Eosuchia

Taxobox
name = "Eosuchia"
fossil_range = Permian-Triassic

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image_width = 200px
image_caption = "Hovasaurus".
regnum = Animalia
phylum = Chordata
classis = Sauropsida
subclassis = Diapsida
ordo = Eosuchia
ordo_authority = Broom, 1924

Eosuchians are an extinct order of diapsid reptiles. Depending on which taxa are included the order may have ranged from the late Carboniferous to the Eocene but the consensus is that eosuchians are confined to the Permian and Triassic.

A definition for inclusion in the order is difficult: it is almost easier to list the primitively-diapsid reptiles that have not been included at one time or another. The order has almost been treated almost as a dustbin for diapsids that are not obviously lepidosaurian or archosaurian. One consequence has been Romer's suggestion of the alternative order Younginiformes to be applied strictly to those forms with the primitive diapsid form, in particular, a complete lowermost arch as the quadratojugal and jugal bones of the skull meet. [http://tolweb.org/articles/?article_id=465 For example and discussion]

The one constant eosuchian has been "Younginia", a small lizard-shaped reptile from the Upper Permian of South Africa. This and a couple of other genera, which may or may not be synonymous with "Younginia", make up the family Younginidae.

The tangasaurids, a family that includes forms apparently adapted for swimming in fresh water, is also usually included. [http://www.fmnh.helsinki.fi/users/haaramo/metazoa/Deuterostoma/Chordata/Reptilia/Neodiapsida.htm Phylogeny treating "Eosuchia" in its strict sense]

In some phylogenies "Eosuchia" has been treated (probably erroneously) as a sister lepidosaur taxon to Squamata and Rhynchocephalia. [http://tolweb.org/Diapsida At one time or another all of the taxa in black in this phylogeny has been placed within "Eosuchia" in one sense or another]

Classification

Eosuchia s.s. (Syn:Younginiformes)::?"Noteosuchus" :Family: Galesphyridae::"Galesphyrus":Family: "Younginidae"::"Heleosuchus"::"Thadeosaurus"::"Younginia":Family: Tangasauridae::"Hovasaurus"::"Tangasaurus"::"Kenyasaurus"

References