During the early 1920s, Charles W. Gilmore, a paleontologist from the Smithsonian Institute in Washington, DC, was prospecting for fossils in Alberta, Canada. While on this trip, he would discover several new species of dinosaurs, including a strange creature known only from a pair of incomplete hands. These hands had long slender fingers, which was highly unusual for theropods known at the time. He officially named and described them as Chirostenotes pergracilis in 1924.
The hands of Chirostenotes pergracilis. Illustration by Tracy Ford. From The Dinosaur Society Dinosaur Encyclopedia, written by Don Lessem and Donald F. Glut. New York: Random House, Inc., 1993. Page 109. Image used with permission.
Chirostenotes was originally believed to be a member of the family Elmisauridae. This is an enigmatic group of dinosaurs, whose members consist of only one genus, Elmisaurus. This animal lived in Mongolia during the late Cretaceous Period about 80 MYA, and the only evidence that we have of its existence is one incomplete foot and a hand found in 1970. Scientists recognized that the hands of Chirostenotes and Elmisaurus looked similar, and so Chirostenotes was placed into that family. By 1990, Elmisauridae was recognized as an invalid family name, and it was discarded.
Chirostenotes is now classified as a member of the family Caenagnathidae, named after the genus Caenagnathus, which might actually be the same animal as Chirostenotes (as early as 1990, scientists suspected that these two might actually be the same animal). The caenagnathids were a group of bird-like theropod dinosaurs who belonged to a much larger group called the oviraptorosaurs, who are well-known from Asia. Their presence in North America only adds further proof to a faunal exchange between Asia and North America. Caenagnathids are distinguished from oviraptorids by their feet, which look more like those of the ornithomimids, more commonly-known as “ostrich dinosaurs”. This suggests that the oviraptorosaurs evolved from the ornithomimids. According to current phylogenic analysis, the ornithomimids are more primitive than the oviraptorosaurs, so this hypothesis might be plausible.
The lower jaw of Caenagnathus collinsi, with a hypothetical upper jaw. Illustration by Tracy Ford. From The Dinosaur Society Dinosaur Encyclopedia, written by Don Lessem and Donald F. Glut. New York: Random House, Inc., 1993. Page 79. Image used with permission.
Because Caenagnathus and Chirostenotes are known from incomplete specimens, nobody can make up their minds as to whether or not they’re two separate genera or if they’re the same animal. Some paleontologists firmly believe the former, while others firmly believe the latter. Because of their incompleteness, we are also not 100% sure what the animal looked like. It’s reasonably certain that it bore a strong resemblance to Oviraptor, Citipati, or Anzu, but any recreation of what the entire animal looked like is guesswork. During the 1980s and 1990s, there were a wide range of images crafted by various paleo-artists which took a stab at what the whole animal would look like if it were fleshed out. Ever since the discovery of Anzu, which is both the largest and most well-known caenagnathid, the diversity of images has largely disappeared. Now, modern depictions of both Caenagnathus and Chirostenotes, if you can find them, are really nothing more than clone copies of Anzu, which I disagree with not only as a paleontology buff but also as an artist.
Below is my own rendition of what I think Caenagnathus, or possibly Chirostenotes, or both, would have looked like. Since no complete skull of either species has been found, the design for the head is based upon a hypothetical skull drawing made by Tracy Ford. My drawing was made on printer paper with No. 2 pencil, Crayola and Prismacolor colored pencils, and a black felt-tipped marker. Since my scanner has a tendency to wash out a lot of the detailing, I had to do a bit of touching-up on my computer to replicate how the image looks in real life. Hope you enjoy, and keep your pencils sharp.
Caenagnathus collinsi. © Jason R. Abdale. May 11, 2018.
UPDATE: In the year 2020, a research paper was published by Gregory F. Funston and Philip Currie which stated that new fossils of Chirostenotes had been discovered in Alberta, Canada. These fossils were distinct enough from those of Caenagnathus to support the idea that Caenagnathus and Chirostenotes ought to be considered as two separate genera.
For more information, please look at the following sources:
- Funston, Gregory F.; Currie, Philip J. “New material of Chirostenotes pergracilis (Theropoda, Oviraptorosauria) from the Campanian Dinosaur Park Formation of Alberta, Canada”. Historical Biology: An International Journal of Paleobiology (February 2020). DOI: 10.1080/08912963.2020.1726908. Published online.
- Funston, Gregory (July 27, 2020). “Caenagnathids of the Dinosaur Park Formation (Campanian) of Alberta, Canada: anatomy, osteohistology, taxonomy, and evolution”. Vertebrate Anatomy Morphology Paleontology, volume 8 (1): Pages 105-153. https://journals.library.ualberta.ca/vamp/index.php/VAMP/article/view/29362.
- Greg Funston Paleontology. “The Caenagnathids of Dinosaur Park” by Gregory F. Funston (July 27, 2020). https://gregfunston.com/2020/07/27/the-caenagnathids-of-dinosaur-park/.