Rats! – (or where Mickey Mouse diverged from Walt Disney)

Updated January 3, 2019, seven years and about 1000+ taxa later.

We don’t talk about mammals much,
but as reptiles they (we) do qualify as subjects to be covered by ReptileEvolution.com.

A new online study by Wu et al. (2012) finds evidence for a post-Cretaceous origin for rodents. Rodents (everything from porcupines and guinea pigs to squirrels, mice and multituberculates) are related to rabbits (lagomorphs).

The Wu et al 2012 study on rodents and their post-Cretaceous appearance.

The Wu et al 2012 study on rodents and their post-Cretaceous appearance.

How are they all related? 
Near (but not at) the base of the primates is an interesting set of taxa known as tree shrews, like Tupaia (Raffles 1821, Fig. 1). Essentially they are basal rodents/rabbits/multituberculates.

Tupaia, the large tree shrew,

Figure 1. Tupaia, the large tree shrew, a living taxon close to the base of rabbits and rodents with origins in the Paleocene, just following the Cretaceous. Click to learn more.

The most common tree shrew, Tupaia was found to be basal to the equally arboreal and highly derived Plesiadapis (Fig. 3) and terrestrial rabbits, and rodents, like the porcupine. It’s worthwhile to see the porcupine skull and how close it resembles that of Plesiadapis.

Plesiadapis

Figure 3. Plesiadapis, formerly considered a basal primate, is here considered a basal arboreal lagomorph (rabbit ancestor).

The other arboreal tree shrew, 
Ptilocercus, is basal to Tupaia, derived from basal primates and carnivores.

Ptilocercus, pen-tailed tree shrew

Figure 2. Ptilocercus, pen-tailed tree shrew, a living relative to the ancestor of bats and colugos.

Based on the nesting of multituberculates
all these tree shrews, rodents and rabbits had their origin in the Jurassic, not the Paleocene (contra Wu et al. 2012.

References
Wu S, Wu W, Zhang Z, Ye J, Ni X, Sun J, Edwards SV, Meng J and Organ CL 2012. Molecular and Paleontological Evidence for a Post-Cretaceous Origin of Rodents. PLoS ONE 7(10): e46445. doi:10.1371/journal.pone.0046445
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0046445

2 thoughts on “Rats! – (or where Mickey Mouse diverged from Walt Disney)

  1. Except that molecular studies like Janecka et al.’s (2007) ” Molecular and Genomic Data Identify the Closest Living Relative of Primates” show that Ptilocercus is closer to Tupaia than colugos, and all molecular analyses agree bats are laurasiatheres with no particular relation to euarchontoglires.

    • I’ve seen molecular studies that support morphological studies and others that do not. Ultimately you have to go with morphological studies, and these can change as more fossils come to the fore, as they have with whales, for instance.

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