Swimming capabilities of Mesozoic marine reptiles:a review

摘要

Mesozoic marine reptiles displayed a range of swimming abilities. Jurassic and Creta-ceous ichthyosaurs, with their deep, streamlined body, narrow caudal peduncle, andlunate tail, were probably efficient, fast sustained swimmers. The elongated bodies andlong, broad tails of the early ichthyosaurs and mosasaurs (and marine crocodiles) suggestthat they were adapted for rapid acceleration and were probably ambush predators. Moreproblematic are the plesiosaurs, which utilized subaqueous flight using two pairs of wing-shaped appendages. The long-necked plesiosauroids were probably slow swimmers andrelied on a sneak attack to capture prey. The pliosauroids, with shorter necks, morecompact bodies, and larger, broader limbs were probably faster swimmers than theplesiosauroids.By estimating the total drag and the amount of energy available for locomotion, relativesustained swimming capabilities can be estimated for reptiles of the same mass butdifferent body forms. Calculations suggest that ichthyosaurs were faster than eitherplesiosaurs or mosasaurs, and plesiosaurs were slightly faster than mosasaurs. If theresults are scaled to body length rather than mass, the differences in sustained swimmingspeeds are even more pronounced. Differences arise from estimates of hydrodynamicefficiency, shape, and metabolic rate for each kind of reptile, the latter being the mostimportant factor.