SuperBarosaurus and Dystylosaurus

I have discovered some very interesting news in the Diplodocid camp lately. An SVPCA abstract by Mike Taylor and Matt Wedel (here, on pg. 30) described some BYU cervicals which belong to Barosaurus. We all know and love Barosaurus of course. From the mighty AMNH 6341, the quintessential Barosaurus specimen:

Fig. 1. AMNH 6341. Image copyright the AMNH.


to ROM 3670, the largest known Barosaurus specimen, at roughly 27m long.

Fig. 2. ROM 3670, skeletal restoration by Scott Hartman.


In this abstract, they describe a set of three dorsal vertebrae from BYU quarry 3GR (which is what I will refer to the specimens as from now on). These vertebrae are of uncertain position exactly, but based on neural spine bifurcation the last one (vertebra C) belongs to C9-C11. The C9-C11 of AMNH 6341 are 685, 737, and 775mm long, respectively.

Image result for amnh 6341

Fig. 3. Left column, C9-12. right column, C14-16. From Taylor & Wedel, 2013b.


Vertebra C from BYU 3GR is 1220mm. This vertebrae is 1.57 to 1.78 times longer than that of AMNH 6341, and belongs to a neck 13.3-15.1m long, as the AMNH Barosaurus has an 8.5m neck. This implies a Barosaurus 33 to 37.38m long. That’s a huge size leap for Barosaurus.

Incredibly though, the story doesn’t end there. BYU 9024 is a very large cervical (in fact it’s the longest Sauropod cervical known, at 1330mm). This cervical was originally referred to Supersaurus, but it shares the same characters with Barosaurus as those of BYU 3GR (elongation, broad prezygapophyseal facets, “hinged” prezygapophyseal rami with dorsomedial and dorsolateral faces, narrow, posteriorly set diapophyses bearing posterior tubercles, and wing-like postzygadiapophyseal laminae). This vertebra (also potentially C9) is twice as long as the C9 of AMNH 6341. Thus this implies a neck twice as long as AMNH 6341, at 17m. Let me reiterate that: 17 METERS! So a nice quick scale up of AMNH 6341 to a 17m long neck yields a total length of 42m for BYU 9024! Just some perspective on this, the total length of Puertasaurus (widely considered to be one of the largest Dinosaurs) is 32m (per my skeletal, see below).

Puertasaurus reuili Paper Me

Fig. 4. Skeletal restoration of Puertasaurus reuili. Scale bar equals 4m.


And here is one of Scott Hartman’s lovely Barosaurus skeletals scaled to a 17m neck.

Super Barosaurus

Fig. 5. Barosaurus with a 17m neck. Chart created by RandomDinos.


Super Barosaurus is awesome, but this isn’t the only news from this abstract. In the abstract, they also state:

Dystylosaurus has also been referred to Supersaurus. Although the holotype and only vertebra is clearly a diplodocid anterior dorsal (it has dual centroprezygapophyseal laminae, a large cotyle and “drooping” parapophyses), its tall, unsplit neural spine and pronounced ventral keel prevent assignment to any known diplodocid. It may be a valid, distinct genus.”

Now, as we all know, Dystylosaurus is a part of the mess that is the Dry Mesa Sauropods. The three, Supersaurus, Ultrasauros, and Dystylosaurus were all described as separate genera, until Curtice, Stadtman, & Curtice (1996) and Curtice & Stadtman (2001) reanalyzed the remains and found that Dystylosaurus was likely Supersaurus, and the holotype dorsal of Ultrasauros actually belongs to Supersaurus, and the giant Ultrasauros scapulocoracoid is Brachiosaurus (which I don’t agree with, but that’s for another time). However, a Taylor & Wedel show, Dystyosaurus can’t be presently referred to any existing Diplodocid species, and may once more be distinct. Wooo! #Dystylosaurushype!

What do you guys think? Let me know below.

References


  1. Taylor, M.P., & Wedel, M. J. (In press). “How big did Barosaurus get?” SVPCA Liverpool 2016 Abstracts: 30.
  2. Curtice, B., Stadtman, K., and Curtice, L. (1996) “A re-assessment of Ultrasauros macintoshi (Jensen, 1985).” Pp. 87-95 in M. Morales (ed.), The Continental Jurassic: Transactions of the Continental Jurassic Symposium, Museum of Northern Arizona Bulletin number 60.
  3. Curtice, B.; Stadtman, K. (2001). “The demise of Dystylosaurus edwini and a revision of Supersaurus vivianae“. In McCord, R.D.; Boaz, D. Western Association of Vertebrate Paleontologists and Southwest Paleontological Symposium – Proceedings 2001. Mesa Southwest Museum Bulletin. 8. pp. 33–40.

 

Thoughts on Aegyptosaurus

Ah Aegyptosaurus. We all know that Ernst Stromer described this for a set of appendicular and axial elements from the Cenomanian epoch of Egypt’s Baharya Oasis. And of course, along with Spinosaurus and Carcharodontosaurus, the remains were obliterated by RAF bombing on April 24/25 1944 (damn Brits…), and the only known specimen of Aegyptosaurus was forever condemned to the history books.

Aegyptosaurus-019

Fossil material of Aegyptosaurus (Stromer, 1932a).


 

Or so it would seem. Fortunately, through communication with several members of the Paleo community, I managed to get my hands on the original description paper. So (naturally) I’ve spent a lot of time looking at the fossil material as figured by Stromer.

So what can we see? Well the middle caudals are procoelous, which means that this is at least beyond Malawisaurus in derivedness (one day will be a post on the different types of articulations in vertebrae). Interestingly, the femur of Aegyptosaurus is very similar to the femora of both Lognkosauria and Euhelopodidae (two unrelated groups who developed VERY similar femoral morphs so much so that sometimes it’s hard to tell which belongs to which (cough Ruyangosaurus cough). Which means that either the femur and caudals are from different genera, or (more likely) that Aegyptosaurus is a Lognkosaurian of sorts. Don’t believe me, check it out below.

Titanosaur Femora

Comparison of various Somphospondyl femora, modified by Paleo King. Note how similar the femora of Ruyangosaurus, Malawisaurus, and Daxiatitan are to Aegyptosaurus. Same massive lateral tuberosity and all.


 

Personally I fully expect this to be a Lognkosaur. Same femur morphology and procoelous middle caudals (as in Mendozasaurus, Futalognkosaurus, and Dreadnoughtus). However, due to the humerus morphology (the proximal humeral head is nowhere near as ridiculously expanded transversely as in Notocolossus, and is still even less so than that of Dreadnoughtus) Aegyptosaurus may be a much more basal Lognkosaur, perhaps intermediate between Malawisaurus and Mendozasaurus.

Notocolossus-003

Notocolossus humerus, along with the pubis and pes. Note how massive the humeral head is compared to Aegyptosaurus.


 

Of particular interest to note is that Aegyptosaurus actually has been included in a phylogenetic analysis before. This is Curry-Rogers (2005). When it was released it was the definitive analysis on Titanosaurs. And even now, 11 years later, it still holds up quite well, despite many former characters no longer being accurate enough, and some of the character codings are wrong (seriously, Argentinosaurus as an Opisthocoelicaudiine?! That makes about as much sense as Huabeisaurus as a Nemegtosaurid). In the only MPT Aegyptosaurus was included in, it was found within a large polytomy of essentially every non-Saltasauroid Titanosaur with the exception of Malawisaurus, Paralititan, and the (definitely not a Titanosaur) Phuwiangosaurus, though this polytomy also includes the oddly out of place Alamosaurus, Aeolosaurus, and Agustinia (which may not even be a Titanosaur!).

One more thing: Lapparent (1960) referred a caudal sequence to Aegyptosaurus, based on “a short, compact vertebral centrum that is flattened laterally and not dorsoventrally; they are strongly procoelous. These characters indicate the family Titanosauridae…leads me to refer these elements to Aegyptosaurus baharijensis.” Now I don’t have the figures in my copy of Lapparent, 1960 (hint hint), but these caudals MAY be referrable to Aegyptosaurus. However in recent years another new Titanosaur emerged, Paralititan stromeri (Smith, et al 2001), and this genus also features procoelous caudals (no middle caudals are known, but the anterior caudals are). As well, the Continental Intercalaire formation from which these caudals were described is from the Albian epoch from Algeria, while both Aegyptosaurus and Paralititan are from the Cenomanian in Egypt. Do I think these caudals belong to Aegyptosaurus or Paralititan? No, but they may be from a close relative of either Lognkosauria or Argyrosauridae (maybe even Euhelopodids, which are also known for procoelous caudals).

So to conclude, Aegyptosaurus  was a potential Lognkosaur which was likely a valid genus, and coexisted alongside the much larger Paralititan. Feel free to leave any comments below if I missed something (or if someone has a copy of Lapparent 1960 with figures).

References