TAXONOMY AND AFFINITIES OF AFRICAN CENOZOIC METATHERIANS

Vicente D Crespo,Francisco J Goin

doi:10.7203/sjp.36.2.20974

Abstract

The record of extinct African metatherians (Mammalia, Theria) is scanty, restricted in time (Eocene–Miocene), and its taxonomy is still subject of debate. A review of all African metatherians, or alleged metatherians, known up to now, led us to the recognition of only three taxa referable to this group: (1) Kasserinotherium tunisiense (Peradectoidea?), from the early Eocene of Tunisia; (2) Peratherium africanum (Herpetotheriidae), from the early Oligocene of Egypt and Oman, and (3) an indeterminate Herpetotheriidae? from the early Miocene of Uganda. Herpetotheriids probably reached Afro-Arabia from Europe in one or more dispersal waves since the early Oligocene. Kasserinotherium , on the contrary, suggests an earlier (Paleocene) arrival from South America, judging from its alleged affinities with South American and Australian taxa. Such a migration event (probably, through a filter corridor such as the Rio Grande Rise-Walvis Ridge system in the South Atlantic) may also explain the enigmatic presence of polydolopimorphian metatherians in the Cenozoic of central Anatolia (Turkey). A more radical hypothesis is that all European (Eurasian?) Marsupialiformes have an ultimate origin in South America, from where they dispersed via Africa by the Paleocene–earliest Eocene.

Highlights

Living metatherians are widely distributed both in Australasia and in the Americas
This material undoubtedly belongs to a metatherian in having three premolars and four molars. These authors followed Crochet (1977, 1980) in referring the species to Peratherium, as the protoconid increases in height from m1 through m4; the anterior face of the metaconid is generally subvertical in lingual view; the entoconids are conical, often tall; the width of m4 talonid is reduced, with the hypoconulid placed between the hypoconid and the entoconid; the molars tend to lengthen from m1 through m4; and the talonid of m4 is strongly reduced. These authors highlighted that P. africanum shares all of these characters to a greater or lesser degree and discarded the genus Herpetotherium because P. africanum does not have its m2 and m3 of subequal length; the m4 is shorter than other molars; the m1-4 metaconids are nearly as tall as the protoconids, and the molar entoconids are strongly lengthened at their buccal bases
The authors discussed on the European origin of this species, Jaeger and Martin (1984) argued on a vicariant origin of this taxon, and the possibility of it being a survivor of an ancestral marsupial stock common to South America and Africa before the opening of the South Atlantic

Summary

INTRODUCTION

Living metatherians are widely distributed both in Australasia and in the Americas. During the last hundred million years, they occupied every single continent on Earth, even though their temporal ranges and diversity were strongly unequal. Only three African taxa are unambiguously referable to the Metatheria: (1) Peratherium africanum Simons & Bown, 1984, from the early Oligocene of Egypt and Oman (Arabian Peninsula); (2) Kasserinotherium tunisiense Crochet, 1986, from the early Eocene of Tunisia, and (3) an indeterminate ?herpetotheriid taxon from the early Miocene of Uganda. Genus and species indet.), and the rest from both their original publications and revisions These taxa have been compared with reference collections of metatheria, both originals and casts, of European, South American, North American and Asian origin housed at Museo de La Plata (Universidad Nacional de La Plata, Argentina), l’Institut des Sciences de l’Evolution de Montpellier (Université de Montpellier, France), and Muséum national d’Histoire naturelle (Paris, France). Lower molars with short talonid and buccally located cristid obliqua; hypoconulid large, taller than the entoconid and close to its lingual margin; shallow distolingual area of talonid, after wear becoming a curved ‘crest’ linking hypoconulid to entoconid (hypoconulid-entoconid talonid fold)

Discussion

DISCUSSION