Sauropods of 2008: Tastavinsaurus
May 20, 2009
Welcome to another episode of the ground-breaking and wonderful Sauropods of 2008 series. Yay! As I’m fond of pointing out, new dinosaurs do not only come from China, or South America: Europe continues to yield surprises. Tastavinsaurus sanzi Canudo et al., 2008 is from the Lower Cretaceous (Aptian) Xert Formation of Spain, and the holotype specimen is pretty good, including dorsal, sacral and caudal vertebrae, ribs, chevrons, and material from the pelvis and hindlimbs (we’ve previously mentioned it here, and figured some of it here). Evidently, only the hindquarters of the animal were preserved. But they’re in good shape, and preserve numerous unique characters: in fact 19 autapomorphies are identified, which is a pretty impressive number and indicates either that Tastavinsaurus was a highly disparate sauropod, or that the morphology of its close friends and relatives is but scrappily known (I have to say that the former possibility looks more likely).
Some of these autapomorphies are in the vertebrae. On the posterior surfaces of their neural spines, the antero-posteriorly short, opisthocoelous dorsal vertebrae sport two small accessory laminae that emerge from the base of a very wide, chunky looking postspinal process. Of more general interest (perhaps) is that the dorsal centra contain ‘big prismatic tubes linked together by slender walls [that exhibit] a honeycomb pattern in cross-section’ (Canudo et al. 2008, p. 713). The ‘honeycomb pattern’ sounds something like somphospondylous texture, but the authors note that the condition present in Tastavinsaurus is distinct, and perhaps represents a new type of pneumatic pattern. Frustratingly, they don’t illustrate the internal texture, so we’re left guessing.
The caudal vertebrae of Tastavinsaurus are not all that different from those of macronarians like Camarasaurus and Brachiosaurus: in the proximal caudals, the centra are wider than they are long, the proximal vertebrae have slightly procoelous centra, and the neural spines are ‘club-shaped’ [proximal caudal above from Canudo et al. (2008), fig. 7]. The more distal vertebrae – those from the 15th position onwards – are slightly amphicoelous. One weird little feature on the distal caudals is a small, centrally placed convexity on both the anterior and posterior articular faces of the centra (see pics below). As Canudo et al. (2008) note, Cedarosaurus and Pleurocoelus nanus both have this as well (Tidwell et al. 1999) [distal caudal below from Canudo et al. (2008), fig. 8].
The rest of Tastavinsaurus suggests that it would perhaps have superficially resembled a cross between Camarasaurus and Brachiosaurus. Its ilium looks like a dorsally stretched version of the ilium of Brachiosaurus and, indeed, in general character the specimen would appear to be a brachiosaur-grade titanosauriform. With pneumatic ribs, a lateral bulge on the femur, and caudal vertebrae that have anteriorly positioned neural arches, the rest of Tastavinsaurus agrees with this classification, and in their phylogenetic analysis, Canudo et al. (2008) found Tastavinsaurus to fall within Somphospondyli within Titanosauriformes, and within this clade to be the sister-taxon of Venenosaurus from Utah. If this is correct it weakens the proposal that six sacral vertebrae are a synapomorphy of Somphospondyli (Wilson & Sereno 1998), for Tastavinsaurus only has five.
Well, yet again I’ve done my best to concentrate on CAUDAL vertebrae, given that we have an obvious (and understandable) bias towards cervicals and dorsals. Someone has to speak up for tails. For previous instalments in the Sauropods of 2008 series please see the articles on Eomamenchisaurus, Dongyangosaurus, and Malarguesaurus.
References
Canudo, J. I., Royo-Torres, R. & Cuenca-Bescós, G. 2008. A new sauropod: Tastavinsaurus sanzi gen. et sp. nov. from the Early Cretaceous (Aptian) of Spain. Journal of Vertebrate Paleontology 28, 712-731.
Tidwell, V., Carpenter, K. & Brooks, W. 1999. New sauropod from the Lower Cretaceous of Utah, USA. Oryctos 2, 21-37.
Wilson, J. A. & Sereno, P. C. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology Memoir 5, 68 pp.
Sauropod Vertebra Picture of the Week 
May 20, 2009 at 3:48 pm
“[The Tastavinsaurus] hindquarters [are] in good shape, and preserve numerous unique characters: in fact 19 autapomorphies are identified, which is a pretty impressive number and indicates either that Tastavinsaurus was a highly disparate sauropod, or that the morphology of its close friends and relatives is but scrappily known.”
I offer a third possibility: I guess that most sauropods known from such good remains as Tastavinsaurus may have healthy handfuls of autapomorphies, but few of them get the kind of detailed treatment that Canudo et al. bestowed on their specimen. For example, when the Rapetosaurus, Jobaria and Nigersaurus monographs finally come out, I bet there and plenty of autapomorphies to go round.
May 21, 2009 at 1:26 pm
Hey! I know this big guy! I finished reconstructing Tastavinsaurus for Royo-Torres monograph some months ago. I hope It will come out soon…
Cheers
May 22, 2009 at 9:19 pm
Could the little round convexities of the caudal centra be the ‘snapping point’ for a self-breaking tail, as found in some of today’s smaller reptiles?
May 22, 2009 at 11:19 pm
As it happens, a couple of days ago I had to remove the tail from a good-sized savannah monitor lizard (111 cm total length), and I found it incredible hard to do — even after I’d carved away the hide and the musculature around the anterior caudals, I just could not find the intervertebral joint to slide the scalpel into. In the end, I was reduced to breaking the tail by brute force (which, luckily, I was able to do without breaking any of the vertebrae). This has left me with a profound respect for lizards that can achieve caudal autotomy. It seems basically impossible to me.
May 23, 2009 at 10:27 am
Lizards that practise caudal autotomy (as it’s known) possess special fracture zones in their caudal centra: these are zig-zagging lines of weakness that are located about half-way along some of the centra. They are absent in varanids, and in fact are absent generally in those lizards that rely on their tails (or their caudofemoral muscles) for locomotion, climbing, self-defense etc.
If you want more info…
Arnold, E. N. 1994. Investigating the evolutionary effects of one feature on another: does muscle spread suppress caudal autotomy in lizards? Journal of Zoology 232, 505-523.
Russell, A. P. & Bauer, A. M. 1992. The m. caudifemoralis longus and its relationship to caudal autotomy and locomotion in lizards (Reptilia: Sauria). Journal of Zoology 227, 127-143.
Zani, P. A. 1996. Patterns of caudal-autotomy evolution in lizards. Journal of Zoology 240, 201-220.
May 27, 2009 at 9:30 pm
No offense DDeden, but it’s pretty hard to imagine a huge sauropod just “dumping” its tail and trying to run away from a predator that’s on average less than half its size (but probably 5x its speed!)….. LMAO!
****One Yangchuanosaurus feasts on the tail, the other two keep chasing the fleeing giant and kill it anyway!**** ALL THE BLOOD that would be spurting out once the tail had broken off! The dinosaur’s escape trick would be its own death sentence!
****Yancuannosaurus # 1 grins to # 2 (I’m too lazy to spell it out again!): “Hunt? WTF dude, we don’t need to hunt! Just scare the poor bloke and and chew on the tail while the rest of him bleeds to death trying to run away at 5 mph!”****
To their credit, lizards seem to be able to compartmentalize their tail capillaries to minimize blood loss. But a 20+ ton sauropod doing that? LOL I’d be struck speechless.
Plus, I’ve heard that skinks (or whatever kind of lizards the disposable-tailed ones are) are able to REGROW the lost portion of the tail within a month or so… this makes them arguably the most advanced animals capable of regenerating an appendage.
It’s even HARDER imagining these sauropods REGROWING a jettisoned tail…. that’s like a couple tons of meat right there – not to mention those foot-wide caudal verts in the picture! Just imagine the immense nutrient drain on the animal! Programmed cell grown/death and all that… unless it was a two-headed mutant and could gather twice the food… a no-tailed two-headed sauropod! STEP RIGHT UP folks, get in line!!! (Hmmmmm… if P.T. Barnum had been a paleontologist….)
When it comes to thwarting predators, I’d rather stick to the good old “tails as weapons” theory which has held up pretty well over the years… but the tail snap idea is just so funny I’m about to die laughing!!!!
May 27, 2009 at 9:35 pm
Whoops!!!! I mean Spanish Cretaceous Allosaur descendant #1 and Spanish Cretaceous Allosaur descendant #2. (As soon as I read “somphospondyli” I inanely assumed the thing was found in China… somehow missed the twenty-odd comparisons to Brachiosaurs in the original post!)
June 7, 2009 at 9:04 pm
[…] Sauropods of 2008: Tastavinsaurus « Sauropod Vertebra Picture of …The m. caudifemoralis longus and its relationship to caudal autotomy and locomotion in lizards (Reptilia: Sauria). Journal of Zoology 227, 127-143. Zani, P. A. 1996. Patterns of caudal-autotomy evolution in lizards. Journal of Zoology … […]
June 12, 2009 at 6:43 am
Well, it seemed like a good idea at the time…