Rhamphorhynchusmuensteri

Overview: One of the largest pterosaurs from Late Jurassic Europe was Rhamphorhynchus, though with an average adult wingspan of just under six feet, it was still fairly small by Cretaceous pterosaur standards. It was discovered in the early 19th Century in the famous Solnhofen Limestone of Bavaria, Germany, and may have lived in England, Portugal, Spain, and Tanzania as well. Due to the remarkable preservation characteristic of the Solnhofen, this nocturnal fisher is known from multiple complete specimens, some of which even preserve soft tissue imprints of the wings and tail!

Discovery: Rhamphorhynchus muensteri was first discovered in the Solnhofen Limestone of Bavaria, Germany, and was brough to the attention of early paleontologist Samuel Thomas von Sömmerring in 1825 by the collector Georg Graf zu Münster. Sömmerring thought it was a species of Pterodactylus, at the time sometimes incorrectly called Ornithocephalus, and it was named Ornithocephalus Münsteri, in honor of Münster. A description of the fossil was published by Georg August Goldfuss in 1831, which made the name official. In 1839, Münster named additional material Rhamphorhynchus longicaulus, Rhamphorhynchus meaning “beak snout” from Greek “rhamphos” (beak) and “rhynchus” (snout). In 1845, Hermann von Meyer changed the genus name from Ornithocephalus to Pterodactylus, since by that time scientists had realized that Pterodactylus had name priority over the synonymous Ornithocephalus. In 1846 and 1847, von Meyer named Rhamphorhynchus longicaulus and Rhamphorhynchus gemmingi based on different material, Rhamphorhynchus meaning “beak snout” from Greek “rhamphos” (beak) and “rhynchus” (snout). It wasn’t until 1861 that the original species was recognized as Rhmaphorhynchus by Sir Richard Owen, becoming Rhamphorhynchus münsteri. 1888 the species name was changed to muensteri to abide by ICZN (International Commission on Zoological Nomenclature) rules which banned non-Latin characters. Over the years, many specimens have been found in the Solnhofen Limestone, and it has been suggested that most or all of these, even those labeled as different species were actually just different growth stages of Rhamphorhynchus muensteri. Additional species may have existed in England, Iberia (Portugal and Spain), and Tanzania.

Evolution: Rhamphorhynchus was a pterosaur in the family Rhamphorhynchidae. Rhamphorhynchids had long tails, identifying them as basal (“primitive”) pterosaurs, though they were more derived (“advanced”) than many other long-tailed pterosaurs, like the earlier Dimorphodon. Rhamphorhynchids first appeared at the end of the Early Jurassic, and Rhamphorhynchus itself appeared in the Late Jurassic.

Description: Like all other pterosaurs, Rhamphorhynchus had wings made of a membrane supported by a hyper-elongated fourth finger. Like other non-pterodactyloid (short-tailed) pterosaurs, Rhamphorhynchus had a long tail with a vane at the end. The shape of the vane changed as the animal matured, starting out as an oval in juvenile specimens, then becoming diamond shaped as it grew, and ultimately becoming triangular in the largest individuals. Rhamphorhynchus had a relatively short skull, large eyes, and it is known for its somewhat upturned bill, the lower jaw of which has an especially strong curve, while the upper jaw is longer and only slightly curved. The bill was lined with relatively large, long, conical teeth. In juveniles, the bill was shorter and more rounded, and lacked the “hook” in the lower jaw. They also had more needle-like teeth. As they grew, the bill became longer and pointier, and the lower jaw developed the “hook” shaped curve at the end. The number of teeth stayed the same, but as they grew, the teeth became thicker. Unlike Pterodactylus, which shared its habitat, Rhamphorhynchus lacked either a boney or a soft tissue crest. Rhamphorhynchus was also larger, with wingspans of around 1.81 (5.9 ft) though some may have grown even larger, achieving wingspans of 3 meters (9.84 ft). Thus, Rhamphorynchus was one of the largest of the long-tailed pterosaurs, and one of the largest pterosaurs of the Jurassic.

Typical of pterosaurs, Rhamphorhynchus was probably warm blooded and covered in a coat of fur-like down called pycnofibers. However, they had a more reptilian growth rate, just slightly higher than that of an alligator’s, and it has been suggested that they might have actually been cold-blooded. However, given their phylogeny (evolutionary relationships), their active lifestyle, and the fact that growth rate isn’t always a perfect proxy for metabolism, it can be reasonably assumed that they were indeed warm-blooded, though they might have run cooler than other warm-blooded animals.

Behavior and Ecology: Rhamphorhynchus lived in the Tithonian age of the Late Jurassic Period. Back then, the Tethys Sea had flooded much of Europe. Island land masses dotted the shallow seas of Europe and provided homes for pterosaurs and dinosaurs. The Solnhofen Limestone of Bavaria was a sheltered tropical lagoon between an island archipelago and a coral reef. Despite being surrounded by water, these islands were somewhat dry, getting little rain, and the plants that grew there were mostly shrubs. Larger trees were rare, with most maxing out around 3 m (10 ft). These would have included conifers and Cycads. The flora would have resembled that of modern New Caledonia, albeit with a drier climate. The sea surrounding the islands would have been warm and shallow, with clear water and abundant carbonate-forming plankton. These plankton used calcite (calcium carbonate) to form tiny shells, and when they died, these shells would collect on the sea floor, eventually becoming limestone. The Solnhofen Lagoon itself would have varied in depth, at times almost drying up and become hyper-saline (saltier than normal seawater). Due to its limited connection to the rest of the sea, the lagoon also had poor circulation which often resulted in anoxia (low to no oxygen). Because of this, there wasn’t always a lot living in the lagoon itself, particularly lower in the water column. Because of the lack of scavengers and the generally calm water, when animals died in the lagoon, they were often gently buried by the carbonate mud (dead calcite plankton) and left undisturbed, resulting in near perfect preservation.

Rhamphorhynchus would have lived on the islands at the edge of the Solnhofen Lagoon, and it shared its environment with numerous other pterosaurs, including the short-tailed pterosaur Pterodactylus. On land, it shared its habitat with the early bird Archaeopteryx, and the small bird-like theropod Compsognathus. Both Archaeopteryx and Compsognathus were predators and may have preyed on Rhamphorhynchus, perhaps especially young Rhamphorynchus, and other small pterosaurs, if they could catch them. Compsognathus, despite only having an adult length of 1.4 m (4 ft 7 in), appears to have been the apex predator on the islands and may have been Rhamphorynchus’s greatest threat on land, though given Rhamphorhynchus’s relatively large size, Compsognathus may not have seen it as prey, and land may have been quite safe. Rhamphorynchus’s main predators lived in the water, which was also where Rhamphorhynchus’s prey lived. Rhamphorhynchus was a piscivore, meaning it ate mostly fish. To feed, it would have left the relative safety of the islands to go hunt in the lagoon, or the open Tethys. Features of the arm bones suggest that like many modern seabirds, Rhamphorhynchus was capable of swimming and taking off from the surface of the water.

However, hunting at sea had its risks. Large predatory fish are known to have preyed upon Rhamphorhynchus thanks to an exquisitely preserved fossil of an Aspidorhynchus which died while attempting to eat a Rhamphorhynchus which had itself just swallowed a smaller fish called Leptolepides. In their struggle, they probably sunk to an oxygen-poor layer of the lagoon where the Aspidorhynchus suffocated and sank to the bottom, still entangled with the drowned pterosaur. Rhamphorhynchus would have also had to be wary of marine reptiles, including the apex predator of the region, the marine crocodylomorph Dakosaurus.

Unlike Pterodactylus and some of the other Solnhofen pterosaurs, analysis of its sclerotic rings (rings of bone that are set in the eyes of some animals) show that Rhamphorhynchus was nocturnal (active at night). By being active and hunting at a different time than diurnal (active during the day) pterosaurs, Rhamphorhynchus and other nocturnal pterosaurs would have helped reduce competition between the numerous species that called the Solnhofen Lagoon their home.

Extinction and Legacy: Rhamphorhynchus seems to have disappeared around 148.5 million years ago, for unknown reasons, though it may have been in part due to competition from pterodactyloid pterosaurs. When Rhamphorhynchus disappeared, that was the end of the long-tailed pterosaurs, with the exception of a few members of the family Anurognathidae which survived into the Early Cretaceous. Pterodactyloids on the other hand, would continue to be successful until the end of the Cretaceous. Now Rhamphorhynchus can be seen in various museums including the Royal Ontario Museum in Toronto, Ontario, Canada, the Yale Peabody Museum in New Haven, Connecticut, USA. Rhamphorhynchus was featured in the third episode of the 1999 BBC documentary Walking with Dinosaurs.