Nonmarine turtles from the Aguja Formation (Late Cretaceous, Campanian) of Chihuahua, Mexico
Nonmarine turtles from the Aguja Formation (Late Cretaceous, Campanian) of Chihuahua, Mexico
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来自墨西哥奇瓦瓦州阿古贾组（白垩纪晚期，坎帕尼亚）的海龟
DOI：
10.1016/j.jsames.2020.102668
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发表时间：
2020
影响因子：
1.8
通讯作者：
M. Montellano
中科院分区：
文献类型：
--
作者：
Oliver A. López;María L. Chavarría;M. Montellano
在墨西哥的几个上白垩纪地层中发现了龟壳碎片，包括索诺拉州的 Corral de Enmedio 和 Packard 页岩；阿古贾和普韦布洛山，科阿韦拉州；奇瓦瓦州圣卡洛斯；下加利福尼亚州埃尔加洛；和恰帕斯州奥科索科奥特拉。海龟是北美洲上白垩纪脊椎动物群的重要成员，被认为是定义生物地理模式的有用工具。阿古贾组中暴露的上白垩统沉积岩记录了西部内陆白垩纪海道的最终海侵/海退序列以及随后从海洋环境到陆地环境的转变。与北美其他地方这些地层的相关暴露相比，露头的总面积很小，尽管如此，仍然收集到了大量的无脊椎动物和脊椎动物化石。德克萨斯州的阿古贾地层保留了北美最南端的上白垩纪（坎帕尼亚）陆生脊椎动物群之一；与奇瓦瓦州北部露头的情况相反，那里的陆生脊椎动物记录很少，尤其是与陆龟相关的记录。阿古贾地层的非海洋地层似乎并不存在于墨西哥更南部的地方，这就是阿古贾动物群与记录坎帕尼亚大陆动物群落的纬度变化相关的原因。本文综述了从奇瓦瓦州阿古贾组三个地点收集的上白垩纪海龟的丰富度。根据具有独特雕刻图案的贝壳碎片识别了六个分类群：干隐菌属，包括 cf. Baenidae，参见 Denazinemys nodosa 和 cf.Compsemys victa，以及冠群隐甲目，包括三甲虫（trionchids 和 Basilemyssp.）和动胸类（参见 Yelmochelys rosarioae）。随着这些类群的认识，阿古贾组（例如 cf.Yelmochelys rosarioae）和墨西哥（例如 cf.Denazinemys nodosa）出现了新的记录。对阿古贾组和墨西哥白垩纪海龟丰富度的了解增加了，并证实了北美地区丰富度变异性的建议。这种纬度变化表明，在任何时候，海龟都会有一个受气候控制的北部分布界限，并且当达到这个界限时，海龟的丰富度就会下降。
Fragments of turtle shell are known from several Upper Cretaceous formations in Mexico, including Corral de Enmedio and Packard Shale, Sonora; Aguja and Cerro del Pueblo, Coahuila; San Carlos, Chihuahua; El Gallo, Baja California; and Ocozocoautla, Chiapas. Turtles are important members of Upper Cretaceous vertebrate assemblages throughout North America and are considered a useful tool to define biogeographic patterns. The Upper Cretaceous sedimentary rocks exposed in the Aguja Formation record the final transgressive/regressive sequence of the Western Interior Cretaceous Seaway and the subsequent transition from a marine to terrestrial environment. The total area of outcrops is small compared to correlative exposures of these strata elsewhere in North America, in spite of this, numerous invertebrate and vertebrate fossils have been collected. The Aguja Formation in Texas preserves one of the southernmost well-studied Upper Cretaceous (Campanian) terrestrial vertebrate faunas in North America; contrary to what happens with the outcrops in northern Chihuahua, where the record of terrestrial vertebrates is scarce and especially those related to Testudines. Non-marine strata of the Aguja Formation do not appear to be present farther south in Mexico, and this is the reason why the Aguja fauna is relevant to documenting latitudinal variation in Campanian continental faunal associations. In this paper, the richness of Upper Cretaceous turtles collected from three localities within the Aguja Formation in Chihuahua is reviewed. Six taxa are recognized based on shell fragments with distinctive sculpture patterns: stem cryptodires, including cf. Baenidae, c.f.Denazinemys nodosaand cf.Compsemys victa, and crown group cryptodires including trionychians (trionchids andBasilemyssp.) and a kinosternoid (cf.Yelmochelys rosarioae). With the recognition of these taxa, new records are reported for the Aguja Formation (e.g. cf.Yelmochelys rosarioae) and Mexico (e.g. c.f.Denazinemys nodosa). The knowledge of Cretaceous turtle richness of the Aguja Formation and Mexico is increased and confirms the proposal of the variability richness along the North American localities. This latitudinal variability suggests that at any time turtles would have had a climatically controlled northern limit of distribution, and the richness of turtles would have decreased as this limit was reached.