“M” is for Mixodectes

“M” is for Mixodectes

Mixodectes is a member of the mammalian Order Insectivora, which is a bunch of mammals grouped together because of they appear to be insect eaters. As it happens, this grouping is best considered a ‘grade’ rather than a ‘clade.’

Clades are natural groups, meaning that they are groups of organisms put together because they are truly closely related (evolutionarily), and usually share several advanced traits. Grades are groups of organisms that are put together because they are equally primitive. They may or may not be actually related to each other by evolutionary processes.

Modern mammals with traits linked to insectivory (eating bugs) have much in common with the earliest mammals. It is likely that the first mammals were also insectivores. These mammals are small, with simple tribosphenic teeth. They are typically shrew-like. However, since insectivory is the starting condition for all mammals, grouping insectivorous mammals together into the Order Insectivora doesn’t help clarify their evolutionary relationships. They are just primitive, but could represent early members of groups that are now very distinct.

Because the teeth represent a primitive insectivore pattern, it can be hard to identify species. Here I had one tooth that I at first thought was Mixodectes.

A sketch on one tooth assigned to Mixodectes from The Breaks. I love this drawing.
A sketch on one tooth, a right upper third molar (despite the fact that I labeled it as a lower third molar), that I thought might belong to Mixodectes. On closer examination, I decided it was Eudemonema. I love this drawing.

I took the specimen with me to the American Museum of Natural History and made some comparisons between it and teeth identified as Mixodectes and another insectivore called Eudemonema. After this comparison, and checking the measurements, I concluded that this tooth was actually Eudemonema.

In looking at my notes, I called this tooth all sorts of things before I finally concluded that it belonged to Eudemonema. Such is the nature of this science.

For the A to Z blogging challenge.

For 4-15-13


  1. Hello, Penny! This is an interesting post. I enjoy blogs where I learn something new. Thanks for sharing!

    Happy A to Z-ing! from Laura Marcella @ Wavy Lines


    1. Penny says:

      Glad you’re enjoying it! It’s been fun to revisit my dissertation work!


  2. Neon Vincent says:

    I’ve found all kinds of interesting people through NaBloPoMo, but I’ve never found a fellow paleontologist before. Cool!

    I did my work at the other end of the Cenozoic studying the mollusks from Rancho La Brea. I posted the list of the fauna at my first blog on LiveJournal.


    1. Penny says:

      Well hi!

      I have spent a bit of time at Rancho La Brea. My postdoc dealt with climate change during the last glacial maximum. I borrowed a few teeth from there for isotopic analysis.

      Mollusks are good times too! Studying them across the Paleocene-Eocene boundary. They’re great for isotopes (’cause that’s my thing).

      It’s a pleasure to meet you!


Leave a Comment

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 )

Facebook photo

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

Connecting to %s