Thursday, 9 October 2014

Plesiorycteropus was a giant tenrec

Innomate (pelvic bone) of Plesiorycteropus an extinct mammal
from Madagascar (Drawing by Forsyth Major 1908)
The recent fauna of Madagascar included species that were much larger than those found today an example being the gorilla-sized lemur Megaladapis. One of these fossils Plesiorycteropus has defied interpretation. It has been compared to the aardvark and other myrmecophagous (termite-eating) mammals such as pangolins and anteaters.

The most thorough study of the subfossil material, by McPhee (here), defined two species, P.  madagascariensis and P. germainepetterae, and erected a new Order Bibymalagasia to accomodate them. More recently Asher (here) assigned Plesiorycteropus to the superordinal clade Afrotheria.

Phylogenetic analysis based on collagen sequencing has
Plesiorycteropus as sister to the tenrecs from Buckley 2013 (here)
A recent study (here) relied on molecular sequencing of collagen from a fossil Plesiorycteropus and a range of living mammals. The technique, which uses soft-ionization mass spectroscopy, is a promising alternative to sequencing of ancient DNA. The resultant tree confirmed that Plesiorycteropus belonged to Afrotheria but related to tenrecs rather than the aardvark. Therefore it is part of the radiation from a single colonisation event (Sweepstakes Distribution).

Tailless tenrec (Tenrec ecaudatus) the largest Malagasy tenrec
weighs about 1 kg. Photo by Markus Fink (GNU Free Documentation Licence)
Estimated size of Plesiorycteropus was 6-18 kg so it certainly was a giant compared with living Malagasy tenrecs and the giant otter shrew which weigh about 1 kg.

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