Yesterday I showed you a sneak preview on some research I am doing. That triggered some rather incredulous emails and private messages, especially after I hinted in a comment that the artificial track is from Plateosaurus. After all, Plateosaurus lived in the Late Triassic, and the track I compared to comes from Early Cretaceous sediments.
So what’s up with this?
First of all, the genus of the real track is Eubrontes, and other species of it are common in the Connecticut River Valley in – ta-dah! – Early Jurassic sediments, prime prosauropod times in North America. Unless the dating is off, and the supposed Early Jurassic sediments in the US SouthWest, where some of these prosauropods have been found, are in fact Late Triassic – I have heard rumors that some recent datings were way off the expected scale, but methodologically much better than previous ones. But I could not get at short notice a scan of a Eubrontes giganteus or other older track. Thus, I took the closest thing I could get.
Secondly, my aim here is not to find the trackmaker of Eubrontes (?) glenrosensis. Rather, this is about a method for finding out what kinds of tracks a certain animal could have made, and comparing them to others. I would have used the same two CAD files even if they had been a total mis-match, that would have made the same point as far as the work method is concerned.
And lastly, Eubrontes has been assigned all over the dinosaurian family tree (well, no – nobody has suggested ankylosaurs, stegosaurs or sauropods). Large theropods, iguanodons, hadrosaurs, prosauropods, you name it. Weems in 2003, in a very detailed study of the pedal morphology and posture of Plateosaurus, noted the excellent correlation between Plateosaurus and the Connecticut Eubrontes tracks, but that view has not really taken hold. Most people still seem to think Plateosaurus made four-toed (tetradactyle) prints. But try as I might, I could not get a digitigrade tetradactyle track out of my models!
Thus, the figure above is both an indirect vindication of Weems’ work, and a warning: many dinosauriformian and dinosaurian lineages are so convergent that they make highly similar tracks across vast distances in space and time! That’s been said before, for example by Klein and Haubold (e.g., 2000; paraphrasing: “Atreipus turns into Grallator when the hand imprints go missing”, etc.), and I can only emphasize the point again.
Klein, H. and Haubold, H. 2000. Die dinosauroiden Fährten Parachirotherium – Atreipus – Grallator aus dem unteren Mittelkeuper (Obere Trias: Ladin, Karn, ?Nor) in Franken. Hallesches Jahrbuch für Geowissenschaften, 22:59–85.
Weems, R.E. 2003. Plateosaurus foot structure suggests a single trackmaker for Eubrontes and Gigandipus footprints, p. 293–313. In LeTourneau, P.M. and Olsen, P.E. (eds.), The Great Rift Valleys of Pangea in Eastern North America, Volume 2: Sedimentology, Stratigraphy, and Paleontology. Columbia University Press.