Restoring Plagiomene (incomplete basal placental)

Wikipedia reports,
Plagiomene multicuspis (Fig. 1; Matthew 1918; MacPhee et al. 1989; YPM VP 030624; Wyoming; Paleocene) is an extinct genus of early flying lemur like mammal from North America that lived during the Paleogene.”

using imagination (Fig. 1) to restore the missing parts, scrappy Plagiomene data turns into a more complete skull. Plagiomene had four small molars and a narrow snout between wide robust cheekbones. Those facts and phylogenetic bracketing suggest forward-pointed eyes sitting atop wide cheekbones for bifocal vision.

Figure 1. What little is known of Plagiomene seems to agree with the North American adapid, Smilodectes, among tested taxa.

Figure 1. What little is known of Plagiomene seems to agree with the North American adapid, Smilodectes, among tested taxa. Plagiomene was not added to the LRT.

Here an attempt at restoring the rest of the skull
(Fig. 1) results in a short-snouted taxon with robust cheekbones, more or less similar to Smilodectes (Fig. 1), which has not four, but only three molars and lived during the middle Eocene. An extremely tall coronoid process requires a similarly tall skull. If valid, Plagiomene would be a basal primate, or basal to Primates + Volantia (where dermopterans are a basal taxa).

Possible outgroups,
such as basal Carnivora and Cheiroptera, do not have a similar mandible or molars.

The basal dermopterans,
(Fig. 1) and Cynocephalus, both have 4 molars, but do not have a tall coronoid process on the mandible.

Earlier we looked at the evidence for
the clade that includes Smilodectes (Adapidae) nesting at the base of the clade of New World monkeys (Platyrrhini). Plagiomene is also from North America.

The last upper premolar
of Plagiomene extends further toward the midline than the molars do. That is unusual in basal mammals. When I find this trait in another basal mammal palate, I will let you know.

MacPhee RDE, Cartmill M and Rose KD 1989. Craniodental morphology and relationships of the supposed Eocene dermopterans Plagiomene (Mammalia). Journal of Vertebrate Paleontology 9(3):329–349.
Matthew WD 1918. A revision of the Lower Eocene Wasatch and Wind River faunas. Part V. Insectivora (Continued), Glires, Edentata. Bulletin of the American Museum of Natural History 38(16):429-483.


Leave a Reply

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

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

Google photo

You are commenting using your Google 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.