Millions of years ago during the early Jurassic period, a baby marine reptile called an ichthyosaur gorged itself on prehistoric calamari. Then, it died abruptly — its belly full of squid.
Roughly 200 million years later, paleontologist Dean Lomax was examining this creature’s fossilized remains at the University of Birmingham’s Lapworth Museum of Geology when he realized he was seeing a few fossil firsts. The two-foot-long skeleton was the first fossilized newborn of its species. So it was certainly the first to be found with leftover squid in its guts. He and paleontologist Nigel Larkin published their findings last week in the journal Historical Biology.
The fossil was a bit of a mystery: there wasn’t any record of where it came from, or how deep underground it had been buried, which would have given them a rough date of when the creature died. But, by looking at the tiny fossils embedded in the stone along with the skeleton, they could roughly date it to the early Jurassic period. The two paleontologists ID’d the skeleton itself as a miniature Ichthyosaurus communis. Now extinct, these fishy-looking swimming reptiles could reach up to 15 feet in length during adulthood — and no babies had ever been discovered.
Larkin and Lomax could tell the little skeleton was a baby and not a small adult because it had a few telltale features. For one thing, the fossilized skull bones were spongy instead of smooth, a possible sign of youth. And its ring-shaped eyeball bones (yes, eyeball bones — most creatures with backbones except mammals have these inside their eyeballs) were huge compared to its eye sockets. That could mean the little guy wasn’t done growing.
Lomax happens to be an expert on the fossilized stomach contents of ancient ichthyosaurs, and he spotted them near the skeleton’s abdomen after Larkin finished cleaning the fossil. “I recognized the various tiny, 'hook-shaped' pieces between the ribs,” Lomax says in an email. The ‘hook-shaped’ pieces were hooklets — barbs made of chitin, the same material that forms the exoskeletons of crabs and insects. Some cephalopod species (both living and extinct) sport these hooks on their arms and tentacles.
“I was very excited to uncover the ichthyosaurs' last meal, especially as it is different to what has been found in another species of ichthyosaur,” Lomax says. The fossilized babies of other species of ichthyosaurs had been found with fish scales in their guts, a sign that distinct species may have had distinct food preferences. Even in the Jurassic period, it looks like babies were picky eaters.