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.
01 October 2020
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).
Chan-gyu, Yun. (2019). "An enigmatic theropod Cryolophosaurus: Reviews and Comments on its paleobiology". Volumina Jurassica. 17: 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 Palaeontology. 12 (1): 1–73.
28 September 2020
Enjoy this video today from the Natural History Museum of Los Angeles County. This is a short tour of the Cryolophosaurus reconstruction that was at the museum late last year. Dr. Nate Smith talks about our friendly crested theropod. If you need more fun videos, check this out too (you know you want to).
27 September 2020
Cryolophosaurus roughly translates to "cold/frozen crest lizard" and for good reason. Being found in Antarctica explains the first part of the name, but the second part of this genus is attributed to the large crest on the top and back of this animal's head. An estimated size of 6.5 m (21.3 ft) and 465 kg (1,025 lb) make Cryolophosaurus the largest theropod of the Early Jurassic. It has been noted that the known remains are not even those of an adult, which means that these size estimates probably are not for a full grown animal. Molina-Pérez and Larramendi (2016) presented estimates of a fully grown adult at approximately 7.7 m (25.3 ft) and 780 kg (1,720 lbs). Regardless of its size, what people notice first is the crest. The dinosaur has been given the nickname "Elvisaurus" (I very much dislike Elvis, but to each their own) because the crest is oriented from one side to the other, making it appear, apparently, like Elvis' pompadour hairstyle. You be the judge on this one.
Molina-Pérez, R. and Larramendi, A. (2016). Récords y curiosidades de los dinosaurios Terópodos y otros dinosauromorfos. Barcelona, Spain: Larousse. p. 254.
Smith, N. D.; Makovicky, P. J.; Hammer, W. R.; Currie, P. J. (2007). Osteology of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica and implications for early theropod evolution. Zoological Journal of the Linnean Society. 151 (2): 377–421. doi:10.1111/j.1096-3642.2007.00325.x
24 September 2020
It is not too often that we are able to say that we have a fossil that comes from an area of the fossil record that basically butts up against the K-Pg boundary (Cretaceous - Paleogene Boundary; the site in time of the extinction event that claimed the non-avian dinosaurs). However, Alamosaurus, is one of those animals that appears to have been one of the very last of the non-avian dinosaurs that roamed the earth. Known largely from the Ojo Alamo Formation (as previously noted) and the Javelina Formation, many of the fossil remains of Alamosaurus are between 69 and 66.5 million years old. There is at least one juvenile skeleton known from the Black Peaks Formation, an area of the fossil record that envelops (contains) the K-Pg boundary. We can infer from this that Alamosaurus was alive (and well, probably) near, if not right up to, the extinction of the non-avian dinosaurs.
In its fossil range, Alamosaurus is one of the most commonly found fossils, along with Quetzalcoatlus, the enormous pterosaur. It has been hypothesized that Alamosaurus represents a reintroduction of enormous sauropod dinosaurs to North America. Opposing hypotheses point to ancestral sauropods originating further inland in western North America (and ultimately from Asia) and that Alamosaurus was essentially endemic (restricted in range to a certain area) to the North American inland plains. Lucas et al. (2016) noted that the dispersal of Alamosaurus fossil across the western inland plains provides evidence that Alamosaurus was actually quite mobile and not endemic, having a large demonstrated range. Their review did concede that Alamosaurus has only been found within inland plain environments and that no fossils of Alamosaurus have yet been found that would indicate that the animal made its way to the coastline or coastal plains of the Western Interior Seaway.
Lehman, T. M., (2001), Late Cretaceous dinosaur provinciality: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 310–328.
Lucas, S., Sullivan, R, Lichtig, A, Dalman, S., and Jasinski, S. (2016). Late Cretaceous dinosaur biogeography and endemism in the Western Interior basin, North America: A critical re-evaluation. New Mexico Museum of Natural History and Science Bulletin. 71. 195-213.
Sullivan, R.M., and Lucas, S.G. (2006). "The Kirtlandian land-vertebrate "age" – faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of western North America." New Mexico Museum of Natural History and Science, Bulletin 35:7-29.
21 September 2020
|Reconstructed and restored skeletons of |
Tyrannosaurus rex harassing an
Alamosaurus sanjuanensis. CC BY 2.0
17 September 2020
It is unclear exactly how most dinosaurs hunted prey. We have hypotheses, some more well supported and considered than others, but unfortunately we do not have any trail cameras or candid videos documenting behaviors of dinosaur hunting. As many of us may have heard, at least once in our lifetime, many dromaeosaurs are thought to have been pack hunters; tracking, ambushing, and taking down prey that was far larger than a single animal to feed a large group of predators. Not all of the species within this group of animals is thought to have exhibited this complex social system. Often, wolves are used in analogy to describe these pack hunting behaviors, and for good reason. Utahraptor, as the largest of the dromaeosaurs, is one of those dinosaurs thought to have hunted this way and is often compared to wolves. Recently Frederickson et al. (2020) analyzed the teeth of Deinonychus and concluded that pack hunting was not likely to have been a characteristic social interaction in these smaller dromaeosaurs, but no such study has been conducted with Utahraptor. For the moment at least the idea of Utahraptor as a pack hunter still exists. This behavior was central to the theme of the novel discussed the other day. Additionally, this behavior is hinted at by a number of studies of Utahraptor including one that looks at a hypothesized quicksand death trap that may have enveloped an entire pack including juvenile animals (Kirkland et al. 2016). It is possible that, in addition to a complex social system wherein pack mentalities developed, that Utahraptor may have been simply too large to chase fast prey and too small to take on large prey alone. The describing paper, Kirkland et al. (2001), concluded that Utahraptor was likely slower than its cousins Velociraptor and Deinonychus.
Rather than post an image directly in here today, I refer you to Julius Csotonyi's interpretation of the quicksand event that may have led to the discovery of a pack of fossilized Utahraptors as described in Kirkland et al. (2016).
Frederickson, J. A.; Engel, M. H.; Cifelli, R. L. (2020). "Ontogenetic dietary shifts in Deinonychus antirrhopus (Theropoda; Dromaeosauridae): Insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysis". Palaeogeography, Palaeoclimatology, Palaeoecology: 109780. doi:10.1016/j.palaeo.2020.109780
Kirkland, J.I.; Simpson, E.L.; DeBlieux, D.D.; Madsen, S.K.; Bogner, E.; Tibert, N.E. (2016). "Depositional constraints on the Lower Cretaceous stikes quarry dinosaur site: Upper yellow cat member, cedar mountain formation, Utah". PALAIOS. 31 (9): 421–439. doi:10.2110/palo.2016.041