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New Eurasian Immigrants in the Late Paleogene of Africa, and the Great Old World Biotic Interchange: A Quantitative Analysis of Mammalian Dispersal
Mattingly, Spencer
Mattingly, Spencer
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Abstract
Following the break-up of West Gondwana in the middle Cretaceous, both Africa and South America existed in “splendid isolation”, devoid of any terrestrial connections to other landmasses. This isolation led to the development of highly endemic mammal faunas on both continents. In Africa, periodic episodes of interchange occurred throughout the Paleogene, presumably via sweepstakes dispersal. These were primarily “into-Africa” invasions, with rodents and primates being among the most successful colonizers. Indeed, the late Paleogene mammal faunas of Africa are characterized by a mix of endemic afrothere taxa, and diverse assemblages of recent Eurasian immigrants. In the early Miocene, however, the Eurasian and Afro-Arabian tectonic plates collided, erasing the final vestiges of the Tethys Sea, and establishing for the first time a continuous terrestrial linkage between Africa and Eurasia. This early linkage, frequently referred to as the “Gomphotherium landbridge”, permitted the movement of previously isolated land mammals in both directions. The resulting exchange is known as the Great Old World Biotic Interchange (GOWBI). The GOWBI is widely recognized as causing a rapid and dramatic transformation of the endemic African fauna, while having an ostensibly minimal effect on Eurasian mammals. The chapters presented herein focus on two major themes: (1) documenting new Eurasian migrants from the late Paleogene of Africa, which arrived prior to the onset of exchange in the GOWBI, and (2) measuring patterns of interchange during the GOWBI for the first time using quantitative approaches. Chapter 1 describes a new species of parapithecine primate from an early Oligocene locality in central Libya. The new species represents an intermediate form between two of the most anatomically recognizable species of stem anthropoids: Parapithecus and Simonsius. The new species, which is roughly contemporaneous with other parapithecines from Egypt, further demonstrates habitat fragmentation and allopatric speciation in the late Paleogene of Africa. Chapter 2 details a new genus of basal carnivoraform from the same locality in Libya. The age and carnassial anatomy of the new taxon indicate that it is the first and only occurrence of a basal carnivoraform in Africa, and evidently another product of sweepstakes dispersal into Africa prior to the tectonic collision with Eurasia. Chapter 3 examines quantitative elements of diversity and evolution in the African and Eurasian faunas prior to and during the GOWBI. In doing so, it numerically documents the rapid replacement of African mammals by Eurasian immigrants, and demonstrates a pattern of asymmetry in large scale intercontinental exchange events. Together, these chapters collectively document the apparent success of Eurasian invaders in Africa both before and after the establishment of a terrestrial connection. Reasons for this success are presently unknown, but likely resulted from a combination of both biotic and abiotic factors. The GOWBI thus provide an excellent comparison for other instances of large-scale interchange in the fossil record.
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2022-08-31
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University of Kansas
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Paleontology, Africa, Anthropoid, Biogeography, Carnivoraformes, Eurasia, Mammalia