Pistosauroidea

Pistosauroidea is a group of marine reptiles within the superorder Sauropterygia that first appeared in the latter part of the Early Triassic and were the ancestors of plesiosaurs. Pistosauroids are rare in Triassic marine assemblages, and are represented by only a few fossils from central Europe, the United States, and China.[1] Recent phylogenetic analyses consider the Triassic pistosauroids to be a paraphyletic grouping, meaning that they do not form a true clade. Plesiosauria is now placed within Pistosauroidea, while the traditional pistosauroids are successively more basal, or primitive, sauropterygians.[2]

Pistosauroidea Temporal range: Early Triassic - Late Cretaceous
Life restoration of Augustasaurus hagdorni
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Clade:	†Eosauropterygia
Clade:	†Pistosauroidea Baur, 1887-90
Subgroups
†Chinchenia †Corosauridae †Cymatosauridae †Kwangsisaurus †Wangosaurus †Pistosauria †Pistosauridae †Bobosaurus †Yunguisaurus †Augustasaurus †Plesiosauria

Below is a cladogram of pistosauroid relationships from Cheng et al. (2006):[1]

Sauropterygia	Placodontia       Pachypleurosauria     Nothosauria    Pistosauroidea    Corosaurus     Cymatosaurus       Pistosaurus       Yunguisaurus       Augustasaurus     Plesiosauria

Below is a cladogram of pistosauroid relationships from Ketchum & Benson, 2011:[3]

Pistosauroidea	Cymatosaurus    Pistosauria    "Pistosaurus postcranium"       Bobosaurus     Pistosaurus     Yunguisaurus       Augustasaurus     Plesiosauria

References

1. Cheng, Y.-N.; Sato, T.; Wu, X.-C.; Li, C. (2006). "First complete pistosauroid from the Triassic of China" (PDF). Journal of Vertebrate Paleontology. 26 (2): 501–503. doi:10.1671/0272-4634(2006)26[501:fcpftt]2.0.co;2. Archived from the original (PDF) on 2011-09-28.
2. Rieppel, O.; Sander, P.M.; Storrs, G.W. (2002). "The skull of the pistosaur Augustasaurus from the Middle Triassic of northwestern Nevada" (PDF). Journal of Vertebrate Paleontology. 22 (3): 577–592. doi:10.1671/0272-4634(2002)022[0577:tsotpa]2.0.co;2. Archived from the original (PDF) on 2011-07-16.
3. Hilary F. Ketchum and Roger B. J. Benson (2011). "A new pliosaurid (Sauropterygia, Plesiosauria) from the Oxford Clay Formation (Middle Jurassic, Callovian) of England: evidence for a gracile, longirostrine grade of Early-Middle Jurassic pliosaurids". Special Papers in Palaeontology. 86: 109–129. doi:10.1111/j.1475-4983.2011.01083.x.CS1 maint: uses authors parameter (link)