Fossilized feces, aka “coprolites,” are an uncommon paleontological find. But fossilized poop inside a fossilized creature? That’s rarer, still, and why researchers are so excited about the pterosaur fossil pictured above.
The specimen dates back 146- to 161-million years, to the Late Jurassic, and is exceptionally well preserved. Its soft tissues, including its wing membranes, are in good shape, and its stomach is full of what paleontologists think was probably its last meal. But what researchers are really excited about is a pair of masses located behind the pterosaur’s sacrum, close to where its cloaca would have been when it was alive. (The cloaca is the multi-purpose posterior orifice that modern birds, amphibians, and reptiles use to mate, urinate, and poop, among other things.)
In the latest issue of the journal PeerJ, a team led by David Hone at Queen Mary University of London proposes that these masses are, in fact, two halves of one “putative coprolite”—which is just a fancy way of saying “fossilized poop, maybe”:
A detailed view of the fossilized poop, maybe. Scale bar is 5 mm. Image Credit: Hone et al. 2015 PeerJ | CC-BY 4.0
This has split in two, but the terminal ends of the separated pieces are largely straight and they are of the same size and shape, suggesting a single mass that split along a weak point, rather than two separate pieces. The smaller part (that is closer to the pterosaur’s pelvis) is poorly preserved and shows calcite crystals and is 11 mm long and 3 mm across. The second mass is 8 mm long and 4 mm across and consists of many tens of small and pale comma-shaped or spike-like elements... These are typically around 0.2–0.3 mm in length, though larger ones are 0.45 mm. Some tiny ones are around 0.05 mm, and are more simple in shape, but these may be partially concealed under other elements as they only appear in the greatest concentration of these pieces.
Of great interest to the researchers are “hooklets” that are clearly visible upon close inspection of the coprolite:
A detailed view of the “hooklets” within the putative coprolites. Image credit: Hone et al., PeerJ
| CC-BY 4.0.
These we originally suggested were hooklets from the arms or tentacles of a cephalopod... but we now tentatively reject this hypothesis as the morphology of the cephalopod hooks are a less good match than we had originally thought. A number of alternatives have also been assessed including the branchial apparatus of a small fish, and possible invertebrate origins such as spines from a small echinoderm or sponge spicules, but none are confident referrals.
If it is, in fact, fossilized crap, it will be the first recorded coprolite for any pterosaur (which, remember, are not dinosaurs), and could help us better understand what these creatures ate and how they lived.
For more details, read the full study in the latest issue of PeerJ.