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Temporal range: Late Triassic - Late Cretaceous, 210–66 Ma
Artist's restoration of Elasmosaurus platyurus
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Superorder: Sauropterygia
Order: Plesiosauria
Clade: Xenopsaria
Family: Elasmosauridae
Cope, 1869

See text


Cimoliasauridae Persson, 1960

Elasmosauridae was a family of plesiosaurs. They had the longest necks of the plesiosaurs and survived from the Late Triassic to the end of the Cretaceous. Their diet mainly consisted of crustaceans and molluscs.


Elasmosaurus platyurus in the Rocky Mountain Dinosaur Resource Center in Woodland Park, Colorado

The earliest elasmosaurids were small, about 3 m (9.8 ft). At the end of the Cretaceous, elasmosaurids grew as large as 14 m (46 ft), such as Elasmosaurus. Their necks were the longest of all the plesiosaurs, with anywhere between 32 to 76 (Albertonectes) cervical vertebrae They weighed up to several tons.


The family Elasmosauridae was erected by Cope in 1869, and anchored on the genus Elasmosaurus.


Elasmosauridae (Cope, 1869) is a stem-based taxon defined in 2010 (and in earlier studies in a similar manner) as "all taxa more closely related to Elasmosaurus platyurus than to Cryptoclidus eurymerus, Leptocleidus superstes, Plesiosaurus dolichodeirus or Polycotylus latipinnis". [6] The cladogram below follows, showing only Elasmosauridae interrelationships, the results of O’Gorman et al. (2015) who performed the most inclusive phylogenetic analysis focusing on Elasmosauridae interrelationships to date.[7]


Eromangasaurus australis

Tuarangisaurus keyesi

Elasmosaurus platyurus

Libonectes morgani

Callawayasaurus colombiensis

"Libonectes" atlasense

Hydralmosaurus serpentinus

Hydrotherosaurus alexandrae

Aphrosaurus furlongi

Terminonatator ponteixensis

Thalassomedon haningtoni

Styxosaurus snowii

Albertonectes vanderveldei

Futabasaurus suzukii

Mauisaurus haasti

Wapuskanectes betsynichollsae

Morenosaurus stocki

Vegasaurus molyi


Aristonectes parvidens

Kaiwhekea katiki


  1. ^ Araújo, R., Polcyn M. J., Schulp A. S., Mateus O., Jacobs L. L., Gonçalves O. A., & Morais M. - L. (2015). A new elasmosaurid from the early Maastrichtian of Angola and the implications of girdle morphology on swimming style in plesiosaurs. Netherlands Journal of Geosciences. FirstView, 1–12., 1
  2. ^ Patrick S. Druckenmiller and Anthony P. Russell (2006). "A new elasmosaurid plesiosaur (Reptilia: Sauropterygia) from the Lower Cretaceous Clearwater Formation, northeastern Alberta, Canada" (PDF). Paludicola (Special Issue, in memory of Elizabeth "Betsy" Nicholls) 5 (4): 184–199. 
  3. ^ Peggy Vincent, Nathalie Bardet, Xabier Pereda Suberbiola, Baâdi Bouya, Mbarek Amaghzaz and Saïd Meslouh (2011). "Zarafasaura oceanis, a new elasmosaurid (Reptilia: Sauropterygia) from the Maastrichtian Phosphates of Morocco and the palaeobiogeography of latest Cretaceous plesiosaurs". Gondwana Research 19 (4): 1062–1073. doi:10.1016/j.gr.2010.10.005. 
  4. ^ F. Robin O'Keefe and Hallie P. Street (2009). "Osteology Of The Cryptoclidoid Plesiosaur Tatenectes laramiensis, With Comments On The Taxonomic Status Of The Cimoliasauridae" (PDF). Journal of Vertebrate Paleontology 29 (1): 48–57. doi:10.1671/039.029.0118. 
  5. ^ Benjamin P. Kear (2005). "A new elasmosaurid plesiosaur from the Lower Cretaceous of Queensland, Australia". Journal of Vertebrate Paleontology 25 (4): 792–805. doi:10.1671/0272-4634(2005)025[0792:ANEPFT]2.0.CO;2. 
  6. ^ Ketchum, H.F.; Benson, R.B.J. (2010). "Global interrelationships of Plesiosauria (Reptilia, Sauropterygia) and the pivotal role of taxon sampling in determining the outcome of phylogenetic analyses". Biological Reviews of the Cambridge Philosophical Society 85 (2): 361–392. doi:10.1111/j.1469-185X.2009.00107.x. PMID 20002391. 
  7. ^ José P. O’Gorman, Leonardo Salgado, Eduardo B. Olivero and Sergio A. Marenssi (2015). "Vegasaurus molyi, gen. et sp. nov. (Plesiosauria, Elasmosauridae), from the Cape Lamb Member (lower Maastrichtian) of the Snow Hill Island Formation, Vega Island, Antarctica, and remarks on Wedellian Elasmosauridae". Journal of Vertebrate Paleontology 35 (3): e931285. doi:10.1080/02724634.2014.931285. 

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