Martin-Silverstone Elizabeth, Witton Mark P, Arbour Victoria M, Currie Philip J
Ocean and Earth Science, National Oceanography Centre, University of Southampton, European Way, Southampton SO14 3ZH, UK; School of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol BS8 1RJ, UK.
School of Earth and Environmental Sciences , University of Portsmouth , Burnaby Building, Burnaby Road, Portsmouth PO1 3QL , UK.
R Soc Open Sci. 2016 Aug 31;3(8):160333. doi: 10.1098/rsos.160333. eCollection 2016 Aug.
Pterosaur fossils from the Campanian-Maastrichtian of North America have been reported from the continental interior, but few have been described from the west coast. The first pterosaur from the Campanian Northumberland Formation (Nanaimo Group) of Hornby Island, British Columbia, is represented here by a humerus, dorsal vertebrae (including three fused notarial vertebrae), and other fragments. The elements have features typical of Azhdarchoidea, an identification consistent with dominance of this group in the latest Cretaceous. The new material is significant for its size and ontogenetic stage: the humerus and vertebrae indicate a wingspan of 1.5 m, but histological sections and bone fusions indicate the individual was approaching maturity at time of death. Pterosaurs of this size are exceedingly rare in Upper Cretaceous strata, a phenomenon commonly attributed to smaller pterosaurs becoming extinct in the Late Cretaceous as part of a reduction in pterosaur diversity and disparity. The absence of small juveniles of large species-which must have existed-in the fossil record is evidence of a preservational bias against small pterosaurs in the Late Cretaceous, and caution should be applied to any interpretation of latest Cretaceous pterosaur diversity and success.
北美坎帕阶-马斯特里赫特阶的翼龙化石已在大陆内部被报道,但来自西海岸的此类化石却鲜有描述。本文所呈现的不列颠哥伦比亚省霍恩比岛坎帕阶诺森伯兰组(纳奈莫群)的第一只翼龙化石,包含一根肱骨、背椎(包括三块融合的荐椎)以及其他碎片。这些化石具有阿兹达奇超目典型的特征,这一鉴定结果与该类群在晚白垩世的主导地位相符。新材料因其尺寸和个体发育阶段而具有重要意义:肱骨和椎骨表明其翼展达1.5米,但组织切片和骨骼融合显示该个体在死亡时已接近成熟。这种尺寸的翼龙在上白垩统地层中极为罕见,这一现象通常归因于较小的翼龙在晚白垩世灭绝,这是翼龙多样性和差异度降低的一部分。化石记录中缺少大型物种的小幼体(它们必然存在过),这证明了晚白垩世对小型翼龙存在保存偏差,因此在对晚白垩世翼龙的多样性和成功进行任何解读时都应谨慎。