Microsauria
Live reconstructions of some genera: (A) Hyloplesion, (B) Pantylus, (C) Pelodosotis and (D) Rhynchonkos
- North America
- Europe?
The Microsauria are a group of extinct land vertebrate animals whose fossil remains from the Mississippian ( " Lower Carboniferous " ) to the early Permian in North America and possibly in Europe are detectable. John William Dawson looked at the group in his first description of 1863 as an early reptiles ( Microsauria = "little lizards " ), today they are classified in the group of amphibians like Hüllenwirbler ( Lepospondyli ).
Features
The Microsauria, 3.5 to 60 centimeters long and were in morphology and lifestyle the most variable Lepospondylen. Most species were salamander -like and lived terrestrial, other amphibious. There were also specialized grave, believed in the soil forms that had long body and short limbs and the skull bones were reduced. Aquatic living Microsauria retained their external gills to the adult stage at ( neoteny ). Terrestrial forms lacked the pits of the lateral line organ. All had limbs, even if they were only short and thin. The tail was never specialized, as in the Nectridea, another group of Lepospondyli. The number of vertebrae was 19 to 44 As with other Lepospondylen the Centra of the vertebral body are fused cylindrical and with the neural arches. The synapomorphies of Microsauria include the lack of intertemporal and supratemporal in the skull. Primitive Microsauria cheeks region is completely covered, whereas deeply indented at three progressive families.
System
The Microsauria are now no more than monophyletic taxon. The eleven families are divided into two main groups, which are differentiated by their skull morphology: The Microbrachomorpha, named after the aquatic Microbrachis are closely related with the Nectridea as with the other Micro dinosaurs. Here, in the skull, the postfrontal no contact with the Tabulare. The Tuditanomorpha (after the genus Tuditanus ), these two cranial bones touch. It includes mainly terrestrial living genera, for example Pantylus. Besides representing Rhynchonchos, who had a long torso and short legs, possibly a separate group. This group would be more closely related to the Microbrachis group than with the Tuditanus Group and is a possible origin of extant caecilians ( Gymnophiona ) talking.
Some scientists believe that the Salamanders ( Caudata ) are descended from dinosaurs Micro. The majority today is however assumed that the origin together with that of the Anura ( Anura ) lies within the Dissorophoidea.