Thursday, May 2, 2019

Don't knock my Smok or I'll clean your clock!

We miss you, Bill Watterson.
A few months ago, I wrote that my favorite paleo story of 2018 was the publication of Lisowicia bojani, a ridiculously large dicynodont from Poland. In that same post, I mentioned Smok wawelski, a similarly-sized predatory archosaur of uncertain phylogenetic affinities that very likely hunted Lisowicia. It strikes me that Smok might be unfamiliar to many of you out there in Readerland, so today’s quick post is a summary of what we know about this mysterious carnivore. By the way, I posted this Calvin & Hobbes strip because every time I hear the name Smok I immediately think of it.
The animals that would eventually be named Smok and Lisowicia were first reported by Dzik (2008), who thought that the former was a theropod dinosaur—not an unreasonable assumption. He did not, however, name either animal. That would come four years later (Niedzwiedzki,Sulej, & Dzik, 2012), although not without a footnote. A good amount of material was recovered: a braincase, skull bones, pelvic and limb bones, a few vertebrae, and a couple partial ribs. The premaxilla, maxilla, and jugal bones indicate a deep skull. The pubis is directed downward and apparently has a large posteriorly-directed boot, which reminds me of Herrerasaurus but the details are very different. The whole animal is estimated to be between 16-20 feet long.

Smok wawelsi, who might not look like this.
A phylogenetic assessment was outside the scope of Niedzwiedzki et al. (2012), as it is the subject of Niedzwiedzki’s PhD thesis. The authors don’t go too much farther than placing Smok in Archosauria, as it shares features in common with theropods and rauisuchians—two groups that converged a great deal during the Late Triassic. Additionally, it presents a few more plesiomorphic (primitive) features that you wouldn’t expect in either a theropod or rauisuchian. Interestingly, Smok shared its environment with with three prominent rauisuchians: Batrachotomus, Polonosuchus, and Teratosaurus. I guess we’ll continue to wait for a full description and/or phylogenetic analysis.

Femur bones of Smok, Lilensternus, and Postosuchus
A second specimen of Smok was briefly described in 2018 by Niedzwiedzki & Budziszewska-Karwowska which may represent a second species. There’s not much to describe—two isolated teeth, a dorsal vertebra, fragments of a humerus, femur, pubic boot, and ischial shaft. The vertebra differ a bit from those in the holotype, and the authors entertain the idea of a second species but without more material that’s impossible to determine. The paper also notes that Smok’s full description is ongoing.









And then, this last January, Qvarnstrom, Ahlberg, &Niedzwiedzki (2019) published a paper discussing osteophagy in Smok based on several coprolites associated with body fossils and footprints assigned to that genus. The authors write:

The material of S. wawelski is associated with numerous bones of a large dicynodont as well as other vertebrates. Many of these bones show deep bite marks; one juvenile dicynodont fibula has had its distal head bitten off. The size of the bite marks matches the teeth of S. wawelski, which suggests that this predator was at least an occasional osteophage.

Analysis of the associated coprolites indicates that animals of all ages, growth rates, and both terrestrial and aquatic were all preyed on by Smok. Some of the teeth match the size and shape of Smok itself, suggesting that it either swallowed its own broken crowns (not unreasonable) or that this predator was not above cannibalism. In addition to coprolites and bone-rich regurgitalites (basically fossil vomit) containing larger pieces of bone mean that Smok threw up larger, indigestible fragments as predatory birds do today.

Three Smok coprolites, packed to the gills with bone fragments
Osteophagy is rare in reptiles and, in fact, the authors note that Tyrannosaurus rex, of all archosaurs, provides a comparable model for the kind of large-scale osteophagy that Smok exhibits:

The coprolites of S. wawelski contain at least as much bone per volume as T. rex, and the size fractions of bones and the degree of etching are very similar. Even though S. wawelski is considerably smaller than these tyrannosaurs, we conclude that it occupied a similar ecological role of osteophagous top predator.

So we might not know exactly what kind of archosaur Smok was, but we do know that it was very large, it ate pretty much everything it came into contact with. The jury's still out on what kind of archosaur it was, exactly, but I'm sure we'll find out before too long. My money's on a theropod identity since there are already a bunch of rauisuchians in the same area. 

2 comments:

  1. The maxilla is a dead ringer for Postosuchus. I'm not convinced all the material belongs together, so maybe there's a dinosaur lurking in there after all, but most is clearly "rauisuchian".

    The scapulocoracoid of "Lisowicia"*, on the other hand, looks like that of a large dinosaur, doesn't it? It doesn't remotely resemble that of any other dicynodont or synapsid more generally, and it was found in isolation.

    * The diagnosis and the statement that the name is new are in the supplementary information. The ICZN doesn't state if the supp. inf. of a validly published paper is itself validly published; the supp. inf. is electronic-only and (like the paper) does not contain evidence of having been registered in ZooBank.

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