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Temporal distribution of Sinemys lens, Ordosemys spp., Shantungosuchus, Euhelopus and Psittacosaurus based on radiometrically dated fossil-bearing deposits. The 145-136 Ma zircon age of the Mengyin Formation is after Xu & Li (2015). The sanidine ages of the basalt and tuff layers of the Yixian Formation of the Jehol Biota yielded 130.6-122.9 Ma (Chang et al., 2009; Chang et al., 2017). Euhelopus spp. the temporal distribution of Psittacosaurus is so far restricted to an age interval between 130.6 Ma (at the bottom of Yixian Formation, (Chang et al., 2009; Chang et al., 2017) and 105 Ma (at the top of Qingshan Group (Ar age of Zhang et al., 2008; Young, 1958; Lucas, 2006). The younger record of Euhelopus is after Barrett & Wang (2007). Full-size DOI: 10.7717/peerj.6229/fig-7
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Chronostratigraphic correlation of terrestrial Early Cretaceous biotas in China is highly problematic due to the lack of marine deposits, few absolute dates, and limited number of index fossils. This often leaves vertebrate faunas as one of the few potential tools for a preliminary biostratigraphy. Taxonomic identity of fragmentary fossils is, howe...
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... to originate from the overlying Jingchuan Formation;Ji & Chen, 2018). Euhelopus-like sauropod teeth ( Hou et al., 2017) and the crocodyliform Shantungosuchus from the Luohandong Formation ( Wu, Brinkman & Lu, 1994) further suggest a faunal composition that is otherwise only known from the Mengyin Formation (Borinder, Poropat & Kear, 2016; Fig. 7). On the other hand, Hou et al. (2017) erroneously cited Young (1958 that Psittacosaurus is also common to both formations with P. sinensis reported from the Mengyin Formation; in fact, this information is not present in Young' paper (1958) (Fig. 7). No absolute dates have been published from the the Luohandong Formation and previous ...
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... composition that is otherwise only known from the Mengyin Formation (Borinder, Poropat & Kear, 2016; Fig. 7). On the other hand, Hou et al. (2017) erroneously cited Young (1958 that Psittacosaurus is also common to both formations with P. sinensis reported from the Mengyin Formation; in fact, this information is not present in Young' paper (1958) (Fig. 7). No absolute dates have been published from the the Luohandong Formation and previous biostratigraphic studies disagree: it has been considered Valanginian-early Hauterivian (Chen et al., 2006), Barremian (Averianov & Skutschas, 2000), or Aptian ( Wan et al., 2013;Li, 2017) in age. The Mengyin Formation has been recently dated to 145- ...
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... DOI: 10.7717/peerj.6229/ fig-7 faunal similarities are most consistent with a Valanginian-early Hauterivian age for the Luohandong Formation (as proposed by Chen et al., 2006, p. 28 based on dinoflagellate, floral, and bivalve correlation). On the other hand, a Valanginian-early Hauterivian age is inconsistent with the presence of the ceratopsid dinosaur, Psittacosaurus, in the Luohandong Formation (e.g., Brinkman & Peng, 1993a;Lucas, 2006;Tong & Brinkman, 2013;Hou et al., 2017) as this taxon is used for defining a biochron between two radiometrically dated horizons: the Yixian / Jiufotang formations (130.6-120 ...
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... 2006;Tong & Brinkman, 2013;Hou et al., 2017) as this taxon is used for defining a biochron between two radiometrically dated horizons: the Yixian / Jiufotang formations (130.6-120 Ma;He et al., 2004;Chang et al., 2009) and the Qingshan Group (120-105 Ma;Zhang et al., 2008;Lucas, 2006). This interval corresponds to the late Hauterivian-Albian (Fig. 7). Three possible scenarios can explain this controversy: (1) either the Mengyin Formation is younger than what the radiometric age result of Xu & Li (2015) suggests; or the fossil record of the Ordosemys-Sinemys community (2) or Psittacosaurus (3) is biased. Since the Mengyin Formation yielded the only radiometrically dated vertebrate ...
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... to originate from the overlying Jingchuan Formation;Ji & Chen, 2018). Euhelopus-like sauropod teeth ( Hou et al., 2017) and the crocodyliform Shantungosuchus from the Luohandong Formation ( Wu, Brinkman & Lu, 1994) further suggest a faunal composition that is otherwise only known from the Mengyin Formation (Borinder, Poropat & Kear, 2016; Fig. 7). On the other hand, Hou et al. (2017) erroneously cited Young (1958 that Psittacosaurus is also common to both formations with P. sinensis reported from the Mengyin Formation; in fact, this information is not present in Young' paper (1958) (Fig. 7). No absolute dates have been published from the the Luohandong Formation and previous ...
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... composition that is otherwise only known from the Mengyin Formation (Borinder, Poropat & Kear, 2016; Fig. 7). On the other hand, Hou et al. (2017) erroneously cited Young (1958 that Psittacosaurus is also common to both formations with P. sinensis reported from the Mengyin Formation; in fact, this information is not present in Young' paper (1958) (Fig. 7). No absolute dates have been published from the the Luohandong Formation and previous biostratigraphic studies disagree: it has been considered Valanginian-early Hauterivian (Chen et al., 2006), Barremian (Averianov & Skutschas, 2000), or Aptian ( Wan et al., 2013;Li, 2017) in age. The Mengyin Formation has been recently dated to 145- ...
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... DOI: 10.7717/peerj.6229/ fig-7 faunal similarities are most consistent with a Valanginian-early Hauterivian age for the Luohandong Formation (as proposed by Chen et al., 2006, p. 28 based on dinoflagellate, floral, and bivalve correlation). On the other hand, a Valanginian-early Hauterivian age is inconsistent with the presence of the ceratopsid dinosaur, Psittacosaurus, in the Luohandong Formation (e.g., Brinkman & Peng, 1993a;Lucas, 2006;Tong & Brinkman, 2013;Hou et al., 2017) as this taxon is used for defining a biochron between two radiometrically dated horizons: the Yixian / Jiufotang formations (130.6-120 ...
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... 2006;Tong & Brinkman, 2013;Hou et al., 2017) as this taxon is used for defining a biochron between two radiometrically dated horizons: the Yixian / Jiufotang formations (130.6-120 Ma;He et al., 2004;Chang et al., 2009) and the Qingshan Group (120-105 Ma;Zhang et al., 2008;Lucas, 2006). This interval corresponds to the late Hauterivian-Albian (Fig. 7). Three possible scenarios can explain this controversy: (1) either the Mengyin Formation is younger than what the radiometric age result of Xu & Li (2015) suggests; or the fossil record of the Ordosemys-Sinemys community (2) or Psittacosaurus (3) is biased. Since the Mengyin Formation yielded the only radiometrically dated vertebrate ...
Citations
... The absence of a preserved second suprapygal is justified by the non-ossified or slightly ossified union of this plate with the first suprapygal in the juvenile state, as happened with the peripheral plates in relation to the costals. In fact, embryological and ontogenetic studies have provided evidence that the suprapygal, pygal and peripheral plates are the last plates to ossify (Gilbert et al., 2001;Lima et al., 2011;Vieira et al., 2016). Consequently, the contact of these plates with other regions of the carapace showed great weakness in the immature stages, being easily disarticulated, to which its position in a peripheral region also contributes. ...
Several British specimens of relatively complete and partial shells of small pleurosternid turtles, found in the Purbeck Limestone Group (Berriasian, Lower Cretaceous), are analysed in detail here. Despite having been found more than a century ago, most of them remained unpublished until now. Due to the scarce knowledge available to date about the small individuals of Pleurosternidae from the British record, their taxonomic status was doubtful. Thus, some authors proposed their attribution to a new but not defined taxon of small size, whereas others suggested that they could represent juvenile individuals of Pleurosternon bullockii, the adults of which were also found in the Purbeck Limestone Group but at different levels. Knowledge about the shell of the adult individuals of Pleurosternon bullockii has notably increased recently, abundant information on its intraspecific variability being currently available. In this context, a detailed study of the small specimens through qualitative and quantitative approaches is performed here. The results are evidence a significant range of shape variability because of ontogenetic development, as well as other types of intraspecific variation such as inter-individual variation. As a consequence, their attribution to juvenile individuals of Pleurosternon bullockii is justified, providing new data on the ontogenetic development of a basal form.
... The eighth neural, nearly square, is the smallest one and shorter than the preceding neurals, as also in PMOL-AR00007 and PMOL-AR00008. A preneural is absent in M. manchoukuoensis, in contrast to Ordosemys spp., which have a preneural (e.g., Brinkman and Peng 1993b;Tong et al. 2004;Li et al. 2019). A shallow and wide depression is extending longitudinally above the neural series. ...
... Ordosemys leios (material published in Brinkman and Peng 1993a;Li et al. 2019), Ordosemys sp. (IVPP V12092, Brinkman and Wu Brinkman and Wu 1999), Ordosemys brinkmania (IVPP V4074, Danilov and Parham Danilov and Parham 2007), Sinemys gamera (IVPP V9532, Brinkman and Peng Brinkman and Peng 1993b), Sinemys brevispinus (IVPP 9538-1, Tong and Brinkman 2013), Sinemys cf. ...
... (IVPP V12092, Brinkman and Wu Brinkman and Wu 1999), Ordosemys brinkmania (IVPP V4074, Danilov and Parham Danilov and Parham 2007), Sinemys gamera (IVPP V9532, Brinkman and Peng Brinkman and Peng 1993b), Sinemys brevispinus (IVPP 9538-1, Tong and Brinkman 2013), Sinemys cf. brevispinus (IVPP V1034, Ye Ye 1963;Tong and Brinkman 2013), Sinemys lens (materials published in Brinkman and Peng 1993b), Ordosemys liaoxiensis (materials published in Tong et al. 2004 andZhou et al. 2019), Jeholochelys lingyuanensis (PMOL-AR00190, AR00211, AR00213, AR00214, AR00217, AR00222, and AR00218, Shao et al. Shao et al. 2018), Xiaochelys ningchengensis (PMOL-AR00210AB, Zhou and Rabi Zhou and Rabi 2015), Judithemys sukhanovi (material published in Parham and Hutchison 2003), and Kirgizemys hoburensis (material published in Sukhanov 2000). ...
Manchurochelys manchoukuoensis is a sinemydid stem-cryptodire turtle known by fossils from the Lower Cretaceous beds exposed in western Liaoning and Inner Mongolia of China. This fossil taxon is important for understanding the origin and evolution of Cryptodira (crown-group hidden-neck turtles). The holotype of M. manchoukuoensis was presumably lost during the Second World War and several aspects of the osteology of the species remains unknown. We here describe a near-complete fossil skeleton coming from the Lower Cretaceous Yixian Formation, western Liaoning, China, 50 km away from the type locality in the same formation. PKUP V1071 represents the most completely preserved specimen of the species and includes a well-preserved plastron, which was otherwise only known partially in the lost holotype. We provide a detailed osteological description of M. manchoukuoensis including data from micro-CT and X-ray computed laminography scanning of PKUP V1071. Of particular significance is the anchor-shaped entoplastron transversely extending to completely separate the small and triangular epiplastra from the hyoplastra; this peculiar morphology is otherwise only present in Sinemys spp. among turtles. Additional novel insights into plastron and cranial anatomy further support a close relationship between Sinemys and Manchurochelys.
... The new specimen (IVPG-T002) was collected from Ningjiagou village, near Xintai City, Shandong Province (Fig. 1A). The skull was extracted from a large block of sandstone containing two different turtle fossils that have been identified as Ordosemys leios and Sinemys lens (see Li et al. 2019). Technical preparation of the specimen exposed the mandibles and part of the palate. ...
... Type locality and horizon North of Ningjiagou village, Xintai, Shandong Province of China; Lower Cretaceous Mengyin Formation (Li et al., 2019; Fig. 1), Berriasian-Valanginian in age (Xu and Li, 2015). ...
Choristoderes were an important clade of semi-aquatic predators that occupied Laurasian freshwater ecosystems from the Middle Jurassic to the Miocene. During the Early Cretaceous, the neochoristodere lineage evolved large size and long snouts, converging on the body plan of modern crocodilians. Here, we describe a new longirostrine choristodere, Mengshanosaurus minimus gen. et sp. nov. from the Lower Cretaceous Mengyin Formation of Shandong Province, China. The holotype is the smallest reported neochoristodere individual, with a skull length of only 35 mm. The poorly ossified braincase, along with retention of a fontanel at the frontal-parietal suture, indicates this individual was a juvenile. Phylogenetic analyses recovered Mengshanosaurus as a neochoristodere, a placement supported by the presence of a single narial opening, fusion of the nasals, and expansion of the temporal fenestrae. In the Neochoristodera, Mengshanosaurus is sister to a clade consisting of Ikechosaurus, Tchoiria, Simoedosaurus, and Champsosaurus. It differs from other neochoristoderes in having the lacrimal foramen between the prefrontal and lacrimal, in addition to having large vomerine teeth (exceeding one-third the width of corresponding maxillary teeth). The closely arranged marginal teeth and large vomerine teeth suggest juvenile choristoderes may have fed on invertebrates and insects, similar to juveniles of modern crocodilians. However, the observation that very young neochoristoderes had similar skull proportions and marginal tooth shapes to adults, along with features suggesting a more fully aquatic ecology, suggest that neochoristoderes exhibited less pronounced ontogenetic niche shifts than modern crocodilians.
... Shao et al., , 2018Li et al., 2019). However, these fossil turtles have been less commonly collected outside the typical western Liaoning area of the Jehol Biota (e.g., Ma, 1986;Li et al., 2015;Li and Tong, 2017;Wu et al., 2018). Recently, as the first record of the Mesozoic turtles from Jilin Province, the sinemydid Ordosemys has been reported from the Early Cretaceous Hengtongshan Formation of Xingling Town, Meihekou City (Wu et al., 2018). ...
... The specimens are similar to Ordosemys spp. and differ from other sinemydids in having a subcircular shell, wide vertebral scales, and large central and lateral fenestrae of plastron (e.g., Brinkman et al., 2008;Li and Tong, 2017;Li et al., 2019). The presence of a preneural plate is also diagnostic for Ordosemys spp. ...
... Three species are widely accepted in the genus Ordosemys: O. leios, O. liaoxiensis, and O. brinkmania (Danilov and Parham, 2007;Brinkman et al., 2008;Li and Tong, 2017;Li et al., 2019). Two further species, O. perforata (i.e., Asiachelys perforata sensu Sukhanov and Narmandakh, 2006;Danilov and Parham, 2007) and O. donghai (i.e., Machurochelys donghai sensu Ma, 1986;Brinkman et al., 2008;Li and Tong, 2017), have been questioned in their affinities to Ordosemys in lacking the preneural plate and wide vertebral scales (e.g., Li et al., 2019). ...
Recently, a vertebrate assemblage of the Jehol Biota has been reported from the Early Cretaceous Hengtongshan Formation of Xingling Town, Meihekou City, Jilin Province, China. It is dominated by the fishes Lycoptera and Sinamia and the sinemydid turtle Ordosemys. Here, we describe the turtle specimens and referral to Ordosemys liaoxiensis, otherwise known from the older Yixian Formation of the Jehol Biota. It is characterized by a subcircular shell, wide vertebral scales, well-developed plastral fenestrae, and a major contribution from the xiphiplastra to enclose the hypo-xiphiplastral fenestra. As the first Mesozoic turtle of Jilin Province, this record represents the first tetrapod to indicate the presence of the Jehol Biota in the region. Given the geographic and temporal distance from the Yixian Formation, future collections from the Hengtongshan Formation have good potential for evaluating spatiotemporal patterns of the Jehol Biota.
The cranium of turtles (Testudines) is characterized by the secondary reduction of temporal fenestrae and loss of cranial joints (i.e., characteristics of anapsid, akinetic skulls). Evolution and ontogeny of the turtle cranium are associated with shape changes. Cranial shape variation among Testudines can partially be explained by dietary and functional adaptations (neck retraction), but it is unclear if cranial topology shows similar ecomorphological signal, or if it is decoupled from shape evolution. We assess the topological arrangement of cranial bones (i.e., number, relative positioning, connections), using anatomical network analysis. Non‐shelled stem turtles have similar cranial arrangements to archosauromorph outgroups. Shelled turtles (Testudinata) evolve a unique cranial organization that is associated with bone losses (e.g., supratemporal, lacrimal, ectopterygoid) and an increase in complexity (i.e., densely and highly interconnected skulls with low path lengths between bones), resulting from the closure of skull openings and establishment of unusual connections such as a parietal–pterygoid contact in the secondary braincase. Topological changes evolutionarily predate many shape changes. Topological variation and taxonomic morphospace discrimination among crown turtles are low, indicating that cranial topology may be constrained. Observed variation results from repeated losses of nonintegral bones (i.e., premaxilla, nasal, epipterygoid, quadratojugal), and changes in temporal emarginations and palate construction. We observe only minor ontogenetic changes. Topology is not influenced by diet and habitat, contrasting cranial shape. Our results indicate that turtles have a unique cranial topology among reptiles that is conserved after its initial establishment, and shows that cranial topology and shape have different evolutionary histories.
Mesozoic continental basins of northern China, including the Junggar Basin, provide some of the most spectacular and important fossil assemblages in the world, but their climatic and environmental contexts have been shrouded in uncertainty. Here we examine the main factors that determine those contexts: palaeolatitude; the effects of changing atmospheric gases on the radiative balance; and orbitally paced variations in insolation. Empirical evidence on these factors is accumulating rapidly and promises to upend many long standing paradigms. We focus primarily on the Junggar Basin in Xinjiang northwest China with the renowned Shishugou Biota and the basins in Liaoning, Hebei, and Inner Mongolia with their famous Jehol and Yanliao Biotas. Accurate geochronology is necessary for disentangling these various factors and we review the Late Triassic to Early Cretaceous U-Pb ages for these areas and supply one new LA-ICP-MS age for the otherwise un-dated Sangonghe Formation of Early Jurassic age. We review climatic-sensitive facies patterns in North China and show that the climatic context changed synchronously in northwestern and northeastern China consistent with a previously proposed huge Late Jurassic-earliest Cretaceous True Polar Wander (TPW) event with all the major plates of East Asia docked with Siberia and moving together since at least the Triassic, when the north China Basins were at Arctic latitudes. We conclude that this TPW shift is was responsible for the coals and ice rafted debris being produced at high latitudes and the red beds and eolian strata being deposited at low latitudes, within the same basin. The climatic and taphonomic context in which the famous Shishugou, Yanlaio and Jehol biotas preserved was thus a function of TPW as opposed to local tectonics or climate change.
Supplementary material at https://doi.org/10.6084/m9.figshare.c.6738045
Yakemys multiporcata n. g. n. sp. is described on the basis of shell elements from the upper part of the Phu Kradung Formation (basal Cretaceous), Khorat Plateau, NE Thailand and assigned to Macrobaenidae. The new taxon is unusually large for an early macrobaenid (with an estimated carapace length about 70 cm) and is characterized by a large, rounded, low shell, the presence of a midline keel and numerous additional strong ridges on the carapace, the anterolateral margin upturned to form a gutter, posterolateral peripherals mesiolaterally expanded, narrow vertebrals, the vertebral 4 triangular and narrowed posteriorly, a greatly reduced plastron with a short bridge, an oval and elongate entoplastron with reduced ventral exposure, and strip-shaped epiplastra. The discovery of a macrobaenid turtle provides further support for an Early Cretaceous age for the upper part of the Phu Kradung Formation.
Arundelemys dardeni is an Early Cretaceous paracryptodire known from a single, incomplete, but generally well-preserved skull. Phylogenetic hypotheses of paracryptodires often find Arundelemys dardeni as an early branching baenid. As such, it has a central role in understanding the early evolution of the successful clade Baenidae, which survived the Cretaceous–Paleogene mass extinction, as well as the diversification of Paracryptodira into its subclades, which recent research suggests to perhaps include helochelydrids, compsemydids, pleurosternids, and baenids. Computer tomography scans of the holotype material that were produced for the initial description of Arundelemeys dardeni reveal several errors in the initial anatomical description of the species, which we correct based on element-by-element segmentation. In addition, we provide entirely novel anatomical information, including descriptions of several previously undescribed cranial bones, the endosseous labyrinth, and the cranial scutes, the latter of which are unknown for most paracryptodires. We provide an interpretation of cranial scutes which homologizes the scutes of Arundelemys dardeni with those of other stem turtles.
The European Paleocene terrestrial and freshwater turtle fauna is radically different from that in the Upper Cretaceous. This Paleocene fauna is largely formed by groups of turtles not found in the Mesozoic record of the continent. However, European Paleocene sites have produced several lineages that dispersed from other continents, including basal turtles (i.e., stem Testudines) and compsemydids (i.e., Paracryptodira). Both groups are well represented at the French upper Paleocene site of Mont de Berru, Marne Department. A new taxon from this locality, Gallica lapparentiana, gen. et sp. nov., is described here and attributed to the eucryptodiran lineage ‘Macrobaenidae.’ Heretofore, no ‘macrobaenid’ has yet been identified in the Cenozoic record of Europe. ‘Macrobaenids’ have their origin in the Upper Jurassic of Asia. In fact, they represent the most diverse group of turtles currently known for the Lower Cretaceous record in that continent. They reach North America in the Upper Cretaceous, where they continue to diversify during the Upper Cretaceous and lower Paleocene. The first justified identification of ‘Macrobaenidae’ from the upper Paleocene of Europe, both in France and in Belgium, provides new data on the replacement process of European Late Cretaceous turtle fauna by new groups from other continents.
http://zoobank.org/urn:lsid:zoobank.org:pub:B417CC80-F47C-4AE5-B8B2-0BAA249A177F
