Monday, December 02, 2019

DINOSAURS!: From Cultural to Pop Culture - 1833: Hylaeosaurus


1833: Hylaeosaurus 

When Sir Richard Owen announced the term "Dinosauria", he used three previously announced and described species as his hallmark for the group. These include the initially announced Megalosaurus, the second dinosaur named, Iguanodon, and the third described dinosaur, which was named Hylaeosaurus.  

In the previous entry, we looked at how Gideon Mantell requested quarry workers to notify him if they noticed anything that might be of interest to him. Well, in 1832 they noticed something rather significant. The quarry workers had blasted a large block of stone and upon noticing some bone in the fragments had contacted Mantell that was documented in his 1833 publication The Geology of the South-East of England.  
"Upon repairing to the quarry, the considerable number of pieces into which the block was broken, the extreme hardness of the stone, and the unpromising appearance of the fragments of bone that were visible, seemed to render the attempt to dissect it alike hopeless and unprofitable. I resolved, however, to collect the scattered fragments together; and after much labour succeeded in reducing the specimen to the state in which it now appears."
The rock that was blasted apart had a large number of bones, which, even though they were not directly articulated, were near enough that they could be placed within the animal. This was something that has not occurred much up until this point. Previous published descriptions were generally localized bones with the occasional connected bones, but nothing to this degree. Within the cluster of bones, Mantell was able to identify, and describe, a large number of vertebrae, ribs, other bones, and most importantly, dermal plates.

Fossil material of the newly announced Hylaeosaurus from Mantell's 1833 book, The Geology of the South-East of England
Although much smaller than either Iguanodon or Megalosaurus, Mantell realized that this was something unique in it's own right. 
"I venture to suggest the propriety of referring it to a new genus of saurians. The generic characters would, of course, be the peculiarity of the sternal apparatus, and the remarkable processes which are distributed around it ; and I propose to distinguish it by the name of Hylaeosaurus, to indicate the locality in which these remains were discovered."
The name Hylaeosaurus is derived from the name of the Wealden Woods, giving it the moniker of "Fossil Lizard of the Weald". Future discoveries eventually identified Hylaeosaurus as the very first anklyosaurus. This is very interesting given his comments on the vertebrae of the tail that he discovered:
"The vertebrae are lumbar, sacral, and caudal; and there are two of the latter anchylosed, and two others disposed to become so; which is remarkable, for in all my skeletons of reptiles an analogous case is not observable, except where the tail has been broken, and then the bone becomes united by exostosis, which is not the case in these fossils: hence it would seem that these must have belonged to an animal making such feeble use of the tail, that the vertebra' were occasionally anchylosed together."
Even though other eventual dinosaurs are named before the term "Dinosauria" is coined, this was the last verifiable dinosaur of the time before the announcement. The other animals won't be identified as dinosaurs until much later.

Dermal bones, otherwise known as scutes, of Hylaeosaurus from Mantell, 1833.

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