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Flipper size in Mesozoic Enaliosaurs.

Friday, June 12, 2015 11:51

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(Before It's News)

Earlier we looked at three tylosaurs distinguished by their widely varying flipper size. Today we’ll do the same with a few closely related pliosaurs (Fig. 1) and ichthyosaurs (Fig. 2).

Figure 1. Three pliosaurs, Trinacromerum, Brachauchenius and Kronosaurus, to scale, all Late Cretaceous. Variations in flipper size, rib count and girdle size mark the major differences here. The girdles anchored large ventral swimming muscles. Scale bar = 1 meter. How flipper size affected speed and agility is a topic that has not been brought up yet, as far as I know.

Pliosaurs were some of the largest marine reptiles of all time.
They reached an acme in the Late Cretaceous with a variety of morphologies derived from smaller ancestors. Shown here are Trinacromerum, Brachauchenius and Kronosaurus, three taxa rarely shown together to scale. The big difference is in flipper size. It’s also worth noting the size of the girdles anchoring each flipper set. In whales, flipper size also varies greatly and not always for swimming advantage.

Ichthyosaurs,
even closely related ones (Fig. 2), also had widely varying flipper sizes. Here we see ‘Cymbospondylus’ buchseri and the related Guizhouichthyosaurus. Both were probably sinuoous swimmers, rather than tail or flipper swimmers.

Figure 2. Two closely related ichthyosaurs, Guizhouichthyosaurus tangae and “Cymbospondylus” buchseri, one with large flippers, one with small.

References
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