Callobatrachus

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Callobatrachus is an extinct frog from the Early Cretaceous, about 125 million years ago, found in the Yixian Formation near Sihetun, Liaoning, China. The species Callobatrachus sanyanensis was named in 1999 by Gao and Wang.

The holotype is a nearly complete skeleton preserved on shale. It shows the animal was about 9.4 cm long from snout to vent, with hind legs about 11.6 cm long. It had a short, wide skull and a mix of primitive and more advanced features. Its backbone had nine presacral vertebrae, one sacral vertebra, and a free urostyle, with ribs attached to some vertebrae. It had many small teeth—roughly 18–20 on the premaxilla and about 40–50 on the maxilla.

This fossil is important because articulated frog fossils from this time are rare and help scientists understand how frogs evolved. There has been debate about its exact family. Some early writers suggested it was a discoglossid or the same as Liaobatrachus, but that view is not universally accepted. A 2017 study placed Callobatrachus in a more modern group of frogs, positioned between some primitive frogs and the more advanced ones.