Updated January 5, 2021
with the note that tree shrews (Scandentia) is indeed a monophyletic clade that also includes whales, horses, bats, every placental other than Carnivora and some post-marsupial civets.
Earlier the large reptile tree
found that several former clades, like Parareptilia, Pterodactyloidea, Cetacea, Testudinata (Chelonia) Notoungulata, Pseudosuchia, Ornithodira and Pinnipedia were not monophyletic… and that list keeps growing.
The large reptile tree (LRT, 1044 taxa) does not replicate the following mammalian clades:
- Scandentia – tree shrews: yes, closely related, but at the bases of different clades… unless this clade also includes all placentals sans Carnivora and a few post-marsupial civets.
- Euarchontaglires – rodents, rabbits, tree shrews, flying lemurs and primates, (Fig. 1)
- Euarchonta – tree shrews, flying lemurs, primates and plesiadapiformes.
- Glires – rodents, rabbits
- Scrotifera – Eulipotyphla (see below), bats, pangolins, Carnivora, Euungulata (including whales)
- Eulipotyphla – hedgehogs, shrews, solenodons, moles (moles are Carnivora))
- Euungulata – perissodactyls, artiodactyls (including whales)
- Tenrecidae – tenrecs, some are closer to shrews, others closer to odontocetes
- Macroscelidea – elephant shrews, some are closer to tenrecs
- Primates – Plesiadapiformes and extant primates, including Daubentonia (the aye-aye. No giant anterior dentary teeth in valid primates.
- there are a few more I’m overlooking. I’ll add them as they come to me.
Let’s focus on Plesiadapiformes
Bloch et al. 2007 found plesiadapiforms (Plesiadapis, Carpolestes and kin) more closely related to primates than to any other group. They did not test against rodents and multituberculates. The LRT does not replicate these results, but finds plesiadapiforms more closely related to multituberculates and rodents when included.
According to Bloch & Boyer 2002
“Plesiadapiforms share some traits with living primates, including long fingers well designed for grasping, and other features of the skeleton that are related to arboreality.” That’s fine, but there are other taxa in the tree topology with long fingers, too.
Krause 1991 reports, “Paromomyids …have long been regarded by most workers as members of the Plesiadapiformes.” Again, the LRT does not support this, but nests Paromomyids, like Ignacius (Fig. 2), with rodents, like Mus and Paramys. Paromomyids have squared off and flat molars, but Paromomys does not.
Beard 1990 thought paromomyids,
as plesiadapiforms, where close to colugos or “flying lemurs”. The LRT (Fig. 1) does not support this relationship. Rather paromomyids, like Ignacius, were squirrel-like, able to scamper both in the trees and on the ground. Ignacius graybullianus (USNM 421608, Fig. 1) is a new taxon that nests as a basal rodent in the LRT.
Remmber, no primates
have giant anterior dentary teeth. The aye-aye, Daubentonia, has such teeth, but the LRT finds it nests with Plesiadapis and multituberculates and rodents, not primates. Yes, plesiadapiformes and Ignacius had long limbs, big brains and binocular vision, but by convergence with primates.
Beard KC 1990. Gliding Behavior and palaeoecology of the alleged primate family Paromomyidae (Mammalia, Dermoptera). Nature 345, 340-341.
Bloch J, Silcox MT, et al. 2007. New Paleocene skeletons and the relationship of plesiadapiforms to crown-clade primates. Proceedings of the National Academy of Science 104, 1159-1164.
Kay RF, Thewissen JG and Yoder, AD 1992. Cranial anatomy of Ignacius graybullianus and the affinities of the Plesiadapiformes. American Journal of Physical Anthropology. 89 (4): 477–498. doi:10.1002/ajpa.1330890409.
Krause DW 1984. Mammal Evolution in the Paleocene: Beginning of an Era. In: Gingerich, P. D. & Badgley, C. E. (eds.): Mammals: notes for a short course. Univ. of Tennessee, Department of Geological Sciences.
Krause DW 1991. Were paromomyids gliders? Maybe, maybe not. Journal of human evolution 21:177-188.
Hey David! Great admirer of your artistic and research work.
I’ve been following the blog for a while, and got curious about something today:
Why do you believe big brains, binocular vision and other primate-like bits are the convergent features of Daubentonia, thus making them rodent relatives, and not the giant anterior dentaries?
What other characteristics informed your proposed association?
I would have to run through the LRT to pick out the traits that, so far, only the computer knows. At present, though, no tested primates, and I have not tested a large number of them, have giant anterior dentary teeth followed by a long diastema. Primates appear to be more conservative in their dentition. My guess is we’ll also see some clade differences in the proportions of manual and pedal elements. And thank you for your kind comment.