Oldest fossil remains of the enigmatic pig-footed bandicoot show rapid herbivorous evolution

Kenny J Travouillon

doi:10.1098/rsos.160089

Abstract

The pig-footed bandicoot, Chaeropus ecaudatus, is one of the most enigmatic Australian marsupials, which went extinct in the late 1950s probably as a result of European colonization. It is unusual in being the only marsupial to have evolved reduction of digits on both fore and hind feet, with the forefeet being pig-like (two toes) and the hind feet being horse-like (one toe). According to molecular phylogenetic analyses, Chaeropus diverged from other bandicoots (Peramelidae), and the bilbies (Thylacomyidae) by the mid-Late Oligocene. This is considerably earlier than suggested by the fossil record, with the current oldest specimens being Late Pleistocene in age. Here, I report the oldest fossils of Chaeropus, representing a new species, Chaeropus baynesi from the Late Pliocene to Early Pleistocene (2.47–2.92 Ma) Fisherman's Cliff Local Fauna, Moorna Formation, New South Wales, Australia, and extending the fossil record of the genus and family by at least 2 million years. Chaeropus baynesi is less high crowned than C. ecaudatus and lacks lateral blade development on lower molars, suggesting that it was unlikely to be grazing. This suggests that Chaeropus must have adapted rapidly to the drying conditions and changes in environments, and would have become a grazer in a very short period of time.

Highlights

The pig-footed bandicoot, Chaeropus ecaudatus, is one of the 30 species of mammals that went extinct in Australia after European settlement [1]
The material of C. baynesi described here shows some of the typical synapomorphies for Chaeropus [13]
The upper molar lacks anterior and posterior cingula as in C. ecaudatus but this feature is found in Perameles

Summary

Introduction

The pig-footed bandicoot, Chaeropus ecaudatus, is one of the 30 species of mammals that went extinct in Australia after European settlement [1]. It went extinct sometime in the late 1950s, probably as a result of competition and predation by introduced species, and change in fire regime [2]. Three species of Chaeropus were first described, 2016 The Authors. C. ecaudatus has been recovered from various sites across Australia dating from Late Pleistocene to Holocene (figure 1). The specimens described here represent a new species of Chaeropus and the oldest fossil record of the genus. Dental nomenclature follows Travouillon et al [12].

Systematic palaeontology

Discussion