Timetree dating in the absence of a fossil record in Asian Horned Frogs

Date: February 23, 2017

Source: Molecular Biology and Evolution (Oxford University Press)

Asian Horned frogs account for approximately half of the ancient family of frogs called Megophryidae. This group was previously estimated to have originated 100-126 million years ago (mya). Frogs of this family hopped alongside the famed Velociraptors and other dinosaurs during the Cretaceous period (145-66 mya). Despite the fact that these animals have been around for a long time, little is known about their evolutionary history. Furthermore, unlike their dinosaur contemporaries, these frogs did not leave behind any known fossils. Methods using information from DNA sequences exist for estimating the age of origin for such groups of animals but these methods rely heavily on fossils of related animal groups, which could prove unreliable for these species.

New research recently published in the scientific journal, Molecular Biology and Evolution, by a team of scientists from Ireland and India resolved a 195-year old confusion regarding relationships between the species of Asian Horned Frogs, an enigmatic group of frogs often with horn-like projections over their eyes. Using DNA sequences, they discovered many potentially new species in this group previously unknown to science. They also estimated the ages of species and groups of species using a method that had previously not been tried on amphibians and inadvertently discovered that until now scientists may have been overestimating the age of many frog families. Their discovery may open a new chapter on how scientists interpret the evolutionary history of many animals that currently have no known fossil record.

"While this research particularly focused on frogs, many other animal groups also lack a fossil record, and so its very difficult to decipher their evolutionary histories. Our hope is that methods used here will prove beneficial for understanding how the distant ancestors of living animals may have coexisted in prehistoric times," explains lead author Dr. Stephen Mahony.

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