All rights reserved. Last updated May 2007. This site first opened in June 2001 and is continuously underconstruction.
Owen (1860) originally proposed the term Sauropterygia to encompass plesiosaurs and 'nothosaurs' (Storrs, 1991). So accurate were Owen's observations that the term has prospered and still represents a valid clade (natural group). Clades are defined by a number of common derived characters (synapomorphies) indicating common ancestry. Synapomorphies of the clade Sauropterygia include (Carpenter, 1997; Sues, 1986; Storrs, 1993):
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Single (upper) supratemporal fenestra (the lower temporal fenestra was lost - an excavated cheek margin is a remnant in many taxa)
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Closed palate of which the pterygoids cover the basis cranii (brain case) ventrally.
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lack of the following bones of the skull supratemporal, postparietal, and tabular (and lachrimal?).
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retracted nares - situated close to the orbit rather than on the snout tip.
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large retroarticular process on the mandible
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three to six sacral vertebrae
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lack of [ossified] sternum (maybe this was a cartilaginous element).
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divided scapulocoracoid
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pectoral and thyroid fenestration
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scapula lies superficially to the clavicle (i.e. the posterior part of the clavicle overlies the anterior part of the scapula)
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small ilium
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humerus lacks ectepicondylar foramen
Sauropterygia - cladogram
(click taxon for details)
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Redundant clade names: 'Nothosauriformes'
sauropterygian clades in alphabetical order
Claudiosaurus Corosaurus CRYPTOCLIDIDAE Cymatosaurus ELASMOSAURIDAE EOSAUROPTERYGIA EUSAUROPTERYGIA NOTHOSAURIA PACHYPLEUROSAURIA PLACODONTIA PLESIOSAURIA PLESIOSAURIDAE PLESIOSAUROIDEA PLIOSAURIDAE PLIOSAUROIDEA POLYCOTYLIDAE RHOMALEOSAURIDAE