Paleoecological and taphonomical aspects of the Late Miocene vertebrate coprolites (Urumaco Formation) of Venezuela
Paleoecological and taphonomical aspects of the Late Miocene vertebrate coprolites (Urumaco Formation) of Venezuela
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DOI：
10.1016/j.palaeo.2017.11.048
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发表时间：
2018-01-15
影响因子：
3
通讯作者：
Sanchez, Rodolfo
中科院分区：
文献类型：
--
作者：
Dentzien-Dias, Paula;Carrillo-Briceno, Jorge Domingo;Sanchez, Rodolfo
粪化石（化石粪便）提供了重要的古生态信息，如生产者的饮食，寄生虫感染和肠道微生物群，这些信息不能通过尸体遗骸获得。位于委内瑞拉西部的上中新统Urumaco组有多种脊椎动物群，包括地懒、啮齿动物、爬行动物、鱼类和两栖动物以及粪化石。在这里，我们描述了106粪化石产生的一系列肉食性和草食性脊椎动物，分为五个不同的形态类型的基础上，他们的大小和形状，建议不同的生产者。草食性形态型（M1、M2和M5）是最丰富的（59%）。在这些粪化石中最常见的内含物是禾本科残余物，尽管也发现了真双子叶植物的碎片、细菌和蓝细菌细丝。Ml形态型具有带纵向凹槽的子弹形状; M2形态型为圆形至椭圆形，具有至少一个独特的锥形端部;并且M5形态型为具有粗糙表面和圆形端部的短圆柱体。与此相反，M3和M4的形态型被我们归因于食肉动物，并有不同的内含物。而M3是一个大圆柱体，有圆形的末端，含有细菌，线虫卵和植硅体，M4是香肠形的，里面保存着肌肉细胞。根据共生动物群和粪化石的形态，推测可能的生产者如下：M1，啮齿动物; M2，无蹄动物; M3，鳄鱼; M4，不确定的食肉动物;和M5，海兽。在地质记录中，在同一地层甚至同一露头中保存有细菌、寄生虫和肌肉的食草性和食肉性粪化石是罕见的。这种独特的关联和保存表明早期的岩化作用是由快速埋藏促进的，尽管在单个标本中存在的钻孔痕迹表明一定程度的时间平均化。
Coprolites (fossil feces) provide important paleoecological information, such as diet of the producer, parasite infestation and gut microbiota, which cannot be accessed through body remains. The Upper Miocene Urumaco Formation, in western Venezuela, has a diverse vertebrate fauna composed of ground sloths, rodents, reptiles, fishes and amphibians, as well as coprolites. Here we describe 106 coprolites produced by a range of carnivorous and herbivorous vertebrates, classified into five different morphotypes based on their size and shape, suggesting different producers. Herbivorous morphotypes (Ml, M2 and M5) are the most abundant (59%). The most common inclusions in these coprolites are Poaceae remains, although Eudicotyledoneae fragments, bacteria and cyanobacteria filaments were also found. The Ml morphotype has a bullet shape with longitudinal grooves; the M2 morphotype is rounded to oval, with at least one distinctive tapered end; and the M5 morphotype is a short cylinder with a rough surface, and rounded ends. In contrast, the morphotypes M3 and M4 are attributed by us to carnivores and have different inclusions. While M3 is a large cylinder with rounded ends and contains bacteria, nematode eggs and phytoliths, M4 is sausage-shaped and has muscle cells preserved inside. Based on the co-occurring fauna and the morphology of the coprolites, the probable producers were inferred as the following: Ml, a rodent; M2, a notoungulate; M3, a crocodilian; M4, an indeterminate carnivore; and M5, a sirenian. The preservation of herbivorous and carnivorous coprolites with bacterial, parasitological and muscle remains in the same formation and even the same outcrop is rare in the geological record. This unique association and preservation suggests early lithification promoted by rapid burial, although the presence of the boring trace Gastrochaenolites in a single specimen indicates some degree of time-averaging.