identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
191987D64176406CDBEBF973F535F72B.text	191987D64176406CDBEBF973F535F72B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Reptilia Laurenti 1768	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Reptilia Laurenti, 1768</p>
            <p>Diapsida Osborn, 1903</p>
            <p>Ichthyosauromorpha Motani et al., 2015a Ichthyosauriformes Motani et al., 2015a</p>
            <p> Chaohusaurus Young &amp; Dong, 1972</p>
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	https://treatment.plazi.org/id/191987D64176406CDBEBF973F535F72B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Gu, Li-Ang;Wolniewicz, Andrzej S.;Liu, Jun	Gu, Li-Ang, Wolniewicz, Andrzej S., Liu, Jun (2024): New information on the dentition of ChaohUSaURUS zhangjiawanenSiS (Reptilia, Ichthyosauriformes) from the Early Triassic of Yuan’an, Hubei Province, China. Swiss Journal of Palaeontology (35) 143 (1): 1-16, DOI: 10.1186/s13358-024-00331-8, URL: https://doi.org/10.1186/s13358-024-00331-8
191987D641764068D83EF9B2F332F6DE.text	191987D641764068D83EF9B2F332F6DE.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Chaohusaurus zhangjiawanensis Chen 2013	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Chaohusaurus zhangjiawanensis Chen et al., 2013</p>
            <p>Diagnosis (modified after Chen et al., 2013; Zhao et al., 2022; Zou et al., 2020).</p>
            <p>Small ichthyosauriform about 1 m in adult length; orbit large and with irregular anterodorsal margin formed by a lateral shelf of the prefrontal; postfrontalprefrontal contact present; dentition heterodont, with slender and pointed anterior teeth and robust and rounded posterior teeth (revised character state); anterior tooth crowns ornamented with sparse apicobasal enamel ridges, posterior tooth crowns ornamented with ridges forming an anastomosing pattern (revised character state); plicidentine present at least in posterior teeth (new character state); maxilla anterior process much longer than posterior process; two pairs of sacral ribs, with only the first pair being distally expanded and the second pair being similar to, but smaller, than the adjacent caudal ribs; caudal peak present; forelimb elements tightly packed; proximal carpals completely ossified; manual pisiform present; distal carpal I unossified/absent; intermedium pentagonal; dorsal process of femur well-developed.</p>
            <p>Referred specimen</p>
            <p>HFUT YAV-10-08, the anterior part of the snout with associated dentition, impressions of the posterior portions of the upper and lower jaws and posterior maxillary and dentary teeth, a single preserved posterior maxillary tooth crown, and abraded fragments of indeterminate skull bones (Fig. 2).</p>
            <p>Type horizon</p>
            <p>Uppermost part of the third member of the Jialingjiang Formation, Olenekian (Spathian), Lower Triassic (see Wolniewicz et al., 2023 for a more detailed discussion of the stratigraphy).</p>
            <p>Type locality</p>
            <p> Zhangjiawan quarry, Yuan’an County, Hubei Province, China . </p>
            <p>Description</p>
            <p> Skull. Te preserved length of the skull measures 146 mm and is comparable in size to an almost complete skull of  Ch. zhangjiawanensis reported by Zhao et al. (2022), which measures 151.22 mm in length. Te anterior part of the snout is exposed in right dorsolateral view (Fig. 2). Te premaxillae are partially preserved, with their anterior tips as well as their posterior portions missing, but they are articulated and form a clearly visible interpremaxillary suture. Only the anteriormost part of the right maxilla is preserved, whereas the left maxilla is heavily abraded, and the bone is preserved mostly as an impression in the rock matrix. Te anterior portion of the right dentary is preserved in semi-occlusion with the right premaxilla. As revealed by surface striations and suture lines visible in the mould of the specimen, the posterior portions of the jaws are represented by the impressions of the left dentary and left surangular exposed in lateral view, and the right mandibular ramus exposed in medial view (Fig. 2 and 5). Several heavily abraded and indeterminate skull bone fragments are preserved in the posterodorsal part of the specimen. </p>
            <p> Dentition—general morphology. Te dentition of  Ch. zhangjiawanensis is heterodont, as demonstrated by specimens HFUT YAV-10-08 (this work) and YGM- Y4701 (Zhao et al., 2022) (crushing posterior teeth were also reported in the holotype of  Ch. zhangjiawanensis , but were only briefly described and were not figured; Chen et al., 2013). Te anterior premaxillary and dentary teeth are conical and pointed, whereas the posterior maxillary and dentary teeth are robust and rounded </p>
            <p> (Figs. 3, 4, 5, 6 and 7). Te morphological transition from conical to rounded teeth occurs in the anterior part of the maxilla, as seen in YGM-Y4701 (Zhao et al., 2022). Tis transitional region is also partially preserved in HFUT YAV-10-08, but the transitional teeth themselves are not preserved. Te mode of tooth implantation of the premaxillary teeth is not possible to determine with confidence. Te maxillary teeth are set within alveoli (Fig. 6), like in  Ch. brevifemoralis , but the presence of a shallow dental groove could not be confirmed (Gu et al., 2024). It is unknown whether an additional tooth row, like the one reported in  Ch. brevifemoralis (Gu et al., 2024; Yin et al., 2021), was present lingually to the only exposed maxillary tooth row. Root impressions indicate the presence of deep, vertical grooves on root surfaces in the posterior dentition, which implies the presence of plicidentine (Maxwell et al., 2011). Selected measurements of the dentition are given in Table 1 and Supplementary Table 1. </p>
            <p>Anterior (conical) dentition. Te anterior teeth of HFUT YAV-10-08 include ten premaxillary teeth (p1–10) and six dentary teeth (d1–6) (Figs. 3 and 4). Te teeth are conical and terminate in a pointed tip (e.g., tooth p2; Fig. 4A). Te crown surfaces are ornamented with sparse apicobasal (longitudinal) ridges (e.g., teeth p2, p4, and p8; Fig. 4). Te roots seem to lack grooves on their surfaces (e.g., teeth p3, p5, and d3; Fig. 4B, D). A slight constriction seems to be present at the crown-root boundary in some of the conical teeth (e.g., teeth p2 and p4; Fig. 4A, B).</p>
            <p>Ten teeth form a single row in the right premaxilla and around five vacant tooth positions are visible among them—between teeth p2 and p3 (two vacant tooth positions), between p6 and p7 (two vacant positions) and between p9 and p10 (one vacant position) (Fig. 3). Tis indicates a total tooth count of 15 teeth for the preserved part of the right premaxilla. Tooth spacing ranges from 1.59 to 3.15 mm (full data available in Supplementary Table 1), but the maximum tooth spacing value of 3.15 mm (between teeth p4 and p5) is likely overestimated, since p4 represents a replacement tooth, which has not reached its maximum size (Fig. 4B, F). In general, tooth size increases posteriorly along the jaw length. Teeth p4 and p8 likely represent replacement teeth, because they are much smaller than the remaining premaxillary teeth. Even though some premaxillary teeth are abraded, details of tooth microanatomy (such as the morphology of the pulp cavity and the presence of infolded dentine) are not preserved due to extensive damage (e.g., teeth p6 and p7, Fig. 3; teeth p3 and p9, Fig. 4). Te right dentary preserves only six teeth; tooth d3 (Fig. 4D, H) is the best-preserved one. Te anterior dentary teeth are only very partially exposed, but they share the same general morphology with the anterior premaxillary teeth, being slightly smaller in size (Fig. 3; Table 1).</p>
            <p>Posterior dentition. Te posterior teeth of HFUT YAV-10-08 are represented by impressions left by four left maxillary teeth (Figs. 5 and 6) and three left dentary teeth</p>
            <p> (Figs. 5 and 7). Tey are rounded with a blunt or slightly pointed (e.g. i/lm 2; Figs. 5 and 6) crown tip. Teir crown surfaces are ornamented with ridges forming a vermiform (anastomosing) pattern, superficially similar to that present in the posterior teeth of the early-diverging durophagous ichthyosaurians Tolodus and  Xinminosaurus (Mulder &amp; Jagt, 2019) . Te widely exposed roots of the maxillary teeth bear clearly visible vertical grooves </p>
            <p>(Figs. 6 and 7).</p>
            <p> Te impressions demonstrate that the maxillary teeth were set in shallow sockets, similar to the condition in  Ch. brevifemoralis (Gu et al., 2024) . However, it is not possible to determine if a shallow dental groove was present along the maxillary tooth row. </p>
            <p>Te maxillary teeth become more robust posteriorly. Tooth lm1 is the smallest preserved maxillary tooth and likely represents a replacement tooth (Fig. 6). Tooth lm4 is the only maxillary tooth that has its crown partially preserved, although it is heavily abraded (Fig. 6). Te crown shape index of tooth m4 has a value of 0.51, indicating that it has the most robust crown out of all preserved maxillary teeth and tooth impressions. Te impression of tooth rd8 indicates that the posterior dentary teeth were also rounded. Its root is well exposed and ornamented with sparse, broad, vertical grooves (Fig. 7). Teeth rd7 and rd9 only left partial impressions of their crowns. Te vermiform (anastomosing) pattern of crown ornamentation is clearly visible in all the preserved impressions of dentary teeth (Fig. 7). Tere is a large empty space present between the impressions of teeth d8 and d9, indicating vacant tooth positions for likely two additional dentary teeth.</p>
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	https://treatment.plazi.org/id/191987D641764068D83EF9B2F332F6DE	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Gu, Li-Ang;Wolniewicz, Andrzej S.;Liu, Jun	Gu, Li-Ang, Wolniewicz, Andrzej S., Liu, Jun (2024): New information on the dentition of ChaohUSaURUS zhangjiawanenSiS (Reptilia, Ichthyosauriformes) from the Early Triassic of Yuan’an, Hubei Province, China. Swiss Journal of Palaeontology (35) 143 (1): 1-16, DOI: 10.1186/s13358-024-00331-8, URL: https://doi.org/10.1186/s13358-024-00331-8
