Xinpusaurus is an extinct genus of thalattosaur from the Late Triassic of Guanling in Guizhou, China. Several species have been named since 2000: the type speciesX. suni along with the species X. bamaolinensis and X. kohi. A 2013 study proposed that all three species are synonymous with each other, in which case X. suni would be the only valid species, although a 2014 study argued that X. kohi was also valid.[1][2] A fourth species, X. xingyiensis, was described in 2016.[3]
Xinpusaurus is a thalattosaur, a group of triassic marine reptiles with long, paddle-like tails and short legs with independently movable digits. Specifically, it is a member of the group thalattosauroidea, which are characterized by their downturned premaxillae. Xinpusaurus had a short neck, a massive quadrate, and one of the few braincases preserved in thalattosaurs. The lower jaws of this genus show two different forms of dentary-surangular sutures, either a v-shaped suture with the surangular cutting into the dentary from the side (type 1) or an oblique suture with the surangular underlying the dentary (type 2). X. bamaolinensis preserves a type 2 suture while X. kohi has a type 1 suture. X. suni's suture differs between specimens while X. xingyiensis seems to have a type 2 suture.[1] The dentary is also narrow and shorter than the snout, with robust, pointed teeth in the front of its jaws and broad crushing teeth in the back of its jaws, suggesting that it fed on hard-shelled prey, although these adaptations are not as extreme as those of Concavispina, which had exclusively short and blunt teeth.[4] This genus also has a uniquely upward-curving maxilla, a wide proximal end of the humerus, and a radius with a convex lateral edge and concave medial edge.[3]
X. bamaolinensis and X. kohi had particularly elongated premaxillae, forming a narrow and pointed rostrum. However, the specimens with the longest snouts are also the smallest in other proportions, so this may be a juvenile trait and cannot be used to distinguish these species from X. suni.[1]
X. xingyiensis is the largest species known and is also probably the least advanced, as it does not have a posterior process of the jugal unlike the other species and shares some similarities with the genus Concavispina.[3]
Historyedit
Xinpusaurus suni was first described by Yin et al. in 2000 based on four specimens: Gmr 010, 011, 012, and 013, with only Gmr 010 (the holotype) receiving an informal description. Other specimens of this species have been found from 2001 to 2002 including GGSr 001 (a well-preserved skull and partial skeleton) IVPP V 11860 (an isolated skull), IVPP V 12673 (a partial skeleton), and IVPP V 14372 (an isolated skull). IVPP V 12673 is the only well described specimen.[1]
Xinpusaurus bamaolinensis was described in 2003 from SPCV 30015, a complete skeleton with a well-preserved skull and jaws found in two isolated slabs. These slabs may not represent the same individual, in which case only the front slab can be safely assigned to the genus.[1] Inconsistencies within its description (such as reporting a quadratojugal, a feature unknown in thalattosaurs) have led to some confusion over its diagnosis, and a redescription would be necessary to resolve these issues and determine if it is a valid species or not.[2]
Xinpusaurus kohi was described in 2004 from GMPKU 2000/05, an incomplete skeleton. This specimen was also found in two slabs, with the rear slab missing most of the hindlimbs and possibly not belonging to the same individual as the first. In addition, there is evidence that some of the bone structure near the break has been tampered with and that most of the pelvic material has been lost. A 2013 analysis showed that many of the traits initially believed to differentiate X. kohi from X. suni were inaccurate, either due to incomplete data, misidentification, or poor preservation.[1] However, a redescription in 2014 resurrected the legitimacy of the species. This redescription provided additional diagnostic features and argued that the alterations were relatively minimal and that the posterior slab was almost certainly from the same individual as the anterior one.[2]
Xinpusaurus xingyiensis was described in 2016 from XNGM WS-53-R3, a nearly complete articulated skeleton from the Zhuganpo member of the Falang formation.
Relationshipsedit
A phylogenetic analysis of thalattosaurs published in 2013 found Concavispina to be the closest relative of Xinpusaurus. Below is a cladogram based on that analysis:[4]
^ abcdefLiu, J. (2013). "On the taxonomy of Xinpusaurus (Reptilia: Thalattosauria)" (PDF). Vertebrata PalAsiatica. 51 (1): 17–23.
^ abcMaisch, M.W. (2014). "On the morphology and taxonomic status of Xinpusaurus kohi JIANG et al., 2004 (Diapsida: Thalattosauria) from the Upper Triassic of China" (PDF). Palaeodiversity. 7: 47–59.
^ abcLi, Z.-G.; Jiang, D.-Y.; Rieppel, O.; Motani, R.; Tintori, A.; Sun, Z.-Y.; Ji, C. (2016-11-01). "A new species of Xinpusaurus (Reptilia, Thalattosauria) from the Ladinian (Middle Triassic) of Xingyi, Guizhou, southwestern China". Journal of Vertebrate Paleontology. 36 (6): e1218340. Bibcode:2016JVPal..36E8340L. doi:10.1080/02724634.2016.1218340. ISSN 0272-4634. S2CID 132418823.
^ abLiu, J.; Zhao, L. J.; Li, C.; He, T. (2013). "Osteology of Concavispina biseridens (Reptilia, Thalattosauria) from the Xiaowa Formation (Carnian), Guanling, Guizhou, China". Journal of Paleontology. 87 (2): 341. Bibcode:2013JPal...87..341L. doi:10.1666/12-059R1.1. S2CID 83684967.
xinpusaurus, extinct, genus, thalattosaur, from, late, triassic, guanling, guizhou, china, several, species, have, been, named, since, 2000, type, species, suni, along, with, species, bamaolinensis, kohi, 2013, study, proposed, that, three, species, synonymous. Xinpusaurus is an extinct genus of thalattosaur from the Late Triassic of Guanling in Guizhou China Several species have been named since 2000 the type species X suni along with the species X bamaolinensis and X kohi A 2013 study proposed that all three species are synonymous with each other in which case X suni would be the only valid species although a 2014 study argued that X kohi was also valid 1 2 A fourth species X xingyiensis was described in 2016 3 XinpusaurusTemporal range Carnian 232 228 Ma PreꞒ Ꞓ O S D C P T J K Pg N Fossil specimen Tianjin Natural History Museum Scientific classification Domain Eukaryota Kingdom Animalia Phylum Chordata Class Reptilia Order Thalattosauria Superfamily Thalattosauroidea Genus XinpusaurusYin 2000 Species X suni Yin 2000 type X bamaolinensis Cheng 2003 X kohi Jiang et al 2004 X xingyiensis Li et al 2016 Contents 1 Description 2 History 3 Relationships 4 ReferencesDescription editXinpusaurus is a thalattosaur a group of triassic marine reptiles with long paddle like tails and short legs with independently movable digits Specifically it is a member of the group thalattosauroidea which are characterized by their downturned premaxillae Xinpusaurus had a short neck a massive quadrate and one of the few braincases preserved in thalattosaurs The lower jaws of this genus show two different forms of dentary surangular sutures either a v shaped suture with the surangular cutting into the dentary from the side type 1 or an oblique suture with the surangular underlying the dentary type 2 X bamaolinensis preserves a type 2 suture while X kohi has a type 1 suture X suni s suture differs between specimens while X xingyiensis seems to have a type 2 suture 1 The dentary is also narrow and shorter than the snout with robust pointed teeth in the front of its jaws and broad crushing teeth in the back of its jaws suggesting that it fed on hard shelled prey although these adaptations are not as extreme as those of Concavispina which had exclusively short and blunt teeth 4 This genus also has a uniquely upward curving maxilla a wide proximal end of the humerus and a radius with a convex lateral edge and concave medial edge 3 X bamaolinensis and X kohi had particularly elongated premaxillae forming a narrow and pointed rostrum However the specimens with the longest snouts are also the smallest in other proportions so this may be a juvenile trait and cannot be used to distinguish these species from X suni 1 X xingyiensis is the largest species known and is also probably the least advanced as it does not have a posterior process of the jugal unlike the other species and shares some similarities with the genus Concavispina 3 History editXinpusaurus suni was first described by Yin et al in 2000 based on four specimens Gmr 010 011 012 and 013 with only Gmr 010 the holotype receiving an informal description Other specimens of this species have been found from 2001 to 2002 including GGSr 001 a well preserved skull and partial skeleton IVPP V 11860 an isolated skull IVPP V 12673 a partial skeleton and IVPP V 14372 an isolated skull IVPP V 12673 is the only well described specimen 1 Xinpusaurus bamaolinensis was described in 2003 from SPCV 30015 a complete skeleton with a well preserved skull and jaws found in two isolated slabs These slabs may not represent the same individual in which case only the front slab can be safely assigned to the genus 1 Inconsistencies within its description such as reporting a quadratojugal a feature unknown in thalattosaurs have led to some confusion over its diagnosis and a redescription would be necessary to resolve these issues and determine if it is a valid species or not 2 Xinpusaurus kohi was described in 2004 from GMPKU 2000 05 an incomplete skeleton This specimen was also found in two slabs with the rear slab missing most of the hindlimbs and possibly not belonging to the same individual as the first In addition there is evidence that some of the bone structure near the break has been tampered with and that most of the pelvic material has been lost A 2013 analysis showed that many of the traits initially believed to differentiate X kohi from X suni were inaccurate either due to incomplete data misidentification or poor preservation 1 However a redescription in 2014 resurrected the legitimacy of the species This redescription provided additional diagnostic features and argued that the alterations were relatively minimal and that the posterior slab was almost certainly from the same individual as the anterior one 2 Xinpusaurus xingyiensis was described in 2016 from XNGM WS 53 R3 a nearly complete articulated skeleton from the Zhuganpo member of the Falang formation Relationships editA phylogenetic analysis of thalattosaurs published in 2013 found Concavispina to be the closest relative of Xinpusaurus Below is a cladogram based on that analysis 4 Diapsida Petrolacosaurus kansensis Youngina capensis Prolacerta broomi Thalattosauria Askeptosauroidea Miodentosaurus brevis Endennasaurus acutirostris Anshunsaurus huangguoshuensis Anshunsaurus wushaensis Askeptosaurus italicus Thalattosauroidea Paralonectes merriami Concavispina biseridens Xinpusaurus suni Clarazia schinzi Hescheleria ruebeli Agkistrognathus campbelli Nectosaurus halius Thalattosaurus alexandrae Thalattosaurus borealisReferences edit a b c d e f Liu J 2013 On the taxonomy of Xinpusaurus Reptilia Thalattosauria PDF Vertebrata PalAsiatica 51 1 17 23 a b c Maisch M W 2014 On the morphology and taxonomic status of Xinpusaurus kohi JIANG et al 2004 Diapsida Thalattosauria from the Upper Triassic of China PDF Palaeodiversity 7 47 59 a b c Li Z G Jiang D Y Rieppel O Motani R Tintori A Sun Z Y Ji C 2016 11 01 A new species of Xinpusaurus Reptilia Thalattosauria from the Ladinian Middle Triassic of Xingyi Guizhou southwestern China Journal of Vertebrate Paleontology 36 6 e1218340 Bibcode 2016JVPal 36E8340L doi 10 1080 02724634 2016 1218340 ISSN 0272 4634 S2CID 132418823 a b Liu J Zhao L J Li C He T 2013 Osteology of Concavispina biseridens Reptilia Thalattosauria from the Xiaowa Formation Carnian Guanling Guizhou China Journal of Paleontology 87 2 341 Bibcode 2013JPal 87 341L doi 10 1666 12 059R1 1 S2CID 83684967 nbsp Palaeontology portal nbsp This article about a Triassic reptile is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Xinpusaurus amp oldid 1191491209, wikipedia, wiki, book, books, library,
