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.
The dating of the Newark Supergroup, and particularly the sequences in the Connecticut River Valley, are very precise and quite secure. There have been some publications suggesting problems with these ages (Weems is a co-author on some), but these are based on very suspect biostratigraphic correlations that ignore the huge volume of precise magnetostratigraphic and radioisotopic age data.
Aargh, that’s what I get for writing blog posts with more content than a photo at midnight!
Yes, obviously, the Eastern tracksites are all well dated. I was referring to the “prime prosauropod times” in the US SW, where direct dating is nearly impossible. I recently had two people from different institutions who both work on this stuff complain about all the dating problems, and both mentioning that there may be some progress in the near future – alas, nothing published or even submitted yet 😦
Fixed now, many thanks for pointing this error out!
” a trackmaker assignment is a hypothesis.
Eubrontes isn’t a dinosaur body-fossil genus. It’s an ichnotaxon–in this case a footprint genus.
There are no Eubrontes skeletons out there.
The name is restricted to the footprint morphotype alone.
Ignoring the issues with slapping Latin bionomials on sedimentary structures, this is a common practice and Eubrontes fossils represent a fairly characteristic type of footprint shape found across North America in Lower Jurassic rocks.
The question of what animal made Eubrontes is a different issue, but identifying a footprint as a Eubrontes track is a matter of studying the footprint itself and comparing it to other footprints.
There need not be dinosaur skeletal feet preserved nearby that fit the tracks.
Again, the issue of who made the fooprint is a different issue from figuring out whether or not the track morphology is consistent with the morphotype that is known as Eubrontes. ”
Comment #8 Josh
Here is another assigment for ; Eubrontes glenrosensis sp. = Acrocanthosaurus(?)
Acrocanthosaurus track with partly mud-collapsed digits
Track name: Eubrontes glenrosensis sp.
Somervell County, Texas
Glen Rose Limestone
Lower Cretaceous (110 million years)
Yes I know it wasn’t your aim to identify the trackmaker of eubrontes (?)glenrosensis
I’m a little confused; Aren’t prosauropods already known from several 4-toed tracks, or is it that only the quadrupedally-walking prosauropods (as opposed to bipedally-walking ones) leave 4-toed tracks for some reason?
Herman, that’s the point, isn’t it? “known from..” – no! Some 4-toed tracks have been CLAIMED to have been made by them. But on what basis? I used the articulated and posed 3D high-res skeleton, what did they use?
I do not have 3D scans of some of the potentially 4-toed prosauropods (Anchisaurus, e.g.), but plateosaurids did not make tracks with 4 functional toes.
OTOH, there must have been proto-sauropods out there, and they are much more likely candidates 😉
I get it now: So it’s a specific plateosaurid thing (as opposed to a general prosauropod thing). Thanks!
as far as this test goes, yes – but remember that many tetradactyle supposed prosauropod tracks were specifically referred to plateosaurids,
Heinrich – I have a 3D mesh of a good Eubrontes print from Warner Valley if that’s any use – I don’t seem to have your institutional email for some reason.
Heinrich.email@example.com or @mfn-berlin.de I prefer gmail as is has a better search and bigger file limit. 🙂