Abstract
The genus Leggadina (colloquially known as ‘short-tailed mice’) is a common component of Quaternary faunas of northeastern Australia. They represent a member of the Australian old endemic murid radiation that arrived on the continent sometime during the late Cenozoic. Here we describe two new species of extinct Leggadina from Quaternary cave deposits as well as additional material of the extinct Leggadina macrodonta. Leggadina irvini sp. nov. recovered from Middle-Upper (late) Pleistocene cave deposits near Chillagoe, northeastern Queensland, is the biggest member of the genus, being substantially larger than any other species so far described. Leggadina webbi sp. nov. from Middle Pleistocene cave deposits at Mount Etna, central eastern Queensland, shares features with the oldest species of the genus, the Early Pleistocene L. gregoriensis. Based on the current palaeoecological interpretation of the type locality, L. webbi, represents the only member of the genus that inhabited rainforest. The succession of Leggadina species through the late Quaternary suggests an ecological replacement of the extinct large-bodied L. irvini with the extant, small-bodied L. lakedownesis at Chillagoe. At Mt. Etna, the extinct rainforest species L. webbi is replaced with the extant xeric-adapted L. forresti during the latest Middle Pleistocene. This replacement is associated with a mid-Pleistocene shift towards progressive intensifying seasonal and arid climates. Our study adds to the growing list of small-bodied faunal extinctions during the late Quaternary of northern Australia.
Highlights
Short-tailed mice (Leggadina spp.) are small-bodied murines that form part of the ‘Australian Old Endemic Radiation’ (Aplin, 2006; Watts & Aslin, 1981), referred to the tribe Hydromyini (Lecompte et al, 2008)
Species of Leggadina are distinguished from all other murids by a unique combination of characters including the possession of: large accessory cusp on M1; large, lingual cusps on M1−2 postero-lingual of associated lophs; commonly diamond-shaped T1 on M1; T1 supplementary cusp commonly present on M1, variably expressed; upper molar cusps sloped posteriorly; M1/1 enlarged; M3/3 reduced, such that M1/1 is longer than M2−3/2−3 combined; large posterior palatal foramen; broad posterior cingulid cuspid on M1; lower molar cusps sloped anteriorly; apex of each lower molar cusp drawn in from margins of base
Leggadina can be separated from all other Australo-Papuan murines by the large accessory cusp on M1, large posterior palatal foramen, enlargement of M1/1 with associated reduction of M3/3 so that M1/1 is more than half the length of the molar row
Summary
Short-tailed mice (Leggadina spp.) are small-bodied murines that form part of the ‘Australian Old Endemic Radiation’ (Aplin, 2006; Watts & Aslin, 1981), referred to the tribe Hydromyini (Lecompte et al, 2008).
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