Mio-pliocene faunal exchanges and african biogeography: the record of fossil bovids.

Faysal Bibi,Peter Ungar

doi:10.1371/journal.pone.0016688

Abstract

The development of the Ethiopian biogeographic realm since the late Miocene is here explored with the presentation and review of fossil evidence from eastern Africa. Prostrepsiceros cf. vinayaki and an unknown species of possible caprin affinity are described from the hominid-bearing Asa Koma and Kuseralee Members (∼5.7 and ∼5.2 Ma) of the Middle Awash, Ethiopia. The Middle Awash Prostrepsiceros cf. vinayaki constitutes the first record of this taxon from Africa, previously known from the Siwaliks and Arabia. The possible caprin joins a number of isolated records of caprin or caprin-like taxa recorded, but poorly understood, from the late Neogene of Africa. The identification of these two taxa from the Middle Awash prompts an overdue review of fossil bovids from the sub-Saharan African record that demonstrate Eurasian affinities, including the reduncin Kobus porrecticornis, and species of Tragoportax. The fossil bovid record provides evidence for greater biological continuity between Africa and Eurasia in the late Miocene and earliest Pliocene than is found later in time. In contrast, the early Pliocene (after 5 Ma) saw the loss of any significant proportions of Eurasian-related taxa, and the continental dominance of African-endemic taxa and lineages, a pattern that continues today.

Highlights

Wallace [1], following Sclater [2], classified the majority of Africa and Arabia into a single ‘Ethiopian’ biogeographic realm, extending from the Tropic of Cancer southwards to the Cape and Madagascar
The Asa Koma Member (ASKM) and Kuseralee Member of the Sagantole Formation (KUSM) mammalian faunas show the greatest taxonomic similarity to contemporaneous assemblages from Kenya, Chad, Libya, and the United Arab Emirates, followed by those from Iran, Spain, Greece, and Italy [35]. Assemblages such as the ASKM and KUSM provide a window onto late Miocene biogeographic configurations in Africa, which already had an African-endemic (Ethiopian) character to them but retain a degree of taxonomic continuity with Eurasia, shortly before early Pliocene advent of increased continental endemism
The bovid taxa recorded from the Asa Koma and Kuseralee Members of the Middle Awash are listed in Table 1, updated to reflect the identification of new taxa and revision of specimens presented in this paper

Summary

Introduction

Wallace [1], following Sclater [2], classified the majority of Africa and Arabia into a single ‘Ethiopian’ biogeographic realm, extending from the Tropic of Cancer southwards to the Cape and Madagascar. Wallace was struck by both the high number of animal groups endemic to this area as well as the absence from it of many widespread Eurasian taxa. "The great speciality indicated by [the Ethiopian realm’s] numerous peculiar families and genera, is still farther increased by the absence of certain groups dominant in the Old-World continent, an absence which we can only account for by the persistence, through long epochs, of barriers isolating the greater part of Africa from the rest of the world.’’. The last 100 years of paleontological exploration have provided a wealth of information that allows for an investigation into the developmental history of African endemism as a whole, and the Ethiopian biogeographic realm in particular. Wallace’s proposal of ‘‘long epochs’’ of isolating barriers can be more precisely formulated and addressed

Results

Discussion

Conclusion