New records of fossil 'waterbirds' from the Miocene of Kenya

摘要

We present a number of new fossil records of "waterbirds" (encompassing several of the traditional living orders of birds) from three important Miocene deposits in western Kenya. These sites surround Lake Victoria-the Ngorora Formation and sediments at Maboko and Rusinga Islands (Kula Formation)-are well-known hominoid localities, and have yielded a diverse assemblage of contemporary fossil mammals. Previously identified avians from this area include a marabou stork (Leptoptilos sp.), the fossil flamingo Leakeyornis aethiopicus, as well as a number of additional unidentified phoenicopterid (flamingo) remains. We add records of an anhinga (Anhinga cf. pannonica), two storks (Ciconia minor, C cf. ciconialnigra), a night heron (Nyeticorax cf. nycticorax) and a threskyornithid (the group that includes the ibises and spoonbills) to the known diversity of Kenyan Miocene waterbirds. We also illustrate, for the first time, the holotype and paratype material of the Kenyan Miocene flamingo Leakeyornis aethiopicus. Comparisons with other known sites of this age across northern Africa, the Mediterranean and northern Pakistan suggest that Miocene waterbird faunas in this region were very similar in their compositions. While Anhinga pannonica, Ciconia minor, and Ciconia ciconia are documented from other Miocene sites across the region, the osteologically distinct fossil flamingo Leakeyornis appears to have been restricted to East Africa. All the avian groups recorded from these Kenyan Miocene sites represent extant genera, in contrast to the described, fossil mammals. As has been widely reported from other African sites of this age, fossil birds thus represent a valid mechanism for building hypotheses about palaeoenvironments.