Mesosaurs Were Slow Swimmers

Optimal swimming speed estimates in the Early Permian mesosaurid Mesosaurus tenuidens (Gervais 1865) from Uruguay

Authors:

Villami et al

Abstract:

Mesosaurid biology has been subject of continuous debate since the first description of Mesosaurus tenuidens by Paul Gervais in 1867. Controversy surrounds their environmental and feeding preferences. Most studies suggested that mesosaurids were marine reptiles and perhaps piscivorous predators. Nonetheless, recent work suggests that they inhabited a salty, eventually hypersaline shallow epicontinental sea and that pygocephalomorph crustaceans were their preferred food item. Here, we present results of the first biomechanical study about optimal swimming capabilities in Mesosaurus tenuidens, which along with the comparative analysis of the limb morphology support the hypothesis that these animals were slow swimmers living in shallow waters. The study is based on the revision of several almost complete mesosaurid specimens and isolated, well-preserved bones housed in palaeontological collections in Uruguay, Brazil, France and Germany. We studied the relative size and proportions of the bones, as well as their morphology and anatomical position to produce a three-dimensional reconstruction of the original appearance of an undamaged, complete skeleton. Our results suggest a fairly low optimal swimming speed for mesosaurids, which is consistent with capture of fairly slow prey like pygocephalomorphs, possibly by filter-feeding, rather than by active pursuit of fast prey.