ORNITHODESMUS & STEGOSAURS

[darren.naish@port.ac.uk]

Responses to a couple of things on Wealden stegosaurs and 
theropods. On _Ornithodesmus_, Simon Clabby wrote...

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A good point of reference would be Regnosaurus' fellow 
Wealden-inhabitant, Ornithodesmus, which was originally 
described as a pterosaur, but has since been identified as a 
theropod. 
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Nope, _Ornithodesmus cluniculus_ was originally described 
as a primitive bird (Seeley 1887a, b). Hulke (1887) then 
suggested that it was a pterosaur and was thus the first to 
propose this. It was only in 1901, when he described 
BMNH R176 (the holotype of _Istiodactylus latidens_), that 
Seeley decided that _O. cluniculus_ might be a pterosaur 
(an opinion based on alleged similarities he saw between 
the specimen and the sacrum of _I. latidens_), and 
consequently he both changed his mind about the identity of 
_O. cluniculus_ and referred _I. latidens_ to 
_Ornithodesmus_. What happened afterwards, of course, is 
history... (see Howse & Milner 1993, Naish et al. 2001 etc.).

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P.S. Actually, by the way Darren, didn't you offer me
a picture of Regnosaurus for DinoWight ages ago?
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Err, yeah, but that was before I realised that your website 
was a mostly uncredited rip-off of my book. I know you do 
mention the book, but not enough IMHO in view of how 
much (*uncredited*) info you took from it.

On stegosaurs, Tim wrote...

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While on the topic of European stegosaurs, I had heard that 
spines originally referred to the French stegosaur 
_Lexovisaurus durobrivensis_ (Middle Jurassic) were not 
spines at all, but gill rakers of a large fish. Can anyone 
verify this?
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Yes, IIRC gill rakers of the immense pachycormid 
_Leedsichthys problematicus_ Woodward, 1889 were 
misidentified by both Hulke (1887) and von Huene (1901) 
as stegosaur dermal plates/spikes. Hulke (1887) referred 
_Leedsichthys_ material to _Lexovisaurus durobrivensis_ 
(at the time still _Omosaurus durobrivensis_ of course) and 
von Huene referred it to _Stegosaurus leedsi_ (the type of 
which is probably referable to _L. durobrivensis_). Given 
that big individuals of _Leedsichthys_ are somewhere 
between 20 and 30 m in length this is not such a stupid 
mistake.

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Finally, I was informed (again off-list) that further stegosaur 
material may be known from the Wealden:

>Hulke, J. W., 1874, Note on a modified form of dinosaurian ilium,
>hitherto reputed scapula. Quarterly Journal of the Geological Society of
>London 30: 521-528.
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Tsk tsk Tim, you clearly haven't read...

Naish, D. & Martill, D. M. 2001. Armoured dinosaurs: 
thyreophorans. In Martill, D. M. & Naish, D. (eds) 
_Dinosaurs of the Isle of Wight_. The Palaeontological 
Association (London), pp. 147-184.

See also...

Blows, W. T. 2001. Possible stegosaur dermal armor from 
the Lower Cretaceous of southern England. In Carpenter, K. 
(ed) _The Armored Dinosaurs_. Indiana University Press 
(Bloomington and Indianapolis), pp. 130-140.

Olshevsky, G. & Ford, T. L. 1996. _Regnosaurus_, _The 
Dinosaur Folios_ 1. Publications Requiring Research 
(Buffalo, NY).

None of the material is impressive or absolutely convincing 
(in fact Pete Makovicky said in a book review that the 
material described by Blows is pretty much useless), but a 
stegosaurian identity for at least some of it seems likely. I 
can't see what BMNH 2516 (a partial left pubis from the 
Isle of Wight, first described by Hulke (1874) as an ilium) 
can be other than a stegosaur pubis.

-- 
Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth UK, PO1 3QL

email: darren.naish@port.ac.uk
tel: 023 92846045