Monday, April 9, 2018

Hamipterus: Beast of the Week

This week we will be checking out a pterosaur that gave us tremendous insight on how pterosaurs reproduced!  Enter Hamipterus tianshanensis!

Hamipterus was a medium-sized pterosaur that lived in what is now China, during the early Cretaceous period, about 120 million years ago.  Judging by its pointed teeth it was likely a meat-eater in life.  The largest individuals of this species have wingspans of about eleven feet.  The genus name translates to "Hami Wing" in reference to the Hami region in China where it was found, and the fact that it's was  pterosaur...which have wings.

Female (left) and male (right) Hamipterus.  It is likely these pterosaurs met in large groups on sandy banks to nest.

Hamipterus is known from over forty individuals, that all died at the same time millions of years ago.  This was sad for them, but awesome for paleontologists, who got a great sample size of individuals to study.  In this large group were two kinds of adults with differently shaped crests.  Like it's relative, Pteranodon, it it likely that these differing crests represent males and females, suggesting sexual dimorphism in yet another pterosaur.  The females likely were the individuals with shallow ridge-like crest that ran from the top of the snout to the top of the cranium, over the eyes.  The males had similar crests, but the front part on the snout was flared out more, rounding out towards the tip of the snout.  In addition, the individuals with the larger crests (probably the males) were larger, with eleven-foot wingspans, while the shorter-crested females typically appear to have only had roughly five-foot wingspans.

Skulls of a  (probably) female Hamipterus on the left and (probably) male on the right,.  Note the males, larger, more protruding crest. (image from Xiaolin's 2017 paper)

The teeth of Hamipterus were pointed, and interlocked when the jaws were closed. It is most likely this pterosaur was eating meat, possibly specializing in grabbing slippery fish and other aquatic prey when alive.

Amazingly enough, eggs were also found buried among the bones of the Hamipterus!  This suggests that all these individuals may have died while in a nesting colony.  Large groups of animals nesting in the same area is a behavior seen by many kinds of modern birds, so the fact that pterosaurs may have done the same is exciting.  However, the eggs, themselves, of Hamipterus weren't very similar to those of birds, which have hard, brittle, outer shells.  Upon close examination, it was discovered that the Hamipterus eggs had very thin outer shells but relatively thick membranes under the shells, meaning they would have been leathery and pliable in life.  This is much more similar to the eggs of many kinds of snakes and lizards.  Like many squamates (snakes and lizards), Hamipterus may have buried its eggs in the fine sediment until they (would have) hatched.

The fossilized egg of Hamipterus (left) compared to that of a  modern Rat Snake's on the right. (image from Xiaolin's 2017 paper)

The embryos, themselves, found in some of these eggs show fully developed legs, but underdeveloped arms.  This lead some to believe that the baby pterosaurs were unable to fly as soon as they hatched, and therefore needed to be taken care of by one or both of their parents until they could better fend for themselves.  However, keep in mind that these were embryos that had underdeveloped arms, so it is very possible that they weren't done growing before hatching and by the time they did hatch, they very well may have had more developed wings, capable of flight right out of the egg.  We still don't know for sure!

That is all for this week!  As always feel free to comment below or on the facebook page!


Xiaolin Wang; Alexander W.A. Kellner; Shunxing Jiang; Qiang Wang; Yingxia Ma; Yahefujiang Paidoula; Xin Cheng; Taissa Rodrigues; Xi Meng; Jialiang Zhang; Ning Li; Zhonghe Zhou (2014). "Sexually dimorphic tridimensionally preserved pterosaurs and their eggs from China". Current Biology24 (12): 1323–1330.

Xiaolin Wang, Alexander W. A. Kellner, Shunxing Jiang, Xin Cheng, Qiang Wang, Yingxia Ma, Yahefujiang Paidoula, Taissa Rodrigues, He Chen, Juliana M. Sayão, Ning Li, Jialiang Zhang, Renan A. M. Bantim, Xi Meng, Xinjun Zhang, Rui Qiu & Zhonghe Zhou (2017). Egg accumulation with 3D embryos provides insight into the life history of a pterosaur. Science 358(6367): 1197-1201.

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