From the Ludwig-Maximilians-Univerität München in Germany:
Fossil fishes found in Kenya
A paleontological expedition to the Tugen Hills in Kenya, led by LMU’s Professor Bettina Reichenbacher, has discovered assemblages of fossil fish at eight previously unexplored localities. “Not only is it very rare to uncover so many specimens of fossil fish, those we have found are also very well preserved,” says Reichenbacher.
The new fossils are between 10 and 12 million years old, and will shed light on the evolutionary history of freshwater fish in East Africa. Moreover, the find is of wider significance, as the anatomy of the various forms is not only of interest to paleontologists. The specimens also provide insights into the ecological and climatic conditions that prevailed in the region during the Middle Miocene. “For instance, we can tell whether these fish lived in tropical lakes or in drier habitats that were subject to periodic droughts,” says Bettina Reichenbacher. This kind of information will help researchers pinpoint the onset of dry conditions in the Middle Miocene, when tropical forests were gradually replaced by open grassland with less tree cover. This is of great interest, as the transformation of woodland into savannah is thought to have favored the diversification of hominids, the evolutionary lineage to which modern humans belong.
The new find site is located in the section of the Rift Valley that runs through Kenya. A whole succession of exciting finds made here by paleoanthropologists since the middle of the last century has made this area one of the most important sources of hominid fossils in the world, and has led to its being dubbed “the cradle of humanity.”
Previously unknown species
“We assume that the fish succumbed to the effects of volcanic activity. The jaws of many individuals are agape, which suggests that they were asphyxiated,” says Bettina Reichenbacher. Volcanism could also account for their good state of preservation. They may have been rapidly buried under layers of volcanic ash, which would have protected them from early post-mortem decay and subsequent erosion.
The researchers expect to identify previously unknown species among the many specimens that they have recovered. Africa today is home to approximately 3000 species of freshwater fish, but this diversity is not reflected in the known fossil record. Fewer than 60 fossil species have been described from the continent, partly because most finds consist of isolated teeth and bones. “Further investigation of the fossils we have found will provide us with valuable information about the evolution of the fish fauna not only in Kenya, but in the whole of Africa,” says Bettina Reichenbacher.
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