STL Science Center

STL Science Center

07 October 2020

Synonyms Everywhere

Hadrosaurs, the so-called "Duck-billed" dinosaurs have been compared to cows on a regular basis. I think the main idea with this comparison is in the idea that there were likely vast herds of these dinosaurs stretching as far as the eye could see in different regions of the world during the Cretaceous. One of those dinosaurs was Edmontosaurus. Possibly not the most exciting in appearance, we know that Edmontosaurus annectens was a well distributed genus across North America, consists of two recognized species (E. regalis, Type species, Lambe 1917 and E. annectens, Marsh 1892) has a number of synonyms associated with it including Anatotitan, Anatosaurus, and Trachodon. Appearing as a "typical" hadrosaur (probably only outshined by the familiar appearance of Iguanodon in this respect), Edmontosaurus is a large herbivore and some might remark that it is quite unremarkable. The type specimen is estimated to have been between 9 and 12 m (30 and 39 ft) long and may have weighed as much as 4 tons. A handful of both species have even been discovered as fossilized mummies or have been associated with skin impressions and even a rhamphotheca, the keratinous portion of the beak-like end of the mouth and snout.

Reconstruction by Nobu Tamura

01 October 2020

A Notable Find

Cryolophosaurus, as a holotype fossil, consists of a partial skeleton that was discovered with a complete skull (cranium and face plus lower jaw and teeth). As far as paleontology goes that is somewhat rare, but it does happen from time to time and the dinosaurs (or other fossil animals) we find as mostly whole are often bewildering and exciting. Obviously, I think, Cryolophosaurus was a very exciting find for a number of reasons: the state of preservation, as just noted; that it was discovered in Antarctica; and the always talked about head crest adorning its cranium. The head of Cryolophosaurus is amazing all by itself though, even without the crest. Approximately 65 cm (26 in) long, Cryolophosaurus' head was a little less than 1/3 the length of the largest Tyrannosaurus skull (1.52 m; 5 ft). The skull was also considerably narrow and tall, from top to bottom, as well. Running from the nasal area to the side-to-side crest is a ridge that runs courses along the midline until it widens and meets with the perpendicular crest that is so iconic of the dinosaur. The purpose of the crest has been discussed many different times in many different ways. It has been considered a fighting implement by some and a social ornamentation by others. Many have hypothesized that the crest was used for mating displays. Much consideration has been given to other characteristics of Cryolophosaurus as well. The crest as well as a large group of other characteristics have led to many different phylogenetic hypotheses for Cryolophosaurus. Rather than revisiting all of these, we can note that currently Cryolophosaurus appears to be nestled in a spot in the family tree that is a little more advanced than Dilophosaurs and Ceratosaurs, but more primitive than Allosaurs and Coelurosaurs (the group that includes Tyrannosaurus as well as ornithomimids and maniraptorans).

Photo by Jonathon Chen while Cryolophosaurus (reconstruction) was on display at the Field Museum, Chicago


References

Chan-gyu, Yun. (2019). "An enigmatic theropod Cryolophosaurus: Reviews and Comments on its paleobiology". Volumina Jurassica17: 1–8.

Hammer, W.R.; Hickerson, W.J. (1999). Tomida, Y.; Rich, T.H.; Vickers-Rich, Y. (eds.). "Gondwana Dinosaurs from the Jurassic of Antarctica". Proceedings of the Second Gondwana Dinosaur Symposium National Science Museum Monographs. 15: 211–217.

Hendrickx, C.; Hartman, S.A.; Mateus, O. (2015). "An Overview of Non- Avian Theropod Discoveries and Classification". PalArch's Journal of Vertebrate Palaeontology12 (1): 1–73.