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EUSAUROPTERYGIA



Adam Smith wrote....
 
> Eusauropterygia was proposed by Storrs (1993)for a
> more exclusive clade within Sauropterygia. However,
> subsequent revision of sauropterygian
> interrelationships (Rieppel, 1998)revealed it to be
> polyphyletic and therefore redundant. I wasn't aware
> the term was still in formal use. Am I missing a key
> reference?

Check any of Rieppel's papers from the last 4-5 years. 
Eusauropterygia (proposed by Tscahnz 1989, not Storrs 
1993) is used as the nothosauroid + pistosauroid clade. 
Pachypleurosaurs, previously argued by Rieppel (1998) as 
sister group to Nothosauroidea, are presently regarded as 
the sister-group to the Eusauropterygia. 

Pachypleurosauria + Eusauropterygia = Eosauropterygia. 

Eosauropterygia + Placodontia = Sauropterygia, thus 
placodonts are the most basal sauropterygians known at 
present.

It's not entirely helpful that eosauropterygians and 
eusauropterygians have names that differ by only one letter.

Refs...

Rieppel, O. 1998. _Corosaurus alcovensis_ Case, and the 
phylogenetic interrelationships of Triassic stem-group 
Sauropterygia. _Zoo. J. Linn. Soc._ 124, 1-41.

- . 1999. Phylogeny and paleobiogeography of Triassic 
Sauropterygia: problems resolved and unresolved. 
_Paleogeography, Paleoclimatology, Paleoecology_ 153, 1-
15.

- . 2000. _Paraplacodus_ and the phylogeny of Placodontia 
(Reptilia: Sauropterygia). Zool. J. Linn. Soc._ 130, 635-
659.

- . 2000. Sauropterygia 1: Placodontia, Pachypleurosauria, 
Nothosauroidea, Pistosauroidea. In Wellnhofer, P. (ed) 
_Encyclopedia of Paleoherpetology, Vol. 12A_. Pfeil, 
Munich, pp. 134.

Tschanz, K. 1989. _Lariosaurus buzii_ n. so. from the 
Middle Jurassic of Monte San Giorgio (Switzerland), with 
comments on the classification of nothosaurs. 
_Palaeontographica A_ 298, 153-179.

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

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