Let’s look at bandicoots!

Although bandicoots
(genus: Perameles, Fig. 1) are omnivores, they are basal taxa in the herbivorous metatherian clade in the large reptile tree (LRT, 1242 taxa, Fig. 4). They are closest to digging and burrowing marsupials, like the golden mole, Notoryctes, yet still close to the ancestry of the fast, leaping kangaroos, like Macropus. And they are derived from a sister to Arctocyon, the large carnivore.

Figure 1. Perameles nasuta, the long-nosed bandicoot, nests as basal member of the herbivorous marsupials.

Figure 1. Perameles nasuta, the long-nosed bandicoot, nests as basal member of the herbivorous marsupials. Look at those huge lumbar vertebrae! Scale bar = 1cm.

Perameles nasuta (Geoffroy 1804, extant, 40 cm long) is the long nosed bandicoot. This basal marsupial is a nocturnal omnivore, like its ancestor Didelphis (Fig. 2). It has a rear-facing pouch, three long digging fingers, two short ones and a pes dominated by pedal digit 4. Digits 2 and 3 were reduced to grooming claws, as in kangaroos. Gestation lasts a mere 12.5 days, then the young spend another 8 weeks in the marsupium. The long nose of bandicoots is a basal trait retained by Ukhaatherium and prototheres like Cronopio and Juramaia.

YouTube videos
of bandicoots show they have a high metabolism and can scoot away rapidly, like rats or rabbits, distinct from their slower moving opossum ancestors. Of course, Perameles was ancestral to kangaroos, like Macropus (Fig. 3), so their leaping ability is nascent here and their odd feet are nearly identical. Kangaroo hands are still primitive with five sub-equal fingers, not evolved for digging, like odd hand of Perameles (Fig. 1).

According to Wikipedia
“The position of the Peramelemorphia within the marsupial family tree has long been puzzling and controversial. There are two morphological features in the order that appear to show a clear evolutionary link with another marsupial group: the type of foot, and the teeth. Unfortunately, these clear signposts point in opposite directions.” The LRT solves this problem by nesting omnivorous Perameles at the base of the herbivores and allowing for convergence between the large kangaroo and wombat anterior dentaries.

Adding taxa
is helping to clarify phylogenetic relationships among the marsupials. We’ll look at these soon.

References
Geoffroy E. 1804. Mémoire sur un nouveau genre de mammifères á bourse, nommé Perameles. Annales de la Musee National d’ Histoire Naturelle de Paris 4: 56–64.

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