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Miocene Freshwater Dolphins from La Venta, Huila, Colombia Suggest Independent Invasions of Riverine Environments in Tropical South America
Journal of Vertebrate Paleontology ( IF 1.4 ) Pub Date : 2020-10-08 , DOI: 10.1080/02724634.2020.1812078
Aldo Benites-Palomino 1, 2, 3 , Gabriel Aguirre-Fernández 1 , Jorge W. Moreno-Bernal 2, 4 , Andres Vanegas 5 , Carlos Jaramillo 2, 6
Affiliation  

ABSTRACT

The two extant genera of strictly freshwater dolphins Inia and Platanista are the result of convergent evolution to freshwater environments with reduced visibility. Characterized by their long snout and small melon, these extant taxa are clustered into two clades, Iniidae in South America and Platanistidae in Southern Asia. Their evolutionary history leading to freshwater environments remains mostly unknown, because many of their related fossil species have been found in marine environments. Here, we report riverine dolphin remains (two rostral fragments and a periotic) from two stratigraphic levels of the late middle Miocene (ca. 12.5 Ma) from La Venta, Colombia. The periotic has a reduced cochlear aqueduct mediodorsally oriented, the anterior process is relatively thin, and the dorsal opening of the facial canal is located lateral to the spiral cribriform tract. The rostral fragments are dorsoventrally flattened; the mandible features two longitudinal ventral grooves, and the premaxilla-maxilla suture of the rostrum is located in a deep lateral groove. These characteristics indicate that the specimens belong to Platanistidae, the lineage of the Ganges river dolphin Platanista. Platanistids had also been recorded on coeval strata from the Fitzcarrald arch, Peru. The occurrence of middle Miocene platanistids in both the La Venta and Fiztcarrald localities suggests that members of this lineage moved into freshwater environments in South America earlier than the ancestors of the modern Amazon river dolphin Inia. The subsequent collapse of the Pebas ecosystem could have played a role in the extinction of non-marine Platanistoidea in South America.



中文翻译:

来自哥伦比亚惠拉La Venta的中新世淡水海豚表明,南美热带地区河流环境的独立入侵

摘要

严格淡水海豚伊尼亚普拉塔尼斯塔的两个现存属是向低能见度汇聚到淡水环境的结果。这些现存的类群以长鼻子和小瓜为特征,聚集成两个分支,南美的Iniidae和南亚的Platanistidae。它们导致淡水环境的进化历史仍然鲜为人知,因为它们的许多相关化石物种都是在海洋环境中发现的。在这里,我们报道了来自哥伦比亚拉万塔中中新世晚期(约12.5 Ma)的两个地层水平的河豚遗骸(两个有喙的碎片和一个蠕动岩)。腹膜的耳蜗导水管向中音方向减少,前突较薄,面管的背侧开口位于筛网状筛道的外侧。延髓头端被扁平化。下颌骨具有两个纵向腹侧沟,并且讲台的上颌前-上颌缝合线位于深侧沟中。这些特征表明这些标本属于恒河豚的血统PlatanistidaePlatanista。在秘鲁菲茨卡拉德拱门的中世纪地层中也记录了普拉坦类动物。拉文塔(La Venta)和菲茨卡尔拉德(Fiztcarrald)地区都出现中世中新世platanistids,这表明该世系的成员早于现代亚马逊河海豚伊尼亚(Inia)的祖先进入了南美的淡水环境。随后的Pebas生态系统崩溃可能在南美非海洋Platanistoidea灭绝中发挥了作用。

更新日期:2020-10-08
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