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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/




Anzu was a caenagnathid from the Hell Creek Formation. I wrote of its discovery and naming in an earlier post that you can read here. The caenagnathids were a primitive group of oviraptorosaurs, the “egg thief” dinosaurs. Anzu is so far the largest species from this group found in North America, measuring 10-13 feet long from nose-tip to tail-tip, and it was also one of the last of its kind.

In terms of this picture, the chicken-like wattles are purely conjecture on my part, as are the types of feathers and color patterns.

News: “Egg thief” dinosaur from Hell Creek FINALLY named!

All I can say is “It’s about time!!!”

After sitting around for years without an official description, a bird-like dinosaur found in the Hell Creek Formation has finally been given a name. I’m very happy about that. What I’m not happy about is the name that was actually chosen – Anzu wyliei, a name that I REALLY don’t find appealing.

Last year, I read that a bird-like dinosaur more commonly found in the Gobi Desert was discovered in North America. Furthurmore, I found out that it was actually on display in Pittsburgh, and had been for several years – it shows just how horribly behind the times I am. However, I was aghast when I learned that this creature didn’t even have a name. I asked “What the hell’s been taking them (meaning the scientists) so long?” Well now the wait is over.

Anzu (I’m actually shuddering as I’m writing the name – I just loathe the way that it sounds) was a member of a family of dinosaurs called Caenagnathidae. The caenagnathids were a sub-group within a super-family of theropods known as the oviraptorosaurs, or “egg thief lizards”. These very bird-like dinosaurs are well-known from Asia, especially China and Mongolia, but they are almost unheard of anywhere else. Oviraptorosaurs ranged in size from five to twenty-five feet long, and might have evolved from the ornithomimids, the “bird mimics”, commonly known as “ostrich mimics” due to their ostrich-like appearance. The most famous of them was Oviraptor, “egg thief” found in Mongolia by the adventurous Roy Chapman Andrews. The name came from the discovery of a partial skeleton lying on top of a nest of eggs. Chapman and his colleagues thought that the animal was in the process of plundering the nest when it was killed. It wasn’t until later when the insides of the eggs were carefully examined that paleontologists discovered that the preserved embryos were that of other oviraptorosaurs. This animal wasn’t preying upon the eggs – it was the mother.

The caenagnathids have had a confusing history, dating back to the early 20th Century. In the early 1920s, the famous paleontologist Charles W. Gilmore was fossil hunting in Alberta, Canada, when he found the remains of a new and strange creature known only from a pair of incomplete hands. In 1924, he gave them the name Chirostenotes pergracilis. Another dinosaur was named based upon an incomplete foot, and it was called Macrophalangia. By the late 1970s, scientists realized that these two animals were the same, and Chirostenotes became the official name.

But what sort of creature was Chirostenotes? It was clearly a theropod – a bipedal meat-eater – but the bone structure was unlike any other theropod known. In fact, it looked very bird-like. It was believed that Chirostenotes was most similar to another mysterious dinosaur called Elmisaurus, which came from Mongolia during the late Cretaceous Period.

For a long time, Chirostenotes was the only North American oviraptorosaur, specifically a caenagnathid. It was found in rocks dated to the Campanian Stage (80-70 MYA) of the Cretaceous Period. Then, in the 1960s, another oviraptorosaur – and a very early primitive one at that – was found, named Microvenator, “the little hunter”. It lived in Montana approximately 100 million years ago alongside Deinonychus and Tenontosaurus. This showed that oviraptorosaurs were present in North America for much longer than previously suspected.

It had been believed for a while that Chirostenotes and its kind had become extinct a millions of years before the dinosaurs’ exinction. However, in the 1990s, fossils of an animal which might have been an oviraptorosaur were found in Montana in rocks that dated to the very end of the Cretaceous Period – the famous Hell Creek Formation, the home of Tyrannosaurus rex. No oviraptorosaur fossils had ever been found there before. In 1994, Canadian paleontologist Phil Currie, an expert on theropod dinosaurs, published a paper on a fragment of a lower jaw found at the “Sue” site. Based upon it’s shape, it was obviously an oviraptorosaur, specifically a member of the family Caenagnathidae. However, this specimen was significantly larger than any previously-known specimens. It could have been a larger specimen of Chirostenotes, or it might have been a new species.

The problem was that Chirostenotes was known only from a few fragmentary finds – a complete or nearly-complete skeleton had never been found. Then, a pair of incomplete skeletons were found in Hell Creek, and were described in 1995. Ever since then, they have been housed in the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. The staff at the Carnegie Museum even took these two skeletons, composited them together, and put the creature on display for the public! However, the creature still did not have a definitive identification. Paleontologists were uncertain as to whether “the Triebold specimens”, as they were called, were Chirostenotes or maybe another larger species.

In 2011, Matt Lamanna and other scientists announced that they were studying the Hell Creek oviraptorosaur in more detail. Based upon a preliminary view, they stated that it was very similar to Chirostenotes, but they shied away from going so far as to claim that it was a distinct species.

In 2013, a team from the Burpee Museum (the same museum famous for “Jane”, which might be either a Nanotyrannus or a juvenile T. rex, depending on who you ask) discovered the partial skeleton of a caenagnathid oviraptorosaur near the small town of Ekalaka, Montana. The bones were so large that they originally thought that they had found a T. rex; Professor Thomas Holtz of Maryland rushed to the site and confirmed the animal’s identity. This specimen was even larger than the Triebold specimens in the Carnegie Museum. It was affectionately nicknamed “Pearl”.

In 2014, Matt Lamanna and three other colleagues published a paper on the Triebold specimens collected from North and South Dakota. After an exhaustive analysis of the bones, they concluded that the Triebold specimens were not Chirostenotes or Caenagnathus, but constituted an entirely separate genus. They called it Anzu wyliei. According to Lamanna’s own report, the dinosaur was named after Anzu, a feathered bird-like demon from Mesopotamian mythology, and measured somewhere between ten to fifteen feet long.

What the heck does a Mesopotamian demon, feathered or otherwise, have to do with a North American dinosaur? I can understand if the fossils were found in Iraq, but they weren’t. I would actually be highly surprised if ANY dinosaur fossils were uncovered in Iraq. It would be a lot more fitting if it was given a traditional Greco-Latin name, something like Dakotaraptor, or maybe even named after a being from native Sioux Indian folklore, like Wakinyanoraptor (“Wakinyan” is the Sioux name for the thunderbird sky spirit).

But then again, what the heck does the white-skinned feathered serpent god from central Mexico have to do with an unusually large pterosaur from Texas, which neither looked anything remotely like a serpent, nor had feathers, nor came from Mexico? I’m talking about Quetzalcoatlus, for those of you who haven’t caught on. So I suppose I shouldn’t be too harsh. Still, Anzu … it just sounds SOOOOO wrong. Unfortunately, we’re all stuck with it.

The specimen uncovered by the team from the Burpee Museum is also likely a specimen of Anzu.