Tuesday, February 28, 2017

Platypterygius: Beast of the Week

This week we will be looking at a successful ichthyosaur.  Enter Platypterygius!

Platypterygius was a relatively large ichthyosaur, group of marine reptiles that converged with fish in their body shape, that could grow to be about twenty three feet long from snout to tail.  The genus encompasses several species that have been found around the world, including Australia, United States, Russia, Colombia, and Argentina.  That, alone, makes this creature a success story in the grand scheme of things.  However, it is when Platypterygius lived that makes it truly impressive.  Most ichthyosaurs lived during the Triassic and Jurassic.  It is thought by most that by the time the Cretaceous came around, the poor ichthyosaurs were outcompeted by newer forms of large marine reptiles like pliosaurs and mosasaurs.  But not Platypterygius!  This gritty reptile persisted all the way through to the late Cretaceous, 131 to 91 million years ago!

Platypterygius sp. native to what was once Texas, USA, life reconstruction by Christopher DiPiazza.  This genus is known to have eaten turtles in life.

Like its closest relatives, Platypterygius had the telltale ichthyosaur profile, which superficially resembles a combination of a tuna and a swordfish at first glance.  It had a long pointed snout, lined with sharp teeth.  It had four flippers that evolved from walking limbs millions of years prior.  The back flippers were proportionally much smaller than the front ones.  It likely had a tail fluke of some kind and dorsal fluke, as well.  It's eye sockets were relatively large so they were likely comfortable hunting in deep water where there was less light and/or during the night.  Platypterygius is defined by having more finger bones than what is typical of ichthyosaurs in its front limbs.  These bones are especially flat and widened to form the broad paddle appendage it used for swimming in life.  It is because of this specific morphology it earned its genus name, which translates to "flat wing".

Platypteregius americanus skeleton at the Royal Tyrrell Museum in Canada.  Photo by By Roland Tanglao

The earlier forms of Platypterygius that lived during the early Cretaceous were specialist hunters as far as we can tell, preferring to hunt fish and cephalopods. (like squid and ammonites)  These species, like Platypterygius hauthali, from South America (lived between roughly 131 and 125 million years ago), had relatively streamlined bodies and longer pectoral (front) flippers.  These are adaptations for fast swimming so they could pursue their quick-moving prey.  Millions of years later, however, we see a shift in strategy.  Species of Platypterygius that lived towards the end of the Cretaceous, like P. americanus (time range of 112 to 91 million years ago), were bulkier, with proportionally shorter flippers. Their teeth were also slightly larger and more robust.  In addition to differences in morphology, the later forms of this genus show evidence of hunting differently, too. Paleontologists have discovered remains of different kinds of prey in their stomach cavities, including bones from birds, and even sea turtles.  This paints a picture of an ichthyosaur that was less picky about what it considered prey, and was able to afford pursuing this wider menu with a little extra muscle at the price of speed.  Platypterygius managed to carve out a more generalist niche when its relatives were going extinct in reaction to increasing competition from other kinds of marine reptiles that were appearing during the Cretaceous, like pliosaurs and mosasaurs.

Platypteregius sp. tooth.  Photo by Nathan Van Vranken.

That is all for this week!  Special thanks to paleontologist, Nathan Van Vranken, who is currently finishing a new scientific publication on ichthyosaurs, including Platypterygius, for lending his brain to this post.  As always leave a comment below or on our facebook page!


Arkhangel’sky, M. S., Averianov, A. O., Pervushov, E. M., Ratnikov, V. Yu, and Zozyrev, N. Yu., 2008, On ichthyosaur remains from the Cretaceous of the Voronezh region: Paleontological Journal, v. 42, n. 3, p. 287-291.

Van Vranken, Nathan, 2017, Texas Cretaceous Ichthyosaurs: A Glimpse of Their Last Days in the Early Late Cretaceous.

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