Early Early Early Relatives of Both Humans and Sea Stars – #365papers – 2017 – 32

#365papers for February 1, 2017

Han, Conway Morris, Ou, Shu, and Huang, 2017, Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China): Nature.

What’s it about?

That title. What does it even mean?

As animals grow from a single fertilized egg to a newborn, they pass through a stage where they are a hollow ball of cells with one opening. Deuterostomes are animals for which this opening later becomes the anus. In everything else (called proterostomes), this opening becomes the mouth.

All animals with bones (including us) are deuterostomes, as are all members of the Phylum Echinodermata – Sea stars, sea urchins, sand dollars, sea lilies, sea cucumbers, and a bunch of fossil groups. So our closest non-bony relatives are starfish. Think about that…

Why does it matter?

This is a fossil deuterostome from the Cambrian, which makes it among the very earliest (oldest) deuterostomes that we know about. This could represent a shared ancestor between echinoderms and vertebrates. Or maybe not.

Why did I read this?

This paper created quite a buzz in my newsfeeds, so I naturally had to read it. It wasn’t presented exactly correctly in the popular press, but nevertheless it is interesting and will get incorporated into my paleontology courses from now on.