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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.

THEROPODS

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 
herbivores.

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.

ORNITHISCHIANS

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 
crest.

SYNAPSIDS

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.

POSTERS

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.

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

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