Asioryctes: Re-restoring a pes, re-nesting a taxon

I should have noticed this pairing earlier.
Evidently it escaped everyone else’s notice, too. Asioryctes nemegetensis (Kielan-Jaworowska 1975, 1984; Figs. 1,2; middle Late Cretaceous, Djadokhta Formation, ~85 mya) is a good match for the living bandicoot, Perameles. Maga and Beck 2017 nested Asioryctes with the coeval Ukhaatherium, and the extant Perameles with another bandicoot, Echymipera.

FIgure 1. Skulls of Asioryctes, Perameles and Macrotis compared.

FIgure 1. Skulls of Asioryctes, Perameles and Macrotis compared. The overall shapes are similar, and so are the teeth, and other details. Historically the feet have been different, and that’s our starting point. 

Figure 2. Left: original restoration of Asioryctes pes. Colors added. Right: New restoration based on phylogenetic proximity to Perameles and other marsupial taxa with vestigial digit 1 and gracile digits 2 and 3 (grooming claws).

Figure 2. Left: original restoration of Asioryctes pes. Colors added. Right: New restoration based on phylogenetic proximity to Perameles and other marsupial taxa with vestigial digit 1 and gracile digits 2 and 3 (grooming claws). 

The first three taxa
are members of the large reptile tree (LRT, 1272 taxa), but the first two don’t nest together. The LRT now nests Asioryctes with Perameles and Macrotis, two extant bandicoots. Ukhaatherium nests with the basalmost members of Theria several nodes earlier.

One of the problems with this
is the original restoration of the Asioryctes pes, based on disarticulated parts (Kielan-Jaworowska 1975; Fig. 2). The REAL problem is no other mammal has gracile lateral metatarsals. Sans the pes, the skull nests with Perameles and Macrotis (Fig. 1), taxa with only a vestige pedal digit 1 and reduced digits 2 and 3.

Hmmm.
That opens up a possibility not foreseen by Kielan-Jaworowska.

A new restoration
of the illustrated elements (Fig. 2) identifies the slender metatarsals as 2 and 3. The tarsal elements are all present (contra Kielan-Jaworowska 1975) just reidentified here in accord with a standard bandicoot foot.

And… so… for the first time
we can see a predecessor taxon demonstrating a transitional morphology to the reduced pedal digits 1–3 seen in bandicoots and kangaroos.

References
Geoffrey Saint-Hilaire E 1803. Note sur les genres Phascolomis et Perameles, nouveaux genres d’animaux à bourse. Bulletin des Sciences par la Société Philomathique de Paris 80, 49–150.
Kielan-Jaworowska Z 1975. 
Preliminary description of two new eutherian genera from the Late Cretaceous of Mongolia. Palaeontologia Polonica 33:5-15.
Kielan-Jaworowska, Z 1984. Evolution of the therian mammals in the Late Cretaceous of Asia. Part VII. Synopsis. Palaeontologia Polonica 4:173-183. online pdf
Maga AM and Beck RMD 2017. Skeleton of an unusual, cat-sized marsupial relative (Metatheria: Marsupialiformes) from the middle Eocene (Lutetian: 44-43 million years ago) of Turkey. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0181712

wiki/Asioryctes
wiki/Perameles
wiki/Macrotis

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.