Geosternbergia: Beast of the Week

 This week we are looing at a famous pterosaur.  Check out Geosternbergia sterngergi!  

I'm going to start this post off with pointing out that Geosternbergia is considered simply a separate species within the genus, Pteranodon, by many experts, which would make its name Pteranodon sternbergi.  That being said, since I already did a post on Pteranodon longiceps, I'm choosing to refer to this pterosaur as Geosternbergia.  (taxonomy is complicated and also subject to change especially with fossils)

Geosternbergia was a large pterosaur that flew over the oceans that covered what is now central United States and southern Canada, during the late Cretaceous period, between 88 and 85 million years ago.  It was a huge pterosaur, the largest individuals sporting wingspans of 20 feet (6m) wide.  When alive they would have eaten meat, most likely primarily fish and other marine prey. The genus name is derived from the name of the paleontologist George Sternberg, who found the first fossils of this pterosaur in the early 1950s.  

Watercolor reconstruction of male and female Geosternbergia by Christopher DiPiazza.

Geosternbergia had a proportionally huge skull, which measured over four feet long in the largest specimens.  Most of this skull comprised on its long, toothless, roughly banana-shaped beak. It is likely it used this beak to dip into the surface of the ocean as it flew, to grab prey.  The top jaw extended past the lower jaw, ending in a sharp point.  The eye sockets were actually proportionally tiny, but it still likely had sharp vision. 

Growing out the top of Geosternbergia's skull was a tall, somewhat triangular crest.  Since only the larger adult specimens possessed this crest, it is likely this pterosaur was sexually dimorphic. In addition the adults with the large crests, who are believed to have been males, also were overall much larger and have narrower hips than the ones thought to be females.  Even more interesting is the fact that out of the many specimens of this pterosaur that have been found, the number of adult females is almost double males.  This has led some experts to suggest that they may have exhibited polygynous mating behavior, where each male mates with multiple females.  This also aligns with males being larger and possessing elaborate display structures, since they'd be competing with each other for mates. Modern examples of this are many, including lions, chicken, and sea lions, just to name a few. 

Skull of male Geosternbergia on display at the Sternberg Museum of Natural History in Kansas.

Geosternbergia's body is almost comically small, with the torso only a fraction of the skull length.  Like most late-surviving pterosaurs, it would have been able to comfortably walk around on all fours, folding its extremely long fourth finger, which forms the wing, upwards while on the ground.  It is likely, however, given what we know about its environment, that Geosternbergia spent most of its time at sea, possibly coming to land mostly just to mate and lay eggs.  Its proportionally huge wingspan also supports this idea, which would have allowed it to stay aloft with without expending too much energy, similar to modern sea birds.

Mostly complete skeleton of what is likely a male Geosternbergia, formerly thought to be a distinct genus, called Dawndraco.  (the short rounded crest is reconstructed)

  When alive, Geosternbergia, would have shared its habitat with many numerous kinds of other pterosaurs and sea birds.  In the water below it would have likely hunted any small fish or mollusk it could snatch.  In turn Geosternbergia would have risked becoming food for larger predators, like sharks and the monstrous marine lizard, Tylosaurus, when it was near or in the water.  

References

Bennett, S.C. (1992). "Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests". Journal of Vertebrate Paleontology. 12 (4): 422–434.

Bennett, S.C. (1994). "Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloida)". Occasional Papers of the Natural History Museum, University of Kansas. 169: 1–70.

Martin-Silverstone E., Glasier J., Acorn J., Mohr S., Currie P. (2017). "Reassesment [sic] of Dawndraco kanzai Kellner, 2010 and reassignment of the type specimen to Pteranodon sternbergi Harksen, 1966". Vertebrate Anatomy Morphology Palaeontology. 3: 47–59.

Miller, H. W. (1971). "A skull of Pteranodon (Longicepia) longiceps Marsh associated with wing and body parts". Transactions of the Kansas Academy of Science. 74 (10): 20–33.

Sternberg, G. F.; Walker, M. V. (1958). "Observation of articulated limb bones of a recently discovered Pteranodon in the Niobrara Cretaceous of Kansas". Transactions of the Kansas Academy of Science. 61 (1): 81–85.

Zimmerman, H., Preiss, B., and Sovak, J. (2001). Beyond the Dinosaurs!: sky dragons, sea monsters, mega-mammals, and other prehistoric beasts, Simon and Schuster.