Apsisaurus

• USA

• Apsisaurus witteri Laurin, 1991

Apsisaurus is an extinct genus formerly Pelycosaurier from the early Permian of North America. In recent times Apsisaurus is classified as basal representatives of Varanopidae. The type species and only representative of the genus is Apsisaurus witteri, which was found due to the poor state of preservation of the holotype originally to the early Diapsiden ( Eosuchia ). Apsisaurus is known only by the holotype, which consists of a skeleton preserved in parts including incompletely preserved skull and lower jaw, as well as remnants of the postcranial skeleton with vertebrae, ribs and proximal parts of the front and hind limbs is.

The fossil comes from the Archer City Formation of the Wichita group near Archer City, Texas.

Description

Apsisaurus was an early, small member of Varanopidae to its characteristics included elongated and high spinous processes of the vertebrae. The genus is also characterized by very slender humerus and differed by the absence of a strong curvature of the lateral teeth distinct from other forms of abgeleiteteren Varanopiden as Mesenosaurus, Mycterosaurus, Aerosaurus and Varanodon.

The original interpretation of the fossil than in the past Diapside is due to the erroneous identification of a further opening below the eye socket ( Suborbitalfenster ), as this is considered to be a synapomorphy of this subclass of reptiles. A comparison with the palate of Mesenosaurus and Archaeovenator in which this part of the skull is particularly well preserved, however, suggests that the mistakenly identified as skull opening area is only damaged in Apsisaurus. In particular, the proposed location of the opening - the center of the wing and leg on the side of the palate and the adjacent Ectopterygoid - differs from that in the early Diapsiden in which the skull opening is bounded laterally by the maxilla or cheekbone.

Apsisaurus possessed relatively large, sharp teeth. A small bump on the cheek bone of the animal is another typical feature of Varanopidae dar. Mycterosaurine Varanopiden also have a small lateral projection on the cheekbone, directly on the ventral edge of the orbit. This characteristic is known by no other clade frühpermischer amniotes.

Archaeovenator

Apsisaurus

Myctosaurus

Mesenosaurus

Elliotsmithia

Aerosaurus

Varanops

Varanodon

Also, the postcranial skeleton of Apsisaurus has surprising similarities to that of Archaeovenator.

Classification

First Apsisaurus was provided in the original description of the Diapsiden. Reisz et al. have shown that Apsisaurus witteri is classified as basal Varanopide due to the described similarities. According to the authors this has on the one hand an increase in the diversity of the known Varanopiden result, on the other hand, this also leads to a reduction of the taxonomic diversity of the early Diapsiden so that the fossil record is extremely low for these reptiles in the Paleozoic. This is all the more surprising when you look in mind that the Diapsiden presented the dominant subclass of amniotes during the Mesozoic.