Early Cambrian shrimp! I just had to share this pretty little fellow, a newly described eucrustacean from the lower Cambrian, about 525 million years ago. It’s small — the larva here is about 1.8mm long, and the adults are thought to have been 3mm long — but it was probably numerous, and I like to imagine clouds of these small arthropods swarming in ancient seas.
There are a couple of notable things about this animal. One is that they’re preserved in full 3-dimensional detail in an Orsten-type lagerstätte, which means they’ve got a dense collection in one spot with beautiful preservation of all the fine structure, right down to the fine setae (hairs) covering it. They also have multiple larval stages, so they have a developmental series revealing the post-embryonic development, and they can see how tiny cuticular structures develop. Look at these pieces:
Two more things make it interesting. One is its age; this creature is very old, from the Atdabanian, which puts it back near the beginning of the Cambrian…yet it’s also a eucrustacean. That means the divergence time of the arthropods has to be pushed back into the pre-Cambrian (which really isn’t much of a surprise). Another is that it possesses curious little flaps of tissue on the limbs which don’t look very impressive, but are actually epipodites, a branch of the limb. Epipods are cool structures that got coopted into respiratory functions and form epipod gills, and most impressively, are thought to have been thoroughly modified to form the wings of insects. Yicaris demonstrates the primitive origins of some very important arthropod characters.
Zhang X-g, Siveter DJ, Waloszek D, Maas A (2007) An epipodite-bearing crown-group crustacean from the Lower Cambrian. Nature 449:595-598.