Fossil bird eggs from the Pliocene of Laetoli, Tanzania: Their taxonomic and paleoecological relationships Terry Harrison * Center for the Study of Human Origins, Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10003, USA Received 25 February 2004; received in revised form 27 April 2005; accepted 1 July 2005 Available online 24 August 2005 Abstract Recent paleontological investigations at the Pliocene site of Laetoli and at neighboring localities on the Eyasi Plateau of northern Tanzania have led to the recovery of a sizable collection of fossil bird eggs. The material comes from the Upper Laetolil Beds, dated at 3.6–3.8 Ma, and the Lower Laetolil Beds, dated at 3.8 Ma to older than 4.3 Ma. The preservation of relatively complete eggs (other than those of ratites) is an extremely rare occurrence in the fossil record, and Laetoli is the only locality in Africa that has produced such well-preserved eggs. Deposition of carbonatite air-fall tuffs led to the rapid burial of the eggs sub-aerially, and they were then preserved in paleosols that were geochemically conducive to their preservation. The collection of fossil eggs from Laetoli can be assigned to at least five different species of ground-nesting birds, including two or three species of francolins, a species of guineafowl, and a larger bird of uncertain taxonomic status about the size of a bustard. Most of the eggs can be assigned to a large species of Francolinus, similar in size to the extant F. afer and F. leucoscepus. A smaller species of francolin, about the size of Francolinus coqui or F. sephaena, is also represented, but is less common. A single egg may represent an even smaller species of francolin, about the size of Francolinus lathami or F. nahani, but its attribution to Francolinus is less cer- tain. The evidence of at least two species of Francolinus at Laetoli indicates that francolins were already taxonomically diverse in East Africa by the mid-Pliocene. Three eggs are similar in their overall dimensions and morphology to the living Numida meleagris, the helmeted guineafowl. An avian community including at least one small species of francolin, a larger francolin, and a guineafowl (as well as ostriches and a vulture) implies that the paleoecology at Laetoli was likely to have been open woodland, bushland, savanna or grassland. However, francolins and guineafowl generally require low brush and thickets for refuge, as well as trees to roost in at night, so they tend to prefer mosaic ecotonal habitats offering open feeding areas with good visibility, but with dense vegetation cover and patches of woodland nearby. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Pliocene; Eggs; Taxonomy; Paleoecology; Francolinus; Numida 1. Introduction Laetoli in northern Tanzania represents one of the most important Pliocene localities in sub-Saharan Africa (Leakey and Harris, 1987; Leakey, 1987a). It is particu- larly renowned for the discoveries of skeletal remains and footprint trails of the early fossil hominin, Australo- pithecus afarensis (Leakey and Hay, 1979; Hay and Lea- key, 1982; Leakey, 1987b,c; Robbins, 1987; Tuttle, 1987). However, paleontological collections at Laetoli have also yielded a diverse associated fauna of fossil ver- tebrates, including over one hundred species of mammals, reptiles, and birds (Harris, 1987a). The previously pub- lished bird remains consist of 32 post-cranial elements (Watson, 1987) and two eggs of ground-nesting birds (Cunningham-van Someren, 1987), as well as eggshell 1464-343X/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jafrearsci.2005.07.002 * Tel./fax: +1 212 998 8581. E-mail address: terry.harrison@nyu.edu www.elsevier.com/locate/jafrearsci Journal of African Earth Sciences 41 (2005) 289–302