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Metriorhynchid size & ostrich origins papers



From: Ben Creisler
bh480@scn.org

A couple of new advance online papers from the Zoological Journal of the
Linnean Society: 

YOUNG, M. T., BELL, M. A., DE ANDRADE, M. B. and BRUSATTE, S. L. (2011)
Body size estimation and evolution in metriorhynchid crocodylomorphs:
implications for species diversification and niche partitioning. 
Zoological Journal of the Linnean Society (advance online publication). 
doi: 10.1111/j.1096-3642.2011.00734.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00734.x/abstract

Metriorhynchids were a peculiar group of fully marine Mesozoic
crocodylomorphs, some of which reached large body size and were probably
apex predators. The estimation of their total body length in the past has
proven problematic. Rigorous size estimation was provided using five
complete metriorhynchid specimens, by means of regression equations derived
from basicranial and femoral length against total body length. The use of
the Alligator femoral regression equation as a proxy to estimate
metriorhynchid total body length led to a slight underestimation, whereas
cranial regression equations of extant genera resulted in an overestimation
of body length. Therefore, the scaling of crania and femora to total body
length of metriorhynchids is noticeably different from that of extant
crocodylians, indicating that extant crocodylians are not ideal proxies for
size reconstruction of extinct taxa that deviate from their semi-aquatic
morphotype. The lack of a correlation between maximum, minimum, or the
range of generic body lengths with species richness demonstrates that
species diversification is driven by factors other than just variation in
body size. Maximum likelihood modelling also found no evidence for
directionality in body size evolution. However, niche partitioning in
Metriorhynchidae is mediated not only by craniodental differentiation, as
shown by previous studies, but also by body size variation.


JOHNSTON, P. (2011)
New morphological evidence supports congruent phylogenies and Gondwana
vicariance for palaeognathous birds. 
Zoological Journal of the Linnean Society (advance online publication) 
doi: 10.1111/j.1096-3642.2011.00730.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00730.x/abstract

There has been little agreement on the phylogeny of palaeognathous birds,
with major differences amongst and between results from morphological and
molecular data. Two recently published phylogenies using nuclear and
mitochondrial DNA have substantial agreement in overall topology, with the
ostrich as sister group of all other extant palaeognaths and a
kiwi-emu-cassowary clade. Here I report a morphological phylogeny based
mainly on new characters from the tongue apparatus and cranial osteology,
with a theoretical ancestor as outgroup. A new interpretation of the
evolution of the avian palate is included. This phylogeny is very similar
to these recent molecular results; this is the first report of such
congruence, and offers a credible basis for understanding the evolution of
this clade. This phylogeny is fully consistent with a Gondwana vicariance
model of evolution. Dates attributed from known geological events place the
first extant radiation (ostrich) in the mid-Cretaceous, and offer a means
of calibration of future molecular clock investigations.


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