Scientists have named the first definite horned dinosaur1 species from the Early Cretaceous in North America, according to a study published December 10, 2014 in the open-access journal PLOS ONE by Andrew Farke from Raymond M. Alf Museum of Paleontology and colleagues. The limited fossil record for neoceraTOPsian--or horned dinosaurs--from the Early Cretaceous in North America restricts scientists ability to reconstruct the early evolution of this group. The authors of this study have discovered a dinosaur skull2 in Montana that represents the first horned dinosaur from the North American Early Cretaceous that they can identify to the species level. The authors named the dinosaur Aquilops americanus, which exhibits definitive3 neoceraTOPsian features and is closely related to similar species in Asia. The skull is comparatively small, measuring 84 mm long, and is distinguished4 by several features, including a strongly hooked rostral bone, or beak-like structure, and an elongated5 and sharply pointed6 cavity over the cheek region. When alive, the authors estimate it was about the size of a crow.This discovery, combined with neoceraTOPsian fossil records from elsewhere, allows the authors to support a late Early Cretaceous intercontinental migratory7 event between Asia and North America, as well as support for a complex set of migratory events for organisms between North America and Asia later in the Cretaceous. However, to better reconstruct the timing8 and mode of these events, additional fieldwork will be necessary.Aquilops lived nearly 20 million years before the next oldest horned dinosaur named from North America, said Andrew Farke. Even so, we were surprised that it was more closely related to Asian animals than those from North America.
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1 dinosaur n.恐龙 参考例句： Are you trying to tell me that David was attacked by a dinosaur你是想要告诉我大卫被一支恐龙所攻击？ He stared at the faithful miniature of the dinosaur.他凝视著精确的恐龙缩小模型。
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