Compsognathuslongipes

Overview: The Late Jurassic Solnhofen Limestone of Bavaria, Germany is known for many creatures of the air and sea, including pterosaurs, fish, marine crocodylomorphs, and the early bird Archaeopteryx, but not known for its large terrestrial animals, namely because it didn't have any. The top terrestrial predator and the only known non-avian dinosaur on the Solnhofen Islands was the pint-sized Compsognathus, a small theropod dinosaur. This petite predator of lizards and other small animals, discovered in the mid-19th Century, was very birdlike, and, along with Archaeopteryx, helped to inform early paleontologists' understanding of the evolution of birds.

Discovery: The original (holotype) skeleton of Compsognathus (BSP AS I 563) was discovered in the 1850s in the Solnhofen of Bavaria, Germany, by fossil collector Joseph Oberndorfer. He lent the fossil, a nearly complete juvenile skeleton preserved in 2-D on a limestone slab, to paleontologist Johann A. Wagner, and in 1859 Wagner published a brief discussion in which he named it Compsognathus longipes, Compsognathus meaning “elegant jaw” in Greek (“kompsos” = “elegant”; “gnathos” = “jaw”), and longipes meaning “long-footed” or “long-legged” in Latin. A complete adult specimen (MNHN CNJ 79) was discovered in the Portland Stone Formation of Canjuers, near Nice, France. These are the only two specimens known to science, though partial remains and teeth Bavaria and Portugal may also be Compsognathus or a close relative.

Evolution: Compsognathus was a theropod in the family Compsognathidae which appeared at least as early as the Late Jurassic and went extinct at the end of the Early Cretaceous. They were a family of small, lightly built predators. Compsognathids were basal (“primitive”) members of the clade Coelurosauria, which also includes tyrannosaurs, dromaeosaurs (“raptors”) and birds. Compsognathids are typically found to be more derived (“advanced”) than tyrannosaurs, but more basal than all other coelurosaurs.

Description: Compsognathus is one of the smallest known non-avian dinosaurs, though there are a few that were smaller. The juvenile specimen from Bavaria is estimated to have measured about 70–79 cm (28–35 in) long weighed 0.32-0.58 kg (0.71-1.3 lbs), while the adult from France would have been about1.4 meters (4.58 ft) in length and weighed 3.5 kg (7.7 lb). Compsognathus was lightly built and birdlike. It had relatively long legs, and shorter arms with two clawed fingers, and a smaller, possibly nonfunctional, third finger. The skull was gracile with a tapered snout, large eyes, and tiny jaws filled with around 86 small, sharp, recurved, teeth which were non-serrated at the front of the mouth but finely serrated toward the back of the mouth. Adults had more tooth positions than juveniles. The tail of Compsognathus was very long, around half its total length, and would have been used for balance. Like other compsognathids, and many other theropods, Compsognathus was probably feathered, though skin impressions from the tail show scales, indicating it may not have been completely covered in feathers. The early ornithischian dinosaur Kulindadromeus is known to have had feathers on its body but not its tail. Compsognathus may have had a similar integumentary arrangement.

Behavior and Ecology: Compsognathus lived in the Tithonian age of the Late Jurassic Period, about 150 million years ago. 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 becoming 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. Due to 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. Late Jurassic France, also home to Compsognathus, was a similar lagoonal environment.

Compsognathus would have lived on the islands at the edge of the Solnhofen Lagoon, and it shared its environment with numerous pterosaurs, including Pterodactylus and Rhamphorhynchus. On land, it shared its habitat with the early bird Archaeopteryx. Both Archaeopteryx and Compsognathus were predators and may have competed with each other for small prey items, including lizards, insects, pterosaurs, and perhaps each other’s young. Both specimens of Compsognathus include preserved stomach contents, showing definitively that if nothing else, Compsognathus was a predator of lizards. Despite its small size, Compsognathus appears to have been the apex predator on the islands, as well as the only non-avian dinosaur present. Compsognathus’s rarity in the Solnhofen Limestone is probably due to it living on land. The juvenile specimen from Bavaria was probably washed into the lagoon (perhaps by a storm) either shortly after it died, or right before it drowned.

Extinction and Legacy: Compsognathus is only known from the Tithonia Age, and by the end of the Jurassic, Compsognathus seems to have disappeared, though it is difficult to ascertain when and why it disappeared because there are only two known specimens. Today, Compsognathus can be seen beautifully preserved in museums. The original specimen is held at the Palaeontological Museum, Munich (Bayerische Staatssammlung für Paläontologie und Geologie) in Munich, Germany. The adult specimen is on display at the National Museum of Natural History (Musee d'Histoire Naturelle) in Paris, France. Replicas can be seen at other museums, including a 3-D reconstruction at the Museum of Ancient Life at Thanksgiving Point in Lehi, UT. Compsognathus featured prominently in the Jurassic Park Franchise, starting in the first sequel in 1997 (The Lost World: Jurassic Park) and in every subsequent film. Their biggest role was in the 1997 movie, where they were incorrectly called Compsognathus “triassicus”, combining Compsognathus with the species name of the outwardly similar coelophysoid Procompsognathus triassicus, which was featured in the novels. The Compsognathus of the Jurassic Park Franchise, nicknamed “Compies”, also lack feathers and are incorrectly depicted as willing to hunt big game (humans).