The bizarre teeth of an ancient marine worm may hold the key to classifying enigmatic fossils. Penis worms, sometimes known by their less-titillating moniker of priapulid worms, lived during the Cambrian Period, a time starting around 540 million years ago when most animal groups appeared on Earth.
New research on a penis worm published in Palaeontology argues that classifying small fossils of teeth and other hardened body parts may be instrumental in figuring out where soft-bodied animals like worms lived millions of years ago, even though their bodies have long since decayed in most places. And if this study is anything to go on, we want to know as much about penis worms as humanly possible.
Ottoia, the most prevalent type of priapulid found in the dense fossil field of Canada’s Burgess Shale Formation, had particularly nasty teeth, shaped like bear claws, hooks, and spines, as the study from the University of Cambridge notes. These were not your average pearly whites.
The penis worm could open up its mouth to reveal a set of teeth inside its throat like a cheese grater. Some were covered in tiny spines, while others were pronged like the footprint of a bird, and still others curved as sharply as a cat’s claw. The penis worm, a formidable predator that would devour anything in its path, could turn its throat inside out and drag itself around by these teeth.
Image Credit: Smith et. al, Palaeontology
Only about a millimeter long, the fossils sometimes are mistaken for algae spores rather than animal teeth, and the researchers had to use microscopy to study the internal structure of the miniscule fossils.
The type of tooth classification system the Cambridge researchers are developing allows scientists to better understand where species once roamed, even though there might not necessarily be a great fossil record. For instance, large Ottoia fossils (those that don’t require a microscope to see them) are only found in rare environments like the Burgess Shale, which was at the bottom of the ocean millions of years ago. But smaller tooth fossils indicate that they also lived in shallower waters.
“Now that we understand the structure of these tiny fossils, we are much better placed to a wide suite of enigmatic fossils,” lead author Martin Smith of the University of Cambridge said in a press statement. “It’s entirely possible that unrecognized species await discovery in existing fossil collections, just because we haven’t been looking closely enough at their teeth, or in the right way.”