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Caenagnathus, or Chirostenotes, or…um…something…

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/

 

Ornithomimus, Before and After

Hello all. I’ve recently finished an important writing project that I’ve been laboring upon for months. Now that it’s finished, I have a little breathing room to do art, and this is what I’ve done so far. I decided to do an updated version of an old illustration that I had made of an Ornithomimus. While the general color scheme was what I had in mind, I was never truly happy with the end-product. This latest version is much more in line with what I was imagining the “Bird Mimic” would look like.

Here is the “before” picture, made in 2013.

 

And here is the “after”, made today.

 

You’ll notice several differences right away, the most noteable of them being the re-shaping of its wing feathers. While Ornithomimus, or perhaps ornithomimids in general, had pennaceous feathers, I don’t think that they had primaries, because those would have been attached onto the wrist and the hand. This would have been difficult for ornithomimids because, unlike “raptor” dinosaurs (dromaeosaurids and troodontids), ornithomimids could not flex their hands backwards. I also increased the size of its tail feathers, made the neck thicker, changed the shape of the skull so that it was more anatomically accurate, and added Secretary Bird-style feathers to the back of its head. So much for form. In terms of color, I made it more vibrant, with deeper richer yellows and oranges and a lot more black patches. I changed the color of its bare skin from pink to a mixture of tan and black. I made its beak black, I changed its eye from yellow to blood red, and gave it black feet.

I can definitely see this character rushing about on the plains of the Hell Creek Formation. This shows that artists should never be stagnant. They must always strive to improve their work, and in so doing, improve their skill.

This drawing was made on computer printer paper with a No. 2 pencil, Prismacolor colored pencils, markers, and a black felt-tiped pen. The size of the drawing, from the tip of its nose to the tip of its tail feathers, measures 10.75 inches long, which is almost 1/12 scale, as the real animal possibly measured 12 feet long with its neck and tail fully stretched out.

Keep your pencils sharp.

Ornithomimus

Ornithomimus (“bird mimic”) is a dinosaur genus belonging to a group commonly known as the “ostrich dinosaurs” or “ostrich mimics”. This name comes from their very ostrich-like appearance, with toothless beaks, long swan-like S-shaped necks, and powerful muscular legs. There are currently two known species of Ornithomimus: O. velox and O. edmontonicus. This genus lived in western North America at the end of the Cretaceous Period, 75-65.5 MYA.

It was most likely omnivorous, and you can tell that by the size of its belly. Plant-eating animals need large guts to process their food, in contrast to carnivorous animals. If you look at specimens of Ornithomimus, or indeed any ornithomimid dinosaur, particularly ones which preserve the gastralia (belly ribs), you will see that they outline the stomach area. In contrast to the somewhat starved bodies portrayed by many paleo-artists following in Gregory Paul’s footsteps, they clearly show a wide belly. Look here to see an example: http://en.wikipedia.org/wiki/File:Ornithomimus_edmontonicus.jpg

People had suspected for a while that Ornithomimus and its kind had feathers. There were two reasons for this. Firstly, there was its obvious bird-like appearance. Anything which looked THAT bird-like just HAD to have feathers! Well, it’s an interesting point in terms of comparative anatomy, but there was really no hard evience to support it, and no real credible analysis of various dinosaur types and their relations to birds which suggested that ornithomimids had feathers. The second reason answered that last point. With advances in phylogeny (determining where different species fit into the scheme of life and how they are related to each other), paleontologists have determined that the ornithomimids belong to a large group of very bird-like dinosaurs called the maniraptorans. This group included the ornithomimids, therizinosaurs, oviraptors, and the “real” raptors – the Jurassic Park-style raptors, specifically the dromaeosaurids and the troodontids. Maniraptorans are the closest ancestors of birds, and many of them are known to have been feathered. This would imply that the ornithomids were feathered as well. This argument was a bit more convincing than the “it looks like a bird so it must have feathers” argument which was around during the 80s and 90s. However, although it made a good point, there was still no physical evidence to back it up. If ornithomimids were feathered, why hadn’t any feather fossils been found in association with their skeletons?

In the early 2000s, that changed. When three specimens were examined more closely, scientists discovered that two of them possessed “quill knobs” (the places where feathers attach onto the bones) on the arms, and a third specimen – a juvenile – actually had feather impressions along its neck, back, and legs. In 2012, a report was published in the academic journal Science demonstrating that at least one ornithomimid species, Ornithomimus edmontonicus, was covered in feathers throughout its life, and that the adults actually had modern pennaceous feathers on their arms forming flightless wings. Click here to see a preview of this article: http://www.sciencemag.org/content/338/6106/510.

Ornithomimus

This is a drawing of Ornithomimus based upon the findings in that report. As you can see, the arms sport fully-developed albeit flightless feathered wings. Also take note that the feathers do not cover the whole body all around, but only the top and sides – the underside is bare. The color is my own aesthetic guesswork. I decided to make the throat bright red, which (I like to imagine) was used as a courtship display similar to modern reptiles and birds.

Take care, everyone.