This suborder includes the Newts (Molge), Salamanders (Salamandra), and Amblystoma.
Order 2. Labyrinthodontia[52].
These are extinct Amphibia with a greatly developed dermal exoskeleton, which is generally limited to the ventral surface. The body and tail are long and in some cases limbs are absent. The teeth are pointed and often have the dentine remarkably folded. The vertebrae are amphicoelous, and are generally well ossified. The skull is very solid, and has a greatly-developed secondary roof which hides the true cranium and is very little broken up by fossae. Paired dermal supra-occipitals are found, and there is an interparietal foramen. The epi-otics and opisthotics form a pair of bones distinct from the exoccipitals. Four simple limbs of moderate length are generally present, and in some cases all four limbs are pentedactylate. Among the better known genera of Labyrinthodonts are Mastodonsaurus, Nyrania, and Archegosaurus.
Order 3. Gymnophiona[53].
These animals form a group of abnormal worm-like Amphibia having an exoskeleton in the form of subcutaneous scales arranged in rings. The vertebrae are biconcave and are very numerous; very few however belong to the tail. The skull has a complete secondary bony roof, the mandible bears teeth and has an enormous backward projection of the angular. The hyoid arch has very slender cornua and no distinct body, it is attached neither to the cranium nor to the suspensorium. The ribs are very long and there are no limbs or limb girdles.
Order 4. Anura.
These are tailless Amphibia, which except in a few instances, are devoid of an exoskeleton. The vertebrae are as a rule procoelous, and are very few in number. The post-sacral part of the spinal column ossifies continuously, forming an unsegmented cylindrical rod, the urostyle. Remains of the notochord persist, lying vertebrally, i.e. enclosed within the centra of the several vertebrae, and not as in Urodela lying between one vertebra and the next. The skull is very short and wide. The mandible is almost always, if not invariably, toothless.
The frontals and parietals on each side are united so as to form a pair of fronto-parietals, and a girdle-like sphenethmoid is present.
The quadrate is not generally ossified. A predentary or mento-meckelian bone is commonly present in the mandible, and a single bone represents the angular and splenial. The branchial arches are much reduced in the adult, and the distal ends of the cornua unite to form a flat basilingual plate of a comparatively large size.
Ribs are very little developed. Clavicles are present. The ilia are very greatly elongated. The anterior limb has four well-developed digits and a vestigial pollex, and is of moderate length; the radius and ulna have fused. The posterior limb is greatly elongated and is pentedactylate; the tibia and fibula are fused, while the calcaneum and astragalus are greatly elongated, and it is largely owing to them that the length of the limb is so great. The group includes the Frogs and Toads, the predominant Amphibia of the present time.