Brownstein Chase Doran
Stamford Museum and Nature Center , Stamford, CT , USA.
PeerJ. 2017 Mar 8;5:e3110. doi: 10.7717/peerj.3110. eCollection 2017.
The fossil record of dinosaurs from the Early Cretaceous of Eastern North America is scant, especially since a few stratigraphic units from the east are fossiliferous. Among these stratigraphic units, the Arundel Clay of the eastern seaboard has produced the best-characterized dinosaur faunas known from the Early Cretaceous of Eastern North America. The diverse dinosaur fauna of the Arundel Clay has been thoroughly discussed previously, but a few of the dinosaur species originally described from the Arundel Clay are still regarded as valid genera. Much of the Arundel material is in need of review and redescription. Among the fossils of dinosaurs from this stratigraphic unit are those referred to ornithomimosaurs. Here, the researcher describes ornithomimosaur remains from the Arundel Clay of Prince George's County, Maryland which may be from two distinct ornithomimosaur taxa. These remains provide key information on the theropods of the Early Cretaceous of Eastern North America. Recent discoveries of small theropod material from the Arundel Clay possibly belonging to ornithomimosaurs are also reviewed and described for the first time. The description of the Arundel material herein along with recent discoveries of basal ornithomimosaurs in the past 15 years has allowed for comparisons with the coelurosaur , suggesting the latter animal was a basal ornithomimosaur rather than a "generalized" coelurosaur as it was originally described. Comparisons between the Arundel ornithomimosaur material and similar Asian and European specimens suggest that both extremely basal ornithomimosaurs and more intermediate or derived forms may have coexisted throughout the northern hemisphere during the Early Cretaceous.
北美东部早白垩世恐龙的化石记录稀少，尤其是因为东部的一些地层单元富含化石。在这些地层单元中，东部沿海的阿伦德尔黏土产出了北美东部早白垩世已知特征最明显的恐龙动物群。阿伦德尔黏土丰富多样的恐龙动物群此前已得到充分讨论，但最初从阿伦德尔黏土描述的一些恐龙物种仍被视为有效属。阿伦德尔的许多化石材料需要重新审视和描述。在这个地层单元的恐龙化石中，有一些被归为似鸟龙类。在此，研究人员描述了来自马里兰州乔治王子县阿伦德尔黏土的似鸟龙遗骸，这些遗骸可能来自两个不同的似鸟龙类群。这些遗骸为北美东部早白垩世的兽脚亚目恐龙提供了关键信息。最近在阿伦德尔黏土中发现的可能属于似鸟龙类的小型兽脚亚目恐龙化石材料也首次得到了回顾和描述。本文对阿伦德尔化石材料的描述以及过去15年中基础似鸟龙类的最新发现，使得与虚骨龙类进行比较成为可能，这表明后者是基础似鸟龙类，而非最初描述的“广义”虚骨龙类。对阿伦德尔似鸟龙化石材料与类似的亚洲和欧洲标本的比较表明，在早白垩世期间，极其基础的似鸟龙类和更多中间或衍生形态可能在整个北半球共存。
