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![Braincase and palatoquadrate of select Asian and North American Mesozoic turtles. A, “Annemys” sp. from Turpan Basin, Mesa Chelonia, (SGP 2009/18, see [28]); B, Xinjiangchelys levensis (PIN 4636-4-2); C, Sinemys gamera (IVPP V9532-11); D, Dracochelys bicuspis (IVPP V4075); E, Hangaiemys hoburensis (PIN 3334-36); F, Basilochelys macrobios (MD8-2); G, Judithemys sukhanovi (TMP 87.2.1); H, Pleurosternon bullockii (UMZC 1041); I, Eubaena cephalica (MRF 571). Abbreviations: bo: basioccipital, bpt: basipterygoid process, bs: basisphenoid, ex: exoccipital, fca: fenestra caroticus, fpccc: foramen posterius canalis carotici cerebralis, fpcci: foramen posterius canalis carotici interni, fpccp: foramen posterius canalis carotici palatinum, ipv: interpterygoid vacuity, pt: pterygoid. Judithemys sukhanovi (G) has a reduced fenestra caroticus (fca, highlighted in green). The fpccp and the fpccc in this species are situated close to one another inside the fenestra caroticus and are therefore not visible in ventral view.](profile/Marton-Rabi/publication/256927156/figure/fig11/AS:214219896168468@1428085411986/Braincase-and-palatoquadrate-of-select-Asian-and-North-American-Mesozoic-turtles-A.png)
Braincase and palatoquadrate of select Asian and North American Mesozoic turtles. A, “Annemys” sp. from Turpan Basin, Mesa Chelonia, (SGP 2009/18, see [28]); B, Xinjiangchelys levensis (PIN 4636-4-2); C, Sinemys gamera (IVPP V9532-11); D, Dracochelys bicuspis (IVPP V4075); E, Hangaiemys hoburensis (PIN 3334-36); F, Basilochelys macrobios (MD8-2); G, Judithemys sukhanovi (TMP 87.2.1); H, Pleurosternon bullockii (UMZC 1041); I, Eubaena cephalica (MRF 571). Abbreviations: bo: basioccipital, bpt: basipterygoid process, bs: basisphenoid, ex: exoccipital, fca: fenestra caroticus, fpccc: foramen posterius canalis carotici cerebralis, fpcci: foramen posterius canalis carotici interni, fpccp: foramen posterius canalis carotici palatinum, ipv: interpterygoid vacuity, pt: pterygoid. Judithemys sukhanovi (G) has a reduced fenestra caroticus (fca, highlighted in green). The fpccp and the fpccc in this species are situated close to one another inside the fenestra caroticus and are therefore not visible in ventral view.
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Most turtles from the Middle and Late Jurassic of Asia are referred to the newly defined clade Xinjiangchelyidae, a group of mostly shell-based, generalized, small to mid-sized aquatic froms that are widely considered to represent the stem lineage of Cryptodira. Xinjiangchelyids provide us with great insights into the plesiomorphic anatomy of crown...
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Context 1
... similar structure was noticed by [18] in Glyptops plicatulus Cope 1877 [97] and he concluded that it is not homologous with the unambiguous basipterygoid process of basal turtles based on topological considerations, a con- cept subsequently confirmed by Sterli et al. [20]. More re- cently, Brinkman et al. [15] identified a paired process of the basisphenoid similar to that seen in Pleurosternon bullockii ( Figure 11H) in a broad selection of Jurassic and Early Cretaceous Asian eucryptodires and interpreted it as being homologous with the basipterygoid process of the earliest turtles, thereby contradicting the homology assess- ment of Gaffney [18] and Sterli et al. [20]. ...Context 2
... as already noted by others [15], when the condition seen in Pr. quenstedti ( Figure 10A; unknown for Gaffney [18]) is compared to that of captorhinomorphs, it is evident that the dorsum sellae is in a derived position similar to that seen in G. plicatulus and Pl. bullockii ( Figure 11H) in that it extends more an- teriorly over the foramen anterius canalis carotici cerebralis ( [19], figures 42-44). This anterior movement of the dor- sum sellae likely resulted in the anterior migration of the foramen nervi abducentis and the foramen posterius caroticus cerebralis (the latter being erroneously named the foramen posterius canalis carotici interni in previous stud- ies [17,18] for G. plicatulus, Pl. bullockii, and Captorhinus sp., as recently demonstrated [20,67]). ...Context 3
... this taxon demon- strates that there was a phase in the evolution of the basicranium when the basipterygoid articulation was already sutured and was in the same level as the rest of the palate. The morphology of the basipterygoid in H. romani is close to that of xinjiangchelyids and "sinemydids/ macrobaenids" (Figures 11A-E). A flat, triangular process projects laterally and slightly ventrally in these taxa to fit into the corresponding pit of the pterygoid in the same plane. ...Context 4
... flat, triangular process projects laterally and slightly ventrally in these taxa to fit into the corresponding pit of the pterygoid in the same plane. There is no basis for interpreting this process as a neomorphic structure and given the identical topological position and the highly comparable shape the lateral basisphenoid process in basal paracryptodires ( Figure 11H), xinjiangchelyids and "sinemydids/macrobaenids" can be confidently interpreted as being homologous with the basipterygoid process of basal turtles and basal amniotes. ...Context 5
... the basipterygoid process is generally interpreted to be a primitive character absent in derived turtles, many published descriptions of Mesozoic turtle skulls fail to report and illustrate the basipterygoid process. This is espe- cially true for various Jurassic and Early Cretaceous Asian forms (i.e., xinjiangchelyids, sinemydids, and macrobaenids, Figure 11A-E). In addition to the taxa listed in a previous study [15] we further identified a laterally facing basipterygoid process in Kallokibotion bajazidi ( Figure 10F), Dracochelys bicuspis ( Figure 11F), Manchurochelys manchoukuoensis, Sinemys brevispinus (as also reported elsewhere [55]), Ordosemys leios, Xinjiangchelys levensis ( Figure 11B), and Xinjiangchelys latiens, the alleged stem- adocusian Basilochelys macrobios ( Figure 11F) and the basal eucryptodire Hoyasemys jimenezi ( Figure 12A). ...Context 6
... is espe- cially true for various Jurassic and Early Cretaceous Asian forms (i.e., xinjiangchelyids, sinemydids, and macrobaenids, Figure 11A-E). In addition to the taxa listed in a previous study [15] we further identified a laterally facing basipterygoid process in Kallokibotion bajazidi ( Figure 10F), Dracochelys bicuspis ( Figure 11F), Manchurochelys manchoukuoensis, Sinemys brevispinus (as also reported elsewhere [55]), Ordosemys leios, Xinjiangchelys levensis ( Figure 11B), and Xinjiangchelys latiens, the alleged stem- adocusian Basilochelys macrobios ( Figure 11F) and the basal eucryptodire Hoyasemys jimenezi ( Figure 12A). In Sandownia harrisi the basipterygoid process is reduced and only visible in the floor of an opening formed by the pterygoids (i.e., the fenestra caroticus, Figure 12B). ...Context 7
... is espe- cially true for various Jurassic and Early Cretaceous Asian forms (i.e., xinjiangchelyids, sinemydids, and macrobaenids, Figure 11A-E). In addition to the taxa listed in a previous study [15] we further identified a laterally facing basipterygoid process in Kallokibotion bajazidi ( Figure 10F), Dracochelys bicuspis ( Figure 11F), Manchurochelys manchoukuoensis, Sinemys brevispinus (as also reported elsewhere [55]), Ordosemys leios, Xinjiangchelys levensis ( Figure 11B), and Xinjiangchelys latiens, the alleged stem- adocusian Basilochelys macrobios ( Figure 11F) and the basal eucryptodire Hoyasemys jimenezi ( Figure 12A). In Sandownia harrisi the basipterygoid process is reduced and only visible in the floor of an opening formed by the pterygoids (i.e., the fenestra caroticus, Figure 12B). ...Context 8
... is espe- cially true for various Jurassic and Early Cretaceous Asian forms (i.e., xinjiangchelyids, sinemydids, and macrobaenids, Figure 11A-E). In addition to the taxa listed in a previous study [15] we further identified a laterally facing basipterygoid process in Kallokibotion bajazidi ( Figure 10F), Dracochelys bicuspis ( Figure 11F), Manchurochelys manchoukuoensis, Sinemys brevispinus (as also reported elsewhere [55]), Ordosemys leios, Xinjiangchelys levensis ( Figure 11B), and Xinjiangchelys latiens, the alleged stem- adocusian Basilochelys macrobios ( Figure 11F) and the basal eucryptodire Hoyasemys jimenezi ( Figure 12A). In Sandownia harrisi the basipterygoid process is reduced and only visible in the floor of an opening formed by the pterygoids (i.e., the fenestra caroticus, Figure 12B). ...Context 9
... Sandownia harrisi the basipterygoid process is reduced and only visible in the floor of an opening formed by the pterygoids (i.e., the fenestra caroticus, Figure 12B). A similar morphology may be present in the macrobaenids Judithemys sukhanovi ( Figure 11C) and Macrobaena mongolica and in the adocid Adocus lineolatus ( Figure 12C) but the corresponding opening is so tight that the basipterygoid process (if any) is not visible. Consequently, we suggest scoring these taxa, including S. harrisi, as lacking the basipterygoid process, since the ventral surface of the basicranium lacks this structure. ...Context 10
... Early and Middle Jurassic turtles Kayentachelys aprix ( Figure 10B) and Condorchelys antiqua together with Cretaceous Mongolochelys efremovi, Kallokibotion bajazidi and Chubutemys copelloi (Figures 10D-F,G) represent a more advanced phase in that the process is more reduced and compressed, but the basisphenoid is still situated dorsal to the pterygoid. The next phase is exemplified by Heckerochelys romani ( Figure 10C), and various members of Xinjiangchelyidae, Sinemydidae, and Macrobaenidae ( Figures 11A-E) where the process is compressed and mainly laterally oriented and the basisphenoid is aligned with the pterygoid. ...Context 11
... to our phylogenetic hypothesis, the complete reduction and reorientation of the basipterygoid process happened independently in a number of turtle clades. The basipterygoid process was lost once within paracryptodires since basal members, such as Glyptops plicatulus and Pleurosternon bullockii ( Figure 11H), still retain a process, whereas it is absent in Compsemys victa and all baenids ( Figure 11I) [106][107][108][109]. The basipterygoid process is further- more lost in derived members of Meiolaniformes (i.e., Niolamia argentina, Peligrochelys walshae and Meiolania platyceps, Figure 10G). ...Context 12
... to our phylogenetic hypothesis, the complete reduction and reorientation of the basipterygoid process happened independently in a number of turtle clades. The basipterygoid process was lost once within paracryptodires since basal members, such as Glyptops plicatulus and Pleurosternon bullockii ( Figure 11H), still retain a process, whereas it is absent in Compsemys victa and all baenids ( Figure 11I) [106][107][108][109]. The basipterygoid process is further- more lost in derived members of Meiolaniformes (i.e., Niolamia argentina, Peligrochelys walshae and Meiolania platyceps, Figure 10G). ...Context 13
... but no matter how we score this character it does not influence the position of these three taxa. Based on detailed photographs we are confident that B. macrobios possesses a sutured basipterygoid process ( Figure 11F; contrary what has been previously reported [61]) and this is clearly the reason for its relatively basal position in our analysis. Y. tatsuensis is recovered as part of Testudines in the Adocusia clade which is consistent with earlier hypotheses [1,16]. ...Similar publications
The newly discovered plattenkalk (platy limestone) locality of Wattendorf, southern Germany, has yielded a diverse fauna and flora dated to the base of the late Kimmeridgian, Late Jurassic. We here describe three fossil turtle specimens that were recovered during systematic excavations of a distinct, 15 cm thick package of plattenkalks by the Natur...
A complete description of the xinjiangchelyid turtles Annemys levensis and A. latiens is provided, based on all available material from the Upper Jurassic type locality of Shar Teg, Mongolia. Annemys latiens was previously known almost exclusively from shell material, but an undescribed skull from Shar Teg is referable to this species and its disti...
Background
Turtles (Testudinata) are a successful lineage of vertebrates with about 350 extant species that inhabit all major oceans and landmasses with tropical to temperate climates. The rich fossil record of turtles documents the adaptation of various sub-lineages to a broad range of habitat preferences, but a synthetic biogeographic model is st...
Proterochersis robusta from the Late Triassic (Middle Norian) of Germany is the oldest known fossil turtle (i.e. amniote with a fully formed turtle shell), but little is known about its anatomy. A newly prepared, historic specimen provides novel insights into the morphology of the girdles and vertebral column of this taxon and the opportunity to re...
Citations
... Below, we argue that the trigeminal foramen sensu stricto was likely confluent with an opening for the mandibular artery, which is closely associated with the canalis cavernosus. This canal of turtles is a result of their basicranial evolution: Testudines have modified their cranioquadrate space during their early basicranial evolution (e.g., Gaffney 1990;Sterli and Joyce 2007;Anquetin et al. 2009;Sterli and de la Fuente 2010;Rabi et al. 2013;Ferreira et al. 2020), thereby trapping the lateral head vein in a canal called the canalis cavernosus (Gaffney 1979), which extends from the anterior aspect of the cavum acustico-jugulare between the pterygoid, quadrate and prootic into the secondary braincase of turtles, where the lateral head vein continues medial to the secondary braincase wall that is generally formed by the pterygoid and parietal (Gaffney 1979;Rollot et al. 2021a). BSPG 1991 II 130 has a morphology of the "cavernous" area that differs strongly from this generalized testudine bauplan. ...
Allaeochelys libyca is a carettochelyid turtle from the Middle Miocene of Libya. The species is the only valid carettochelyid taxon recovered from Africa and was named based on fragmentary material that includes a partial cranium and isolated shell remains. The description of the holotype cranium was limited to external aspects, and micro-computed tomography was only performed later on that material. Here, we use these micro-computed tomography scans to reinvestigate the external and internal anatomy of the holotype cranium to document several erroneous anatomical interpretations and provide new insights into the morphology of the trigeminal foramen area, the endosseous labyrinth, and circulatory system of Allaeochelys libyca. The anatomical insights provided herein have the potential to be translated into new phylogenetic characters that are expected to improve the resolution among the Anosteira and Allaeochelys lineages, which are still poorly resolved.
... Stem turtles such as Proganochelys quenstedtii and Meiolania platyceps had roofed skulls, Jurassic forms such as Annemys levensis developed temporal emarginations, and roofed skulls were independently reacquired multiple times thereafter in descendent lineages (Figs. 1 and 5 and fig. S13) (18,20,37,38,39). Our data suggest that the widespread expression of upstream osteogenic genes in the embryonic temporal mesenchyme is likely conserved across testudinatans and crucial for the evolutionary reacquisition of an anapsid skull in this group. ...
Amniote skulls display diverse architectural patterns including remarkable variations in the number of temporal arches surrounding the upper and lower temporal fenestrae. However, the cellular and molecular basis underlying this diversification remains elusive. Turtles are a useful model to understand skull diversity due to the presence of secondarily closed temporal fenestrae and different extents of temporal emarginations (marginal reduction of dermal bones). Here, we analyzed embryos of three turtle species with varying degrees of temporal emargination and identified shared widespread coexpression of upstream osteogenic genes Msx2 and Runx2 and species-specific expression of more downstream osteogenic genes Sp7 and Sparc in the head. Further analysis of representative amniote embryos revealed differential expression patterns of osteogenic genes in the temporal region, suggesting that the spatiotemporal regulation of Msx2 , Runx2 , and Sp7 distinguishes the temporal skull morphology among amniotes. Moreover, the presence of Msx2- and/or Runx2 -positive temporal mesenchyme with osteogenic potential may have contributed to their extremely diverse cranial morphology in reptiles.
... The metacarpal and phalangeal are somewhat mixed, making it difficult to estimate the width of the right manus. Rabi et al. (2013) reported on Annemys sp. with two forelimbs and one hindlimb (PMOL-SGP A0100-1-2), which are from the Upper Jurassic Qigu Formation in Turpan Basin, Xinjiang. PMOL-SGP A0100-1 preserved the complete right manus, about 2.8 cm in width, with five digits. ...
... The distal end of the left pes digit V was absent, and the phalanges II-IV were deformed during preservation. Rabi et al. (2013) assigned these specimens to X. wusu, while Averianov et al. (2016) assigned them to A. wusu . Sun et al. (2001) reported on Xinjiangchelys from the Middle Jurassic Yanliao biota, which preserved a partial carapace and a broken left manus (dorsal view). ...
... They are mainly found in the Middle Jurassic (bashuchelyids, sichuanchelyids, xinjiangchelyids) and the Upper Jurassic (xinjiangchelyids), providing a wealth of evidence for the study of the distribution, evolution, and diversity of the xinjiangchelyids in the Jurassic of Asia (Tong et al. 2012a(Tong et al. , 2012b(Tong et al. , 2014Hu et al. 2020). Xinjiangchelyidae is a family of the basal eucryptodiran turtles that are widely distributed across Central and East Asia (mainly Mongolia and China) and Southeast Asia (Ye 1986;Peng and Brinkman 1993;Nessov 1995;Sukhanov 2000;Tong et al. 2012aTong et al. , 2012bRabi et al. 2013Rabi et al. , 2014Tong et al. 2015;Tong 2017;Tong et al. 2019;Hu et al. 2020;Obraztsova et al. 2022). The earliest fossil records of Xinjiangchelyidae came from the late Early to early Middle Jurassic of Asia (Hu et al. 2020). ...
... The seventh and the eighth neurals of QJPNR 1001 are not directly connected; there is a short suture on the eighth neural anteriorly, which allows for a brief and medial contact of the seventh pair of costals. This feature is not present in any other studied specimen of C. latimarginalis but is visible in Xinjiangchelys junggarensis , X. wusu (Rabi et al. 2013), and X. oshanensis (Tong et al. 2015). The eighth neural is short in CMNH C.1007 ( Figure 7D) and CMNH unnumbered ( Figure 7F), but it elongates in CMNH C.1323 ( Figure 7A), CMNH C.1530 ( Figure 7B), CMNH C.1537 ( Figure 7C), CDUT 13088 ( Figure 7E), IVPP V6746 ( Figure 7G), and QJPNR 1001 ( Figure 7I). ...
A new Chengyuchelys latimarginalis (Xinjiangchelyidae) specimen is reported based on a well-preserved, nearly complete shell from the upper part of the Upper Jurassic Shangshaximiao Formation of Qijiang District, Chongqing Municipality, China. The Xinjiangchelyidae were widely distributed in Asia during the Jurassic and were the dominant turtle group in Asian freshwater ecosystems during the Late Jurassic. The Qijiang specimen adds a new element to the yet poorly known freshwater vertebrate fauna and extends the geographical distribution of C. latimarginalis. This paper discusses the intraspecific variation in C. latimarginalis for the first time. It provides a new insight for studying the evolution, habitat, and diversity of xinjiangchelyids.
... The cerebral branch of the internal carotid artery enters the basicranium through the basisphenoid in Proganochelys quenstedtii (Gaffney, 1990;Müller et al., 2011), and the turtle cerebral blood circulation only becomes internalized in later evolutionary stages (Rabi et al., 2013;Rollot et al., 2021;Sterli et al., 2010). Besides the two expected foramina posterius canalis carotici basisphenoidalis (following the nomenclature of Rollot et al., 2021) for the right and left arteries, SMF 09-F2 has a third, centrally placed foramen (Fig. 4F), which we interpret as abnormal individual variation of the specimen. ...
Proganochelys quenstedtii represents the best-known stem turtle from the Late Triassic, with gross anatomical and internal descriptions of the shell, postcranial bones and skull based on several well-preserved specimens from Central European fossil locations. We here report on the first specimen of P. quenstedtii from the Late Triassic (Klettgau Formation) Frickberg near the town of Frick, Canton Aargau, Switzerland. Similar to other Late Triassic 'Plateosaurus-bearing bonebeds', Proganochelys is considered to be a rare faunal element in the Swiss locality of Frick as well. The specimen, which is largely complete but was found only partially articulated and mixed with large Plateosaurus bones, overall resembles the morphology of the classical specimens from Germany. Despite being disarticulated, most skull bones could be identified and micro-computed tomography (CT) scanning of the posterior skull region reveals new insights into the braincase and neurovascular anatomy, as well as the inner ear region. These include the presence of a fenestra perilymphatica, potentially elongated cochlear ducts, and intense vascularization of small tubercles on the posterior end of the skull roof, which we interpret as horn cores. Other aspects of the skull in the braincase region, such as the presence or absence of a supratemporal remain ambiguous due to the fusion of individual bones and thus lack of visible sutures (externally and internally). Based on the size of the shell and fusion of individual elements, the specimen is interpreted as a skeletally mature animal.
Supplementary information:
The online version contains supplementary material available at 10.1186/s13358-022-00260-4.
... to the canalis caroticus cerebralis ofRabi et al., 2013; Figure 10b). The anterior foramen of the abducens nerve is located lateral to the mid-length of the pituitary fossa (Figure 9b). ...
Galianemys is one of the three genera of Cearachelyini (Pleurodira, Bothremydidae) so far defined, being the only one identified in Africa (in the Cenomanian of Morocco). It is represented by two species, Galianemys whitei and Galianemys emringeri, both being identified by several skulls. The other two representatives of Cearachelyini are both South‐American forms, and only the species Cearachelys placidoi (from the Albian of Brazil) preserves cranial remains, including a partial skull corresponding to its holotype. However, despite the relatively great number of skulls identified for both Galianemys spp. and Cearachelys placidoi, information about the neuroanatomy of this lineage is very limited. The three‐dimensional (3D) reconstruction of the skulls of two specimens belonging to the genus Galianemys, each of them representing a different species, is performed here for the first time. All of the cranial bones of one of them are also virtually reconstructed to accurately characterize them. In addition, the 3D models of the main neuroanatomical structures (i.e., cranial, nasal, and labyrinthic cavities, and nervous and carotid canals) of both specimens were generated, most of them being described in detail for first time in Cearachelyini. Neuroanatomical differences are recognized when the skulls of both species of Galianemys analyzed here are compared. In addition, the comparison between the neuroanatomy of Galianemys spp. and that of other non‐Cearachelyini bothremydids allow us to identify some differences between those lineages, but also recognize other shared characters for the entire lineage of Bothremydidae, to providing a more precise characterization within Pleurodira.
... Due to their modified postcranial skeleton (notably the presence of a shell), turtles primarily use the skull for interactions with their environment, including food acquisition, for which neck mobility is a key feature (Pritchard 1984;Herrel et al. 2008;Anquetin et al. 2017a). The evolution of individual anatomical aspects of the turtle skull is well-understood (e.g., fusion of intracranial joints: Rabi et al. 2013). However, the skull ecomorphology is poorly constrained, and functional aspects such as neck retraction have not been included in previous attempts at its understanding (e.g., Claude et al. 2004;Foth et al. 2017). ...
Turtles have a highly modified body plan, including a rigid shell that constrains postcranial anatomy. Skull morphology and neck mobility may therefore be key to ecological specialization in turtles. However, the ecological signal of turtle skull morphologies has not been rigorously evaluated, leaving uncertainties about the roles of ecological adaptation and convergence. We evaluate turtle cranial ecomorphology using three-dimensional geometric morphometrics and phylogenetic comparative methods. Skull shape correlates with allometry, neck retraction capability, and different aquatic feeding ecologies. We find that ecological variables influence skull shape only, whereas a key functional variable (the capacity for neck retraction) influences both shape and size. Ecology and functional predictions from three-dimensional shape are validated by high success rates for extant species, outperforming previous two-dimensional approaches. We use this to infer ecological and functional traits of extinct species. Neck retraction evolved among crownward stem-turtles by the Late Jurassic, signaling functional decoupling of the skull and neck from the shell, possibly linked to a major episode of ecomorphological diversification. We also find strong evidence for convergent ecological adaptations among marine groups. This includes parallel loss of neck retraction, evidence for active hunting, possible grazing, and suction feeding in extinct marine groups. Our large-scale assessment of dietary and functional adaptation throughout turtle evolution reveals the timing and origin of their distinct ecomorphologies, and highlights the potential for ecology and function to have distinct effects on skull form.
... The expanded and restricted concepts of these two groups have been followed by different authors, but no consensus has been reached concerning the family name nor their content, as well as the monophyly of this large group of turtles (see [37] for a thorough review). For some authors, Sinemydidae sensu lato is a monophyletic group [38], while other authors consider this group as a polyphyletic assemblage [39,40]. In order to stabilize the nomenclature, some authors have suggested to use a more restricted concept, the clade containing Macrobaena and excluding Sinemys forming the Macrobaenidae [7,41], while the clade containing Sinemys and excluding Macrobaena forms the Sinemydidae [37,41]. ...
... Moreover, the entoplastron of SM KS39 is oval in shape and elongate anteroposteriorly in dorsal view, but in the ventral view, its outer surface is reduced to an irregular triangle with strong interfingering sutures with the hyoplastra. This is reminiscent of the condition in the macrobaenid Ordosemys liaoxiensis [27], whereas the entoplastron in xinjiangchelyids has a more regular oval ventral exposure [2,7,40,74]. ...
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.
... Our anatomical nomenclature follows that of Gaffney (1972b) with modifications in regard to the terminology of the carotid and facial nerve system as recently summarized by Rollot et al. (2021). Following the rationale outlined by Rollot et al. (2021), however, we introduce two additional terms, which are modifications of previous terms introduced by Rabi et al. (2013b). ...
... Foramen posterius canalis carotici basisphenoidalisthe posterior foramen to the canalis caroticus basisphenoidalis (foramen posterius canalis carotici cerebralis of Rabi et al., 2013b), which serves as an entry for the cerebral artery into the skull. The foramen posterius canalis carotici basisphenoidalis is typically located in the lateral margin of the parabasisphenoid and concealed when the carotid split is not exposed. ...
... Foramen posterius canalis carotici lateralis-the posterior foramen to the canalis caroticus lateralis (foramen posterius canalis caroticus palatinum of Rabi et al., 2013b), which serves as an entry for the palatine artery into the skull. The foramen posterius canalis carotici lateralis is located along the pterygoid-parabasisphenoid suture lateral to the foramen posterius canalis carotici basisphenoidalis, and typically exposed on the ventral side of the skull when the branching off of the internal carotid artery into its primary branches is not ventrally covered by bone. ...
We study the Late Jurassic (Tithonian) turtle Uluops uluops using micro-computed tomography scans to investigate the cranial anatomy of paracryptodires, and provide new insights into the evolution of the internal carotid artery and facial nerve systems, as well as the phylogenetic relationships of this group. We demonstrate the presence of a canalis caroticus lateralis in Uluops uluops, the only pleurosternid for which a palatine artery canal can be confidently identified. Our phylogenetic analysis retrieves Uluops uluops as the earliest branching pleurosternid, Helochelydridae within Pleurosternidae, and Compsemydidae including Kallokibotion bajazidi within Baenidae, which suggests at least two independent losses of the palatine artery within paracryptodires. We expect future studies will provide additional insights into the evolution of the circulation system of paracryptodires, as well as clarifying relationships along the turtle stem.
Supplementary information:
The online version contains supplementary material available at 10.1186/s13358-021-00234-y.
... In the past two decades, five more turtle taxa have been described from the Jehol Biota of western Liaoning and adjacent Inner Mongolia, including Ordosemys liaoxiensis Ji, 1995 (see also Tong et al. 2004); Liaochelys jianchangensis Zhou 2010a; Perochelys lamadongensis Li et al. 2015; Xiaochelys ningchengensis Zhou and Rabi 2015; and Jeholochelys lingyuanensis Shao et al. 2018. Except for the pan-trionychid turtle P. lamadongensis, the other five species are usually referred to Sinemydidae or Macrobaenidae (Joyce et al. 2016;Li and Zhou 2017;Shao et al. 2018), which are widely accepted as groups of stem-Cryptodira (e.g., Joyce 2007;Rabi et al. 2010;Zhou 2010aZhou , 2010bZhou and Rabi 2015;Joyce et al. 2016;Shao et al. 2018), although recovered as the stem lineage of crown turtles in some studies (e. g., Rabi et al. 2013). ...
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.
