Do Trilobites Bite?

Physics

By Allison Kubo Hutchison

You are enjoying a sunny beach day, showing off a new swimsuit. You take a dip in the water, you feel something brush your foot. You look down and it’s a trilobite. Your first panicked thought: Do trilobites bite?

Other than the fact that trilobite went extinct 252 million years ago, this is actually a quite complicated question.

First, we have to define bite. If that definition includes any mention of a jaw structure, then the answer is no, you have nothing to worry about. Jaws, like humans have, did not evolve until 440 million years ago in the Placoderms. Trilobite did not have jaws the way humans or fish or dogs do. For a creature to bite, does it have to have a jaw? That’s a question for the philosophers. The question for the paleontologists is: what did trilobite have instead of a jaw?

First off, trilobites, the class of trilobita, a category which comprised 10 orders, 150 families, 5,000 genera, and 20,000 unique species. And are known for their remarkable niche filling diversity. Trilobites likely dwelt in a wide range of ocean habitats including the ocean floor, reefs, floating in the water column, or in deep water.

The majority of early trilobites were predators or scavengers. They walked along the ocean floor eating other dead trilobites, worms, and other small creatures. The trilobite walked with “legs” called gnathobases on either side of the body similar to a pillbug (shown in the photo). The gnathobases which are along both sides of the trilobite could grab and pass food along the centerline of the trilobite where the majority of “eating” occurred. The trilobite would likely hold a worm or other prey against the hard centerline and the gnathobases would rip and crush the food then pass it toward the mouth. The final processing, “chewing”, would occur as the gnathobases crushed the food against the hypostomes. The hypostome, made of a stiff exoskeleton, is the large mainly flat plate at the head of the trilobite that was the closest a trilobite had to a jaw. The hypostome is basically a built-in plate for their food.

If the hypostome was large and rigidly attached to the exoskeleton, it was likely a predator. The large variety of hypostomes tell us that different species of trilobite were specialized to eat specific types of prey. Different hypostomes had ridges or forks used to saw into their prey. Hypostomes that were not well attached, just attached at two points like a hinge, were likely sediment filters and the hypostome scooped up sediment to sort for food. Of course, this is just a taste of trilobite ecology. Trilobites were a deliciously diverse group and had a variety of different feeding mechanisms and preferred foods, including an amazing trilobite that lived in symbiosis with sulfur-producing bacteria deep in the ocean. They had a variety of different feeding methods and no jaws but they still had their own unique ways to “bite”.

But don’t worry your toes are safe; trilobites died off 252 million years ago.

Photo Attributions: 

 Trilobite_tracks_at_World_Museum_Liverpool.JPG: Rept0n1xderivative work: JMCC1, CC BY-SA 3.0, https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons 
 Recreation of the Ventral side of the Olenoides serratus by Dr. Sam Gon III, from http://www.trilobites.info/
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