Rhamphorhynchus: Beast of the Week

Rhamphorhynchus was a pterosaur that lived in what is now Germany during the late Jurassic period, between 150 and 148 million years ago.  The adults measured about four feet (1.2 meters) long from beak to tail and had wingspans of about six feet (1.8 meters) wide.  When alive Rhamphorhynchus would have eaten meat, mostly in the form of fish and other marine life.  The genus name translates to "Beak Snout" from Greek.  Rhamphorhynchus muensteri is by far the most well known species of Rhamphorhynchus, known from many individual specimens, however, there is also a species known from a single wing fossil found in what is now Dorset, England, called Rhamphorhynchus etchesi.

Rhamphorhynchus muensteri life reconstruction in watercolors by Christopher DiPiazza.

Rhamphorhynchus belonged to the group of pterosaurs that existed from the Triassic to the early Cretaceous periods, characterized by their proportionally smaller heads short legs, and long narrow tails, called rhamphorhynchoids. (named after Rhamphorhynchus, itself.)  In addition to their wings, which form from flexible skin attached from the tip of their fourth finger (which was extremely long and sturdy) to about the ankle, pterosaurs from this group also sported a membrane between their legs, which likely aided in flight.  Pterosaurs from this group also sported teeth, and Rhamphorhynchus was no exception.  The teeth of Rhamphorhynchus, were particularly long, slightly curved, and interlocked when the jaws were closed.  The tip of its jaws also curved into each other and were beaklike.  This seems to be an adaptation for grasping fish, cephalopods, and other slippery marine prey.  

Rhamphorhynchus skeleton on display at the Royal Ontario Museum that showcases preserved soft tissue, like wing membranes and the tail vane.

At the tip of its tail, Rhamphorhynchus sported a fan-like structure, called a tail vane, which may have helped it steer during flight.  Since Rhamphorhynchus is known from many individuals of different stages of maturity when they died with soft tissue preserved, we know that the shape of this structure changed as the animal aged.  The youngest individuals sported narrow, oval-shaped vane, slightly older individuals had vanes that were more pointed and diamond-like, while in the most mature individuals the tip of the vane flared out into an almost sideways triangle shape.  Because of this change it is possible the vane may have had a role in some sort of communication, like sexual display within the species, as well.  Originally, scientists thought Rhamphorynchus consisted of several more species than the two listed at the top of this post, grouping them based on size and tail vane shape.  More recently, however, it was determined they more likely mostly the same species at different developmental stages of life. 

Rhamphorhynchus fossil with imprints of the wing membranes and tail vane cast on display at the American Museum of Natural History in New York.

Since Rhamphorhynchus is known from many specimens of various sizes, paleontologists were able to study and predict how it would have grown as it aged when alive.  Thanks to a study in 2012, examining various specimens of different stages when they died, it was determined that like many modern reptiles, Rhamphorhynchus would have been able to survive on its own soon after hatching, meaning it was likely able to fly right away, and would have grown rapidly early in life.  This growth spurt seemed to slow down at about three years of age, which also seems to be when they were fully mature.  

The environment that Rhamphorynchus lived in would have been a series of islands with lagoons in a relatively shallow sea.  It likely would have hunted over the water, snatching small fish and other marine animals off the surface of the water while flying.  It would have coexisted with fellow pterosaur, Pterodactylus, and the dinosaurs Archaeopteryx and Compsognathus.  

References

Bennett, S. C. (1995). "A statistical study of Rhamphorhynchus from the Solnhofen Limestone of Germany: Year-classes of a single large species". Journal of Paleontology. 69 (3): 569–580.

Prondvai, E.; Stein, K.; Ősi, A.; Sander, M. P. (2012). Soares, Daphne (ed.). "Life history of Rhamphorhynchus inferred from bone histology and the diversity of pterosaurian growth strategies". PLOS ONE. 7 (2): e31392.

O'Sullivan, Michael; Martill, David M. (June 2015). "Evidence for the presence of Rhamphorhynchus (Pterosauria: Rhamphorhynchinae) in the Kimmeridge Clay of the UK" Proceedings of the Geologists' Association. 126 (3): 390–401.