Triadobatrachus massinoti (Piveteau 1936) Early Triassic ~250 mya, ~10 cm in length, is considered the oldest frog known. Although distinct from all living frogs and toads, Triadobatrachus is considered a frog due to its reduced vertebral count, the relative length of its hind legs, the presence of elongated ankle bones (tibiale and fibulare) and the anterior extension of its ilium. Derived from a sister to Gerobatrachus, Triadobatrachus phylogenetically preceded modern frogs like Rana.
Distinct from Gerobatrachus, the skull of Triadobatrachus was relatively smaller with a narrower skull roof and a larger orbit that extended into the cheek where the bones were reduced. The frontal and parietal were fused together, but note the parietals were not completely fused to each other! The intertemporal was fused to the parietal. A large postparietal shelf was absent. The lower jaw was toothless.
The presacral vertebral count was reduced to 14. The tail was reduced to a nub of at least six vertebrae. The ilium included a larger anterior process, but note the thigh muscles did not extend to the anterior tip of the ilium as in reptiles and mammals. The femur, tibia and fibula were elongated as were two proximal ankle bones, the tibiale and fibulare. Unfortunately the hands and feet remain unknown.
Despite the much longer hind legs, Triadobatrachus was considered not an effective jumper.