Abstract
An additional specimen of a fossil galagid was recently recovered from the Upper Laetolil Beds at Laetoli in northern Tanzania. This new find represents the most complete specimen of a galagid known from Laetoli, and comprises associated partial right and left mandibular corpora. The galagid material from Laetoli can all be attributed to a single species, previously referred to as Galago sadimanensis. However, the taxon is sufficiently distinct from all extant galagids, as well as stem galagids from the Miocene of East Africa, to be placed in its own genus, Laetolia. The fossil record of galagids from the Pliocene of Africa is exceedingly poor, and Laetolia sadimanensis represents the best-known form. Laetolia can be distinguished from other galagids by its unique suite of morphological features. The stout and vertical implantation of P2, the steeply inclined and robust symphysis, and the relatively deep corpus are all specialized features that are probably functionally linked. However, Laetolia has a less molariform P4 than extant galagids, and it can be inferred to represents their primitive sister taxon. Based on molecular clock estimates, extant galagids shared a last common ancestor during the late Oligocene. It is interesting, therefore, to discover a sister taxon of extant galagids surviving in East Africa until at least the Pliocene, contemporary with more advanced crown members of the clade. From a paleoecological perspective, the occurrence of fossil galagids at Laetoli implies the presence of habitats with at least a sparse coverage of trees and/or thorn bush.
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Acknowledgements
The author is grateful to the Tanzania Commission for Science and Technology and the Unit of Antiquities in Dar es Salaam for permission to conduct research in Tanzania. Special thanks go to Paul Msemwa (Director) and Amandus Kweka, as well as to all of the staff at the National Museum of Tanzania in Dar es Salaam, for their support and assistance. The Government of Kenya and the National Museums of Kenya are thanked for permission to study the collections in Nairobi. Thanks to Emma Mbua, Mary Muungu, Meave Leakey (Kenya National Museum), Jerry Hooker, Peter Andrews, Paula Jenkins, Daphne Hills (Natural History Museum, London), Nancy Simmons, Ross MacPhee, and Eileen Westwig (American Museum of Natural History, New York) for access to specimens in their care. For their advice, discussion, and help I gratefully acknowledge the following individuals: P. Andrews, E. Delson, C. Jolly, D.M.K. Kamamba, M.G. Leakey, C.S. Msuya, S. Odunga, M. Pickford, L. Pozzi, and D. Su. I am especially grateful to R. Kay and H. Wesselman for their feedback on the manuscript. Research on the Laetoli galagids was supported by grants from the National Geographic Society, the Leakey Foundation, and NSF (grants BCS-9903434 and BCS-0309513).
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Harrison, T. (2011). Galagidae (Lorisoidea, Primates). In: Harrison, T. (eds) Paleontology and Geology of Laetoli: Human Evolution in Context. Vertebrate Paleobiology and Paleoanthropology Series. Springer, Dordrecht. https://doi.org/10.1007/978-90-481-9962-4_5
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