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From K–T to Kermit

UF's David Blackburn Unlocks the Frog Tree of Life

Among UF’s renowned team of extinction experts is David Blackburn, whose appreciation for frogs has led to his work on a groundbreaking new study. A paper published in July in the Proceedings of the National Academy of Sciences shows that although frogs have been around for longer than dinosaurs, most of the world’s 6,700-plus living species of frogs evolved after a mass extinction 66 million years ago made way for new biodiversity.

Perhaps best known among mass extinctions, if not actually the most devastating, is the one that killed the dinosaurs. This event, called the Cretaceous–Tertiary extinction (K–T for short, to remind you that “Cretaceous” has a hard C), or more precisely the Cretaceous–Paleogene (K–Pg) extinction, caused a global die-off of 75 percent. Evolutionarily, these closed doors allowed others to open. Frogs, a highly adaptive type of creature, occupied many new niches, especially those created by a bloom of angiosperms, or flowering plants. Frogs took to the trees, which well suited their reproductive and self-defense needs.


This new analysis shows that the frog family tree's new crop of branches spread out from the extinction event between the Cretaceous and Paleogene periods — the K–Pg boundary, formerly called K–T — not 100 million years ago. The results were surprising to both the researchers and the scientific community, because previous mitochondrial DNA analysis traced major extant frog lineages to about 35 million years earlier than the K–T extinction, in the middle of the Mesozoic era.

Frogs also took on very different forms, with some retaining the commonly known tadpole stage and others evolving direct development, in which minuscule frogs hatch out of the eggs. They now occupy a wide range of habitats, from semi-arid regions of Africa to the super-humid South American rainforests, from clumps of leaves on the forest floor to the tops of trees.

The goliath frog (Conraua goliath) of Africa can grow up to 32cm (12.6in)!
"Except for a small handful of species, all other North American frogs are 'post-dinosaur' colonists. If you could travel back to the time of T. rex in North America, there would be frogs, but the chorus you would hear at night would have been nothing like you'd hear today. They're not even the same families." – David Blackburn

Frogs diversified after the extinction of non-avian dinosaurs. They were not, however, used to fill in gaps of DNA to resurrect dinosaurs.

by the numbers

6,700+ species of extant frogs (55 families )

200 million years ago: frogs first appeared

88 percent of living species stemmed from post-K–T explosion in 3 lineages (Hyloidea, Microhylidae and Natatanura)

95 genes sampled in this study, from 156 species (within 44 out of the 55 living families) and combined with previous research on additional 145 species

interesting Hyloidea

The Argentine horned frog (Ceratophrys ornata), sold in pet stores as the Pacman frog, will try to eat almost anything.
The northern glass frog (Centrolenella fleischmanni) is one of many translucent-skin frogs.
The beloved red-eyed tree frog (Agalychnis callidrya​s) is often able to scare off predators with its shocking eyes.

interesting Microhylidae

The painted burrowing frog (Scaphiophryne gottlebei) of Madagascar is a beautiful frog equipped with claws for climbing walls.
Males of the recently discovered Oreophryne furu (a type of cross frog) guard egg sacs that cling to the undersides of leaves.
The tomato frog (Dyscophus antongilii), sometimes found in U.S. pet stores, produces a toxic goo that affects predators' eyes and mouth.

interesting Natatanura

For decades, the Fiji ground frog was thought extinct due to human hunting and invasive mongooses, but was rediscovered in 2008.
The South African sharp-nosed frog (Ptychadena oxyrhynchus) can leap 50 times its body length.
The Philippine wrinkled ground frog (Platymantis corrugatus), like other members of the P. dorasalis group, evolved to blend in with leaves.

about david blackburn

David Blackburn is the Associate Curator of Herpetology at the Florida Museum of Natural History and an Affiliate Professor of Biology in the College of Liberal Arts and Sciences. He also is part of the Tropical Conservation and Development program, the School of Natural Resources and Environment, and the Center for African Studies.

Visit the Blackburn Lab website.

Herpetology classes were offered again in Spring 2017 for the first time in a decade, taught by Blackburn and fellow biology professor Harvey Lillywhite. Add herpetology to your UF education.

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Paper citation:

Yan-Jie Feng et al. Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous–Paleogene boundary. PNAS, 2017 DOI: 10.1073/pnas.1704632114

Footnote: Content curated by Rachel Wayne.