Laboratoire de Paléontologie, Institut des Sciences de l'Évolution de Montpellier (ISE-M, UMR 5554, CNRS/UM/IRD/EPHE), c.c. 064, Université de Montpellier (UM), Place Eugène Bataillon, 34095 Montpellier Cedex 05, France.
Department of Mammalogy, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA.
Proc Biol Sci. 2020 Feb 12;287(1920):20192806. doi: 10.1098/rspb.2019.2806.
By their past and present diversity, rodents are among the richest components of Caribbean land mammals. Many of these became extinct recently. Causes of their extirpation, their phylogenetic affinities, the timing of their arrival in the West Indies and their biogeographic history are all ongoing debated issues. Here, we report the discovery of dental remains from Lower Oligocene deposits ( 29.5 Ma) of Puerto Rico. Their morphology attests to the presence of two distinct species of chinchilloid caviomorphs, closely related to dinomyids in a phylogenetic analysis, and thus of undisputable South American origin. These fossils represent the earliest Caribbean rodents known thus far. They could extend back to 30 Ma the lineages of some recently extinct Caribbean giant rodents ( and ), which are also retrieved here as chinchilloids. This new find has substantial biogeographic implications because it demonstrates an early dispersal of land mammals from South America to the West Indies, perhaps via the emergence of the Aves Ridge that occurred 35-33 Ma (GAARlandia hypothesis). Considering both this new palaeontological evidence and recent molecular divergence estimates, the natural colonization of the West Indies by rodents probably occurred through multiple and time-staggered dispersal events (chinchilloids, then echimyid octodontoids (spiny rats/hutias), caviids and lastly oryzomyin muroids (rice rats)).
通过它们过去和现在的多样性，啮齿动物是加勒比地区陆地哺乳动物中最丰富的组成部分之一。其中许多最近已经灭绝。它们灭绝的原因、它们的系统发育关系、它们到达西印度群岛的时间以及它们的生物地理历史都是正在争论的问题。在这里，我们报告了在波多黎各下始新世（2950 万年前）沉积物中发现牙齿遗骸的情况。它们的形态证明了两种不同的 chinchilloid 有袋动物的存在，在系统发育分析中与 dinomyids 密切相关，因此具有无可争议的南美起源。这些化石代表了迄今为止已知的最早的加勒比啮齿动物。它们可以将一些最近灭绝的加勒比巨型啮齿动物（和）的谱系追溯到 3000 万年前，这些啮齿动物也在这里被归为 chinchilloid。这一新发现具有重要的生物地理意义，因为它证明了陆地哺乳动物从南美洲向西印度群岛的早期扩散，可能是通过发生在 35-3300 万年前的鸟类脊（GAARlandia 假说）。考虑到这一新的古生物学证据和最近的分子分歧估计，啮齿动物对西印度群岛的自然殖民可能是通过多次和时间交错的扩散事件发生的（chinchilloid，然后是 echimyid octodontoids（刺鼠/hutias）、caviids 和最后的 oryzomyin muroids（rice rats））。
