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EARLY MANIRAPTORS ETC
Dr. Holtz said.. (yes, that's _*Dr*_ Holtz, Nick...)
[ Oh just call him Tim. :-) Just kidding. *Don't* do that or Tom may put a
bounty on my head! -- MR ]
> ... Troodontid teeth (or something very much like them) are known
> from the Morrison (Late Jurassic), and teeth resembling those of
> dromaeosaurids and troodontids are known as far back as the Middle
> Jurassic in Great Britain. ...
Those of you who get DCC newsletter will note a big error in my letter of ish
19 - - or whatever the most recent issue is. I said that eastern Asia may
probably be 'the home of the tyrannosaurs closest relatives - ornithomimids and
troodonts', when in fact there is no good reason to suspect this. _Koparion_,
the earliest fossil referred to the Troodontidae of which I'm aware, is
Morrison (Kimmeridgian), while the earliest ornithomimid, _Pelecanimimus_, is
from Spain's Las Hoyas Fm (err, Berriasian?). Indet. bits and pieces from early
Cret ornithomimids have been reported from the US (e.g. by Ostrom in his
Cloverly Fm report) and parts of Asia I think. I'm aware of a few references
that mention or describe purported dromaeosaurid teeth from the
Bajocian-Bathonian from here in the UK, but I don't recall any troodonts. Tom?
A troodont-like tooth (stout, with big curved denticles on the posterior
carinae) may have been figured in Mike Benton's paper in _NERC News_, but I'd
have to check. It'd be Berriasian or so.
On a very similar note, some of you may have seen things in the press about the
bizarre and poorly studied mudsprings of Wooten Bassett, somewhere here in
England. The deposit that is being spewed onto the surface (mechanism not
understood, but it involves lots of mud!;-)) is Jurassic, with abundant
pyritized ammonites. One of my colleagues here at the SOC is doing his
dissertation on the palaeontology and sedimentology of the site, and I checked
out the microfossils for vertebrates. Loads of forams, little bivalves, junk
like that - one or two shark teeth (teeny tiny things, only 1-2 mm high) - and
limb segments from decapod crustaceans... then, there's a few tiny, isolated,
serrated teeth. I expect land microvertebrates to turn up, so I'll keep you
posted. Where are the goddam marine reptiles?!
And Stan (email@example.com) said..
> I still do not have an answer to my question: what is the distribution
> of anisodactyl feet (first toe turned backwards) in dinosaurs?
It's never wise to talk about these things without having literature there to
back you up, but as I understand it, none of the known non-avians has a foot
condition like the anisodactyl one in birds. Trackways, and the degree of
movement you can guess from articulated specimens, show that the hallux is/was
quite mobile in many theropods. But its metatarsal articulates with the lateral
side of met II, rather than on the caudal surface of the metatarsus: thus no
non-avian has a _truly_ reversed hallux. In _Archaeopteryx_, the hallux is
orientated as to be directed backwards - a useful perching adaptation - when at
rest. The new Montana dromaeosaurid may, just maybe, have a similar adaptation:
photos show the hallux to be real low down on the foot.
As I may be talking complete nonsense here, it might be a good idea for Jim
Farlow or someone else to, err, step in ('scuse the pun).
Seemingly, perching adaptations only became important in dinosaur feet when the
early birds took up full-time arboreality, so a reversed hallux is very well
developed by the time of the earliest enantiornithines. Of course, you have to
ask why non-avian dinosaurs had a reduced hallux in the first place... 2
schools; (1) reduced from terrestrial ancestors for cursoriality (cf. ungulates
of all stripes); (2) reduced as arboreal ancestors take up cursoriality (cf.
carnivorans, which started off as plantigrade, functionally 5-toed miacoids).
Many of the climbing mice also have big inner digits which have dwindled or
become reduced in non-climbing forms.
As for Feduccia's comments on syndactyly and other foot conditions in birds, I
don't really understand how it can be correlated with function _except_ where,
as in ospreys, mousebirds or the trogon-roller assemblage, it correlates nicely
with grasping or climbing. Err, doesn't that just about cover all of the non-
standard foot conditions in birds? Incidentally, it's my guess that syndactyly
(where at least two of the digits are fused for at least part of their length)
is related to stiffening of the foot as it loses its importance in grasping.
This is well known (but pretty much unstudied so far as I know) in alceldinoids
(kingfishers): as some of them have lost two of their toes (there's a whole
group called the Two-toed kingfishers), it may be that reductionism of the foot
is a trend.
The GS mystery, white whales, brown bulls, pears, punch, ice cream, and why am
I mentioned in a French newspaper?