ...
We describe a new, small-bodied rhynchocephalian reptile, Opisthiamimus gregori gen. et sp. nov., from the Upper Jurassic Morrison Formation of Wyoming, USA. Whereas many fossil rhynchocephalians are based on isolated incomplete jaws, the holotype of O. gregori includes most of the skull and postcranium and therefore represents one of the most complete specimens of Rhynchocephalia known from North America. We used micro-computed tomography to examine its skeletal anatomy in detail and to develop a three-dimensional reconstruction of the skull. The skull of O. gregori is similar to that of several non-neosphenodontian rhynchocephalians such as Planocephalosaurus (e.g. large orbits) and Clevosaurus (e.g. parietal parasagittal crests) yet exhibits a suite of other features related to the proal shearing mechanism that becomes increasingly elaborated among more phylogenetically nested taxa such as Sphenodon (e.g. lateral palatine tooth row parallels maxillary tooth row along its entire length, pyramidal dentary teeth with mesial shearing crests). The postcranial skeleton of O. gregori exhibits characteristics typical of a terrestrial rhynchocephalian. Our phylogenetic analyses use a substantially updated data set of 118 characters and 46 taxa, and both maximum parsimony and Bayesian frameworks. Results place O. gregori inside Eusphenodontia but outside Neosphenodontia, and therefore in a key position for contributing to character polarity for more deeply nested clades such as Clevosauridae, Sphenodontidae and Pleurosauridae. We also erect Leptorhynchia taxon nov., composed primarily of aquatically adapted taxa (e.g. Pleurosaurus, Sapheosaurus), which is supported by both cranial and postcranial characters. Because O. gregori is not particularly closely related to the other named Morrison rhynchocephalians (e.g. Opisthias rarus), it increases both the alpha and beta taxonomic diversities within the formation. Similarly, major differences in body size and inferred diet of the Morrison taxa imply considerable concomitant palaeoecological diversity just prior to a major global decline in rhynchocephalian diversity around the close of the Jurassic.
http://zoobank.org/urn:lsid:zoobank.org:pub:888E055B-8AC1-4BD0-A37C-8CB192F79673
... Starting in the mid 1980s a number of authors suggested that taxon names could be defined by reference to a part of a phylogenetic tree, prompting an extensive theoretical discussion, as well as the first attempts to generate phylogenetic definitions (Ghiselin 1984;Gauthier and Padian 1985;Gauthier 1986;Rowe 1987;de Queiroz 1987de Queiroz , 1988Gauthier et al. 1988 al. 1988). A phylogenetic definition represents a formal statement that describes a clade in a phylogeny. ...
Evolutionary and organismal biology have become inundated with data. At the same rate, we are experiencing a surge in broader evolutionary and ecological syntheses for which tree-thinking is the staple for a variety of post-tree analyses. To fully take advantage of this wealth of data to discover and understand large-scale evolutionary and ecological patterns, computational data integration, i.e., the use of machines to link data at large scale, is crucial. The most common shared entity by which evolutionary and ecological data need to be linked is the taxon to which they belong. We propose a set of requirements that a system for defining such taxa should meet for computational data science: taxon definitions should maintain conceptual consistency, be reproducible via a known algorithm, be computationally automatable, and be applicable across the Tree of Life. We argue that Linnaean names, the most prevalent means of linking data to taxa, fail to meet these requirements due to fundamental theoretical and practical shortfalls. We argue that for the purposes of data-integration we should instead use phylogenetic definitions transformed into formal logic expressions. We call such expressions phyloreferences, and argue that, unlike Linnaean names, they meet all requirements for effective data-integration.
