分类： 生物学 >> 动物学 提交时间： 2023-11-30 合作期刊: 《古脊椎动物学报》
摘要：描述了印度北部比拉斯布尔区喜马偕尔邦Haritalyangar地区中西瓦利克的猪类化石 上、下颌及牙齿材料。Haritalyangar地区以晚中新世动物群、古人类和其他灵长类动物的 多样性而闻名。研究材料为作者之一(ARS)在该地区多次野外季采集的猪类化石；猪类化 石地点和最近报道的长鼻类化石地点(含古猿化石地点)也被绘制在地图上。这些化石地点 广泛分布于Makkan Khad到 Sir Khad区域内的“Lower Alternations”层和“Upper Alternations” 层。猪类化石被鉴定为三个属：Propotamochoerus (P. hysudricus)、Hippopotamodon (H. sivalense) 和Yunnanochoerus (Y. dangari)。 Propotamochoerus hysudricus 为中西瓦利克最 常见的化石猪类，新发现的Yunnanochoerus dangari化石进一步证明这种古猪类化石仅在 Haritalyangar地区有少量遗存。Haritalyangar地区新发现的猪类化石组成与巴基斯坦的Nagri 动物群相近。基于猪类化石进行的的Potwar高原年代地层学对比表明，Haritalyangar地区的 “Lower Alternations”层的年龄范围为~10–9 Ma, 与最新的磁极性地层学年代范围很接近。
分类： 生物学 >> 动物学 提交时间： 2023-10-13 合作期刊: 《古脊椎动物学报》
摘要：Renewed fieldwork in 2003 produced a rich micromammal assemblage from the basal part of the Jiaozigou Formation in the Yagou area of Linxia Basin. 17 genera distributed among 13 families of three orders were recovered. The micromammal fauna is a typical Oligocene assemblage for Central and Eastern Asia. 14 genera (~82% of the fauna) are common in the Oligocene of Asia. Of them four genera and four species of Eucricetodon are restricted to the Oligocene, one genus (Bagacricetodon) is restricted to Late Oligocene and Glis and Eomyodon made their first appearances in the Late Oligocene. Based on this micromammal composition, the basal part of the Jiaozigou Formation in the Yagou area could be mainly of Late Oligocene in age, which is in accordance with the conclusion based on large mammal fossils. In comparison with the other Late Oligocene micromammal faunas in Central and East Asia, the Yagou Fauna is slightly older than the Ulan III biozone of Nei Mongol and biozone C of Mongolia, because it has two Eocene genera and lacks more advanced genera. This is roughly in accordance with the recent palaeomagnetic interpretation for the Maogou section, where the lower boundary of the Jiaozigou Formation was correlated with Chron C10r (~29 Ma). The presence of large number of xerophilous zapodines, ctenodactylids, cricetids and lagomorphs combined with fossorial Tsaganomys and the lithology of the fossil-bearing deposits, composed of gypsiferous reddish brown mudstone, tend to show a semiarid woodland-shrubland habitat during the Late Oligocene in Yagou area. In Late Oligocene more frequent faunal interchange might have occurred between Asia and Europe (4 genera commonly shared) rather than between Asia and America (only 1 genus shared), partly because of the disappearance of the Turgai Strait.
分类： 生物学 >> 动物学 提交时间： 2023-09-20 合作期刊: 《古脊椎动物学报》
摘要：间型三棱齿象(Trilophodon connexus Hopwood, 1935)长期以来被认为是中国嵌齿象属 (Gomphotherium)的一个代表种。然而，由于其下颌联合部与下门齿的形态未知，这一归入 存疑。重新研究了来自新疆准噶尔盆地北缘乌伦古河地区哈拉玛盖组的一件此前归为陕西嵌齿象相似种(Gomphotherium cf. G. shensiensis)的下颌。该下颌联合部伸长，呈深槽状， 下门齿缺失，因此确定可归入豕棱齿象科(Choerolophodontidae)。进一步将间型三棱齿象 的正型标本与其相比较，两者颊齿的关键特征完全一致，包括：高度丘型化，m3伸长， 具有四脊，上下颊齿第二脊“人字型”(chevron)很弱，第二脊中附锥与前中心小尖不愈合， 釉质褶皱、齿谷中小锥及白垩质发育弱或缺失。因此，间型三棱齿象事实上是一种豕棱齿 象类而非嵌齿象。综上所述，暂将其改定为间型“豕棱齿象” (“Choerolophodon” connexus (Hopwood, 1935))。同时，以上特征与北美的索普颌门齿象(Gnathabelodon thorpei)比较接 近。此外，在颌门齿象属和间型“豕棱齿象”中，颊齿第二脊呈“人字型”, 釉质褶皱、齿谷中 小锥及白垩质发育强这些典型的豕棱齿象属(Choerolophodon)的特征较弱甚至缺失，但m3 齿脊数变多，这表明颌门齿象属可能起源于东亚的间型“豕棱齿象”。
分类： 生物学 >> 动物学 提交时间： 2023-08-11
摘要：对目前已知3,000余种蛇类的研究可为它们的基因组进化提供有价值的见解。尖吻蝮，也被称为尖鼻蝮、百步蛇或五步蛇，是一种具有重要经济、医学和科学价值的毒蛇。其广泛分布于中国东南部和东南亚，主要用于蛇毒研究。本文采用二代测序技术，组装和注释了一个高度连续的尖吻蝮基因组。基因组大小为1.46 Gb; 其scaffold N50长度为6.21 Mb，重复序列含量为42.81%，共注释出24,402个功能基因。本研究有助于在遗传水平上进一步认识和利用尖吻蝮及其毒液。
分类： 生物学 >> 动物学 提交时间： 2023-07-12 合作期刊: 《古脊椎动物学报》
摘要：The previously alleged ‘eugnathid amiiform’ Sinoeugnathus kueichowensis is a small-sized halecomorph from the Middle Triassic (Ladinian) marine deposits of Guizhou and Yunnan, China. A morphological redescription and taxonomic revision of this taxon are provided based on a detailed examination of 15 new specimens. Among them, IVPP V24315 (standard length = 64 mm) is appointed as the neotype, given that the holotype is missing. Studies of these specimens revealed some morphological details previously undescribed or misidentified for this taxon, including a hatchet-shaped antorbital, two broad suborbitals, a sensory canal in the maxilla, and three pairs of extrascapulars. For the first time, Sinoeugnathus was incorporated into an analysis of halecomorph phylogeny, and the results recover it as the sister taxon of the Anisian Subortichthys from Luoping, Yunnan, and both are grouped with two Ladinian genera Allolepidotus and Eoeugnathus from the Monte San Giorgio area into a monophyletic group (namely Subortichthyidae fam. nov. herein) at the base of Ionoscopiformes. This taxonomic reassessment of Subortichthys provides new insights into the phylogeny and paleogeographic evolution of Ionoscopiformes.
分类： 生物学 >> 动物学 提交时间： 2023-07-12 合作期刊: 《古脊椎动物学报》
摘要：The Shuitangba subbasin lignite deposits of the Zhaotong Basin in northern Yunnan Province have produced vertebrate fossils of terminal Miocene age. We conducted test wet screening of fossiliferous sediment in 2014 to increase representation of small mammals. This effort produced four teeth of a very large bamboo rat, much larger than the previously known bamboo rat present at Shuitangba, and representing a new species. This new species is characterized by its molars being remarkably larger than those of other known species of Miorhizomys, and being hypsodont with cementum, and less anterorposteriorly compressed. The age of this new species from Shuitangba is in the range of 6.2 to 6.7 Ma. It appears that diverse bamboo rats of the extinct genus Miorhizomys were present in the Late Miocene of Yunnan, somewhat before the 6 Ma appearance of extant Rhizomys to the north in the vicinity of Shanxi Province.
分类： 生物学 >> 动物学 提交时间： 2023-05-25 合作期刊: 《古脊椎动物学报》
摘要：描述了缅甸中部邦塘组Myaukse Kyitchaung地点原始反刍类古鼷鹿科小包康鼷鹿 (Paukkaungmeryx minutus Ducrocq et al., 2020)的牙齿新材料。新材料的上臼齿与正型标本 相比形态上仅有微小的变异，如更加发育的颊侧和舌侧齿带。下颊齿具有原始的特征， 包括：简单的p4, 下臼齿呈丘月齿型，以及下三角座后壁无“褶”状结构。新材料的发现使 Paukkaungmeryx成为邦塘发现的第二个同时保存上、下牙齿的古鼷鹿科成员，也展现了古 鼷鹿科早期演化的复杂历史。
分类： 生物学 >> 动物学 提交时间： 2023-03-14 合作期刊: 《古脊椎动物学报》
摘要：The zygodont proboscideans from the Miocene strata of China are widely distributed. However, the materials are scarce, and their classification has experienced a longtime controversy, from the chaotic state of multiple Zygolophodon species to the only one species, Zygolophodon gobiensis. The combined species Z. gobiensis comprises both the gracile type with a high degree of zygodonty and the robust type that is between the typical bunodont and zygodont morphology. Recently, as the robust type has been re-allocated to another genus Miomastodon and new fossil remains were discovered, it is necessary to further evaluate and classify the zygodont proboscideans from the Miocene of China. In the present paper, we restudied the previously published zygodont specimens of the gracile type, as well as several unpublished Mammutidae specimens. The former including Z. nemonguensis, Z. gromovae, Z. jiningensis, Z. chinjiensis and two specimens of Gomphotherium xiaolongtanensis, represents Zygolophodon in the original sense in China. In these specimens, the tip of the loph(ids) are sharp. The anterior and posterior pretrite central conules are absent or very weak, and the anterior and posterior crescentoids are sharp and slender. The posttrite mesoconelets are well subdivided and the zygodont crests are developed. In buccal view, the loph(id)s are “Ʌ-shaped” and the interloph(id) s are “V-shaped”. Their molar morphology resembles that of Z. turicensis, and hereby, they were identified as Zygolophodon cf. Z. turicensis. Several unpublished specimens from Hezheng, Gansu, Tunggur, Nei Mongol, Tongxin, Ningxia and Junggar, Xinjiang exhibit a lower degree of zygodonty, corresponding to the “robust type of Zygolophodon” in which the molar morphology is between the typical bunodonts and zygodonts. The pretrite crescentoids are thicker than Zygolophodon cf. Z. turicensis, and the pretrite central conules usually present on the first and second interloph(id)s. According to the stratigraphic age and characteristics, two species, Miomastodon gobiensis and Mio. tongxinensis were identified. The anterior and posterior pretrite crescentoids of Mio. tongxinensis are weaker and the pretrite central conules are larger than Mio.gobiensis. Geographical distribution indicates that Miomastodon is the predominant member of zygolophodonts in the Early and Middle Miocene in northern China. The discovery of new materials and the reclassification of zygolophodonts provide further evidence for dispersal of Mammutidae from Eurasia to North America and the evolutionary relationships among the species of the family Mammutidae in China.
分类： 生物学 >> 动物学 提交时间： 2023-03-14 合作期刊: 《古脊椎动物学报》
摘要：Chondrocytes with remnants of nuclei and biomolecules were recently reported in two Cretaceous dinosaurs from North America and China. For multiple reasons, it was hypothesized that calcified cartilage (CC) had a better potential than bone to preserve ancient cells. Here we provide the first experimental test to this hypothesis by focusing on the most important variable responsible for cellular preservation: the postmortem blockage of autolysis. We compare the timing of autolysis between chondrocytes and osteocytes in an avian model (Anas platyrhynchos domesticus) buried for up to 60 days under natural conditions that did not inhibit autolytic enzymes. Within 15 days post-burial, almost all osteocytes were already cytolyzed but chondrocytes in CC were virtually unaffected. All osteocytes were cytolyzed after 30 days, but some chondrocytes were still present 60 days post-burial. Therefore, even in harsh conditions some CC chondrocytes still survive for months postmortem on a time scale compatible with permineralization. This is consistent with other data from the forensic literature showing the extreme resistance of hyaline cartilage (HC) chondrocytes after death and does support the hypothesis that CC has a better potential than bone for cellular preservation, especially in fossils that were not permineralized rapidly. However, because the samples used were previously frozen, it is possible that the pattern of autolysis observed here is also a product of cell death due to ice crystal formation and not strictly autolysis, meaning a follow-up experiment on fresh (non-frozen samples) is necessary to be extremely accurate in our conclusions. Nevertheless, this study does show that CC chondrocytes are very resistant to freezing, suggesting that chondrocytes are likely better preserved than osteocytes in permafrost fossils and mummies that underwent a freezingthawing cycle. It also suggests that cartilage (both hyaline and calcified) may be a better substrate for ancient DNA than bone. Moreover, even though we warrant follow-up taphonomy experiments with non-frozen samples paired with DNA sequencing, we already urge ancient DNA experts to test CC as a new substrate for ancient DNA analyses in fossils preserved in hot and temperate environments as well.
分类： 生物学 >> 动物学 提交时间： 2023-02-17 合作期刊: 《古脊椎动物学报》
摘要：The Enantiornithes is the most speciose clade of Mesozoic avialans with over 60 named taxa reported from most continents that span the whole Cretaceous. Most of the fossil remains of this clade, as well as those of other early diverging avialans are preserved in twodimensions. This complicates to extract detailed anatomical information from the skull, in which the composite elements are delicate and thus not easily observable through conventional methods. The scarcity of well-preserved early avialan skulls, as well as the limited number of specimens that have been analyzed using computed tomography scanning, consequently circumscribes a large morphological gap in the fossil record during the transition from the heavy and akinetic dinosaurian skull to the lightweight and kinetic bird skull. Here, we present a threedimensional digital reconstruction of the skull and part of the cervical vertebrae of a new specimen of the enantiornithine Parabohaiornis martini from the Early Cretaceous of China. Our results demonstrate that Parabohaiornis retains the plesiomorphic non-avialan dinosaurian temporal and palatal reinforcing the recent hypothesis that the temporal and palatal regions are evolutionarily conservative and that the akinetic skull has been conserved well into of early branching avialans.
分类： 生物学 >> 动物学 提交时间： 2022-11-25 合作期刊: 《古脊椎动物学报》
摘要：New middle Eocene rodent fossils discovered from the lower part of the Shara Murun Formation of Ula Usu, Erlian Basin, Nei Mongol, China, the classical locality of Sharamurunian mammalian fauna, were identified as 9 separate species (the ctenodactyloids Yuomys cavioides, Gobiomys neimongolensis, G. exiguus, and G. asiaticus, the dipodids Allosminthus uniconjugatus and Primisminthus shanghenus, the cricetid Pappocricetodon rencunensis, the ischyromyid Hulgana cf. H. ertnia, and the cylindrodontid Proardynomys ulausuensis) belonging to 7 genera, 4 families, and 1 superfamily of Rodentia. The Ula Usu rodent assemblage shares a high degree of similarity with that from the “Lower Red” beds of the Erden Obo, and they both represent the typical Sharamurunian rodent assemblages found in northern China. The Sharamurunian rodent fauna in the Erlian Basin is analyzed by the minimum number of individuals based on the rodent materials from the lower part of the Shara Murun Formation in the Ula Usu and the “Lower Red” beds of the Erden Obo. In the Sharamurunian rodent fauna of the Erlian Basin, ctenodactyloids are the most dominant elements, and dipodids and cricetids follow next in prevalence. By analyzing the evolution of the rodent species richness in the Erlian Basin, the rodent faunas show a transformation from a ctenodactyloid dominant assemblage to a cricetid-dipodid dominant one in chronological order. The Sharamurunian rodent fauna from the Erlian Basin differs from that of the Yuanqu Basin and the differences in the rodent assemblages may be a response to the differences between the regional environments.
分类： 生物学 >> 动物学 提交时间： 2022-11-25 合作期刊: 《古脊椎动物学报》
摘要：The pelvic morphology, and whether the pelvic fin is present or absent in the earliest jawed vertebrates are key in interpreting the origin of vertebrate paired fins. Parayunnanolepis xitunensis, an antiarch placoderm from the Early Devonian of Yunnan, South China, was previously described to possess the earliest evidence of both dermal and endoskeletal pelvic girdles, presumably for the attachment of the pelvic fins. Here, we redescribe the pelvic region of the holotype based on high-resolution computed tomographic data. Instead of having two large plates previously designated as dermal pelvic girdles, Parayunnanolepis possesses three pairs of lateral pelvic plates, and one large oval median pelvic plate. The paired pelvic plates are flat ventral plates, and differ from other dermal pelvic girdles in lacking a dorsal extension. There is no definitive evidence for the presence of an endoskeletal pelvic girdle in Parayunnanolepis, although the possibility cannot be ruled out. A comparison of the dermal pelvic plates in various jawed stem-gnathostomes suggests the presence of both paired and median pelvic plates is shared by different lineages and might be plesiomorphic. The jawed stem-gnathostomes may have recruited the ventral dermal skeleton of the post-thoracic body into different functional units.
分类： 生物学 >> 动物学 提交时间： 2022-10-16 合作期刊: 《古脊椎动物学报》
摘要：The saurichthyiform fishes, characterized by a pointed rostrum and a streamlined long and slender body plan, ranked among the top predators of the ichthyofauna in the Early Mesozoic oceanic ecosystem. In a cosmopolitan pattern, these fishes rapidly radiated after the end-Permian mass extinction (EPME) and diversified morphologically and ecologically during the Middle Triassic. Thereafter, they seemingly showed a notable shrinkage from a global distribution to an occurrence basically restricted to the western Paleo-Tethys realm since the Late Triassic. Specifically, there is no saurichthyiform fossil record so far from the marine Late Triassic of South China (eastern Paleo-Tethys), where contrastingly they were highly diversified in stratigraphically older Lagerstätten (Middle Triassic Panxian-Luoping and Xingyi biotas). Here we report the discovery of Saurichthys taotie sp. nov. from the Guanling biota of Guizhou and Yunnan provinces, southwestern China. This new species is a medium-sized Saurichthys featured by subtriangular subopercles ornamented with densely arranged vertical striae, faint ornamentation on the posterior part of the skull roof, and strong longitudinal ridges decorating the anterodorsal surface of the rostrum. By marking its own group’s first occurrence in the Late Triassic of eastern Paleo-Tethyan province, Saurichthys taotie suggests that the saurichthyiform fishes were actually much more widespread than previously thought during that geological stage when they showed a considerable decline in the diversity. By still possessing some features previously only seen in its Early Triassic congeners elsewhere, Saurichthys taotie sheds new light on the evolutionary and paleobiogeographical history of saurichthyiform fishes.
分类： 生物学 >> 动物学 提交时间： 2022-09-29 合作期刊: 《古脊椎动物学报》
摘要：Abundant mammalian fossils were uncovered during the field exploration for Nihewan beds at the beginning of the 1980s along Xinyaozi Ravine at Nangaoya Township of Tianzhen County, Shanxi Province in North China. But most equid material was not yet described except that of Equus stenonis. Six forms of Nihewanian equids were confirmed from the Xinyaozi specimens in the present study, five of which were described for the first time. They include four stenonids such as Equus sanmeniensis, E. teilhardi, E. huanghoensis and E. stenonis, and two hipparionines such as Hipparion (Proboscidipparion) sinense and H. (Plesiohiparrion) shanxiense. The diversification of stenonids in the Early Pleistocene was significant in North China with four taxa in Xinyaozi alone. The persistence of Neogene relics such as hipparionines was still present in the Early Pleistocene with two hipparionine taxa in Xinyaozi. Equus sanmeniensis and H. (Proboscidipparion) sinense were two representative equids not only coexisted in the Early Pleistocene but also widely distributed in China. The diversity of equids also implies the diversified vegetation on which they depended. The hypsodont dentitions and well developed cement, as well as completely molarized premolars of Xinyaozi equids indicate their abrasive diet mostly on monocotyledonous and grassland habitats with considerable scales enough to nourish six taxa of equids.
分类： 生物学 >> 动物学 提交时间： 2022-08-02 合作期刊: 《古脊椎动物学报》
摘要：齐陶(1990)命名了采自内蒙古二连盆地额尔登敖包中始新统地层的蹄齿犀新属种——威氏乌兰兽Ulania wilsoni, 但该属名已经被一种寒武纪的三叶虫Ulania Lin & Zhang, 1979所占用；因此我们提出以乌兰齿犀属Ulanodon gen. nov.取代Ulania Qi, 1990。“Ulan” (乌兰)在蒙古语中意为“红色”, 希腊语“-odon”是蹄齿犀科中常用的词根，意为“牙齿”。感谢John Ponting先生告知Ulania的异物同名以及王元青研究员对新属名Ulanodon的建议
分类： 生物学 >> 动物学 提交时间： 2022-08-02 合作期刊: 《古脊椎动物学报》
摘要：云南西部丽江盆地中始新世丽江组中的哺乳动物群以奇蹄类占据优势，之前已经报道了13个种，丽江动物群的时代被认为从伊尔丁曼哈期延续到沙拉木伦期。重新研究了丽江盆地的部分奇蹄类化石，认为Rhodopagus yunnanensis是Lijiangia zhangi 16 Vertebrata PalAsiatica的次同物异名，而后者具有和Lophiohippus相似的特征，所以将Lijiangia置于古兽科(Palaeotheriidae)的Anchilophini, 而不是最初有疑问地归入的蹄齿犀科(Hyracodontidae)。Lunania也代表了一类和Paranchilophus相似的古兽而不是爪兽；如果Lophiohippus的正型标本代表了Lunania的上臼齿，那么Lophiohippus是Lunania的次同物异名。通过对戴氏貘科(Deperetellidae) Diplolophodon的厘定，认为该属包括了3个种：D. similis, D. lunanensis 和D.xiangshanensis (新组合), 其中丽江盆地的Teleolophus xiangshanensis应归入到Diplolophodon xiangshanensis。丽江盆地的奇蹄类化石组合和垣曲盆地河堤组任村段的奇蹄类化石相似性最高，且丽江动物群的时代应限于中始新世沙拉木伦期
分类： 生物学 >> 动物学 提交时间： 2022-08-02 合作期刊: 《古脊椎动物学报》
摘要：报道了哈密南湖戈壁首次发现的恐龙蛋，包括长形长形蛋(Elongatoolithus elongatus)和椭圆形蛋未定种(Ovaloolithus oosp.)。这些恐龙蛋的发现不仅扩展了长形蛋类和椭圆形蛋类的古地理分布，而且表明南湖戈壁含蛋岩层地质时代为晚白垩世末期；该地层是否可与吐鲁番盆地的苏巴什组进行对比还有待进一步工作确认
分类： 生物学 >> 动物学 提交时间： 2022-06-08 合作期刊: 《干旱区地理》
摘要：红外相机技术目前已成为监测陆栖哺乳动物和地栖鸟类的常用技术手段。为监测新疆天池博格达峰自然保护区内鸟类和兽类资源，于2019年7月—2020年9月，在保护区内选取30个红外相机位点共布设58台红外相机，累积工作29730个工作日，共获得99850份图像及视频数据，采集独立有效照片5744张；共观测到野生陆生脊椎动物9目19科29种，其中兽类5目10科15种，鸟类4目9科14种。观测到的动物中有国家I级重点保护野生动物雪豹（Panthera uncia），国家II级重点保护野生动物6种，分别为北山羊（Capra sibirica）、马鹿（Cervus canadensis）、猞猁（Lynx lynx）、赤狐（Vulpes vulpes）、黑鸢（Milvus migrans）以及暗腹雪鸡（Tetraogallus himalayensis）。森林生境中，兽类相对多度指数最高的是马鹿（RAI=60.569），鸟类相对多度指数最高的是山斑鸠（Streptopelia ori⁃entalis，RAI=0.854）；高山草甸及裸岩生境中，兽类相对多度指数最高的是马鹿（RAI=18.693），鸟类相对多度指数最高的是暗腹雪鸡（RAI=0.316）和黄嘴山鸦（Pyrrhocorax graculus，RAI=0.854）。物种累积曲线结果显示：兽类物种数在200 d之后几乎不再增长，而鸟类物种数在100 d之后增速放缓但一直持续增长，表明时长450 d的红外相机监测力度对保护区中的兽类而言较为充分，对鸟类而言还不够充分。研究结果可为新疆天池博格达峰自然保护区野生陆生脊椎动物多样性监测与评估提供数据参考，为该保护区的保护管理工作提供科学依据。
分类： 生物学 >> 动物学 提交时间： 2022-06-07 合作期刊: 《古脊椎动物学报》
摘要：Nothosaurus luopingensis n. sp. from Member II of the Guanling Formation (Anisian, Middle Triassic) of Luoping, Yunnan, China is described based on a specimen comprising the skull and most of the postcranial skeleton. The specimen is assigned to Nothosaurus of Eosauropterygia as suggested by a series of skull characters, such as the maxillary tooth row extending posteriorly beyond the level of the anterior margin of the upper temporal fenestra, the longitudinal diameter of the upper temporal fenestra is more than twice as long as that of the orbit, and the presence of maxillary fangs. Compared with Lariosaurus, the following morphological features of the pectoral girdle and the limbs also support the assignment of the specimen to Nothosaurus, i.e., the clavicles with expanded anterolateral corners, the characteristically curved humerus with a straight preaxial angle and a postaxial concavity, the distinct deltopectoral crest on the proximal part of the humerus, no hyperphalangy in the manus, and the absence of pachyostosis in the vertebrae and ribs. On the other hand, the specimen possesses some postcranial features that were previously considered to occur mainly in Lariosaurus, such as there being more than three ossifications in the carpus, having four sacral ribs, and an interclavicle without any trace of a posterior stem. These postcranial characters may no longer be used as the diagnostic features of Lariosaurus. N. luopingensis is distinguished from other Nothosaurus species by a unique combination of derived characters, including that the jugal enters the orbit, the nasals are separated, the posterior end of the frontal is bifurcate, pedal digits V and IV are long and subequal in length, and the ungula phalanx is stout. Our phylogenetic analysis reconfirms the monophyly of Nothosaurus and suggest that N. luopingensis is the sister group of N. yangjuanensis within the genus.
分类： 生物学 >> 动物学 提交时间： 2022-06-07 合作期刊: 《古脊椎动物学报》
摘要：Shaanbeikannemeyeria is a common tetrapod from the lower part of the Ermaying Formation of the Ordos Basin, China. There are taxonomical questions surrounding this genus, such as the validity of the genus, and how many species are included within it. Several specimens have been collected since 1978. Shaanbeikannemeyeria first appeared from the top of the Heshanggou Formation. These specimens are described to clarify the diagnostic characters, the individual variations and the phylogenetic position of Shaanbeikannemeyeria. Only one species, S. xilougouensis, is recognized. It is characterized by the following autapomorphies: occiput strongly inclined relative to the palate such that the skull is much shorter basally than dorsally, sword tip-like premaxillary posterodorsal processes, tall and dorsally-convex cutting blade on the medial edge of the dorsal surface of the dentary, reflected lamina with a separated posteroventral process, and 15 dorsal vertebrae. This species shows variations on the cranial morphology, such as the occiput height relative to the width, the snout tip (sharp or obtuse), the shape of the orbital portion of the zygomatic arch, and the shape of caniniform process. Some variations could be ontogenetically related, such as the development of the caniniform process and tusk, the posterior extension of the maxilla on the zygomatic arch, the distance between the frontal and the premaxilla, the intertemporal bar width, and the exposing degree of the parietals. Based on postcranial bones, the second dicynodont genus (possibly Parakannemeyeria) is present in the lower Ermaying Formation.
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