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SVPCA 50, REPORT IV
Hopefully this'll be the last email from on SVPCA.
MORE GENERAL DINOSAUR STUFF
Paul Upchurch discussed the methods behind his recent
analysis of dinosaur biogeography.Using Components
Analysis, significant area relationships correspond closely
with those predicted from Mesozoic palaeogeography. At
least some of the evidence therefore supports the idea that
dinosaur distribution was mostly vicariance-driven. For the
full story see the Upchurch et al. _Proceedings_ paper.
Paul Barrett showed that Norell et al's recent claim of filter-
feeding and the presence of laminae in ornithomimids was,
err, somewhat questionable (which makes you wonder how
this paper got into _Nature_). In fact the pillar-like vertical
structures seen on the median surface of the ornithomimid
rostrum are pretty much identical to the same structures
seen in sea turtles and ornithischians and are more to do
with the presence of rhamphothecae than anything else
(Nick Longrich and I were already onto this.. Paul has
beaten us to it). Paul also investigated the energetics of
filter-feeding and showed that it would not have been
ecologically possible for ornithomimids to survive this way,
even given a variety of postulated metabolic regimes. More
likely (rediscovery of GSP 1988), ornithomimids were
Aha, how relevant... Marco Signore argued that mantids and
theropods may have exhibited similar snap-capture forelimb
devices and that this may explain the avian flight stroke.
Marco proposed that the bowed ulna evolved to resist
impact. Apparently some martial arts use forelimb strikes
similar to those postulated for maniraptorans and this seems
to be part of Marco's inspiration. As I pointed out in the
Q&A session, the problem with comparing mantids and
theropods is that mantids grab prey by impaling them on
spikes between the distal-most limb segment and the 'lower
arm'. Conversely, the theropod strike has a prominent
medial component and prey could not have been held
between the hand and lower arm. In that case are the two
systems really that analogous?
Gareth Dyke talked about the new Maastrichtian ornithurine
just published in _Naturwissenschaften_ and not all that
different from _Ichthyornis_, though bigger. The larger
picture of bird evolution around and across the KT
boundary was discussed and Gareth stated that 'at face
value' the data supports Feduccia's bottleneck hypothesis. I
don't see how this can be so though seeing as there is at
least some evidence of neornithine lineages originating in
the Late Cretaceous. Furthermore, I've just looked at the
abstract and Gareth says otherwise there, stating 'Range
correlations of lineages of Cretaceous birds, combined with
gap analysis and the estimation of clade confidence
intervals shows that there is little evidence for a 'bottleneck'
in diversity at the K-T boundary'. Tsk tsk.
David Waterhouse gave details on a new well-preserved,
quite complete Green River Formation charadriiform. In his
phylogenetic analysis, David did recover a monophyletic
Charadriiformes but is appears pretty different from
published versions with a radically polyphyletic
Scolopacidae scattered all about the tree. The new taxon
grouped closest to plovers, coursers and kin.
There was only one ornithischian talk in the whole
meeting.. Jo Parish's on ankylosaur evolution and
palaeobiology. Shamosaurine characters were regarded as
weak and _Cedarpelta_ and _Shamosaurus_ did not group
together: _Cedarpelta_ and _Minmi_ were basal
ankylosaurs outside of Ankylosauridae + (Polacanthidae +
Nodosauridae). Polacanthids show convergences with
ankylosaurids, especially in cranial characters. The
development of the acromion process appears to correlate
with the presence of pectoral spines and the form of dp
Matt Allison covered gorgonopsian taxonomy and
phylogeny (but I was in the pub and missed it) and Percy
Butler argued that MTBs must be derived from harimiyids
and that both groups are more primitive than most other
mammals (hmm, same talk as SVPCA Portsmouth).
Assorted presentations on mysticete feeding, ungulates,
carnivorans and primates followed, making mammals better
represented at this SVPCA than most others.
As mentioned earlier in these reports, marine reptiles simply
didn't get represented in the talks at all. Consequently there
were more poster presentations on these animals than
normal. Dino Frey and Marie-Celine Buchy showed how a
new Mexican pliosaur simply could not have the same flow-
through internal narial system as proposed by Cruickshank,
Small and Taylor; Marcela Gomez presented details on a
new _Kronosaurus_ species (most similar to _K.
boyacensis_) from Colombia; Richard Forrest revealed that
plesiosaurs exhibit 'M-type' and 'E-type' neck stiffening (M-
type forms raise the zygapophyses higher onto the neural
arch, E-types lock the neural spines together but lower the
zygapophyses) and that these two types may be
fundamentally different (genetically and phylogenetically);
and Adrian Doyle and Sandra Chapman showed that the
type specimen of _Stenopterygius acutirostris_ has been
relocated in the NHM collections.
As for stuff other than marine reptiles.. Steve Sweetman
illustrated a plethora of new Isle of Wight Wessex Fm
microvertebrates (including albanerpetontids, frogs, lizards,
tiny ornithischians etc) and Barry Clarke presenting a very
interesting re-interpretation of anuran origins (saltation has
been over-emphasised and walking must have been more
important in evolution of the basal frog body plan).
There was more but I've run out of time. Bye-bye.
School of Earth & Environmental Sciences
University of Portsmouth UK, PO1 3QL
tel: 023 92846045