Abstract:

The Neogene interval witnessed three major waves of intercontinental dispersals by carnivoran mammals, mainly migrating from Eurasia to North America but with rare occurrences going in the opposite direction (e.g., Sthenictis, Leptarctus). The timing and composition of dispersers are thought to be controlled by filter-bridge mechanisms, but it is unclear what types of regional conditions promoted occasional dispersals outside of the three major waves. We study and report on new occurrences of small-bodied carnivorans from late Clarendonian-aged Black Hawk Ranch and Cuyama Valley fossil mammal assemblages in California. The relatively late occurrences of the mustelids Sthenictis and Hoplictis and the ailurid Alopecocyon in coastal regions of western North America suggest that nearshore dispersal corridors both facilitate and preserve faunal elements later than they might otherwise occur further inland. The availability of both marine- and terrestrially-derived food resources may be an important factor in allowing coastally dispersing taxa to be accommodated in those ecological communities compared to less heterogenous environments further inland.

Key words: California, Cenozoic, paleobiogeography, mammals, Carnivora

摘要： 全北界的新近纪脊椎动物化石记录了至少三次大规模的食肉类动物迁移，物种在北美和欧亚大陆之间双向交流。参与这些大规模迁移的类群以及其事件发生的地质年代被认为受白令陆桥过滤性机制主导，但是目前对于在这三波主要的迁移事件之外更罕见的其他物种迁徙现象却缺乏类似的框架来诠释。针对美国加利福尼亚州晚中新世Black Hawk Ranch (黑鹰牧场)和Cuyama Valley (库亚玛谷)动物群里还未报道的小型食肉类化石进行了描述和研究。结果显示鼬科Sthenictis, Hoplictis两个属和小熊猫科Alopecocyon属在北美洲西部的化石记录相对这些属在其他全北界的化石出现时代更晚，这表明北美洲西部沿岸的迁移路线可能代表了比内陆地区更为稳定和有利的生态环境，甚至可能作为残遗种的保护区。居住于现代沿海生态过渡地区的哺乳动物群拥有同时利用海生和陆生资源的地理优势，这一现象指示晚中新世时期，加州、俄勒冈州及华盛顿州一带的生态环境条件可能是促进跨大陆迁移成功的重要因素之一。

关键词: 加利福尼亚, 新生代, 动物地理, 哺乳动物, 食肉目