September 2, 2016 | David F. Coppedge

Birds and Pterosaurs Flew Together

Does it make evolutionary sense to find birds flying with pterosaurs?

Patagonia has yielded a new medium-sized pterosaur fossil with a wingspan on 1.5 meters, reports Live Science. Evolutionists are dating it between 175 and 200 million years old in the middle Jurassic. Because its skull was preserved along with an intact brain case, paleontologists think it might yield information about brain evolution in pterosaurs. That brain must have been pretty sophisticated, though. Stephanie Pappas writes,

Pterosaurs had a suite of adaptations that made them strong fliers. Their bones were feather-light, and they sported air sacs extending from their lungs to keep their body density down and their air exchange efficient, a 2009 study found.

Surprisingly, Pappas said nothing about another pterosaur story that appeared on the same day that challenges evolutionary thought.

That part is told on The Conversation by Elizabeth Martin-Silverstone, a PhD student at the University of Southampton, who worked with the discovery team of a late-Cretaceous pterosaur in British Columbia. Her headline reads: “Our new pterosaur fossil shows birds and small reptiles flew side by side.” She takes issue with the evolutionary explanation of why small pterosaurs have generally not been found from the period. According to the old story, small pterosaurs disappeared “because they were out-competed by early birds who forced them to evolve into much bigger animals.” Finding a relatively small one will force some revisions to the story (she shows her pterosaur reconstruction about the size of a cat).

But this mature pterosaur shows that small pterosaurs were living side-by-side with birds, coexisting, not competing.

Palaeontologists have had a big debate about what happened to pterosaurs during this time because few small fossils have been found. Older studies typically found no link between the decline of pterosaurs and the rise of birds, but recent work has suggested small pterosaurs just couldn’t compete with birds and only the biggest creatures survived.

However, this new specimen adds to some previous finds suggesting that small-bodied pterosaurs did exist during this time – it’s just that their fossils have rarely been found. Pterosaur fossils in general are notoriously poorly preserved because their bones were hollow and more easily damaged. This bias against pterosaur preservation, combined with the fact that places like the Dinosaur Park Formation exhibit a documented preservation size bias against small animals, with small dinosaurs and vertebrates rarely being found, means the odds are stacked against a small pterosaur being preserved and then discovered. We’ve also found very few young, large-bodied pterosaurs for the same reasons.

All this suggests that pterosaurs may have been more diverse at the end of the Cretaceous than previously thought, living side-by-side with their bird contemporaries.

This adds to the conundrum of what happened to the pterosaurs. If they were not stressed by competition, but lived right alongside flying birds, why did they go extinct with the dinosaurs? They were “strong flyers,” Pappas points out. They inhabited much of the globe from Patagonia to Canada. They seemed pretty successful. They came in all sizes. “While some pterosaur species were tiny, others grew to be the size of giraffes,” she notes. “These behemoths may have used their limbs to leapfrog into flight, paleontologists say.” See also Mindy Waisberger’s report in Live Science that concurs the small pterosaur likely flew with the birds.

To be sure, there is some doubt the fossil is a pterosaur instead of a bird, National Geographic points out (but Nature disagrees, saying the discoverer did due diligence to identify the fossil). But there doesn’t seem to be any evolutionary trend in pterosaurs. What they thought was a trend turns out to be a selection effect called taphonomic bias: a difference in preservation potential based on size. This one may not be the last. Nature quotes USC paleontologist Michael Habib: “If there’s one, there were probably others. Then we’d need to rethink what we previously thought about survivability of these little ones.”

Pterosaurs appear fully formed in the fossil record, already as strong flyers. They survive over 100 million Darwin Years, and then vanish. Does that make evolutionary sense?

Answer to the rhetorical question: No, it doesn’t. It can’t, because “evolutionary sense” is a sophoxymoronic phrase.

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