Paleontological Study of Hemphillian (Late Miocene to Early Pliocene) Vertebrate Localities in Central Mexico

已知的晚亨菲利亚（上新世早期）陆生脊椎动物遗址在墨西哥是罕见的，显然，在该国任何地方都没有明确的早期亨菲利亚化石（晚中新世）的报道（这些时代的化石在整个中美洲都极为罕见）。在目前提出的研究范围之外，只报告了三个亨菲利亚时代晚期的地点：伊达尔戈州的特韦契拉；米却肯州的La Goleta（可能比Hemphillian时代的化石包含更多的Blancan化石）；以及北部奇瓦瓦州的耶波梅拉。前两个地点没有很好的地层学记录，尽管第三个，也是最有生产力的地点，有。然而，它位于美墨边境以南约150英里处。在目前提出的研究区域内，位于墨西哥中部瓜纳华托州的中东部，有两个报道的亨菲利亚脊椎动物遗址。其中一个是El Ocote，已经在几份报告中讨论过；另一种是Coecillo，尚未被很好地收集或研究。第三个是新发现的Rinconada。最后一个遗址包含了大量保存完好的化石，这些化石似乎代表了早期和晚期亨菲利亚人的形态。了解来自中美洲的早期亨非利亚脊椎动物很重要，原因有几个。这些包括更好地理解晚新生代北美和南美之间最早的扩散时间，确定扩散是偶发的还是连续的，比较中美洲相对不太为人所知的亨菲利亚动物群和美国知名的亨菲利亚动物群，以及关于许多突然出现在美国大平原地区的哺乳动物属和物种的起源和多样化的宝贵信息，这些哺乳动物可能是在墨西哥高原上进化而来的。这些属和种包括马和环状啮齿动物等重要群体。此外，在拟议的研究期间收集的数据将提供关于在一个重要时间间隔内气候和生态条件变化的宝贵信息。这项拟议研究的主要目的是在林科纳达和科西略遗址的地层背景下仔细收集化石和数据。清洗化石将是行动的一部分。然后准备和研究化石，以获得与上述项目相关的知识。

Known late Hemphillian (Early Pliocene) terrestrial vertebrate sites are rare in Mexico, and apparently, unequivocal early Hemphillian fossils (Late Miocene) have not yet been reported from anywhere in the country (fossils of these ages are extremely rare in all Central America). Outside the area of the presently proposed study only three localities of late Hemphillian age have been reported: Tehuichila in the state of Hidalgo; La Goleta in the state of Michoacan (which probably contains more Blancan than Hemphillian age fossils); and Yepomera in the northern state of Chihuahua. The first two sites have not been well documented stratigraphically, although the third, and most productive site, has. It is, however, only about 150 miles south of the U.S.-Mexican border. Inside the presently proposed study area, which lies within the east- central part of the state of Guanajuato in central Mexico, are two reported Hemphillian vertebrate sites. One, El Ocote, has been discussed in several reports; the other, Coecillo, has not been well collected or studied. A third, Rinconada, is newly discovered. The last site contains very abundant, well preserved fossils which appear to represent early as well as late Hemphillian forms. Knowledge of early Hemphillian vertebrates from Central America would be important for several reasons. These include a better understanding of the earliest times of dispersals in the Late Cenozoic between North and South America, determination whether dispersals were episodic rather than continual, comparison of relatively poorly known Hemphillian faunas in Central America with well known ones in the United States, and valuable information concerning the origin and diversification of a number of mammalian genera and species which appeared suddenly in the United States' Great Plains area that probably evolved on the Mexican Plateau. These genera and species include such important groups as horses and cricetid rodents. Additionally, data gathered during the proposed research would provide valuable information on changing climatic and ecologic conditions during an important time interval. The major objective of this proposed research is to carefully collect fossils and data in a stratigraphic context at the Rinconada and Coecillo sites. Screen washing for fossils would be part of the operation. Fossils would then be prepared and studied in order to obtain knowledge relevant to the items stated above.