Jiucaiyuangnathus, new therocephalian from Lower Triassic of China + Thaisaurus (icthyosauromorph) dated to late Early Triassic + lizard tooth replacement + Late Cretaceous turtles
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Ben Creisler
Jul 27, 2024, 1:11:30 PM7/27/24
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Ben Creisler
Some recent or not yet mentioned tetrapod and reptile papers:
Jiucaiyuangnathus confusus gen. et sp. nov.
LIU Jun & Fernando ABDALA (2024)
A new small baurioid therocephalian from the Lower Triassic Jiucaiyuan Formation, Xinjiang, China
Vertebrata Palasiatica (advance online publication)
DOI: 10.19615/j.cnki.2096-9899.240726
https://www.vertpala.ac.cn/EN/10.19615/j.cnki.2096-9899.240726
Several therocephalian species, mainly represented by cranial material from the late Permian, have been reported from China in recent years. Here we describe a tiny new baurioid therocephalian, Jiucaiyuangnathus confusus gen. et sp. nov., from the Jiucaiyuan Formation, Xinjiang, China. The new taxon is represented by a partial snout with occluded partial lower jaw and two postcranial skeletons. Although juvenile in stage, the new species is diagnosed by the following features: round pit in middle of lateral surface of maxilla; lacrimal contact nasal; fossa for dentary tooth on the posterior end of the premaxilla, lateral to the anterior choana; two small vertical triangular ridges extending dorsally and ventrally on the vomerine anterior portion, and bordering a thin vomerine foramen laterally; anterior projection of the lateral part of the frontal on the nasal; symphyseal region of the dentary projected anteriorly; 5 upper premaxillary teeth, upper and lower canines absent, diastema between the last premaxillary upper incisor and first maxillary tooth present, no diastema separating anterior from posterior dentition in the mandible, 10 maxillary teeth and 12 dentary teeth, posterior postcanine expands mesiodistally, having a main large cusps and tiny anterior and posterior accessory cusps in line; neural arches of the atlas fused by the neural spine, neural spine of the axis projected posteriorly, procoracoid foramen lies between procoracoid and scapula. Features of the dentition resembles those of the small baurioid Ericiolacerta parva from South Africa and Silphedosuchus orenburgensis from Russia. The specimens provide the rare opportunity to know in detail the postcranial skeleton of baurioids.
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A review of the common origins of teeth and other ectodermal specializations
Introduction to adult reptile teeth which undergo life-long organ regeneration
Review of RNA expression profiling of reptilian dentitions and insights into the molecular mechanisms of tooth replacement
A review of pulse-chase experiments to define the locations of tissue-resident, dental epithelial stem cells
The review covers the broad impact of studies on reptilian dentitions to evolution, stem cell biology, organ replacement and dental pathology.
Abstract
The dentition is critical to animal survival and teeth are present in modern vertebrates including teleost fish, sharks, amphibians, mammals and reptiles. The developmental processes that give rise to teeth are not just preserved through evolution but also share high level of similarity with the embryogenesis of other ectodermal organs. In this review we go beyond the embryonic phase of tooth development to life-long tooth replacement. We will address the origins of successional teeth, the location of putative tissue-resident stem cells, how de novo tooth formation continues throughout life and how teeth are shed in a spatially and temporally controlled manner. We review the evidence that the dental epithelium, which is the earliest recognizable dental structure in the reptilian dentition, serves as a putative niche for tissue-resident epithelial stem cells and recent molecular findings from transcriptomics carried out in reptilian dentitions. We discuss how odontoclasts clear the eruption pathway and allow shedding of functional teeth. The reptiles, particularly lizards, are emerging as some of the most accessible animals to study tooth replacement which has relevance to evolution of the dentition and human dental disorders.
====
Ignacio J. Maniel (2024)
Pelomedusoid turtles from the Bajo de la Carpa Formation (Santonian, Upper Cretaceous), Río Negro Province, Patagonia, Argentina.
Ameghiniana (advance online publication)
doi: 10.5710/AMGH.12.06.2024.3591
https://www.ameghiniana.org.ar/index.php/ameghiniana/libraryFiles/downloadPublic/111
The fossil record of pleurodiran turtles in the Cretaceous of Patagonia is diverse throughout all basins, with Pelomedusoides being scarce compared to the Chelidae. In this article, new records of pelomedusoids are reported from the Bajo de la Carpa Formation (Santonian) at the La Bonita site, Río Negro Province, Argentina. Two specimens are described and referred to Podocnemidoidea by the combination of the following features: posterior marginals not extending over the costals, a straight xiphiplastron with rounded tips, short and U-shaped anterior lobe, a rhomboidal entoplastron, and a humero-pectoral sulcus that crosses the entoplastron. The observed variability of the pelomedusoid plastron in the specimens recorded in the Neuquén Group shows that these new specimens present a new scute scheme. Evaluating the diversity observed in the Cretaceous pelomedusoids in the Neuquén Group, three stages of their evolution are defined. A first stage in the Cenomanian where the Bothremydidae appear; a second stage in the late Turonian-Coniacian interval where the Bothremydidae and Podocnemidoidea coexist, and a final stage in the Santonian-Campanian where only the Podocnemidoideapersist and increase the diversity and abundance of morphotypes.
Free pdf:
Jiucaiyuangnathus confusus gen. et sp. nov.
LIU Jun & Fernando ABDALA (2024)
A new small baurioid therocephalian from the Lower Triassic Jiucaiyuan Formation, Xinjiang, China
Vertebrata Palasiatica (advance online publication)
DOI: 10.19615/j.cnki.2096-9899.240726
https://www.vertpala.ac.cn/EN/10.19615/j.cnki.2096-9899.240726
Several therocephalian species, mainly represented by cranial material from the late Permian, have been reported from China in recent years. Here we describe a tiny new baurioid therocephalian, Jiucaiyuangnathus confusus gen. et sp. nov., from the Jiucaiyuan Formation, Xinjiang, China. The new taxon is represented by a partial snout with occluded partial lower jaw and two postcranial skeletons. Although juvenile in stage, the new species is diagnosed by the following features: round pit in middle of lateral surface of maxilla; lacrimal contact nasal; fossa for dentary tooth on the posterior end of the premaxilla, lateral to the anterior choana; two small vertical triangular ridges extending dorsally and ventrally on the vomerine anterior portion, and bordering a thin vomerine foramen laterally; anterior projection of the lateral part of the frontal on the nasal; symphyseal region of the dentary projected anteriorly; 5 upper premaxillary teeth, upper and lower canines absent, diastema between the last premaxillary upper incisor and first maxillary tooth present, no diastema separating anterior from posterior dentition in the mandible, 10 maxillary teeth and 12 dentary teeth, posterior postcanine expands mesiodistally, having a main large cusps and tiny anterior and posterior accessory cusps in line; neural arches of the atlas fused by the neural spine, neural spine of the axis projected posteriorly, procoracoid foramen lies between procoracoid and scapula. Features of the dentition resembles those of the small baurioid Ericiolacerta parva from South Africa and Silphedosuchus orenburgensis from Russia. The specimens provide the rare opportunity to know in detail the postcranial skeleton of baurioids.
====
Si-Yao Ye, Kui Wu, Zuo-Yu Sun, P. Martin Sander, Adun Samathi, Yuan-Yuan Sun, Cheng Ji, Varavudh Suteethorn & Jun Liu (2024)
Conodonts suggest a late Spathian (late Early Triassic) age for Thaisaurus chonglakmanii (Reptilia: Ichthyosauromorpha) from Thailand
Palaeoworld (advance online publication)
doi: https://doi.org/10.1016/j.palwor.2024.07.004
https://www.sciencedirect.com/science/article/abs/pii/S1871174X24000945
The timing of the emergence of marine reptiles following the Permian–Triassic mass extinction is crucial for studying the recovery of marine ecosystems in the Triassic. Conodonts, key index fossils in the Triassic, are widely used to date the marine reptiles, especially in the Early Triassic. Triassospathodus anhuinensis is a conodont species originally discovered in the upper Spathian of South China, but lacked a comprehensive description, leading to misidentifications and confusion in previous research. Here, we reevaluated Tr. anhuinensis and summarized its morphological characteristics and spatial and temporal distribution based on a review of the literature. We then critically evaluated the age of the primitive ichthyosaur Thaisaurus chonglakmanii from Thailand based on the updated knowledge of Tr. anhuinensis. We sampled the Khao Thong section where T. chonglakmanii was found for conodont study. Tr. anhuinensis elements were obtained from the bed where T. chonglakmanii was collected and also in the bed five metres above the T. chonglakmanii fossil horizon, suggesting a late Spathian age for T. chonglakmanii. A late Spathian age for T. chonglakmanii questions the hypothesis of Thailand as the place of origin of ichthyosaurs in the late Induan or early Spathian.
Conodonts suggest a late Spathian (late Early Triassic) age for Thaisaurus chonglakmanii (Reptilia: Ichthyosauromorpha) from Thailand
Palaeoworld (advance online publication)
doi: https://doi.org/10.1016/j.palwor.2024.07.004
https://www.sciencedirect.com/science/article/abs/pii/S1871174X24000945
The timing of the emergence of marine reptiles following the Permian–Triassic mass extinction is crucial for studying the recovery of marine ecosystems in the Triassic. Conodonts, key index fossils in the Triassic, are widely used to date the marine reptiles, especially in the Early Triassic. Triassospathodus anhuinensis is a conodont species originally discovered in the upper Spathian of South China, but lacked a comprehensive description, leading to misidentifications and confusion in previous research. Here, we reevaluated Tr. anhuinensis and summarized its morphological characteristics and spatial and temporal distribution based on a review of the literature. We then critically evaluated the age of the primitive ichthyosaur Thaisaurus chonglakmanii from Thailand based on the updated knowledge of Tr. anhuinensis. We sampled the Khao Thong section where T. chonglakmanii was found for conodont study. Tr. anhuinensis elements were obtained from the bed where T. chonglakmanii was collected and also in the bed five metres above the T. chonglakmanii fossil horizon, suggesting a late Spathian age for T. chonglakmanii. A late Spathian age for T. chonglakmanii questions the hypothesis of Thailand as the place of origin of ichthyosaurs in the late Induan or early Spathian.
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Joaquin I. Henriquez & Joy M. Richman (2024)
Resilience of the replacing dentition in adult reptiles
Developmental Biology (advance online publication)
doi: https://doi.org/10.1016/j.ydbio.2024.07.013
https://www.sciencedirect.com/science/article/abs/pii/S0012160624001933
Highlights
Resilience of the replacing dentition in adult reptiles
Developmental Biology (advance online publication)
doi: https://doi.org/10.1016/j.ydbio.2024.07.013
https://www.sciencedirect.com/science/article/abs/pii/S0012160624001933
Highlights
A review of the common origins of teeth and other ectodermal specializations
Introduction to adult reptile teeth which undergo life-long organ regeneration
Review of RNA expression profiling of reptilian dentitions and insights into the molecular mechanisms of tooth replacement
A review of pulse-chase experiments to define the locations of tissue-resident, dental epithelial stem cells
The review covers the broad impact of studies on reptilian dentitions to evolution, stem cell biology, organ replacement and dental pathology.
Abstract
The dentition is critical to animal survival and teeth are present in modern vertebrates including teleost fish, sharks, amphibians, mammals and reptiles. The developmental processes that give rise to teeth are not just preserved through evolution but also share high level of similarity with the embryogenesis of other ectodermal organs. In this review we go beyond the embryonic phase of tooth development to life-long tooth replacement. We will address the origins of successional teeth, the location of putative tissue-resident stem cells, how de novo tooth formation continues throughout life and how teeth are shed in a spatially and temporally controlled manner. We review the evidence that the dental epithelium, which is the earliest recognizable dental structure in the reptilian dentition, serves as a putative niche for tissue-resident epithelial stem cells and recent molecular findings from transcriptomics carried out in reptilian dentitions. We discuss how odontoclasts clear the eruption pathway and allow shedding of functional teeth. The reptiles, particularly lizards, are emerging as some of the most accessible animals to study tooth replacement which has relevance to evolution of the dentition and human dental disorders.
====
====
Free pdf:
Pelomedusoid turtles from the Bajo de la Carpa Formation (Santonian, Upper Cretaceous), Río Negro Province, Patagonia, Argentina.
Ameghiniana (advance online publication)
doi: 10.5710/AMGH.12.06.2024.3591
https://www.ameghiniana.org.ar/index.php/ameghiniana/libraryFiles/downloadPublic/111
The fossil record of pleurodiran turtles in the Cretaceous of Patagonia is diverse throughout all basins, with Pelomedusoides being scarce compared to the Chelidae. In this article, new records of pelomedusoids are reported from the Bajo de la Carpa Formation (Santonian) at the La Bonita site, Río Negro Province, Argentina. Two specimens are described and referred to Podocnemidoidea by the combination of the following features: posterior marginals not extending over the costals, a straight xiphiplastron with rounded tips, short and U-shaped anterior lobe, a rhomboidal entoplastron, and a humero-pectoral sulcus that crosses the entoplastron. The observed variability of the pelomedusoid plastron in the specimens recorded in the Neuquén Group shows that these new specimens present a new scute scheme. Evaluating the diversity observed in the Cretaceous pelomedusoids in the Neuquén Group, three stages of their evolution are defined. A first stage in the Cenomanian where the Bothremydidae appear; a second stage in the late Turonian-Coniacian interval where the Bothremydidae and Podocnemidoidea coexist, and a final stage in the Santonian-Campanian where only the Podocnemidoideapersist and increase the diversity and abundance of morphotypes.
===
Free pdf:
Haiyan Tong, Lu Li, Yuzheng Ke, Yanyin Wang, Gongqing Jie and Laiping Yi (2024)
Remarkable Carapace Morphology of Nanhsiungchelys (Testudines: Nanhsiungchelyidae) Revealed by New Material from Ganzhou Basin, Jiangxi Province, China
Geosciences 14(7): 184
doi: https://doi.org/10.3390/geosciences14070184
https://www.mdpi.com/2076-3263/14/7/184
Haiyan Tong, Lu Li, Yuzheng Ke, Yanyin Wang, Gongqing Jie and Laiping Yi (2024)
Remarkable Carapace Morphology of Nanhsiungchelys (Testudines: Nanhsiungchelyidae) Revealed by New Material from Ganzhou Basin, Jiangxi Province, China
Geosciences 14(7): 184
doi: https://doi.org/10.3390/geosciences14070184
https://www.mdpi.com/2076-3263/14/7/184
Two nanhsiungchelyid carapaces from the Upper Cretaceous of Ganzhou Basin, Jiangxi Province, Southern China, are reported and assigned to Nanhsiungchelys sp. The new material reveals an unusual carapace morphology that was either not or poorly preserved in previously known Nanhsiungchelys specimens, including differentiated neurals, alternating costals, significantly modified scutes with vertebrals 4–5 contacting each other at a point, reduced pleurals 2–4 and greatly expanded lateral and posterior marginals. The discovery extends the geographical distribution of Nanhsiungchelys to the Ganzhou Basin.
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