Teretocnemidae

From Palaeos

o Ichthyopterygia
`--o ICHTHYOSAURIA
   |--Cymbospondylus
   `--+--Mixosaurus 
      `--o--Guanlingsaurus
         `--o Merriamosauria
            |--Shastasauridae
            `--o Euichthyosauria 
               |--Teretocnemidae
               `--+--Californosaurus
                  `--o Parvipelvia 
                     }--Macgovania
                     `--+--Hudsonelpidia
                        `--+--Suevoleviathan
                           `--+--Temnodontosaurus
                              |--Leptonectidae
                              `--o Thunnosauria 
                                 |--Stenopterygius
                                 |--Ichthyosaurus
                                 `--Ophthalmosauria

Introduction

The Teretocnemidae, along with Californosaurus, represent a poorly known group of basal euichthyosaurs; a paraphyletic assemblage of Late Triassic forms from which more advanced ichthyosaurs developed. The family Teretocnemidae was posited by Maisch & Matzke, 2000 to include the genera Teretocnemus and Qianichthyosaurus. However it is possible that Teretocnemus may actually, along with Delphinosaurus, be a synonym of Californosaurus. In the past all these forms were included in the Shastasauridae.

Thus what we have with the Teretocnemids/Californosaurs is a grade of medium sized Carnian ichthyosaurs that are similar to but more advanced then their often larger Shastasaur and Shonisaur cousins. With the extinction of the Shastasaur clade at the end of the Triassic, the descendents of the the Teretocnemid/Californosaur assemblage became, with the plesiosaurs the dominant marine reptiles of the Early Jurassic.

o Euichthyosauria 
|--o TERETOCNEMIDAE
|  |--Qianichthyosaurus zhoui Li, 1999
|  `--o Teretocnemus Merriam, 1903
|     |--T. californicus Merriam, 1903
|     `--T. zitteli (Merriam, 1903)
`--+--Californosaurus
   `--o Parvipelvia 

References

• Maisch, M. W. & Matzke, A. T. (2000) The ichthyosauria. Stuttgarter Beitraege zur Naturkunde. Serie B. Geologie und Palaeontologie. 2000; (298): 1-159.

Credits

MAK070121