Liao Chun-Chi, Moore Andrew, Jin Changzhu, Yang Tzu-Ruei, Shibata Masateru, Jin Feng, Wang Bing, Jin Dongchun, Guo Yu, Xu Xing
Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China.
CAS Center for Excellence in Life and Paleoenvironment, Beijing, Beijing, China.
PeerJ. 2021 Aug 20;9:e11957. doi: 10.7717/peerj.11957. eCollection 2021.
Brachiosauridae is a lineage of titanosauriform sauropods that includes some of the most iconic non-avian dinosaurs. Undisputed brachiosaurid fossils are known from the Late Jurassic through the Early Cretaceous of North America, Africa, and Europe, but proposed occurrences outside this range have proven controversial. Despite occasional suggestions that brachiosaurids dispersed into Asia, to date no fossils have provided convincing evidence for a pan-Laurasian distribution for the clade, and the failure to discover brachiosaurid fossils in the well-sampled sauropod-bearing horizons of the Early Cretaceous of Asia has been taken to evidence their genuine absence from the continent. Here we report on an isolated sauropod maxilla from the middle Cretaceous (Albian-Cenomanian) Longjing Formation of the Yanji basin of northeast China. Although the specimen preserves limited morphological information, it exhibits axially twisted dentition, a shared derived trait otherwise known only in brachiosaurids. Referral of the specimen to the Brachiosauridae receives support from phylogenetic analysis under both equal and implied weights parsimony, providing the most convincing evidence to date that brachiosaurids dispersed into Asia at some point in their evolutionary history. Inclusion in our phylogenetic analyses of an isolated sauropod dentary from the same site, for which an association with the maxilla is possible but uncertain, does not substantively alter these results. We consider several paleobiogeographic scenarios that could account for the occurrence of a middle Cretaceous Asian brachiosaurid, including dispersal from either North America or Europe during the Early Cretaceous. The identification of a brachiosaurid in the Longshan fauna, and the paleobiogeographic histories that could account for its presence there, are hypotheses that can be tested with continued study and excavation of fossils from the Longjing Formation.
腕龙科是泰坦巨龙形蜥脚类恐龙的一个分支，其中包括一些最具代表性的非鸟类恐龙。在北美洲、非洲和欧洲，从晚侏罗世到早白垩世的腕龙科化石是无可争议的，但在此范围之外的疑似化石发现一直存在争议。尽管偶尔有人提出腕龙科扩散到了亚洲，但迄今为止，没有化石能为该类群在泛劳亚大陆的分布提供令人信服的证据，而且在亚洲早白垩世富含蜥脚类恐龙化石且采样充分的地层中未能发现腕龙科化石，这被视为它们确实未在该大陆存在的证据。在此，我们报告了一件来自中国东北延吉盆地中白垩世（阿尔布阶—赛诺曼阶）龙井组的孤立蜥脚类恐龙上颌骨。尽管该标本保存的形态信息有限，但它显示出轴向扭曲的齿列，这是一个共同的衍生特征，目前仅在腕龙科中发现。在同等加权和隐含加权简约法的系统发育分析下，将该标本归入腕龙科得到了支持，这提供了迄今为止最令人信服的证据，表明腕龙科在其进化历史中的某个时期扩散到了亚洲。将来自同一地点的一件孤立蜥脚类恐龙齿骨纳入我们的系统发育分析中（该齿骨与上颌骨可能有关联，但不确定），并未实质性改变这些结果。我们考虑了几种古生物地理情景，这些情景可以解释中白垩世亚洲腕龙科的出现，包括在早白垩世从北美洲或欧洲扩散而来。在龙山动物群中鉴定出腕龙科，以及可以解释其存在的古生物地理历史都是假设，可以通过对龙井组化石进行持续的研究和挖掘来检验。
