GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 162-60
Presentation Time: 9:00 AM-6:30 PM


MCMENAMIN, Mark A.S.1, FLEURY, Douglas2, SCHULTE MCMENAMIN, Dianna L.1, HUSSEY, Meghan C.1, ORR, Lydia1 and BOUSE, Leta A.1, (1)Geology and Geography, Mount Holyoke College, South Hadley, MA 01075, (2)Caterpillar Catalyst, Inc, National Science Education Outreach, 48 Arden Street, Holyoke, MA 01040,

An unusual ichthyosaur skeleton (Ichthyosaurus cf. I. breviceps Owen, 1881), collected from Holzmaden strata (Schomberg Quarry) some time before 1975 and currently in the collection of P. Reiter, shows evidence for trauma that involved breaking the neck by twisting the skull, leaving it 180° out of place while maintaining its orientation in line with the body axis. Evidence for trauma in the ichthyosaur skeleton is exceptional. We interpret this damage as indicative of an attack by a Jurassic cephalopod. Skeletal evidence indicates that the animal was held tightly in at least four places while its neck was twisted. The attack might be described as a twisting headlock with quadruple bear hugs, a trauma that would require at least 5 limbs, which leads us to conclude that it was inflicted by a large cephalopod with powerful tentacles. The damage observed also implies a high degree of coordination, similar to that seen in the modern Giant Pacific octopus (Enteroctopus dofleini). The otherwise undamaged skeleton suggests that the attack was motivated by territoriality (or perhaps defense of the cephalopod's young prior to dispersion from their den) rather than by predatory foraging behavior. However, if the cephalopod did intend to consume its prey, but dropped the ichthyosaur for some reason (in, say, a confrontation with another predator), the ichthyosaur carcass may have slipped from the cephalopod's grasp and been lost. Alternatively, the cephalopod may have carried the carcass and deposited it on the sea floor.