I’ve just been doing – if you will – Parasaurolophus for the day job. As in, writing about the history of its discovery and interpretation. William Parks first described Parasaurolophus walkeri (the first of several species to be named) in 1922, and noted in his paper that the skeleton was odd in possessing a weird roughened pad on the neural spine of one of the dorsal vertebrae. He proposed that this structure might have been connected to the tip of the bizarre tube-like crest: it was already thought by this time (thanks to Barnum Brown’s Corythosaurus of 1914 and other specimens) that the bony crests of crested hadrosaurs were connected to continuous skin frills that ran the length of the neck and back. Parks now wondered if muscles and ligaments might have linked the crest-tip with the pad as well (Parks 1922). However, this is so weird, and so without precedent, that the possibility of a pathology was considered likely too. A while later, Lull & Wright (1942) noted that the condition displayed by the specimen was ‘if not pathologic, showing a condition utterly unknown elsewhere’ (p. 211) and concluded that they ‘still hold to the idea of injury’, despite Parks’ idea that this was a normal anatomical feature [adjacent image from the Senckenberg site].
As if this isn’t strange enough, the P. walkeri holotype is also odd in that the dorsal vertebra immediately posterior to the one with the ‘pad’ has an anteriorly inclined neural spine. Most workers have just ignored this and there are hardly any comments on it in the literature. It could be the result of fortuitous disarticulation, but could it also be a natural feature: one which indicates that, in life, Parasaurolophus possessed a sort of notch on its back? As is well known thanks to David Norman’s The Illustrated Encyclopedia of Dinosaurs, Andrew Milner once suggested that the crest’s tip may actually have ‘locked in’ to this notch, thereby providing some sort of foliage deflecting device that might allow the animal to put its head down and leg it like jiggery through the woods without worrying about brain injury (Norman 1985). So far as I can tell, this idea was never published anywhere other than in The Illustrated Encyclopedia of Dinosaurs (please correct me if you know otherwise). It seems a remarkably daft idea as a Parasaurolophus crest is not going to last long if it gets smacked against a branch. Besides, other hadrosaurs and other animals that run through wooded environments did or do just fine without such special adaptations.
Nowadays we’re pretty sure that both the ‘pad’ and the inclined neural spine are pathological and/or fortuitous, and tube-crested hadrosaurs were not, after all, in the habit of locking their crests into special notches on their backs, nor were there special muscles or tendons linking the crest tip to the shoulder region. However, while checking one of Martin Wilfarth’s papers on hadrosaurs I discovered the illustration shown here. Thanks to David Marjanovi?, I can confirm that Wilfarth (1938) was proposing the presence of a muscular link between the crest and the ‘pad’. Note also the bizarre straightened neck (you have to disarticulate the zygapophyses to get it to do that: Tarsitano did this for theropods (Tarsitano 1983), here it is in ornithopods). Wilfarth thought that hadrosaurs were aquatic animals that used their crests as snorkels, and if he’s well known for anything it’s for having lots of bizarre views.
What’s not so widely known about Parasaurolophus is that it was one of the most robustly built of hadrosaurs, with proportionally stocky forelimbs, a robust pelvis and a large scapula (Brett-Surman & Wagner 2007). Exactly why this was so is unknown. During the 1920s Charles Knight illustrated Parasaurolophus for the Field Museum of Natural History mural (in keeping with what Parks had said, he gave it a large skin frill connecting the bony crest with the neck). While he showed Corythosaurus in the water, he showed Parasaurolophus on the land. I always assumed that this was done purely for compositional reasons, but now I wonder if Knight was trying to show that Parasaurolophus was ‘more terrestrial’ than other crested hadrosaurs. He did a similar trick with sauropods, showing lightly built Diplodocus foraging on land while the more robust Apatosaurus wallowed in the swamps.
If you like this sort of stuff – well, I’m working on a whole book about it at the moment. Speaking of which… crap, I need to get back to it.
Next: sleep behaviour. Yes, really.
Refs – -
Brett-Surman, M. K. & Wagner, J. R. 2007. Discussion of character analysis of the appendicular anatomy in Campanian and Maastrichtian North American hadrosaurids – variation and ontogeny. In Carpenter, K. (ed) Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs. Indiana University Press (Bloomington & Indianapolis), pp. 135-169.
Lull, R. S. & Wright, N. E. 1942. Hadrosaurian dinosaurs of North America. Geological Society of America, Special Papers 40, 1-242.
Norman, D. B. 1985. The Illustrated Encyclopedia of Dinosaurs. Salamander Books, London.
Parks, W. A. 1922. Parasaurolophus walkeri: a new genus and species of crested trachodont dinosaur. University of Toronto Geological Series 13, 5-32.
Tarsitano, S. F. 1983. Stance and gait in theropod dinosaurs. Acta Palaeontologica Polonica 28, 251-264.
Wilfarth, M. 1938. Gab es rüsseltragende Dinosaurier? Deutsche geol. Gesell. Zeitchr. 90, 88-100.