Their earliest frog-like relatives include Triadobatrachus massinoti, a small amphibian from Madagascar that lived about 250 million years ago during the Early Triassic.
By the Early Jurassic, roughly 190 million years ago, frogs such as Prosalirus bitis possessed elongated hind limbs, reinforced hips and shortened bodies better suited to leaping.
Their fossil record is rather patchy. Frog skeletons are small, lightly built and inclined to fall apart after death—excellent for jumping, less impressive for becoming immortalized in stone. Many fossil frogs are therefore represented by isolated hip bones, vertebrae and limb fragments.
British Columbia has produced Quaternary frog and toad remains from Bear Flat in northeastern BC. Researchers identified bones belonging to Rana, the group containing the true frogs; Bufo, a traditional grouping of toads; and other members of the order Anura.
Vancouver Island has also produced fossils bearing the frog name—but belonging to an entirely different branch of the animal kingdom.
Fossil frog crabs are marine crustaceans named for their broad, frog-like appearance and digging adaptations, not for any amphibian ancestry.
In 2020, Torrey Nyborg, Loma Linda University and team described a new genus Amphoranina from Eocene and Oligocene deposits of Washington State and Vancouver Island. The well-preserved specimens represent two new species, Amphoranina blandi and Amphoranina multispinata. The genus appears to have been endemic to the northeastern Pacific during the middle to late Paleogene.
Torrey does some wonderful research on fossil crabs from the Pacific Northwest and further afield.
He was also on the team with Jan Fischer and Margorie Johns who published on the recent late Eocene chimaroid egg capsule from lower Carmanah Group strata on the far western shores of Vancouver Island, British Columbia.
This is the fourth Paleogene chimaeroid egg capsule discovered from the Pacific Northwest. All four fossils were fossilized in tectonic foreland basins in bathyal water depths, which perfectly correlates with the known bathyal habitats and nesting sites of extant rhinochimaerids.
If you're reading this, Torrey, great to see your breadth of work. As a friendly nudge, there is a lobster from Tyaughton I am still looking to see you publish on.
Today, frogs and toads belong to the order Anura—meaning “without a tail.” More than 8,000 living species are currently recognized, ranging from fingernail-sized rainforest frogs to hefty bullfrogs and wonderfully peculiar burrowing forms.
So, British Columbia’s fossil record offers both genuine frogs and frog crabs: one built to leap, the other built to scuttle—and neither especially interested in clearing up the confusion.
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