by Zach Lyons-Weiler
Both visitors and staff love Carnegie Museum of Natural History’s Dinosaurs in Their Time exhibition for many reasons. For some people, it is the huge dinosaurs such as Tyrannosaurus and Diplodocus that capture the imagination. For others, it is the Quetzalcoatlus that soars above the latest Cretaceous display, or the cute Psittacosaurus with its strange tail ornamentation. But for me, my favorite specimen is a rather obscure fossil replica hidden in plain sight in the Triassic and Early Jurassic area of the hall. Its name is Icarosaurus, and it is quite possibly one of the strangest animals that we have on display. When one first sees it, it looks like a cast of a jumble of bones on a background of dark shale. However, as you will come to realize, Icarosaurus is far more than just that!
The Carnegie Museum’s Icarosaurus (which is a high-quality replica of the only known original fossil) is displayed in a glass case alongside many other casts and fossils from what is known as the Newark Supergroup, a large deposit of rocks that snake their way from South Carolina to New Brunswick and Nova Scotia. These rocks were deposited during the Triassic and early Jurassic periods, or from roughly 230 to 190 million years ago. The sedimentary rocks here are intermittently intruded by younger volcanic rocks, indicating that this area was undergoing tremendous geological change at this time. During the Triassic and Early Jurassic, the supercontinent Pangaea was in the process of splitting up. The eastern coast of North America was rifting from western Africa, opening a furrow that would become the Atlantic Ocean. Before it was ocean, though, the rift was filled with lakes that were similar to Lake Victoria and Lake Tanganyika in today’s Great Rift Valley in Africa. The climate was warmer, too, and so the environment was wet and tropical. Due to climatic changes and natural oscillations in Earth’s orbit, these ancient rift environments would go through stages, from deep lakes to mudflats. Each layer preserved the remains of life that lived during that specific interval. Layers of rock deposited in deep lakes often contain abundant fossils of fishes, invertebrates, and reptiles. Other layers preserve footprints of early dinosaurs and other animals. Still others preserve the remains of cynodonts, which were the forerunners of mammals.
Dating to the late Triassic Period, the remains of Icarosaurus were discovered in one of the deep lake deposits by three teenagers in a quarry near North Bergen, New Jersey, which is just outside New York City. Upon discovering the fossil, they realized its importance and donated it to New York’s American Museum of Natural History, where it was named in 1966 as Icarosaurus siefkeri. This is, to this day, the only known specimen of this reptile, so it is of tremendous scientific value. Other lizard-like reptiles had been found in these deposits, but what made Icarosaurus so unique were the extremely long and unusual ribs that extended from its body. These ribs are similar in form to those of lizards in the extant genus Draco, which have elongated ribs connected by membranes of skin that they extend to glide between trees in their Southeast Asian rainforest homes. Because the rib anatomy of this modern group is so similar to that of Icarosaurus, scientists reasoned that the latter would have glided between trees in a comparable manner.
Icarosaurus was not the first reptile to have evolved this trait, though. During the Permian Period, around 260 million years ago, reptiles such as Coelurosauravus had adapted to a gliding lifestyle. Other extinct reptiles that evolved gliding morphologies include Mecistotrachelos from the Triassic of Virginia and Xianglong from the Cretaceous of China. The extreme similarity between these distantly related reptile groups is a remarkable example of convergent evolution, which is a process where organisms evolve the same traits due to their populations facing similar selective pressures. Other examples of convergent evolution that can be seen in the Triassic and Early Jurassic exhibits in Dinosaurs in Their Time are the phytosaurs Redondasaurus and Rutiodon, which resemble their distant relatives, crocodiles, and ichthyosaurs such as Ichthyosaurus and Stenopterygius, which bear an uncanny resemblance to dolphins.
The high school students that discovered Icarosaurus were lauded for their donation, and the discovery of such an odd animal made headlines in both the local and national news. Unfortunately, though, the fame and unique nature of the fossil caused some issues. The man for whom Icarosaurus siefkeri was named, Alfred Siefker, repossessed the fossil to put it in his personal collection in 1989. It stayed there until 2000, when he tried to sell it at auction. Understandably, the scientific community was upset with this decision, because if the fossil were to be sold into a private collection then it would be unavailable for scientific study. It was bought at the auction for well under its appraised value, and the buyer, Dick Spight, donated it back to the American Museum that same year. The original Icarosaurus specimen is currently on display at that venerable New York institution.
Overall, Icarosaurus is a remarkable little animal that deserves more attention than it gets. Look for it and other unique prehistoric animals the next time you visit the Dinosaurs in Their Time exhibition.
Zach Lyons-Weiler is a Gallery Experience Presenter in CMNH’s Life Long Learning Department. Museum staff, volunteers, and interns are encouraged to blog about their unique experiences and knowledge gained from working at the museum.
Colbert, Edwin Harris. “The Triassic gliding reptile Icarosaurus.” Bulletin of the American Museum of Natural History; v. 143, article 2. (1970). https://www.scientificamerican.com/article/icarosaurus-home-to-roost/
Colbert, Edwin Harris. “Adaptations for gliding in the lizard Draco.” American Museum Novitates; no. 2283. (1967).
Carnegie Museum of Natural History Blog Citation InformationBlog author: Lyons-Weiler, Zach
Publication date: July 30, 2021