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The second mamenchisaurid dinosaur from the Middle Jurassic of Eastern China
Historical Biology
Abstract
A new mamenchisaurid dinosaur, Anhuilong diboensis gen. et sp. nov. from the Middle Jurassic of Eastern China is reported here. The holotype consists of complete left humerus, ulna and radius of an individual. Comparative study and cladistic analysis shows this new taxon belongs to Mamenchisauridae and bears a unique combination of characters, such as low ratios of the average of the greatest widths of the proximal end, mid-shaft and distal end of the humerus/length of the humerus, total length of ulna to humerus and total length of radius to humerus; the lateral edge of the deltopectoral crest directs caudolaterally, the lateral accessory condyle on the craniodistal edge of humerus is more robust than the medial one, and the cross-sectional shape of the ulna at mid-shaft is elliptical with highest ratio of transverse to craniocaudal diameter among mamenchisaurids. Phylogenetically, Anhuilong is the sister taxon of Huangshanlong, and with Omeisaurus they together form the sister clade to all other members of Mamenchisauridae. Including Huangshanlong, two mamenchisaurids have been found in eastern China, and indicates that Mamenchisauridae was already a diverse sauropod clade in China by the Middle Jurassic.
... Additionally, fossils of the sauropod dinosaurs of genera Huangshanlong anhuiensis and Anhuilong diboensis were excavated in the Hongqin Formation, which underlies the Tunxi Formation (e.g., Huang JD et al., 2014;Ren XX et al., 2018). The dinosaurs of both genera are phylogenetically categorized as mamenchisaurids (Ren XX et al., 2018). ...
... Additionally, fossils of the sauropod dinosaurs of genera Huangshanlong anhuiensis and Anhuilong diboensis were excavated in the Hongqin Formation, which underlies the Tunxi Formation (e.g., Huang JD et al., 2014;Ren XX et al., 2018). The dinosaurs of both genera are phylogenetically categorized as mamenchisaurids (Ren XX et al., 2018). China Yang SY et al., 2021). ...
... JNO-Jiangnan orogen. is well known for its diverse array of eusauropod dinosaur fossil-bearing strata such as the Shaximiao Formation in southwestern China (e.g., Peng GZ et al., 2019;Ren XX et al., 2022. Among these, Mamenchisauridae (Young CC and Chao XJ, 1972) serves as a significant clade for research into the evolution of Asian sauropod dinosaurs (e.g., Young CC, 1939;Ouyang H, 1989;Fang XS et al., 2004;Jiang S et al., 2011;Xing LD et al., 2015;Ren XX et al., 2021), emerging as the most prosperous non-neosauropodan sauropod clade predominating East Asia (e.g., Xing LD et al., 2015;Ren XX et al., 2018;Moore AJ et al., 2023). The fauna of mamenchisaurid dinosaurs, traditionally determined at the Middle-Late Jurassic ages, includes 14 genera (consisting of 28 species) from China, two from Africa, and one from Australia (e.g., Huang JD et al., 2014;Xing LD et al., 2015;Ren XX et al., 2018;Mannion PD et al., 2019;Ren XX et al., 2021;Moore AJ et al., 2023). ...
... This hypothesis is potentially supported by sauropod specimens recovered from the Shishugou Formation. Whereas Tienshanosaurus, Klamelisaurus and Mamenchisaurus sinocanadorum have been consistently recovered as close relatives of species of Mamenchisaurus (Moore et al., 2020;Ren et al., 2020;Sekiya, 2011;Upchurch et al., 2021;Xing et al., 2015), there is near-universal agreement that Bellusaurus represents a neosauropod or close relative thereof (Carballido & Sander, 2014;Mannion et al., 2019a;Mo, 2013;Moore et al., 2020;Royo-Torres & Upchurch, 2012;Royo-Torres et al., 2017;Upchurch et al., 2004;Wilson & Upchurch, 2009). Moreover, the Shishugou Formation has recently been proposed to harbour other possible neosauropods. ...
... Although anatomical information derived from Mamenchisaurus sinocanadorum and other species of Mamenchisaurus was included in the first cladistic analysis of sauropod dinosaurs (Russell & Zheng, 1993), it is only relatively recently that the monophyly of the genus, and the broader interrelationships of the many named species of Mamenchisaurus and other Middle-Late Jurassic East Asian eusauropods, have been critically evaluated (Moore et al., 2020;Ren et al., 2020Ren et al., , 2021Sekiya, 2011;Tan et al., 2021;Upchurch et al., 2021;Xing et al., 2015). Differences in taxonomic sampling, character matrix composition and mode of phylogenetic inference across studies have resulted in widely divergent topological hypotheses (Moore et al., 2020). ...
... species and other East Asian eusauropods (Ren et al., 2020;Sekiya, 2011;Xing et al., 2015), but Moore et al. (2020) However, the taxon remains highly labile within Mamenchisauridae, perhaps reflecting the limited number of characters that can be scored confidently from its original description (Moore et al., 2020;Young, 1954). ...
The sauropod genus Mamenchisaurus, from the Late Jurassic–Early Cretaceous of East Asia, has a convoluted taxonomic history. Although included in the first cladistic analysis of sauropods, only recently has the monophyly of Mamenchisaurus, and the anatomical diversity of the many penecontemporaneous East Asian eusauropods, been evaluated critically. Here, we re-describe the holotype and only specimen of M. sinocanadorum. Although the original diagnosis is no longer adequate, we identify several autapomorphies that support the validity of this species, including an elongate external mandibular fenestra and distinctive pneumatic structures on the cervical centra. We incorporate new data into a phylogenetic character matrix that also includes Bellusaurus and Daanosaurus, both of which are known only from juvenile material and are often hypothesized to be neosauropods (or close relatives thereof). We recover all species of Mamenchisaurus as part of a radiation of predominantly Middle–Late Jurassic East Asian eusauropods, but the genus is non-monophyletic, underscoring the need for further systematic revision of mamenchisaurid taxonomy. Analyses that score ontogenetically variable characters ambiguously recover Bellusaurus and Daanosaurus as juvenile mamenchisaurids, a hypothesis supported by several features that are unique to mamenchisaurids or exhibit little homoplasy, including anteriorly bifurcate cervical ribs. Finally, computed-tomography reveals extensive vertebral pneumaticity in M. sinocanadorum that is comparable to that of the largest sauropods, and updated scaling analyses imply a neck over 14 m long, rivalling estimates for other exceptionally long-necked sauropods. Previous work has suggested that the elongated cervical ribs of particularly long-necked sauropods such as M. sinocanadorum stabilized the neck by limiting its mobility. Given that extent of pneumaticity responds dynamically to a bone’s habitual loading, we propose that long cervical ribs – and other structural modifications that limited flexibility – promoted the evolution of increasingly long necks by producing a more predictable biomechanical milieu amenable to increased pneumatization.
... It terminates at ∼44% of humerus length from the proximal end: by comparison, values among other sauropods range between 35-50% (Upchurch et al., 2015:table 2). In this respect, Rhomaleopakhus is almost identical to several other CMTs: for example, these values are 44% in Anhuilong and Omeisaurus tianfuensis, and 43% in Huangshanlong (Ren et al., 2018). In anterior view, the anterolateral margin of the deltopectoral crest has a sigmoid profile and is relatively narrow throughout its length. ...
... There is a small amount of torsion in the shaft, such that the long-axes of the proximal and distal end surfaces are slightly rotated relative to each other, but Rhomaleopakhus lacks the marked torsion (c. 40°) seen in many diplodocids (Tschopp et al., 2015a) and some CMTs (e.g., at least 30°in Klamelisaurus [Moore et al., 2020] and 25°in Huangshanlong [Huang et al., 2014] and Anhuilong (Ren et al., 2018]). Huang et al. (2014) regarded such humeral torsion as a synapomorphy of Mamenchisauridae, but there is clearly some variation among CMTs and homoplasy within Sauropoda, especially given that a strong degree of torsion of the humeral shaft is the plesiomorphic sauropodomorph condition that is lost in early sauropods (e.g., Yates, 2007;McPhee et al., 2014). ...
... Although the relative size of these anterodistal processes is difficult to quantify, they are very reduced or absent in Chubutisaurus and titanosaurs (D'Emic, 2012), and are particularly large in several CMTs (Remes, 2008), such as Chuanjiesaurus (Sekiya, 2011) and Huangshanlong (Huang et al., 2014). Enlarged (Huang et al., 2014) and/or anteriorly directed (Ren et al., 2018) anterodistal processes have been regarded as a synapomorphy of Mamenchisauridae: however, reduction and loss of these processes appears to be the derived state (D'Emic, 2012), and increased process size requires quantification and more comparative work before it can provide support for mamenchisaurid affinities. In Rhomaleopakhus, the distal articular surface is rugose and does not expand up onto the anterior face of the shaft, unlike the humeri of some titanosaurs (Wilson and Carrano, 1999;Wilson, 2002). ...
Hudiesaurus sinojapanorum is a Late Jurassic sauropod from northwestern China that was erected on the basis of a cervicodorsal vertebra, four teeth, and a nearly complete forelimb. However, re-evaluation of this material, and comparisons with other taxa, indicate that there are few grounds for regarding these specimens as congeneric. Consequently, although we retain the vertebra as the holotype specimen of Hudiesaurus, the forelimb is assigned to a new taxon—Rhomaleopakhus turpanensis, gen. et sp. nov. The teeth previously referred to Hudiesaurus are poorly preserved but resemble those of several other ‘core Mamenchisaurus-like taxa’ (CMTs) from East Asia, such as Mamenchisaurus sinocanadorum. Phylogenetic analyses confirm that Hudiesaurus is a CMT and the sister taxon of Xinjiangtitan. Despite some uniquely shared features, their large size, and close geographic provenance, Hudiesaurus and Xinjiangtitan are retained as distinct genera based on their stratigraphic separation and numerous anatomical differences. Rhomaleopakhus is also shown to be a CMT in all analyses, being most closely related to Chuanjiesaurus and Analong. We link the convergent evolution of robust antebrachia and an enlarged olecranon in CMTs, titanosaurs, and some ornithischians (e.g., ceratopsids) to a more flexed orientation of the forearm, an enhanced role for the forelimb in locomotion, and an anterior shift in the whole-body center of mass. CMTs and titanosaurs potentially converged on a feeding strategy in which the ability to increase browse height via bipedal rearing was sacrificed in return for more efficient locomotion that improved travel between patchily distributed food sources.
... Young 1937Young , 1939Young , 1954Yeh 1975;Dong et al. 1983;Dong & Tang 1984;Dong 1990;Zhao 1993;Martin et al. 1994;Martin-Rolland 1999;Fang et al. 2000;Tang et al. 2001;Ouyang & Ye 2002;You et al. 2003You et al. , 2006You et al. , 2008Peng et al. 2005;Ye et al. 2005;Ksepka & Norell 2006;L€u et al. 2008K. Li et al. 2010;Mo et al. 2010;Sekiya 2011;Wu et al. 2013;Xing et al. 2013Xing et al. , 2015Ren et al. 2018;Zhou et al. 2018). The Middle and Late Jurassic strata of the Sichuan and Junggar basins are particularly rich in sauropod fossils, with no fewer than 14 genera, including eight species of Omeisaurus (Young 1939(Young , 1958He et al. 1988;Tang et al. 2001;Jiang et al. 2011;Tan et al. 2020) and six species of Mamenchisaurus (Young 1954;Young & Zhao 1972;Dong et al. 1983;Russell & Zheng 1993;He et al. 1996;Pi et al. 1996;Y. ...
... Zhang et al. 1998), named from the Shishugou, Shaximiao, Qiketai and Suining formations. Omeisaurus and Mamenchisaurus are often included as outgroups in phylogenetic analyses of neosauropod lineages, but despite an abundance of fossils, the anatomy of these and related taxa from the Middle-Late Jurassic of China remain poorly documented in the literature and very little concerted effort has been made to clarify their taxonomy or evolutionary interrelationships (Sekiya 2011;Xing et al. 2015;Ren et al. 2018). ...
... The ulna is triradiate, with distinct anterolateral and anteromedial processes enclosing a radial fossa positioned opposite the posterior process (Fig. 19A) fig. 36), but unlike in Omeisaurus tianfuensis (ZDM ?T5701), Cetiosaurus (OUMNH J.13612), Anhuilong (Ren et al. 2018) and Bellusaurus (IVPP V17768), the angle between the long axes of the anterolateral and anteromedial processes is < 80. Zhao (1993) described the proximal end of the ulna as autapomorphic in its degree of expansion, but the ratio of the maximum proximal dimension to the proximodistal length of the ulna (~0.36) is comparable to that in various other eusauropods (e.g. Shunosaurus, ~0.36 [Y. ; Chuanjiesaurus, ~0.36 [Sekiya 2011]; Omeisaurus maoianus, ~0.34 [Tang et al. 2001]; Vouivria, 0.35 [Mannion et al. 2017]) and less than in Bellusaurus (~0.43; ...
Fossil-rich deposits from the Middle and Late Jurassic of China have yielded a diverse array of sauropod dinosaurs, including numerous species referred to Mamenchisaurus and Omeisaurus. Despite an abundance of fossils and a proliferation of taxa, the anatomy of Middle–Late Jurassic Chinese sauropods remains poorly documented. Here, we comprehensively redescribe and illustrate Klamelisaurus gobiensis from the Middle–Late Jurassic Shishugou Formation of northwest China. Phylogenetic analyses conducted under parsimony and time-calibrated Bayesian optimality criteria consistently recover Klamelisaurus as a member of a predominantly Chinese radiation of exceptionally long-necked eusauropods that includes Mamenchisaurus spp., Chuanjiesaurus, Qijianglong and Wamweracaudia. In most analyses, this lineage also includes Euhelopus, reviving a ‘traditional’ Euhelopodidae and calling into question the macronarian affinities of Euhelopus. Klamelisaurus shares several features with Euhelopus that are unique to a subset of East Asian taxa or rare among sauropods, including a convex ventral margin of the prezygodiapophyseal lamina in middle–posterior cervical vertebrae, a ventrally bifurcated postzygodiapophyseal lamina in posterior cervical vertebrae, and development of a rugose projection extending anteriorly from the epipophysis into the spinodiapophyseal fossa in most cervical vertebrae. Anatomical comparisons of the cervical vertebrae of Klamelisaurus to several other sauropodomorphs and insights from myological studies of extant archosaurs strongly suggest that this latter structure, often considered part of an epipophyseal-prezygapophyseal lamina, is an epaxial muscle scar that is distinct from pneumatic structures of the lateral surface of the neural spine. The phylogenetic and comparative anatomical data presented here provide a foundation for future revision of the taxonomy and systematics of sauropods from the Junggar and Sichuan basins.
... Sekiya (2011)'s re-examination suggested that this assemblage was composed of at least two individuals (a holotype and a referred specimen), and through cladistic analysis found Chuanjiesaurus belongs to Mamenchisauridae. Its mamenchisaurid affinity has since been confirmed by other studies (Xing et al. 2015b;Ren et al. 2018). However, based on our re-examination, the holotype and referred specimen possess numerous differences. ...
... Both of the processes are nearly triangular. Additionally, the medial accessory process is more robust than the lateral one, which is similar to that in most mamenchisaurids, except for Anhuilong diboensis (Ren et al. 2018). The anconeal fossa is shallow on the posterodistal portion of the humerus, and two processes are semiround in posterior view. ...
... Coding of these new characters are based on extensive review of the literatures (e.g. Upchurch 1998; Wilson and Sereno 1998;Wilson and Upchurch 2003;Sekiya 2011;Mannion et al. 2013;Huang et al. 2014;Poropat et al. 2016;Ren et al. 2018), as well as our personal observations. Some characters were treated as ordered (as in Xu et al. 2018). ...
We present a revision of the referred specimen (LFGT LCD 9701–1) of Chuanjiesaurus anaensis from the Middle Jurassic Chuanjie Formation of Yunnan Province, southwest China, and demonstrate that LCD 9701-1 is differentiated from the holotype by numerous features. Therefore, it can be referred to a new taxon (Analong chuanjieensis gen. et sp. nov.). Analong bears a unique combination of characters, such as caudal transverse processes persisting until the 10th caudal (15th in Chuanjiesaurus); weakly developed posterior condylar ball in anterior caudal vertebrae (well developed in Chuanjiesaurus); ulnar anterolateral and anteromedial processes sub-equal in length and forming an angle of about 45 degrees (unequal in length and 60 degrees in Chuanjiesaurus anaensis); proximal width of metacarpal II 7% the length of radius (lowest value among mamenchisaurids); pubic distal width approximately 40% of its total length (greatest value among mamenchisaurids). Comparative study and cladistic analysis show Analong chuanjieensis is the earliest branching of Mamenchisauridae, while the (Mamenchisaurus + Chuanjiesaurus anaensis) branching is the latest branching of this clade. Our revision of Analong chuanjieensis increases the diversity of Mamenchisauridae and indicates the evolution of Mamenchisauridae is a complex than previously realised.
... They appeared in Early Jurassic, and achieved a global distribution throughout Middle Jurassic to Late Cretaceous (Weishampel et al. 2004). Sauropods had relatively small skulls, extremely elongate necks and tails, as shown in the early diverging clade of Mamenchisauridae Chao 1972；Ouyang andYe 2002;Russsell and Zheng 1993;He et al. 1988;Suteethorn et al. 2012;Ren et al. 2018;Mannion et al. 2019). Mamenchisauridae is the most taxonomic diverse and specific abundant sauropod lineage in the Middle and Late Jurassic in East Asian, especially in the Sichuan Basin in southwestern China, represented by Mamenchisaurus from the upper member of Shaximiao Formation and Omeisaurus from the lower member of Shaximiao Formation Chao 1972；Ouyang andYe 2002;He et al. 1988). ...
... Shunosaurus lii, Omeisaurus tianfuensis). Moreover, the edge of the deltopectoral crest is oriented posterolaterally, similar to that in Anhuilong diboensis (Ren et al. 2018). The cross section of the mid-shaft is ovoid, similar to that in Vulcanodon, Shunosaurus lii, and Omeisaurus tianfuensis (Cooper 1984;Zhang 1988;He et al., 1988). ...
... The 'U' shape of proximal surface is transformed into a circular cross section at mid-shaft, similar to most of sauropods such as Omeisaurus tianfuensis. There is a convex area on distal portion of anteromedial surface where it received the posteromedial surface of distal end of the radius, resembling to that in Omeisaurus tianfuensis, Huangshanlong anhuiensis, Anhuilong diboensis, and Mamenchisaurus youngi (He et al. 1988;Huang et al. 2014;Ouyang and Ye 2002;Ren et al. 2018). The distal surface of the ulna is oval, similar to Omeisaurus tianfuensis (He et al. 1988). ...
A new species of Omeisaurus, O. puxiani sp. nov., from the Middle Jurassic of Southwest China is reported. The holotype consists of partial articulated vertebrae, forelimb, hind limb and other materials of an individual. Comparative study and cladistic analysis show that this new taxon belongs to Omeisaurus, and bears a unique combination of character states, such as all presacral vertebrae opisthocoelous, complex pneumatic fossa system in middle cervical centra, lateral fossae of dorsal centra divided by secondary septa, end of anterior caudal neural spines expanding posteriorly, edge of humerus deltopectoral crest turning posterolaterally and ratio of length of ulna to humerus of 0.69. The previously reported single middle cervical (S66) from the same locality and horizon can be referred to this new species. The discovery of Omeisaurus puxiani enriches the diversity of the genus of Omeisaurus and provides additional information to help understanding the evolutionary history of this genus in Eastern China.
Abbreviations No. 208 HEGT: Chongqing Laboratory of Geological Heritage Protection and Research, No. 208 Hydrogeological and Engineering Geological Team, Chongqing Bureau of Geological and Mineral Resource Exploration and Development Chongqing, Chongqing, China; GSC: Chongqing Institute of Geological Survey, Chongqing, China; IVPP: Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China; ZDM: Zigong Dinosaur Museum, Zigong, Sichuan, China
... These dinosaurs have the distinction of being the sauropods with the longest necks (Mannion et al., 2019;Moore et al., 2020Moore et al., , 2023Ouyang & Ye, 2002;Ren et al., 2020;Russell & Zheng, 1993;Suteethorn et al., 2012;Tang et al., 2001;Upchurch et al., 2004;Wu et al., 2013;Xing et al., 2015;Young, 1958;Zhang et al., 1998). The mamenchisaurid record in Thailand derives from many locations, including the world-renowned Upper Jurassic Phu Noi locality in the lower part of the Phu Kradung Formation (Boonchai et al., 2020;Buffetaut et al., 2014;Tong et al., 2015). ...
... C. anaensis, Huangshanlong anhuiensis, Anhuilong diboensis, and titanosaur Rapetosaurus kiausei (Ren et al., 2020(Ren et al., , 2021Upchurch et al., 2021). with an acceleration voltage of 120 kV and a current of 300 mA. ...
Here we report on an osseous abnormality and multiple fractures in an ulna of a subadult basal Eusauropod (Mamenchisauridae) from the Late Jurassic Phu Kradueng Formation in Thailand. The anatomical deformities were studied using a multi‐method approach that included an assessment of its gross morphology, computed tomography (CT), and osteohistology to aid in its diagnosis. The intracortical lesion in the bone is irregularly shaped, has well‐defined margins with scattered irregular bony trabeculae especially in its center, and it is surrounded by sclerotic bone and spiculated periosteal reactive tissue. The analysis of the radiology and the histopathological characteristics indicates that the lesion in the ulna is an osteogenic tumor, although we are unable to confidently commit to a more specific diagnosis. CT scan data indicated that the multiple fractures evident in the ulna occurred postmortem and are unrelated to the pathology. This is the first report of an osteogenic tumor in a basal Eusauropoda.
... The ratio of the anteroposterior length to the dorsoventral height of the posterior process is 0.9. This ratio is 0.83 in Shunosaurus 35 3,7,10,12,13,[30][31][32][33]82,[86][87][88][89][90][91][92][93] , and most of them are reported from the western of China 93 . Therefore, at least five different non-neosauropodan sauropod lineages exist in the Middle Jurassic of East Asia: the basal-most eusauropods (e.g. ...
Sauropod dinosaurs were gigantic quadrupedal herbivores. They range from Early Jurassic to Late Cretaceous and have been found on all continents. The rich sauropod faunas in the Middle and Late Jurassic of China are mainly from southern or western China. Here, we describe a non-neosauropod eusauropod from the Middle Jurassic Xinhe Formation of Gansu Province, northwestern China, based on an associated partial skeleton that includes a nearly complete skull with mandible, the five anteriormost cervical vertebrae appressed with the skull and the posterior 29 articulated caudal vertebrae. It can be diagnosed as a new taxon Jinchuanloong niedu gen. et sp. nov. based on several cranial and postcranial autapomorphies. In Jinchuanloong, the posterior margin of the external naris lies in front of the posterior margin of the antorbital fenestra, similar to that in basal eusauropods, and the base of the maxillary ascending process presents a foramen, similar to that in neosauropods. The finding of Jinchuanloong adds diversity and helps elucidate the evolution of the sauropods in East Asia.
Supplementary Information
The online version contains supplementary material available at 10.1038/s41598-025-03210-5.
... D'Emic (2012) defined the Euhelopodidae (including six Eary-Middle Cretaceous East Asian genera), but the members or even the existence of this group is still controversial (e.g. Carballido and Sander, 2013;Xing et al., 2015;Ren et al., 2018;Mannion et al., 2019aMannion et al., , 2019bMoore et al., 2020;Upchurch et al., 2021). However, Poropat et al. (2022) suggest the similarity of the teeth between Euhelopus and multiple other Lower Cretaceous materials in China may partly support the notion of the endemic Asian clade. ...
Neosauropods were the dominant sauropod clade with a global distribution as early as the Late Jurassic. However, its distribution and biogeography in the Middle Jurassic are unclear due to the paucity of phylogenetic evidence for neosauropod taxa of this age. In China, the only reported Middle Jurassic neosauropod, the diplodocoid, has challenged the traditional East Asian Isolation Hypothesis for dinosaur paleobiogeography. Here, based on phylogenetic analysis including Dashanpusaurus dongi from the early Middle Jurassic of southwest China, we demonstrate that this taxon represents the earliest diverging macronarian as well as the stratigraphically lowest neosauropod globally. Our biogeographic analysis together with other geological evidence further indicates that neosauropods achieved a global distribution at least in the early Middle Jurassic while Pangaea was still a coherent landmass.
... Sauropods are noted for their great size, but truly giant forms arose in the late Middle and Late Jurassic. Large sauropods include African Macronaria such as Jobaria tigidensis (21 m, Callovian to Oxfordian of Niger; Sereno et al., 1999) and Atlasaurus imalakei (17 m, Callovian of Morocco; Monbaron et al., 1999), Asian mamenchisaurids such as Analong chuanjieensis (20 m, Bathonian of China; Ren et al., 2021), Anhuilong diboensis (20 m, Aalenian to Bathonian of China; Ren et al., 2020), Chuanjiesaurus anaensis (25 m, Callovian of China; Sekiya, 2012), ...
The Early Jurassic Jenkyns Event (~183 Ma) was characterized in terrestrial environments by global warming, perturbation of the carbon cycle, enhanced weathering and wildfires. Heating and acid rain on land caused a loss of forests and affected diversity and composition of land plant assemblages and the rest of the trophic web. We suggest that the Jenkyns Event, triggered by the activity of the Karoo-Ferrar Large Igneous Province, was pivotal in remodelling terrestrial ecosystems, including plants and dinosaurs. Macroplant assemblages and palynological data show reductions in diversity and richness of conifers, cycadophytes, ginkgophytes, bennetitaleans, and ferns, and continuation of seasonally dry and warm conditions. Major changes occurred to sauropodomorph dinosaurs, with extinction of diverse basal families formerly called ‘prosauropods’ as well as some basal sauropods, and diversification of the derived Eusauropoda in the Toarcian in South America, Africa, and Asia, and wider diversification of new families, including Mamenchisauridae, Cetiosauridae and Neosauropoda (Dicraeosauridae and Macronaria) in the Middle Jurassic, showing massive increase in size and diversification of feeding modes. Ornithischian dinosaurs show patchy records; some heterodontosaurids and scelidosaurids disappeared, and major new clades (Stegosauridae, Ankylosauridae, Nodosauridae) emerged soon after the Jenkyns Event, in the Bajocian and Bathonian worldwide. Among theropod dinosaurs, Coelophysidae and Dilophosauridae died out during the Jenkyns Event and a diversification of theropods (Megalosauroidea, Allosauroidea, Tyrannosauroidea) occurred after this event with substantial increases in size. We suggest then that the Jenkyns Event terrestrial crisis was marked especially by floral changes and origins of major new sauropodomorph and theropod clades, characterized by increasing body size. Comparison with the end Triassic Mass Extinction helps to understand the incidence of climatic changes driven by activity of large igneous provinces on land ecosystems and their great impacts on early dinosaur evolution.
... D'Emic (2012) defined the Euhelopodidae (including six Eary-Middle Cretaceous East Asian genera), but the members or even the existence of this group is still controversial (e.g. Carballido and Sander, 2013;Xing et al., 2015;Ren et al., 2018;Mannion et al., 2019aMannion et al., , 2019bMoore et al., 2020;Upchurch et al., 2021). However, Poropat et al. (2022) suggest the similarity of the teeth between Euhelopus and multiple other Lower Cretaceous materials in China may partly support the notion of the endemic Asian clade. ...
... In MCF-PVPH-233/12, the ulnar condyle is rounded and with a slight anteromedial inclination in distal view, whereas the radial condyle is shorter and shallower. Anteriorly, the radial condyle is divided into two robust, medially convergent and anteriorly prominent processes (Fig. 20C, F), as in several sauropods (D'Emic, 2012;D'Emic et al., 2016;Ren et al., 2020), excluding titanosaurians and some somphospondylans (e.g. Chubutisaurus and Sauroposeidon; Rose, 2007;Carballido et al., 2011), in which the radial condyle is undivided. ...
Osteological knowledge of the sauropod dinosaur Ligabuesaurus leanzai is increased by the description of new postcranial elements assigned to the holotype MCF-PVPH-233. Furthermore, a newly referred specimen, MCF-PVPH-228, is recognized after a detailed revision of the abundant sauropod material collected from the Lohan Cura Formation outcrops in the Cerro de los Leones locality (southern Neuquén Basin, Patagonia, Argentina). Recent laboratory preparation and fieldwork allowed us to recognize several new morphological features of the pectoral and pelvic girdles and the cervical and caudal anatomy. Thus, a new diagnosis of Ligabuesaurus is proposed that includes new autapomorphies and a unique combination of features. A phylogenetic analysis based on this new material recovers Ligabuesaurus as a non-titanosaurian somphospondylan, more derived than Sauroposeidon. Therefore, we discuss the palaeobiogeographical implications for the diversification and distribution of South American somphospondylans, especially in the Neuquén Basin, which are closely related to the early stages of evolution of Titanosauria. In this context, Ligabuesaurus represents one of the more complete Early Cretaceous Titanosauriformes and the earliest non-titanosaurian somphospondylan of South America. Finally, the new information on Ligabuesaurus contributes not only to reconstruction of the sauropod faunal composition of south-western Gondwana, but also sheds light on the early stages and emergence of titanosaurians.
... Recent cladistic analyses (Sekiya, 2011;Yang, 2014;Xing et al., 2015) questioned the monophyletic interpretation of the genus Mamenchisaurus. The exceedingly long chronological gap (~30 million years) between M. anyuensis and earlier Mamenchisaurus (Fig. 5) (Upchurch et al., 2004;Ye, 2008;Sekiya, 2011;Xing et al., 2013;Yang, 2014;Huang et al., 2014;Xing et al., 2015;Ren et al., 2018). Notably, Xing et al. (2015) recently also reported a mamenchisaurid, Qijianglong guokr, from the Suining Formation as it occurs at a different locality from that of M. anyuensis. ...
Mamenchisauridae, a sauropod group named after the largest known proto-Asian sauropod Mamen-chisaurus, is generally believed to range from the Early to the Late Jurassic in age. Fossil remains of Mamenchisaurus are primarily found in the Upper Shaximiao Formation and less frequently in the overlying Suining Formation in the Sichuan Basin. An accurate absolute age for Mamenchisaurus is critical for understanding the evolution and radiation of the mamenchisaurids. However, reliable age de-terminations for the Mamenchisaurus-bearing formations are lacking. In this study, we provide robust detrital zircon U/Pb ages (mean ages of 114.4 ± 1.1 Ma; Aptian) for rocks from the classic fossil outcrops of the Suining Formation in the Sichuan Basin. Our data indicate an extremely long chronological gap between M. anyuensis (114.4 ± 1.1 Ma) and the earlier Mamenchisaurus (Late Jurassic). This indicates mamenchisaurids may have lived at least 30 million years longer than previously thought.
... Recent cladistic analyses (Sekiya, 2011;Yang, 2014;Xing et al., 2015) questioned the monophyletic interpretation of the genus Mamenchisaurus. The exceedingly long chronological gap (~30 million years) between M. anyuensis and earlier Mamenchisaurus (Fig. 5) (Upchurch et al., 2004;Ye, 2008;Sekiya, 2011;Xing et al., 2013;Yang, 2014;Huang et al., 2014;Xing et al., 2015;Ren et al., 2018). Notably, Xing et al. (2015) recently also reported a mamenchisaurid, Qijianglong guokr, from the Suining Formation as it occurs at a different locality from that of M. anyuensis. ...
The dorsal vertebrae of Xinjiangtitan shanshanesis (SSV12001) from the Late Jurassic Qigu Formation of Xinjiang Uygur Autonomous Region, China, are redescribed based on the further exposure and preparation of the holotype. As a mamenchisaurid sauropod dinosaur, Xinjiangtitan shanshanesis displays a unique combination of autapomorphic and plesiomorphic features, such as the presences of both lateral spinopostzygapophyseal laminae (L.SPOL) and medial spinopostzygapophyseal lamina (M.SPOL) in dorsal vertebrae and a shallow intralaminar fossa (SPOL-F) between the L.SPOL and M.SPOL; anterior spinodiapophyseal laminae (A.SPDL), posterior spinodiapophyseal laminae (P.SPDL) and middle spinodiapophyseal lamina (M.SPDL) in dorsals 3–5; bifurcated anterior and middle dorsal neural spines with the median tubercle and the triangular lateral processes. Phylogenetic analysis and morphological comparison show that Xinjiangtitan shanshanesis probably shares a close relationship with Hudiesaurus and Mamenchisaurus and provide new information for future taxonomic revision of the mamenchisaurids.
The Middle Jurassic lower Shaximiao Formation in Sichuan Province of south-western China has yielded a diverse terrestrial vertebrate fauna dominated by sauropod dinosaurs. However, many of these sauropods lack detailed descriptions or explicit phylogenetic diagnoses. Here, we present a comprehensive redescription of Dashanpusaurus dongi, a species of sauropod found only in the lower Shaximiao Formation. We define the revised autapomorphies of the species as follows: neural canals are sub-square in anterior dorsal vertebrae; the presence of a thin accessory lamina that contacts the prezygodiapophyseal and paradiapophyseal laminae of the middle dorsals, forming an angle of 75° to the horizontal; and four ridges on the anterodistal edge of the humerus. Often considered part of the epipophyseal-prezygapophyseal lamina, a strut invades the spinodiapophyseal fossa in the cervical and anterior dorsal vertebrae. Anatomical comparisons indicate that this feature was widespread among early-diverging Middle Jurassic eusauropod lineages. This comparative anatomical data provides an opportunity to revisit the phylogenetic position of Dashanpusaurus and the relationships of the neosauropod clade. Recovered as a macronarian, a better understanding of Dashanpusaurus dongi will allow for clarification of the origin, early evolution, and palaeogeographical distribution of neosauropods. This study also suggests that the diversity and dispersity of the neosauropod clade occurred much earlier than previously realized.
Cranial elements of Suuwassea emilieae (Sauropoda: Diplodocoidea) from the Upper Jurassic Morrison Formation of Montana, U.S.A., represent one of only a few flagellicaudatan skulls known. Preserved elements include a left premaxilla, a fragment of right maxilla, a right squamosal, a right quadrate, a basicranium and skull roof lacking only the rostral end of the frontals, basipterygoid processes, and parasphenoid rostrum. Autapomorphic features of the skull include: premaxillary teeth projecting parallel to long axis of premaxilla; single optic nerve foramen; postparietal foramen present and larger than parietal foramen; supraoccipital with elongate ventral process contributing little to dorsal margin of foramen magnum; basioccipital not contributing to floor of median condylar incisure; and antotic processes with no dorsal contact with frontals. The basicranium more closely resembles that of Apatosaurus rather than Diplodocus and is also unlike the skull of Dicraeosaurus, despite its possession of a similar postparietal foramen, a feature unique among Morrison Formation sauropods. Pending reanalysis of Tornieria africana, which also possesses it, the postparietal foramen must be viewed as a symplesiomorphic retention in the Dicraeosauridae, with its loss a synapomorphy of the Diplodocidae, or at least of the North American members of the latter clade.
Preparation of an approximately two-thirds complete, well-preserved Camarasaurus skeleton has recently been finished. Its detailed osteological description presented here provides a number of interesting characters, some not previously reported for the genus. This specimen (BYU 9047) was earlier named Cathetosaurus lewisi, n. gen. et sp., based on seven characters cited by Jensen (1988). Of these characters, four appear to be age related (this skeleton represents a very old individual) and not of taxonomic significance. Nevertheless, they are useful in advancing our understanding of the ligamentation associated with the sacral and posterior dorsal regions, not only of Camarasaurus but of the sauropods in general. These characters also contribute to a greater knowledge of the ontogenetic development and fusion of the sacral elements. Camarasaurus lewisi (Jensen, 1988) is a valid species whose diagnostic characters include (1) a deep but narrow cleft in the neural spines of presacral vertebrae, which most significantly persists to the sacrum rather than ending in the mid-dorsal region, as in all other species of Camarasaurus; (2) a forward rotation of the ilium with respect to the long axis of the sacrum, a hitherto unreported major character of the genus Camarasaurus; and (3) a steep angle that the posterior chevron articulating facets make with the horizontal plane.
ABSTRACT—Qijianglong guokr, gen. et sp. nov., represents a mamenchisaurid eusauropod from the Late Jurassic of southern China. The holotype consists of an incomplete skull, partly articulated axial skeleton, and fragmentary appendicular skeleton. A well-preserved braincase and skull roof provide rare insights into the poorly known neurocranial anatomy of mamenchisaurids and reveal a unique combination of characters such as an accessory tuber at the base of planar basipterygoid process and parietal excluding frontal from the anterior margin of the supratemporal fenestra. The cervical vertebrae have a distinct finger-like process extending from the postzygapophyseal process beside a zygapophyseal contact. Qijianglong is the first mamenchisaurid from the Late Jurassic of China that is definitively distinct from Mamenchisaurus, indicating greater morphological and taxonomic diversity of the poorly represented Late Jurassic mamenchisaurids. The occurrence of Qijianglong is consistent with a scenario in which mamenchisaurids formed an endemic sauropod fauna in the Late Jurassic of Asia. Phylogenetically, Qijianglong represents a relatively plesiomorphic mamenchisaurid lineage. The mamenchisaurids form an ancient clade of basal eusauropod dinosaurs that likely appeared in the Early Jurassic. A cladistic analysis highlights the interrelationships of mamenchisaurids and suggests guidelines for mamenchisaurid taxonomic revision. It may be desirable to restrict generic names to the type species in order to avoid confusion.
Key words Huili, Sichuan; Lower Jurassic; Yimen Formation; Sauropoda; Tonganosaurus
The English summary can be seen in the attachment.
Omeisaurus jiaoi, a new species of giant sauropod is described in this paper. The specimen (ZDM 5050) was discovered from the Xiashaximiao Formation of the Middle Jurassic of Zigong Dinosaur National Geopark, Sichuan. ZDM 5050 is a nearly complete skeleton. Its main features can be summarized as follows: dorsal vertebrae are tall and large. The anterior dorsal vertebrae (dorsals 1 to 6) are opisthocoelous. The pleurocoels of the dorsal vertebrate are well developed except on the 1st dorsal. The neural spines are club-like and the neural spines of the anterior dorsal vertebrae are not bifurcated. Caudal vertebrae are relatively short and thick. The anterior caudal vertebrae are slightly amphicoelous. The chevron of the 1st caudal vertebrae is connected with the 1st caudal and is shallow and small. Whereas the 1st caudal vertebrae of Omeisaurus tianfuensis have no chevron. The rib of the 1st caudal vertebrae are laterally directed, while the first caudal rib of the other species of Omeisaurus are prominently enlarged distally, being slightly fan-shaped. Humerus is long and straight, with slightly expanded proximal end and greatly expanded distal end. The deltopectoral crest is well-developed and relatively low. Femur has a slender shape, with a greatly expanded proximal and distal ends. The fourth trochanter is well-developed. The ratio of the humerus length to femur length is approximately 0.83, the ratio of the ulna length to humerus length is approximately 0.72, the ratio of the tibia length to femur length is approximately 0.63.
Titanosauriforms represent a diverse and globally distributed clade of neosauropod dinosaurs, but their inter‐relationships remain poorly understood. Here we redescribe Lusotitan atalaiensis from the Late Jurassic Lourinhã Formation of Portugal, a taxon previously referred to Brachiosaurus. The lectotype includes cervical, dorsal, and caudal vertebrae, and elements from the forelimb, hindlimb, and pelvic girdle. Lusotitan is a valid taxon and can be diagnosed by six autapomorphies, including the presence of elongate postzygapophyses that project well beyond the posterior margin of the neural arch in anterior‐to‐middle caudal vertebrae. A new phylogenetic analysis, focused on elucidating the evolutionary relationships of basal titanosauriforms, is presented, comprising 63 taxa scored for 279 characters. Many of these characters are heavily revised or novel to our study, and a number of ingroup taxa have never previously been incorporated into a phylogenetic analysis. We treated quantitative characters as discrete and continuous data in two parallel analyses, and explored the effect of implied weighting. Although we recovered monophyletic brachiosaurid and somphospondylan sister clades within Titanosauriformes, their compositions were affected by alternative treatments of quantitative data and, especially, by the weighting of such data. This suggests that the treatment of quantitative data is important and the wrong decisions might lead to incorrect tree topologies. In particular, the diversity of Titanosauria was greatly increased by the use of implied weights. Our results support the generic separation of the contemporaneous taxa Brachiosaurus, Giraffatitan, and Lusotitan, with the latter recovered as either a brachiosaurid or the sister taxon to Titanosauriformes. Although Janenschia was recovered as a basal macronarian, outside Titanosauria, the sympatric Australodocus provides body fossil evidence for the pre‐Cretaceous origin of titanosaurs. We recovered evidence for a sauropod with close affinities to the Chinese taxon Mamenchisaurus in the Late Jurassic Tendaguru beds of Africa, and present new information demonstrating the wider distribution of caudal pneumaticity within Titanosauria. The earliest known titanosauriform body fossils are from the late Oxfordian (Late Jurassic), although trackway evidence indicates a Middle Jurassic origin. Diversity increased throughout the Late Jurassic, and titanosauriforms did not undergo a severe extinction across the Jurassic/Cretaceous boundary, in contrast to diplodocids and non‐neosauropods. Titanosauriform diversity increased in the Barremian and Aptian–Albian as a result of radiations of derived somphospondylans and lithostrotians, respectively, but there was a severe drop (up to 40%) in species numbers at, or near, the Albian/Cenomanian boundary, representing a faunal turnover whereby basal titanosauriforms were replaced by derived titanosaurs, although this transition occurred in a spatiotemporally staggered fashion. © 2013 The Linnean Society of London
The sauropod dinosaur, Barapasaurus tagorei, is known from the Early Jurassic Kota Formation (Sinemurian to Pliensbachian) of India. The taxon is represented by c. 300 bones that were found associated with large fossilized tree trunks and were collected from the interface of sandstone and mudstone units covering an area of c. 276 m2. The collection includes one partial skeleton; most of the remainder of the bones were disarticulated, disassociated and dispersed, but taphonomic analysis permits recognition of associated elements comprising several individuals. Skeletal anatomy of Barapasaurus includes several teeth, vertebrae from the caudal cervicals rearward to the terminal caudals, and most elements of the appendicular skeleton. Barapasaurus is characterized by spoon-shaped teeth with bulbous bases and grooves on the anterolabial and posterolingual sides of the crown, coarse tubercles on the carina, acamerate cranial and dorsal vertebrae, lateral laminae of the middle and caudal dorsal neural spines composed of spinodiapophyseal and spinopostzygapophyseal laminae, neural canal of the mid-dorsal vertebrae opens dorsally through a narrow slit into a large cavity and sacrum with four co-ossified vertebrae. Phylogenetic analysis reveals that Barapasaurus is basal in comparison with Vulcanodon and is removed from Eusauropoda.
Plateosaurus from the late Triassic of Central Europe is one of the best known dinosaurs. Despite the large number of finds, including complete and articulated skeletons, its posture and locomotion capabilities are still being debated. While recent assessments of the range of motion of the forelimb indicate that Plateosaurus was incapable of manus pronation, and thus an obligate biped, practically all other possible alternatives have been suggested in the literature. Here, I present evidence, derived from a detailed mounting of a 3D digital skeleton and a computer-aided engineering assessment of a digital 3D model of the living animal, that Plateosaurus was indeed an obligate biped. The position of the center of mass is assessed in several variations of the basic model to account for differing interpretations of soft tissue amounts. All models allow a stable bipedal pose with a subhorizontal back that is consistent with the requirements of both slow and rapid locomotion. Quadrupedal models, in contrast, suffer from locomotion restrictions due to highly uneven limb lengths and a limited motion range in the forelimb, and result in a smaller feeding envelope.
Titanosaurians were a flourishing group of sauropod dinosaurs during Cretaceous times. Fossils of titanosaurians have been found on all continents and their remains are abundant in a number of Late Cretaceous sites. Nonetheless, the cranial anatomy of titanosaurians is still very poorly known. The Spanish latest Cretaceous locality of “Lo Hueco” yielded a relatively well preserved, titanosaurian braincase, which shares a number of phylogenetically restricted characters with Ampelosaurus atacis from France such as a flat occipital region. However, it appears to differ from A. atacis in some traits such as the greater degree of dorsoventral compression and the presence of proatlas facets. The specimen is, therefore, provisionally identified as Ampelosaurus sp. It was CT scanned, and 3D renderings of the cranial endocast and inner-ear system were generated. Our investigation highlights that, although titanosaurs were derived sauropods with a successful evolutionary history, they present a remarkably modest level of paleoneurological organization. Compared with the condition in the basal titanosauriform Giraffatitan brancai, the labyrinth of Ampelosaurus sp. shows a reduced morphology. The latter feature is possibly related to a restricted range of head-turning movements.
The sauropod Lirainosaurus astibiae Sanz et al., 1999, a mediumsized, gracile titanosaur (about 8-10 m in length), is known by a fragmentary skull, teeth and postcranial bones from the Late Cretaceous (late Campanian to early Maastrichtian) of Laño, northern Iberian Peninsula. The aim of this paper is to describe new fossil bones of Lirainosaurus which constitute the first record of Lirainosaurus outside its type locality.
The new material, recovered from lacustrine levels of the Sierra Perenchiza Formation (late Campanian to early Maastrichtian) at Chera locality (Valencia Province, eastern Spain), consists of vertebral remains, pectoral girdle elements and limb bones. The material is referred to Lirainosaurus cf. astibiae on the basis of the presence of the following
autapomorphies: (1) posterior caudal centra characterized by a restricted articular condyle with a sagittal condylar groove, (2) prominent ridge on the ventral margin of the scapular blade, and (3) coracoidal foramen located close to the scapular border and to the dorsal margin of the coracoid. This combination of features is exclusive of Lirainosaurus.
Other diagnostic features of L. astibiae are not preserved or can not be recognised in the recovered material. Lirainosaurus has been previously related with the Saltasaurinae of South America, but clear phylogenetic affinities can be only recognized with a more inclusive clade, the Eutitanosauria. This interpretation is coherent with the wide biogeographical distribution of the eutitanosaurians during the Late Cretaceous.
We describe sauropod material from the Lower Cretaceous (Aptian-Albian) Puesto Quiroga Member of the Lohan Cura Formation, exposed at the Cerro Aguada del León locality (La Picaza area, Neuquén Province, Argentina). The remains consist of disarticulated elements of at least three individuals, and are assigned to an indeterminate species of the rebbachisaurid diplodocoid Limaysaurus gen. nov. Elements from various parts of the skeleton are represented: a tooth, partial dorsal, sacral, and caudal vertebrae, a haemal arch, coracoid, humerus, ilium, pubes, ischium, femora, a tibia fragment, and an incomplete fibula. The Lohan Cura specimens are strongly reminiscent of corresponding elements in the holotype of Limaysaurus tessonei (=“Rebbachisaurus” tessonei, “Rayososaurus” tessonei) from the overlying Upper Cretaceous (lower Cenomanian) Candeleros Formation. We evaluate the phylogenetic relationships of Limaysaurus gen. nov. and other diplodocoids, and provide hypotheses regarding sauropod evolution during the Cretaceous.
The Jurassic climate of China was analysed mainly based on the data of palaeontology, sedimentology, geochemistry and stomatal index and stomatal ratio of fossil plants. Both the temperature and humidity of China experienced drastic alteration in the Jurassic, and the temperature was obviously higher than that of the present. There were five climatic evolution stages including the early-middle of Early Jurassic, the late Early Jurassic, the early of Middle Jurassic, the late of Middle Jurassic and the Late Jurassic. Each of them had distinct characteristic of regionalization. In the early-middle of Early Jurassic stage (Hettangian-Plinsbachian) there were five climate regions, namely, Wushuli warm-cool climatic region in Eastern Heilongjiang, North China warm-temperate humid climatic region, Southeast China tropic-subtropical humid climatic region, Southwest China tropic-subtropical semi-arid and semi-humid climatic region and Tibet-western Yunnan tropical oceanic arid climatic region. Among these regions, the warm-temperate humid climatic region was the widest one, occupied the vast area north of the Kunlun Mountains-Qinling Mountains-Dabie Mountains. It was becoming warmer and tending to be dry in the late of Early Jurassic stage (Toarcian), while there were still five climate zones. However, the warm temperate humid climate zone in North China was shrinking because the south boundary of which was dramatically moved northwards. The largest one was the tropical-subtropical zone in central China. The temperature had a dramatic decrease and becoming in the early of Middle Jurassic (Aalenian-Bajocian). The area of the warm temperate humid climate zone in North was restored almost to that of the early-middle of Early Jurassic by extending southwards, and Southeast China was occupied by tropical-subtropical semi-arid and semi-humid climatic. It became hot and dry again in the late of Middle Jurassic (Bathonian-Callovian) and the area of warm temperate humid climate zone in North was sharply reduced to restrict in the Yanliao (northern Hebei Province and western Liaoning Province) area and Northeast China. The subtropical semi-arid and semi-humid climate zone extended to the whole North and Northwest China. The temperature continued warming in the Late Jurassic (Oxfordian-Tithonian). The warm temperate humid climate zone was shrunk away to a corner of Northeast China. It was hot and dry and appearing desertification in the vast area of China except the Tibet-western Yunnan region which belonged to tropical oceanic climate. © 2017, Editorial Office of Earth Science Frontiers. All right reserved.
A juvenile specimen of the titanosaurid sauropod Alamosaurus sanjuanensis, recovered from just below the Cretaceous/Tertiary boundary horizon in Big Bend National Park, Texas, is from an individual less than half the size of adult specimens referred to this species. The disarticulated skeleton was preserved in deposits of a shallow flood-plain pond and includes elements not previously described, allowing for an improved diagnosis for this species. The elongate opisthocoelous cervical vertebrae have non-bifid posteriorly deflected neural spines with deep postspinal fossae. The dorsal vertebrae have wide spatulate neural spines with strong prespinal laminae, and lack hyposphene-hypantrum articulations. Alamosaurus sanjuanensis exhibits a unique morphology of the ischium, evident even in this juvenile specimen. Comparison with other titanosaurid species suggests that A. sanjuanensis is most closely related to an unnamed titanosaur from Peiropolis, Brazil and Neuquensaurus australis from Argentina.
Five periods of structural deformations in the Late Mesozoic era have been identified by systematic field investigation and structural analyses. The first one is the NEE trending thrust structure, which took place from the end of the Middle Jurassic to the beginning of the Early Cretaceous, approximately 160-150 Ma. The second one is characterized by the high-angel normal fault and the NNE trending left-laterastrike-slipfault which formed at the beginning of the Early Cretaceous, approximately 150-135 Ma. The third one is the NEE trending left-lateral strike-slip faults, which formed at the late Early Cretaceous, approximately 125-120 Ma. The forth one is the NE-NEE trending right-lateral strike-slip faults formed at the end of the Early Cretaceous, approximately 100 Ma. The last main structural deformation is the top to the NWW thrust with an NNE striking, which formed at the early Late Cretaceous after 75 Ma. The multi-stage deformations are associated with the latest collision of the North China and the South China plate, and with the different directional subduction of the Pacific plate towards the Euro-Asian plate at different stages, and even with the eastward remote extrusion effect of the collision between Indian plate and Euro-Asian plate. © 2016, Editorial Office of Earth Science Frontiers. All right reserved.
Version 1.5 of the computer program TNT completely integrates landmark data into phylogenetic analysis. Landmark data consist of coordinates (in two or three dimensions) for the terminal taxa; TNT reconstructs shapes for the internal nodes such that the difference between ancestor and descendant shapes for all tree branches sums up to a minimum; this sum is used as tree score. Landmark data can be analysed alone or in combination with standard characters; all the applicable commands and options in TNT can be used transparently after reading a landmark data set. The program continues implementing all the types of analyses in former versions, including discrete and continuous characters (which can now be read at any scale, and automatically rescaled by TNT). Using algorithms described in this paper, searches for landmark data can be made tens to hundreds of times faster than it was possible before (from T to 3T times faster, where T is the number of taxa), thus making phylogenetic analysis of landmarks feasible even on standard personal computers.
This chapter investigates a number of potential macroevolutionary mechanisms that may account for sauropodomorph diversity, including various potential clade-clade interactions (coevolution and competition). It also examines the possibility that the observed changes may be at least partially accounted for by fluctuations in the frequencies of different sauropodomorph feeding mechanisms through time. There was considerable temporal overlap between prosauropods and sauropods, extending from the late Carnian to the end of the Pliensbachian. Moreover, the possible roles of several biological processes that may have influenced sauropod diversity through time are assessed. Comparisons of sauropodomorph diversity with information on Mesozoic floras reveal one possible incidence of coevolution, between titanosaurs and angiosperms, in the Late Cretaceous. The strong correlation between diversity and feeding ecology shows that herbivory and the various adaptive complexes that arose to deal with a diet of plants were central to the radiation of sauropodomorphs in the Middle and Late Jurassic.
The dinosaur fossils at Sanxingzhen, Jianyang, Sichuan, are found in the Latter Jurassic Penglaizhen Formation. They are identified as Mamenchisaurus sp. through abundant researches. This is the first time to find the Mamenchisaurus fossils in the top of the Latter Jurassic Penglaizhen Formation. The discovery not only enlarges the range of Mamenchisaurus' geographical history, but also points out a new way to look for sauropoda of Latter Jurassic in Sichuan and the neighbouring areas. At the same time, according to the continuous discovery and the progressive expansion of geographical history of Mamenchisaurus, this paper suggests that the geologic age of Mamenchisaurus should be reconsidered.
Mamenchisaurus (Young, 1954), composed of seven species, is the most representative dinosaur in the Late Jurassic of China. It is the biggest individual among dinosaurs of that time in China, and has the longest neck, the most species, and the widest geographical distribution. Mamenchisaurus undoubtedly belongs to Bothrosauropodoidea with a high skull and spatulate teeth. Mamenchisaurus developed in the Sichuan Basin in the early part of the Late Jurassic. Its geographical distribution is restricted to East Asia, and it is the sauropod with the most endemic features in the Late Jurassic of East Asia. Its ancestor appears to be the main genus of dinosaur in the Middle Jurassic - Omeisaurus (Young, 1939).
Mamenchisaurus jingyanensis, a new species of sauropod dinosaur, from the Upper Jurassic of Sichuan Basin, China, is desribed in this paper. Diagnosis of M. jingyanensis: A gigantic sauropod, about 20-26 m in length. Skull moderately high and light. Naris small and situated in the anterior part of skull. Mandible slender. Teeth typically spatulate in form. Cervical vertebrae extremely long. The pleurocoels of dorsals poorly developed. The spines of the anterior dorsals bifurcated. The anterior caudals remarkably procoelous. Humerus robust and straight.
This chapter examines the evolutionary relationships of sauropods using cladistic analysis. It also describes in the detail their paleobiology, taphonomy, and paleoecology. Sauropod dinosaurs include the largest terrestrial animals ever to have existed. At present, Sauropoda comprises twenty-two genera. Sauropods have small skulls in relation to their body size, extremely elongate necks and tails, columnar limbs, and stout, barrel-shaped bodies. Sauropod remains have been recovered from all continents except Antarctica. They are found in mass accumulations (bone beds) in the Morrison Formation of the western United States, in the Tendaguru Beds of East Africa, in the Kota Formation of India, in the Lower Shaximiao Formation of the Sichuan Basin in China, and in the Cañodon Asfalto Formation of Patagonia.
Many sauropod ghost lineages cross the Middle Jurassic, indicating a time interval that requires increased sampling. A wide taxonomic spectrum of sauropodomorphs is known from the Middle Jurassic of China, but the braincase of a new sauropod, named here Nebulasaurus taito gen. et sp. nov., is distinct. Nebulasaurus is sister taxon to Spinophorosaurus from the Middle Jurassic of Africa and represents a clade of basal eusauropods previously unknown from Asia. The revised faunal list indicates dramatic transitions in sauropodomorph faunas from the Jurassic to Cretaceous of Asia; these are consistent with geographic isolation of Asia through the Late Jurassic. Non-sauropod sauropodomorphs, non-ma-menchisaurid eusauropods (including basal macronarians), and mamenchisaurids successively replaced previous grades through the Jurassic, and titanosauriforms excluded all other sauropod lineages across the Jurassic–Cretaceous boundary.
: A new mamenchisaurid dinosaur, Eomamenchisaurus yuanmouensis gen et sp. nov. is erected based on an incomplete skeleton from the Zhanghe Formation, the Middle Jurassic of Yuanmou, Yunnan Province. The new taxon is characterized by absence of pleurocoels in dorsal vertebrae and the dorsal verterbrae with slightly convex anterior articular surfaces, moderately concave posterior articular surfaces; the fourth trochanter is developed posteromedially on the femur; length ratio of the tibia to the femur is approximately 0.64; and the shaft of the ischium is rod-like. Two fused centra of the posterior dorsal vertebrae (the presumed 9th and the 10th dorsal vertebrae) are similar to those in other mamenchisaurid dinosaurs, including Mamenchisaurus hochuanesis, M. youngi and Chuanjiesaurus anaensis. Therefore, fusion of centra of the ninth and the tenth dorsal vertebrae can be recognized as a synapomorphic character of the Mamenchisauridae.
The earliest record of titanosaurids anywhere in the world was established in India in 1877. Further collections from fossiliferous pockets near Jabalpur were made by C. E Matley during 1917–1919. This material formed the basis of a number of taxa from the Indian Late Cretaceous, even though most of the bones were isolated and fragmented. New titanosaurid skeletal material (collected during 1984–1986) described here represents part of an individual in associated and mostly articulated condition, though skull, hind limb and foot bones are missing. Paucity of associated skeletal remains of titanosaurids anywhere in the world makes the present find valuable in understanding these specialized sauropods. A new taxon, Titanosaurus colberti, is erected for the reception of the new material. The genus Titanosaurus is diagnosed and three species are identified from India: T. indicus, T. blanfordi, and T. madagascanensis.
The skull of Turiasaurus is known from a nearly complete posterior section (e.g. braincase, skull roof, quadrates and left mandible) and fragments of the snout (e.g. portions of premaxilla, maxilla, nasal and lacrimal). Skull material of the holotypic individual was discovered in close association. Comparisons with other sauropods suggest that the Turiasaurus skull most closely resembled those of Jobaria, Camarasaurus and Mamenchisaurus youngi, possessing large spatulate teeth, enlarged and partially retracted external nares, and a broadly rounded muzzle. The list of autapomorphies for Turiasaurus is augmented by the new cranial data, including features such as: (1) a shelf-like projection of bone from the medial surface of the distal end of the maxillary ascending process; and (2) a rounded boss-like area on the lateral surface of the jugal. There are also unusual character states, such as the excavation of the posterior surfaces of the basal tubera (present in Turiasaurus and Losillasaurus) that probably have a wider phylogenetic significance. Phylogenetic analyses, using two different datasets, support the view that Turiasaurus, Losillasaurus and Galveosaurus form a monophyletic Turiasauria clade that lies just outside of Neosauropoda. The addition of the new cranial data slightly strengthens the support for this topology, but the relationships of other taxa (such as Jobaria) become less stable. The Turiasauria might represent a distinct group of non-neosauropods with a wide geographic distribution across Europe and Africa during the Late Jurassic.
Dinosaurian biogeography may have been largely controlled by the Mesozoic fragmentation of Pangea and the reassembly of its fragments into a new, boreal supercontinent (Laurasia). Although Late Triassic and Early Jurassic dinosaurs were globally distributed, Chinese assemblages were dominated by endemic forms from Middle Jurassic into Early Cretaceous time. The affinities of Aptian - Albian immigrants to Asia were strongest with North America and Europe rather than Gondwana, indicating that the northern and southern hemispheres had by then attained their biogeographic identity. This distinctiveness was maintained through Cretaceous time. Europe seems to have been a buffer area between Paleolaurasia and Gondwana; of the northern continents it was the most strongly influenced by Gondwana dispersants. Late Jurassic dinosaur assemblages in North America exhibited Gondwana affinities, but by Late Cretaceous time they were dominated by forms of Asian ancestry.
Three classifications of the Dinosauria have been proposed, which differ from each other in the principles on which their authors proposed to make the divisions. First in time is Professor Cope’s classification (‘Philadelphia, Acad. Nat. Sci. Proc.,’ November 13th, 1866, and December 31st, 1867; ‘Amer. Phil. Soc. Trans.,’ vol. 14, Part I). He relied upon the characters of the tarsus and the ilium; and on their varied condition divided Dinosaurs into three orders named Orthopoda, Goniopoda, and Symphopoda. In the Orthopoda , the generic types associated are Scelidosaurus, Hylæosaurus, Iguanodon, and Hadrosaurus. And in this group the relations of the tibia and fibula are compared to those of modern Lizards, the proximal tarsals being distinct from each other and from the tibia. The ilium has a narrowed anterior prolongation.
The nearly complete skeleton of a large sauropod discovered at Wawmda (High Central Atlas of Morocco) in strata of Bathonian-Callovian age represents a new taxon: Atlasaurus imelakei n.g., n.sp. The sauropod appears to be closer to Brachiosaurus than any other known sauropod, but possesses (relative to the length of the dorsal vertebral column) a larger skull, shorter neck, longer tail and more elongated limbs. The presence of large sauropods of Middle Jurassic age is very important in understanding the history and the evolution of these Mesozoïc giants.
The Late Jurassic-Early Cretaceous site of La Cañada (Barranco de Escáiz, Losilla, Aras de Alpuente, Valencia) has delivered several pieces of a new Sauropod dinosaur called Losillasaurus giganteus. The material includes a cranial fragment, several vertebral fragments and complete cervical, dorsal, sacral and caudal vertebrae; appendicular skeleton (humerus, ulna, radius, metacarpal); sternal plates; and pelvic elements (ilium, ischium and pubis). The diagnosis of Losillasaurus giganteus is based on two autapomorphies and singular combination of synapomorphies. The two autapomorphies are: neural spine of the proximal caudal vertebrae with a laterally bowed outline in dorsal view (cutlass-like shape). Moreover, the ratio of the proximodistal dimension of the neural spine to the total height is around 0.5.
The incompletely known sauropod Tornieria africana from the Upper Jurassic (Tithonian) of Tendaguru, Tanzania, has for over 80 years been regarded to represent a Gondwanan species of the North American genus Barosaurus Marsh (Morrison Formation: Kimmeridgian-Tithonian), but this identification has recently been questioned. The holotype and referred specimens are redescribed here, and the characters present are reevaluated in light of current knowledge of sauropod phylogeny. Synapomorphies of the skull (prefrontal with triangular posterior process) and anterior caudal vertebrae (procoelous centra, presence of diapophyseal laminae, and presence of a pleurocoel) indicate that the Tendaguru material represents a member of the Diplodocinae (Diplodocoidea, Diplodocidae) and is therefore very closely related to Barosaurus and Diplodocus. It differs from all other diplodocine genera in several characters, such as robust anterior caudals with pleurocoels located in the upper third of the centrum and ventral excavations, and stout hind limb proportions similar to Apatosaurus (tibia:femur length ratio less than 0.64). In a phylogenetic analysis, the African form consistently emerges as the sister taxon to Barosaurus+Diplodocus. Therefore, previous suggestions that Tornieria africana is the available name for this taxon are supported by this analysis. The existence of this form in Gondwana contradicts the idea of Laurentian endemism of the diplodocid clade, and is best explained by a vicariance model of diplodocoid paleobiogeography. This implies an extensive ghost lineage of this group, extending back at least as far as the upper Middle Jurassic.
Sauropod cranial elements, despite their rarity, contain a significant
proportion of the known phylogenetically important character
data (see Wilson, 2002; Upchurch et al., 2004). In particular,
cranial characters are important in distinguishing between the
two main neosauropod lineages, Diplodocoidea and Macronaria,
as well as between the various lineages of diplodocoid sauropods.
One recently described diplodocoid, Suuwassea emilieae, has
proven difficult to place phylogenetically despite a relative wealth
of cranial data (Harris, 2006a). As a putatively basal member
of the Late Jurassic radiation of diplodocoids, Suuwassea is an
important taxon for the understanding of diplodocoid sauropod
evolution. Although it has been variously recovered as a member
of either the primarily Laurasian diplodocids or the Gondwanan
dicraeosaurids, the precise relationship between those lineages
and Suuwassea has remained uncertain.
Here we describe a recently discovered dentary assignable to
the holotypic specimen of Suuwassea emilieae (Academy of Natural
Sciences 21122). This dentary possesses important character
data that suggest dicraeosaurid affinities for Suuwassea; as a consequence,
Suuwassea is potentially the only recognized Laurasian
member of Dicraeosauridae. The description of this dentary also
adds to our scarce knowledge of sauropod dentaries.
The isolated skulls of Nemegtosaurus mongoliensis and Quaesitosaurus orientalis from the Nemegt Basin of Mongolia are among the most complete sauropod cranial remains known from the Late Cretaceous, yet their evolutionary relationships to other neosauropods have remained uncertain. Redescription of the skull of Nemegtosaurus identifies key features that link it and its closely related counterpart Quaesitosaurus to titanosaur sauropods. These include a posterolaterally orientated quadrate fossa, ‘rocker’-like palatobasal contact, pterygoid with reduced quadrate flange and a novel basisphenoid–quadrate contact. Other features are exclusive to Nemegtosaurus and Quaesitosaurus, such as the presence of a symphyseal eminence on the external aspect of the premaxillae, a highly vascularised tooth bearing portion of the maxilla, an enclosed ‘maxillary canal’, orbital ornamentation on the postorbital, prefrontal and frontal, exclusion of the squamosal from the supratemporal fenestra and dentary teeth smaller in diameter than premaxillary and maxillary teeth.
Abstract Yuanmousaurus jiangyiensis gen. et sp. nov. is erected based on an incomplete skeleton. It is characterized by more complex structures of the neural arches in the dorsal vertebrae than those in Omeisaurus, but less complex than those of Euhelopus; the dorsal vertebra bears 9 laminae, forming three cavities on the lateral surface of the neural arch; the dorsal vertebral neural spines with dorsoventrally-oriented cavities are similar to those of Omeisaurus and Patagosaurus. Yuanmousaurus is more primitive than Euhelopus, but more derived than Omeisaurus. The similar dorsal vertebral structure between Yuanmousaurus and Patagosaurus may indicate that they have a close relationship to each other.