|A modern reconstruction of Plateosaurus engelhardti as a relatively bird-like, bipedal animal rather than a tubby, sprawling quadruped|
'New looks' for Plateosaurus are not rare, however. Our perceptions of this dinosaur have been rather changeable since its discovery, and few dinosaurs have been through as many iterations of posture, gait and general appearance. Since its discovery in the early 1800s, we've seen Plateosaurus reconstructed in numerous ways. Perhaps the oldest known reconstruction, by O. Jaekel, dates to 1913-1914 and depicts a very different animal to the one we know today. This frequently proportionally inaccurate image shows a very odd-looking bipedal dinosaur which almost has a therizinosaur-like appearance, but perhaps is better compared to Igor from an early Universal horror film. Later depictions of Plateosaurus were of a sprawling quadruped with a barrel-like chest; an erect biped with a dragging tail; a lithe quadruped capable of galloping; a very sauropod-like animal with straight, columnar limbs and a long, low biped with a heavy balancing tail. These interpretations, and others, have been compiled and thoroughly discussed by Heinrich Mallinson, a man who clearly loves Plateosaurus as much as a man can love a fossil species (below, from Mallinson 2010a).
|The many faces of Plateosaurus, compiled by Mallison (2010a). Check out Heinrich's open-access publication for sources of the reconstructions.|
|SMNS F33, one of the most famous articulated fossils of Plateosaurus engelhardti. Note the narrowness of the chest and shoulders. Photograph by FunkMonk, from Wikipedia Commons.|
(Interesting bonus knowledge to stem from recent Plateosaurus studies include new insights into the suppleness of the Plateosaurus neck, which permitted 360° to their owners. Presumably, this reflects a need to keep an eye out for predatory archosaurs which, in the Late Triassic landscapes occupied by Plateosaurus, would not be predatory theropods but large rausuchians like Teratosaurus. [How come there's not many illustrations of predatory interactions between these species? Would probably make for a cool image]. Perhaps even more interestingly, the pedal claws of Plateosaurus show evidence of being used in scratch digging, which may reveal how these animals dug their nests. Neat stuff indeed.)
Junk about the trunk
But it's not just Plateosaurus specific topics that have fuelled the latest changes in its appearance. It's very likely that the tail of Plateosaurus was more massive and heavy than portrayed in most reconstructions because, along with many other dinosaur species, it bore substantial hindlimb musculature along the base of its tail. We can see how large the hindlimb retractor muscles of dinosaurs should have been by looking at homologous anatomies in lizard and crocodile tails (warning: that link is not for the squeamish), and the take-home message is that most dinosaurs had extremely beefy proximal tail regions (e.g. Persons and Currie 2011). As Heinrich covers here, we can see osteological evidence for expansive, tail-anchored hindlimb muscles in Plateosaurus as clearly as we can in nearly all other Mesozoic dinosaur species. The Plateosaurus anterior tail regions was effectively a big tube of meat bulging from a thread of vertebrae, which were themselves enlarged for the attachment of powerful muscles. In life, the hindlimb protractors would probably run continuously from the tail to the hindlimb, with no obvious 'join' between these two body sections. These bulging tails are a world away from the slender and compressed tails seen in many pieces of palaeoart. Furthermore, all this proximal tail muscle probably reduced the flexibility of the tail somewhat (Persons and Currie 2011) suggesting that another palaoart trope - dinosaurs with laterally wavy, sinuous tails - were probably impossible. The extensive muscles at the base of the tail can only be compressed so far by a wiggling tail. Thus, although the tail bones of Plateosaurus seem to offer a fair amount of lateral motion (below; also see Mallison 2010a), there probably wasn't anything close to that level of flexibility available in life. In the picture above, the tail is deliberately a little lifeless, acting purely as a site for hindlimb retractor muscle anchorage and a counterbalance to the heavy, gut-filled torso.
|Digital model of Plateosaurus caudal vertebrae in dorsal view, showing 10° flexion between each joint. From Mallison (2010a).|
So, new posture, new build, new tail, and now new integument? We're very used to seeing Plateosaurus and with virtually all other sauropodomorphs with scales, but this may not have been the case (hat tip here to recent blog posts on this topic by the Internet's favourite sauropod workers, Matt Wedel and Mike Taylor). Sauropodomorphs may not have provided any fuzzy revelatory fossils over the last few years but, because lots of other dinosaur groups have, the landscape of dinosaurian integument has shifted considerably around their feet. Nowadays, it's a commonly known possibility that dinosaurs, and perhaps all ornithodirans, were ancestrally fuzzy. Although we have a few skin impressions from sauropods (Czerkas 1992; Coria and Czerkas 2007), they remain pretty rare across the group as a whole and, to my knowledge, we don't have any from non-sauropodan sauropodomorphs. Our few scraps of sauropod skin suggest they bore typically archosaurian, non-overlapping scales but, even if that's standard for the group (and, given what we know about modern animal integument, it may well not be), it isn't clear when this trait became a typical part of the sauropod bauplan. Thus, it is not inconceivable that some early sauropodomorphs were feathered and, until we have some direct evidence either way, it's probably just as parsimonious (and, arguably, speculative) to draw them with fuzzy hides as it is with scales. In the case of the picture here, I figured throwing an ostrich-like distribution of feathers over a modern Plateosaurus reconstruction added a suitably symbolic purpose to show how far interpretations of this animal have come since its first discovery.
And that may be enough novelties for one day: time to crack on with other things. Here's hoping that this reconstruction of Plateosaurus will stand the test of time, though I'm sure I'm merely tempting fate with those words. Next week, hopefully, we'll see something to do with animals bearing membranes, because this thing isn't very far from being released on the world any more.
- Bonnan, M. F., and P. Senter. 2007. Were the basal sauropodomorph dinosaurs Plateosaurus and Massospondylus habitual quadrupeds? In: Barrett, P.M. and Batten, D.J. (eds.), Evolution and palaeobiology of early sauropodomorph dinosaurs. Special Papers in Palaeontology, 77, 139-155.
- Coria, R. A. and Chiappe, L. M. 2007. Embryonic skin from Late Cretaceous sauropods (Dinosauria) of Auca Mahuevo, Patagonia, Argentina. Journal of Paleontology, 81, 1528-1532.
- Czerkas, S. A. 1992. Discovery of dermal spines reveals a new look for sauropod dinosaurs. Geology 20, 1068-1070.
- Mallison, H. 2010a. The digital Plateosaurus II: an assessment of the range of motion of the limbs and vertebral column and of previous reconstructions using a digital skeletal mount. Acta Palaeontologica Polonica, 55,433-458.
- Mallison, H. 2010b. The digital Plateosaurus I: body mass, mass distribution and posture assessed using CAD and CAE on a digitally mounted complete skeleton. Palaeontologia Electronica 13.2.8A
- Persons IV, W. Scott, and Philip J. Currie. 2011. The tail of Tyrannosaurus: reassessing the size and locomotive importance of the M. caudofemoralis in non‐avian theropods. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology, 294.1, 119-131.