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47-422: Pantestudines or Pan-Testudines is the proposed group of all reptiles more closely related to turtles than to any other living animal. It includes both modern turtles ( crown group turtles, also known as Testudines) and all of their extinct relatives (also known as stem -turtles). Pantestudines with a complete shell are placed in the clade Testudinata . The identity of the ancestors and closest relatives of
94-555: A clade ( monophyletic group) including birds, though the precise definition of this clade varies between authors. Others prioritize the clade Sauropsida , which typically refers to all amniotes more closely related to modern reptiles than to mammals . The earliest known proto-reptiles originated from the Carboniferous period, having evolved from advanced reptiliomorph tetrapods which became increasingly adapted to life on dry land. The earliest known eureptile ("true reptile")
141-700: A single species , Sinosaurosphargis yunguiensis . Saurosphargis is known from several individuals, all of which were collected from Member II of the Guanling Formation , dating to the Pelsonian substage of the latest Anisian stage of the early Middle Triassic , about 243 million years ago . The holotype IVPP V 17040 and paratype IVPP V 16076 are housed at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, and represent
188-447: A temnospondyl ). A series of footprints from the fossil strata of Nova Scotia dated to 315 Ma show typical reptilian toes and imprints of scales. These tracks are attributed to Hylonomus , the oldest unquestionable reptile known. It was a small, lizard-like animal, about 20 to 30 centimetres (7.9 to 11.8 in) long, with numerous sharp teeth indicating an insectivorous diet. Other examples include Westlothiana (for
235-514: A combination of fossil and genetic evidence, both suggest that sauropterygians , the group of prehistoric marine reptiles including the plesiosaurs and the often superficially turtle-like placodonts , are themselves stem-turtles. This hypothesis had been previously investigated in the 19th century. Lee (2001) found that forcing the turtle group to cluster with archosauromorphs resulted in Rhynchosauria becoming Testudinata's sister clade. Forcing
282-501: A group of tetrapods with an ectothermic ('cold-blooded') metabolism and amniotic development . Living reptiles comprise four orders : Testudines ( turtles ), Crocodilia ( crocodilians ), Squamata ( lizards and snakes ), and Rhynchocephalia (the tuatara ). As of May 2023, about 12,000 living species of reptiles are listed in the Reptile Database . The study of the traditional reptile orders, customarily in combination with
329-606: A nearly complete articulated skeleton and skull , and a partial disarticulated postcranial skeleton including dorsal vertebra , ribs , with osteoderms and gastral rib fragments, respectively. ZMNH M 8797, an incomplete postcranial skeleton showing a very well preserved right forelimb housed at the Zhejiang Museum of Nature History of Hangzhou, was also referred to Saurosphargis in its original description. The holotype and ZMNH M 8797 were collected at Yangmazhai of Luoping County , Yunnan Province, while
376-488: A relationship with lepidosaurs resulted in turtles being close relatives of sauropterygians within Lepidosauromorpha. The anapsid hypothesis was still better supported, although an archosauromorph affinity could not be rejected. Although morphology-based analyses usually do not support a turtle-archosaur clade ( Archelosauria ), Bhullar & Bever (2009) identified a laterosphenoid bone, typical of Archosauriformes , in
423-490: A section of the clade Amniota : The section that is left after the Mammalia and Aves have been hived off. It cannot be defined by synapomorphies , as is the proper way. Instead, it is defined by a combination of the features it has and the features it lacks: reptiles are the amniotes that lack fur or feathers. At best, the cladists suggest, we could say that the traditional Reptilia are 'non-avian, non-mammalian amniotes'. Despite
470-565: A tiny gecko, Sphaerodactylus ariasae , which can grow up to 17 mm (0.7 in) to the saltwater crocodile , Crocodylus porosus , which can reach over 6 m (19.7 ft) in length and weigh over 1,000 kg (2,200 lb). In the 13th century, the category of reptile was recognized in Europe as consisting of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, lizards, assorted amphibians, and worms", as recorded by Beauvais in his Mirror of Nature . In
517-782: A ventrally open cheek. Its trunk region is short and rounded, and covered by a shield composed of small osteoderms , just like its neck and the proximal portions of all four limbs. Its back vertebrae show elongated, distally expanded transverse projections. The chest ribs are broadened and flat, contacting one another along their length, and forming a closed chest rib basket. Li et al. (2014) found some of these traits to be shared with all saurosphargids , while others are exclusive to Saurosphargis and Sinosaurosphargis . These genera have broader and flatter rib baskets than basal saurosphargids like Largocephalosaurus , and also transverse projections of back vertebrae and proximal portions of chest ribs that are much more robust, being much wider than
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#1732899002772564-545: Is derived from the names of the neighboring Yunnan and Guizhou Provinces, where the fossils were found. Sinosaurosphargis was a small reptile, measuring 70–80 cm (2.3–2.6 ft) long without the missing tail. It is a basal marine reptile , closely related to Saurosphargis from the Lower Muschelkalk of southwestern Poland and eastern Netherlands . Sinosaurosphargis possesses retracted external nostrils , and shows closed upper temporal fenestrae , and
611-479: Is equivalent to the more common definition of Sauropsida, which Modesto and Anderson synonymized with Reptilia, since the latter is better known and more frequently used. Unlike most previous definitions of Reptilia, however, Modesto and Anderson's definition includes birds, as they are within the clade that includes both lizards and crocodiles. General classification of extinct and living reptiles, focusing on major groups. The cladogram presented here illustrates
658-418: The amniotic egg . The terms Sauropsida ("lizard faces") and Theropsida ("beast faces") were used again in 1916 by E.S. Goodrich to distinguish between lizards, birds, and their relatives on the one hand (Sauropsida) and mammals and their extinct relatives (Theropsida) on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, and other features, such as
705-519: The archosaurs (crocodiles, bird, and relatives) or the lepidosaurs (lizards, tuatara, and relatives). An early proponent of this scenario was Goodrich (1916), who defended a diapsid origin of turtles based on morphological evidence. Genetic analysis strongly favors the hypothesis that turtles are the closest relatives of the archosaurs, though studies using only fossil evidence often continue to recover them as relatives of lepidosaurs or as non-diapsids. Studies using only fossils, as well as studies using
752-1733: The "family tree" of reptiles, and follows a simplified version of the relationships found by M.S. Lee, in 2013. All genetic studies have supported the hypothesis that turtles are diapsids; some have placed turtles within Archosauromorpha, though a few have recovered turtles as Lepidosauromorpha instead. The cladogram below used a combination of genetic (molecular) and fossil (morphological) data to obtain its results. Synapsida ( mammals and their extinct relatives) [REDACTED] † Millerettidae [REDACTED] † Eunotosaurus † Lanthanosuchidae [REDACTED] † Pareiasauromorpha [REDACTED] † Procolophonoidea [REDACTED] † Captorhinidae [REDACTED] † Paleothyris † Araeoscelidia [REDACTED] † Claudiosaurus [REDACTED] † Younginiformes [REDACTED] † Kuehneosauridae [REDACTED] Rhynchocephalia ( tuatara and their extinct relatives) [REDACTED] Squamata ( lizards and snakes ) [REDACTED] [REDACTED] † Eosauropterygia [REDACTED] † Placodontia [REDACTED] † Sinosaurosphargis † Odontochelys † Proganochelys Testudines ( turtles ) [REDACTED] † Choristodera [REDACTED] † Prolacertiformes [REDACTED] † Rhynchosauria [REDACTED] † Trilophosaurus [REDACTED] Archosauriformes ( crocodiles , birds , dinosaurs and extinct relatives) [REDACTED] [REDACTED] The placement of turtles has historically been highly variable. Classically, turtles were considered to be related to
799-453: The 18th century, the reptiles were, from the outset of classification, grouped with the amphibians . Linnaeus , working from species-poor Sweden , where the common adder and grass snake are often found hunting in water, included all reptiles and amphibians in class "III – Amphibia" in his Systema Naturæ . The terms reptile and amphibian were largely interchangeable, reptile (from Latin repere , 'to creep') being preferred by
846-480: The French. J.N. Laurenti was the first to formally use the term Reptilia for an expanded selection of reptiles and amphibians basically similar to that of Linnaeus. Today, the two groups are still commonly treated under the single heading herpetology . It was not until the beginning of the 19th century that it became clear that reptiles and amphibians are, in fact, quite different animals, and P.A. Latreille erected
893-657: The anapsid condition has been found to occur so variably among unrelated groups that it is not now considered a useful distinction. By the early 21st century, vertebrate paleontologists were beginning to adopt phylogenetic taxonomy, in which all groups are defined in such a way as to be monophyletic ; that is, groups which include all descendants of a particular ancestor. The reptiles as historically defined are paraphyletic , since they exclude both birds and mammals. These respectively evolved from dinosaurs and from early therapsids, both of which were traditionally called "reptiles". Birds are more closely related to crocodilians than
940-450: The basal saurosphargid Largocephalosaurus , and several species of eosauropterygian , including both pachypleurosaurs and nothosaurids . Sinosaurosphargis was first described and named by Chun Li, Olivier Rieppel, Xiao-Chun Wu, Li-Jun Zhao and Li-Ting Wang in 2011 and the type species is Sinosaurosphargis yunguiensis . The generic name is derived from Greek sino , meaning "China", sauros , meaning "lizard", and sphargis ,
987-421: The class Batracia (1825) for the latter, dividing the tetrapods into the four familiar classes of reptiles, amphibians, birds, and mammals. The British anatomist T.H. Huxley made Latreille's definition popular and, together with Richard Owen , expanded Reptilia to include the various fossil " antediluvian monsters", including dinosaurs and the mammal-like ( synapsid ) Dicynodon he helped describe. This
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#17328990027721034-554: The early proposals for replacing the paraphyletic Reptilia with a monophyletic Sauropsida , which includes birds, that term was never adopted widely or, when it was, was not applied consistently. When Sauropsida was used, it often had the same content or even the same definition as Reptilia. In 1988, Jacques Gauthier proposed a cladistic definition of Reptilia as a monophyletic node-based crown group containing turtles, lizards and snakes, crocodilians, and birds, their common ancestor and all its descendants. While Gauthier's definition
1081-453: The fetus develops within the mother, using a (non-mammalian) placenta rather than contained in an eggshell . As amniotes, reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land. Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals , with some providing initial care for their hatchlings. Extant reptiles range in size from
1128-1100: The hypotheses of a parareptilian origin and a diapsid origin. However, this study was criticised in a response paper, which charged that the matrix the paper used was outdated and did not take into account the previous two decades of literature about parareptiles. The cladogram below follows the analysis of Li et al . (2018). It agrees with the placement of turtles within Diapsida but finds them outside of Sauria (the Lepidosauromorpha + Archosauromorpha clade). † Parareptilia [REDACTED] † Captorhinidae [REDACTED] † Paleothyris [REDACTED] † Araeoscelidia [REDACTED] † Hovasaurus [REDACTED] † Youngina † Acerosodontosaurus † Claudiosaurus † Eunotosaurus † Pappochelys [REDACTED] † Eorhynchochelys [REDACTED] † Odontochelys Testudinata [REDACTED] Archosauriformes [REDACTED] [REDACTED] Reptile See text for extinct groups. Reptiles , as commonly defined, are
1175-460: The hypothesis that turtles belong to a separate clade within Sauropsida , outside the saurian clade altogether. The origin of the reptiles lies about 310–320 million years ago, in the steaming swamps of the late Carboniferous period, when the first reptiles evolved from advanced reptiliomorphs . The oldest known animal that may have been an amniote is Casineria (though it may have been
1222-508: The late 19th century, a number of definitions of Reptilia were offered. The biological traits listed by Lydekker in 1896, for example, include a single occipital condyle , a jaw joint formed by the quadrate and articular bones, and certain characteristics of the vertebrae . The animals singled out by these formulations, the amniotes other than the mammals and the birds, are still those considered reptiles today. The synapsid/sauropsid division supplemented another approach, one that split
1269-499: The latter are to the rest of extant reptiles. Colin Tudge wrote: Mammals are a clade , and therefore the cladists are happy to acknowledge the traditional taxon Mammalia ; and birds, too, are a clade, universally ascribed to the formal taxon Aves . Mammalia and Aves are, in fact, subclades within the grand clade of the Amniota. But the traditional class Reptilia is not a clade. It is just
1316-796: The living reptiles, there are many diverse groups that are now extinct , in some cases due to mass extinction events . In particular, the Cretaceous–Paleogene extinction event wiped out the pterosaurs , plesiosaurs , and all non-avian dinosaurs alongside many species of crocodyliforms and squamates (e.g., mosasaurs ). Modern non-bird reptiles inhabit all the continents except Antarctica. Reptiles are tetrapod vertebrates , creatures that either have four limbs or, like snakes, are descended from four-limbed ancestors. Unlike amphibians , reptiles do not have an aquatic larval stage. Most reptiles are oviparous , although several species of squamates are viviparous , as were some extinct aquatic clades –
1363-572: The moment considered a reptiliomorph rather than a true amniote ) and Paleothyris , both of similar build and presumably similar habit. However, microsaurs have been at times considered true reptiles, so an earlier origin is possible. Sinosaurosphargis Sinosaurosphargis is an extinct genus of basal marine saurosphargid reptile known from the Middle Triassic Guanling Formation of Yunnan and Guizhou Provinces, southwestern China . It contains
1410-612: The most likely result found by another analysis of turtle relationships, this one using only fossil evidence, published by Rainer Schoch and Hans-Dieter Sues in 2015. This study found Eunotosaurus to be an actual early stem-turtle, though other versions of the analysis found weak support for it as a parareptile. Archosauria † Kuehneosauridae Squamata Rhynchocephalia † Eosauropterygia † Sinosaurosphargis † Placodontia † Eunotosaurus † Pappochelys † Odontochelys † Proganochelys Testudines Bever et al . (2015) redescribed
1457-401: The necessity to investigate the possibility that parareptiles are actually archelosaurs instead of non-saurian sauropsids. Lepidosauria † Choristodera † Trilophosaurus † Rhynchosauria Archosauriformes † Eosauropterygia † Placodontia † Sinosaurosphargis † Odontochelys † Proganochelys Testudines The cladogram below follows
Pantestudines - Misplaced Pages Continue
1504-530: The old genus name for the leatherback turtle , (in reference to the many similarities Sinosaurosphargis shares with Saurosphargis , a taxon whose holotype was lost and was thus considered a mystery), following the pattern of Sinosauropteryx . Like the name of Saurosphargis itself, it also refers to Sinosaurosphargis' dorsal osteoderm "body armor" and broadened ribs forming a closed chest rib basket - traits which are seemingly transitional between turtles and other reptiles. The specific name yunguiensis
1551-422: The other euryapsids, and given the older name Parapsida. Parapsida was later discarded as a group for the most part (ichthyosaurs being classified as incertae sedis or with Euryapsida). However, four (or three if Euryapsida is merged into Diapsida) subclasses remained more or less universal for non-specialist work throughout the 20th century. It has largely been abandoned by recent researchers: In particular,
1598-476: The paratype came from Yangjian of Pan County , Guizhou Province. An additional uncatalogued LPV specimen was also referred to S. yunguiensis . These specimens all came from the Lagerstätte discovered during a 2007 geological mapping project with a diverse record of marine life called Luoping Biota , that yielded, apart from Sinosaurosphargis , various invertebrates, fish, basal ichthyosaurs , Atopodentatus ,
1645-416: The primitive anapsid reptiles. Molecular work has usually placed turtles within the diapsids. As of 2013, three turtle genomes have been sequenced. The results place turtles as a sister clade to the archosaurs , the group that includes crocodiles, non-avian dinosaurs, and birds. However, in their comparative analysis of the timing of organogenesis , Werneburg and Sánchez-Villagra (2009) found support for
1692-438: The reptiles into four subclasses based on the number and position of temporal fenestrae , openings in the sides of the skull behind the eyes. This classification was initiated by Henry Fairfield Osborn and elaborated and made popular by Romer 's classic Vertebrate Paleontology . Those four subclasses were: The composition of Euryapsida was uncertain. Ichthyosaurs were, at times, considered to have arisen independently of
1739-521: The skull of Eunotosaurus , identifying a lower temporal fenestra, with a juvenile specimen also having visible upper temporal fenestrae. This instigated a reinterpretation of this taxon as a diapsid instead of an anapsid. Their phylogenetic analyses strongly supported Eunotosaurus' s state as a stem-turtle and the placement of Pantestudines in Diapsida, though they couldn't determine a well-defined position within that clade. Sauropterygia and Acerosodontosaurus also end up as possible stem-turtles in some of
1786-758: The spacing between them. The following cladogram is simplified after the phylogenetic analysis of Li et al. (2011) and shows the placement of Sinosaurosphargis within Sauria . Ichthyopterygia was removed from the tree, as it caused a less resolved topology. Saurosphargis was coded solely based on the holotype, as the Netherlands material remains unprepared. Lepidosauromorpha Odontochelys Proganochelys Chelydra Helveticosaurus Eusaurosphargis Placodontia Eosauropterygia Thalattosauriformes Saurosphargis Sinosaurosphargis Li et al. (2014) presented an updated version of
1833-426: The stem-turtle Proganochelys . It may serve as a synapomorphy for this proposed clade. The cladogram shown below follows the most likely result found by an analysis of turtle relationships using both fossil and genetic evidence by M.S. Lee, in 2013. This study found Eunotosaurus , usually regarded as a turtle relative, to be only very distantly related to turtles in the clade Parareptilia . However, Lee discusses
1880-789: The structure of the forebrain. According to Goodrich, both lineages evolved from an earlier stem group, Protosauria ("first lizards") in which he included some animals today considered reptile-like amphibians , as well as early reptiles. In 1956, D.M.S. Watson observed that the first two groups diverged very early in reptilian history, so he divided Goodrich's Protosauria between them. He also reinterpreted Sauropsida and Theropsida to exclude birds and mammals, respectively. Thus his Sauropsida included Procolophonia , Eosuchia , Millerosauria , Chelonia (turtles), Squamata (lizards and snakes), Rhynchocephalia , Crocodilia , " thecodonts " ( paraphyletic basal Archosauria ), non- avian dinosaurs , pterosaurs , ichthyosaurs , and sauropterygians . In
1927-693: The study of modern amphibians , is called herpetology . Reptiles have been subject to several conflicting taxonomic definitions. In Linnaean taxonomy , reptiles are gathered together under the class Reptilia ( / r ɛ p ˈ t ɪ l i ə / rep- TIL -ee-ə ), which corresponds to common usage. Modern cladistic taxonomy regards that group as paraphyletic , since genetic and paleontological evidence has determined that birds (class Aves), as members of Dinosauria , are more closely related to living crocodilians than to other reptiles, and are thus nested among reptiles from an evolutionary perspective. Many cladistic systems therefore redefine Reptilia as
Pantestudines - Misplaced Pages Continue
1974-748: The trees. Benton (2015) compiled 2 synapomorphies of Ankylopoda (which would also include Sauropterygia, Thalattosauria and Ichthyosauria close to lepidosaurs): prootic-parietal contact and hooked fifth metatarsal. Time-calibrated phylogeny recovered by Shaffer et al. (2017) dated the split of Pantestudines from its sister clade (the clade containing archosaurs and all tetrapods more closely related to archosaurs than to any other living animals) to mid- Carboniferous . Laurin and Piñeiro (2017) placed turtles close to pareiasaurs among parareptiles once more. However, parareptiles were considered derived diapsids in this analysis. The authors interpreted these results as an indication that there might be no conflict between
2021-566: The turtle lineage was a longstanding scientific mystery, though new discoveries and better analyses in the early 21st century began to clarify turtle relationships. They had traditionally been considered relatives of the captorhinids , which also possessed an anapsid skull configuration. Later, the consensus shifted towards Testudinata's placement within Parareptilia , another "anapsid" clade. Analysis of fossil data has shown that turtles are likely diapsid reptiles, most closely related either to
2068-585: The years following Gauthier's paper. The first such new definition, which attempted to adhere to the standards of the PhyloCode , was published by Modesto and Anderson in 2004. Modesto and Anderson reviewed the many previous definitions and proposed a modified definition, which they intended to retain most traditional content of the group while keeping it stable and monophyletic. They defined Reptilia as all amniotes closer to Lacerta agilis and Crocodylus niloticus than to Homo sapiens . This stem-based definition
2115-625: Was Hylonomus , a small and superficially lizard-like animal which lived in Nova Scotia during the Bashkirian age of the Late Carboniferous , around 318 million years ago . Genetic and fossil data argues that the two largest lineages of reptiles, Archosauromorpha (crocodilians, birds, and kin) and Lepidosauromorpha (lizards, and kin), diverged during the Permian period. In addition to
2162-592: Was close to the modern consensus, nonetheless, it became considered inadequate because the actual relationship of turtles to other reptiles was not yet well understood at this time. Major revisions since have included the reassignment of synapsids as non-reptiles, and classification of turtles as diapsids. Gauthier 1994 and Laurin and Reisz 1995's definition of Sauropsida defined the scope of the group as distinct and broader than that of Reptilia, encompassing Mesosauridae as well as Reptilia sensu stricto . A variety of other definitions were proposed by other scientists in
2209-615: Was not the only possible classification scheme: In the Hunterian lectures delivered at the Royal College of Surgeons in 1863, Huxley grouped the vertebrates into mammals , sauroids, and ichthyoids (the latter containing the fishes and amphibians). He subsequently proposed the names of Sauropsida and Ichthyopsida for the latter two groups. In 1866, Haeckel demonstrated that vertebrates could be divided based on their reproductive strategies, and that reptiles, birds, and mammals were united by
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