ICHTHYOSAURS, SNAKES, TEMNOSPONDYLS

[darren.naish@port.ac.uk]

Made a homage to the library yesterday (funnily enough, to pick up 
some old Van Valen papers) and ran into some new stuff that will be 
of interest to some.

Lingham-Soliare, T. 1999. Rare soft tissue preservation showing 
fibrous structures in an ichthyosaur from the Lower Lias (Jurassic) of 
England. _Proc. R. Soc. London_ B: 2367-2373.

This is kind of a companion paper to Lingham-Soliare and Reif (1998) 
and describes two superimposed skin layers that consist of fibres that 
extend in opposite directions. Noted in the skull of an 
?_Ichthyosaurus_ specimen. Is suggested that such structures produced 
a smooth, strong skin texture and, as in scombroids and lamnids, this 
assisted in fast locomotion (on that note, this topic was addressed by 
Motani at SVP and was discussed in a recent _Science_ article). I have 
heard suggestion that these fibres were not dermal in origin (but 
presumably rock or bone fabric) - such criticisms are addressed. 

Rybczynski, N. 2000. Cranial anatomy and phylogenetic position of 
_Suminia getmanovi_, a basal anomodont (Amniota: Therapsida) from 
the Late Permian of Eastern Europe. _Zool. J. Linn. Soc._ 130: 329-
373.

_Suminia_ is a robust-skulled taxon with leaf-shaped teeth and 
chewing apparatus that recalls that of dicynodonts. Detailed skull 
description. Venyukovioidea is rediagnosed to include _Suminia_ + 
_Ulemica_ + _Otsheria_. _Galeops_ is found to be the sister-taxon to 
dicynodonts while _Patronomodon_ is the most basal anomodont... I 
haven't read the whole paper so I don't know if Anomodontia as used 
here corresponds to dinocephalians + dicynodonts but there is certainly 
a venyukovioid + _Galeops_ + dicynodont clade.

Coates, M. and Ruta, M. 2000. Nice snake, shame about the legs. 
_Trends in Ecology and Evolution_ 15: 503-507.

As usual for TREE, an excellent review that covers the current 
controversy over snake phylogeny and cites all the papers. Following 
the Lee, Scanlon and Caldwell hypothesis about _Pachyrhachis_ being 
the most basal snake, and with Serpentes as the sister-taxon to 
Mosasauroidea, there is the Rieppel and Zaher response: the characters 
that support pythonomorph phylogeny are different in detail and maybe 
due to convergence, snakes fall into a clade with amphisbaenians and 
dibamids, and _Pachyrhachis_ may not be that basal (in which case was 
there a lineage of persistently-limbed snakes, are pachyophiid limbs 
atavistic, or was there repeated loss of limbs in scolecophidians, 
anilioids and macrostomatans?). Different authors also find different 
positions in the tree for the new Cretaceous limbed snakes 
_Haasiophis_ and _Podophis_. The relationships between 
scolecophidians, anilioids and macrostomatans (and where _Dinilysia_ 
fits) is also covered... and what are madtsoiids? Snakes are the new 
dinosaurs!! (well, they're not, but you get the point..)

Steyer, J-S. 2000. Ontogeny and phylogeny in temnospondyls: a new 
method of analysis. _ZJLS_ 130: 449-467.

By coding character states in supposed larval, juvenile and adult stages 
of various temnospondyls, Steyer finds the resulting trees to be 
incongruent - suggesting that there were either a bunch of 
heterochronic events, or that identification of some specimens as 
larvae or juveniles is innaccurate. There's a lot more to it than this, 
sorry. Read the paper.

Bennett, A.F., Hicks, J.W. and Cullum, A. J. 2000. An experimental 
test of the thermoregulatory hypothesis for the evolution of 
endothermy. _Evolution_ 54: 1768-1773.

By increasing the metabolic rate of lab varanids, the authors hoped to 
test the hypothesis that endothermy evolved through an incremental 
rise in metabolic rate. Though the lizard's metabolic rates were tripled 
or quadrupled (producing basic metabolic rate 'indistinguishable' from 
that of a hedgehog), body temp only rose 0.5 degree C. They conclude 
that endothermy did not evolve by selective increase in visceral 
metabolic rate, but that other factors were responsible. OR, increased 
BMR evolved first and was only later refined to endothermy and 
homeothermy. Some discussion at the end of therapsid RTs and their 
function.

Also collected new stuff on phylogeny of Galapagos ground finches 
and bowerbirds. Alas have ran out of time. Wishing everyone a happy 
xmas and New Year and all that and see you in 2001.

"Of course, a fun day wouldn't be fun unless there was something there 
to traumatise the psyches of little children, and in this case it was a life-
sized, moving replica of a sabre-tooth tiger attempting to rip the 
innards out of a poor little baby mammoth" - - Hallowell, 2000.

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