Plesiosaur Peril and the Prehistoric Survivor Paradigm

Thick-boned, robust ribs and gastralia (here in the Jurassic pliosaur Pachycostasaurus dawni) were probably used as ‘bone ballast’ in these animals. Image by Darren Naish.

In overall body form, all plesiosaurs were generally alike. Their skeletons possess large, plate-like limb girdles mostly positioned on the ventral surface of the body, and there are two pairs of slender, wing-like paddles and a relatively short tail. An interlocking basket of heavy-boned belly ribs (or gastralia) fill in the space between the pectoral and pelvic girdles and presumably helped keep the body stiff during life. There’s no question that plesiosaurs were limb-propelled swimmers. The question is: what sort of limb-propelled swimming did they use? Were they ‘rowers’, ‘fliers’, some combination of the two, and did they use their forelimbs and hindlimbs synchronously, asynchronously, or what? These issues have been much discussed in the literature (Robinson 1975, Tarsitano & Riess 1982, Halstead 1989, Riess & Frey 1991, O’Keefe 2001a, Carpenter et al. 2010) and are the subject of current investigation.

What about the biology, behaviour and lifestyles of these amazing animals? Invaluable studies of jaw biomechanics, tooth form and stomach contents give us insights into what and how plesiosaurs ate, and on how they collected and processed their food (Massare 1987, Taylor 1987, 1992), and some extremely interesting ideas on breathing and olfactory behaviour have been proposed (Cruickshank et al. 1991, Buchy et al. 2006). Trough-like feeding traces preserved on an ancient sea floor provide possible data on plesiosaur foraging behaviour (Geister 1998), and the amazing discovery of a proportionally enormous baby preserved within the body of its mother has given us substantial food for thought as goes the reproductive biology and social lives of these animals (O’Keefe & Chiappe 2011).

In general, however, we of course know very little about plesiosaur biology and behaviour, and I’d say that most questions we might ask can only be informed by inference: by extrapolating or guessing based on what we see in living reptiles and other animals. Remember that, when it comes to interesting questions about the behaviour of long-extinct animals (especially weird ones without precise modern analogues), we’re always constrained by a frustrating lack of information.

Nevertheless, a long interest in both plesiosaurs and the amazing behaviour of extant marine tetrapods means that I’ve long had thoughts about diving behaviour, feeding ecology, social behaviour, intentional beaching and so on in plesiosaurs – I even have a half-finished manuscript done on this subject. So it was fitting that, back in October 2012, Daniel Loxton contacted me to ask if I’d like to be the technical consultant on his new book, Plesiosaur Peril. As with his previous works in the same series – Ankylosaur Attack (Loxton 2011) and Pterosaur Trouble (Loxton 2013) – Plesiosaur Peril is a fantastically illustrated children’s book that uses the fictional story of an individual animal to paint a picture of the lifestyles of ancient animals, using scientific data where possible.