ABSTRACT

The Birket Qarun Formation, sampling upper Eocene deposits of the Fayum Depression, has been the subject of disagreement in terms of the environmental deposition. The formation has traditionally been considered to be a marine deposit but, more recently, one particular site, Birket Qarun Locality 2 (BQ-2), has been reported to have freshwater vertebrates, indicating that at least this locality in the formation contains terrestrial deposits. We here report a new varied assemblage of fossil catfishes from BQ-2, which adds new information with which to interpret the paleoenvironment of the locality. The new BQ-2 catfish assemblage includes the earliest record of the freshwater family Bagridae in Africa, as well as the oldest records of Fajumia and Socnopaea, otherwise known only from the overlying marine deposits of the Qasr el-Sagha Formation. Notable among the finds are remains of Arius fraasi and two additional species of marine ariid catfishes, representing the first such occurrences from the Fayum deposits. These occurrences indicate that BQ-2 likely had marine influences, or perhaps that Fajumia, Socnopaea, and Arius were euryhaline. In addition, the freshwater families Claroteidae and Mochokidae are represented among our collection. The new material documents the presence of a variety of taxa, and in addition it documents the variation in body size of members of the same family. Most evidence from other vertebrate fossils indicates that BQ-2 is a freshwater deposit, but some elements of the new catfish collection suggest the presence of nearshore marine influences, indicating that a much more complex environment was present.

摘要

在Fayum凹陷的上新世沉积中取样的Birket Qarun组在环境沉积方面一直存在争议。传统上，该地层被认为是海洋沉积物，但是最近，据报道有一个特定地点Birket Qarun Locality 2（BQ-2）拥有淡水脊椎动物，这表明该地层中至少该位置包含陆生沉积物。 。我们在这里报告了来自BQ-2的化石cat鱼的新组合，它增加了新信息，可用来解释该地区的古环境。新的BQ-2 fish鱼组合包括非洲淡水家族Bagridae的最早记录，以及Fajumia和Socnopaea的最古老记录。，否则只能从Qasr el-Sagha组上覆的海相沉积中得知。这些发现中值得注意的是Arius fraasi遗骸和另外两个海洋干旱id鱼物种，代表了Fayum矿床中的首例此类事件。这些事件表明BQ-2可能对海洋有影响，或者表明Fajumia，Socnopaea和Arius是euryhaline。此外，淡水科Claroteidae和Mochokidae也代表了我们的收藏。新材料记录了各种分类单元的存在，此外，它记录了同一家庭成员体型的变化。来自其他脊椎动物化石的大多数证据表明，BQ-2是淡水沉积物，但是新的cat鱼收集的某些元素表明存在近岸海洋影响，表明存在更为复杂的环境。