If you’re a fan of palaeontology, chances are you’ve heard of Prehistoric Times Magazine. It is run by the ever hard working Mike Fredericks, and instead of having staff illustrators for each issue, it leaves it open to the readers to send in their art in advance. For this issue (#119), the featured animals were Acrocanthosaurus and Eohippus (which I was not able to paint due to time constraints) (1). Instead of doing just any old Theropod, I decided to try doing one in a pose that, to my knowledge, had not been done before.
The idea was partially inspired by Luis Rey’s painting of a scene in Bakker’s book “Raptor Red”, showing several Utahraptors climbing trees to escape a flash flood. In the background you can see a vortex of sorts carrying drowned Dinosaurs to their watery graves (2). I was also inspired by a recent canoe trip down the Teslin river, in which there were at many stages large “log jams”, where driftwood had accumulated.
Remembering this experience when brainstorming brought me to this story; the large Theropod, when attempting to cross a river, is swept downstream by a sudden flash flood, along with several downed logs. Managing to survive a small waterfall along its route, the carnivore is swept up against a natural log pile, and, before it can move free, a new series of logs is swept in, one pinning its leg underneath it.
While many large predators may have been able to wiggle free, two features that I remembered when painting this were the animal’s characteristic spines and its unusually stiff arms.
When first described, the authors of the paper bringing Acrocanthosaurus to palaeontology noted the large muscle attachments on the animal’s large neural spines. In this case, Acrocanthosaurus was less of a Spinosaur (the well known carnivorous dinosaurs that make Acrocanthosaurus look small), and more like a bison, with a large, thick ridge running along its back (3). While they did not elaborate on the implications of this on the animal’s movement, I highly doubt that a massive ridge of bone and muscle would have increased spinal flexibility. Were this predator trapped in this situation, I think it likely the large spines would have hampered its ability to escape. As would its arms, for that matter. A 2005 study noted the rigidity of Acrocanthosaurus‘ forelimbs, a feature that may have been useful for catching prey, but not for escaping a log jam (4).
With this in mind I drew the animal and its environment, giving it a more resigned air (really due to the massive exertions of trying to escape tiring it out). The trees there are known from both before and after in this location, so I thought it reasonable to include them, they being Cheirolepidiaceae (5) & Taxodiaceae conifers, the latter a surviving taxon to this day (6). Even if these did not exist in this environment, the presence of tall sauropods implies the presence of some large trees, and the fact that these trees would have been present in an environment described as fluvial means that though a log jam is speculative, it is plausible (7).
Here it is. It’s not my favourite, but with the time constraints, it’s all I can pull off for now. If accepted, you may see it in the next issue of Prehistoric Times.
Title: Log Jam
Temporal range: Early Cretaceous (Aptian)
Species shown: Acrocanthosaurus atokensis, Cheirolepidiaceae sp. and Taxodiaceae sp.
Geologic setting: Antlers Formation
That’s all for now. See you soon,
1 “Next Issue.” Prehistoric Times Magazine. N.p., n.d. Web. 11 Sept. 2016.
2 “THE 1000 YEAR FLOOD.” Luis V. Rey’s Art Gallery. N.p., n.d. Web. 11 Sept. 2016.
3 Stovall, J. Willis, and Langston Wann. “Acrocanthosaurus Atokensis, a New Genus and Species of Lower Cretaceous Theropoda from Oklahoma.” American Midland Naturalist 43.3 (1950): 696-728. Web. 11 Sep. 2016.
4 Senter, P. and Robins, J. H. (2005), Range of motion in the forelimb of the theropod dinosaur Acrocanthosaurus atokensis, and implications for predatory behaviour. Journal of Zoology, 266: 307–318. doi:10.1017/S0952836905006989
5 “†family Cheirolepidiaceae Turutanova-Ketova 1963 (conifer).”Fossilworks: Gateway to the Paleobiology Database. N.p., n.d. Web. 11 Sept. 2016.
6 “Family Taxodiaceae Saporta 1865 (conifer).”Fossilworks: Gateway to the Paleobiology Database. N.p., n.d. Web. 11 Sept. 2016.
7 “McLeod Prison (OMNH V706), Tomato Hill (Cretaceous to of the United States).” Fossilworks: Gateway to the Paleobiology Database. N.p., n.d. Web. 11 Sept. 2016.