Paleontologists studying a fossil unearthed in southern Manitoba, Canada, have identified what they believe are two bite marks on the internal skeleton of the ancient giant cephalopod Enchoteuthis, offering rare evidence of predator-prey interactions in the Cretaceous seas that once covered the middle of North America.
Reconstruction of a mosasaur and large fish preying on an injured Enchoteuthis, representing potential candidates for the bite marks on the octopod. Image credit: Kaitlin Lindblad.
“In the Mesozoic, cephalopods were one of the most abundant and diverse groups in the marine realm,” University of Manitoba paleontologist Melina Jobbins and colleagues wrote in their paper.
“Cephalopods, including coleoids and ammonites, served as a great food source for predators such as marine reptiles and fish.”
“These predator-prey dynamics are supported by direct evidence, such as specimens with preserved stomach contents, as well as indirect evidence including individuals with fractures or breakage interpreted as bite marks.”
“However, identifying the specific predator from indirect evidence carries some uncertainty.”
In the new study, the paleontologists examined the fossilized gladius — the internal, pen-like support structure — of Enchoteuthis, a squid-like creature that swam in the Cretaceous seas around 81 million years ago.
The specimen, named Q80.05.14, was originally collected in 1980 from the Pierre Shale of Manitoba, and is housed at the Canadian Fossil Discovery Centre.
“Q80.05.14 is ca. 49 cm (19 inches) long and comprises a gladius with a nearly complete rachis and partial patella, with the anterior and posterior edges missing,” the researchers wrote.
“We provide a rough estimate of total length of the gladius to be around 60 cm (24 inches), and a total body length of less than 1 m (39 inches).”
Using 3D scanning and silicone casts, the researchers analyzed two sub-triangular pathologies preserved on Enchoteuthis’ gladius.
One, near the front of the structure, is interpreted with more confidence as a bite mark inflicted shortly before or at the time of the animal’s death, since it shows no sign of healing.
The second mark, near the back, is more ambiguous: it could represent a second bite from the same attack, damage from a separate encounter, or delamination caused by the gladius splitting along its natural fibrous layers, either during the attack or afterward as the carcass decayed.
Because the marks lack embedded teeth or the kind of regular tooth spacing that would point to a specific attacker, the scientists could not identify the predator with certainty.
Both a mosasaur such as Latoplatecarpus, and a predatory fish such as Cimolichthys, lived alongside Enchoteuthis in the same ancient seaway and remain plausible culprits.
