Based on current amphibian larval phylogenetic analysis, fossils have identified the Notobatrachus tadpole as being closely related to the group that includes all present-day frogs and toads.
On October 30, the National Scientific and Technical Research Council of Argentina (CONICET) announced that an archaeologist from the country had discovered a dinosaur tadpole fossil measuring 16 cm in length, dating back approximately 165 million years, in the southern province of Santa Cruz.
The specimen belongs to the species Notobatrachus degustoi – the ancestor of modern frogs and toads. This is the oldest tadpole fossil discovered in the world, dating to the mid-Jurassic period in Patagonia, Argentina.
Specimen belonging to the species Notobatrachus degustoi – the ancestor of modern frogs and toads. (Photo: phys.org).
Dr. Matías Motta at CONICET stated that the discovery of this fossil was quite accidental while he was on an expedition organized by scientists from the Bernardino Rivadavia Natural Science Museum and the Chinese Academy of Sciences to search for dinosaur fossils at a farm named La Matilde in Santa Cruz. He picked up a stone during a lunch break and noticed bones and imprints on the rock.
This tadpole species has been known since 1957 when scientists discovered skeletons at the farm, preserving “primitive” features that are not found in today’s frogs and toads. The discovery of this well-preserved dinosaur tadpole will allow scientists to understand more about the evolution of frogs and toads.
Biologist Mariana Chuliver, an expert from the Félix Azara Natural History Foundation and the first specialist involved in this archaeological project, noted that some researchers suggest that most ancient toad species likely did not undergo a tadpole stage. However, this finding indicates that such assumptions may be inaccurate.
Team member Federico Agnolín, a specialist at the Bernardino Rivadavia Natural Science Museum of CONICET, emphasized that the scarcity of tadpole fossils makes the origins and early evolution of the larval stage a mystery.
Frogs have been present in the fossil record since the late Triassic period (about 217-213 million years ago), but tadpoles have not been documented before the Cretaceous period (around 145 million years ago).
According to CONICET, based on genetic analysis of current amphibian larvae, the fossil has helped identify the Notobatrachus tadpole as being very close to the group that includes all modern frogs and toads. The head, most of the body, and part of the tail, along with the eyes, nerves, and forelimbs of the fossil, are all observable. This indicates that the tadpole was in the final stages of evolution to become a mature amphibian.
Scientists believe that the evolutionary process of the larval stage has undergone very few changes over 160 million years, and primitive tadpoles fed in a manner similar to tadpoles today.
