CURSORIAL STEGOSAURS?

[<darren.naish@port.ac.uk>]

First off, can I suggest that people stop hypothesising about imaginary 
dinosaurs. This list is supposed to be for dinosaur science, not science 
fiction. Please keep in mind how painful it can be when wading 
through 200-odd emails all on the same subject, especially when 
several of the list-members involved insist on repeating substantial text 
from previous list emails and then add little text of their own.

For those interested, some of my thoughts on hypothetical dinosaurs 
are at...
http://www.cmnh.org/fun/dinosaur-archive/1995May/0552.html
http://www.cmnh.org/fun/dinosaur-archive/2000Mar/msg00148.html
The first one is pretty dated (it was 1995!).

On early stegosaur evolution and the evolution of their feet, George 
wrote...

> I'm not talking about what stegosaurs >became<, I'm talking about
> their Triassic to Early Jurassic forms, as yet undiscovered, which
> (even if they were early thyreophorans, which I am not convinced that
> they were) were still good cursors somewhat resembling Scutellosaurus.
> 
> Otherwise, explain why graviportal forms would lose digit >and<
> metatarsal I in the hind foot. Didn't happen in any other graviportal
> dinosaur group, why in stegosaurs?

One _Stegosaurus_ specimen retains a vestige of a fourth metatarsal. 
George has argued that reappearance of a lost digit is effectively 
impossible so..  does this indicate that metatarsal I was retained within 
Stegosauria right up to the ancestor of _Stegosaurus_? I suppose the 
alternative is that this individual was teratological.

It is also worth noting that Le Loeuff et al. (1999) described a possible 
stegosaur track from the Hettangian of France. The hindfoot track had 
three main digits and an indistinct impression of a first. However, the 
phalanges appear to have been very short in this specimen: thus, 
phalangeal shortening (indicative of graviportality) appears to have 
preceded digit reduction (indicative of cursoriality). *IF* this track 
does belong to an early stegosaur, it suggests that the animals became 
heavyweights >before< they evolved the fully reduced tridactyl foot of 
advanced stegosaurs (rather than vice versa as per George: reduced 
foot first for cursoriality, then graviportal foot as advanced stegosaurs 
become heavyweights).

Le Loeuff, J., Lockley, M., Meyer, C. and Petit, J-P. 1999. Discovery 
of a thyreophoran trackway in the Hettangian of central France. _C. R. 
Acad. Sci. Paris_ 328: 215-9.

As someone who thinks the evidence for a monophyletic Thyreophora 
is pretty good, I would suggest that a quadrupedal ancestry for 
stegosaurs is more likely than a bipedal, cursorial ancestry.

SOME THOUGHTS ON PALAEONTOLOGY IN THE MEDIA

Finally, WRT the treatment in the media of palaeontological issues, it 
is an artefact of western culture that science seemingly has to be 
presented in a, for example, WWD 'mock nature show' format. There is 
plenty of scope for showing real bones, the people that work on them, 
reconstructions, animatronics etc without dissolving into fantastic 
speculation and antiscience: it's just that TV production people aren't 
as turned on by this, often because they themselves come from a very 
arty background. 

A similar problem is afflicting documentaries on live animals: more 
and more series of the so-called 'extreme natural history' genre are 
appearing. While some of the characters involved are qualified 
zoologists who do technical research and emphasise the importance of 
conservation, they frequently abuse the animals they are handling 
(Mark O'Shea, for example, is often shown holding live animals in his 
mouth). There was never anything wrong with natural history TV 
programmes in the past: they got good ratings and people liked 
watching them. But now that a new element of sex and rock'n'roll has 
been added, TV people are adopting this as the template they MUST 
follow. 

I've worked with satellite TV stations, Channel 4, BBC and other 
companies within recent years: let me say that it's been the satellite 
channels (whose biggest audiences are in India and SE Asia) that have 
been most willing to portray science in an honest way without a climb-
down to present things in the most sensationalistic manner possible.

I think it was Albert Einstein who said "Everything should be made as 
simple as possible, but no simpler".

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth & Environmental Sciences
UNIVERSITY OF PORTSMOUTH
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