Neogene sloth assemblages (Mammalia, Pilosa) of the Cocinetas Basin (La Guajira, Colombia): implications for the Great American Biotic Interchange

We describe sloth assemblages from the Cocinetas Basin (La Guajira peninsula, Colombia), found in the Neogene Castilletes and Ware formations, located in northernmost South America, documenting otherwise poorly known biotas. The tentative referral of a specimen to a small megatherioid sloth, Hyperleptus?, from the early–middle Miocene Castilletes Formation, suggests affinities of this fauna with the distant Santa Cruz Formation and documents a large latitudinal distribution for this taxon. The late Pliocene Ware Formation is much more diverse, with five distinct taxa representing every family of ‘ground sloths’. This diversity is also remarkable at the ecological level, with sloths spanning over two orders of magnitude of body mass and probably having different feeding strategies. Being only a few hundred kilometres away from the Isthmus of Panama, and a few hundred thousand years older than the classically recognized first main pulse of the Great American Biotic interchange (GABI 1), t...本研究记述了产自南美洲最北端哥伦比亚瓜希拉半岛科西内塔斯盆地的树懒化石组合，该组合发现于新近纪卡斯蒂列斯组（Castilletes Formation）与瓦尔组（Ware Formation）中，填补了此前鲜为人知的生物群的记录空白。针对早中新世-中中新世卡斯蒂列斯组中的一件标本，我们将其暂归入小型大地懒类树懒（megatherioid sloth）*Hyperleptus*？属，这一归类表明该动物群与遥远的圣克鲁斯组（Santa Cruz Formation）存在亲缘关联，同时证实了该类群拥有广阔的纬度分布范围。晚上新世的瓦尔组物种多样性显著更高，共包含5个独立类群，涵盖了所有‘地懒’科的类群。该类群的生态多样性同样引人注目：树懒类的体重跨度超过两个数量级，且大概率具备各异的取食策略。该盆地距巴拿马地峡仅数百公里，其生物群的形成时间较经典认知中首次主要生物交换脉冲——大美洲生物群交换（Great American Biotic interchange, GABI 1）——早数十万年，……