A new old ape and fish that could walk

Scientists say they have found an important ancient ape and more fish they suspect could probably walk.

Two different studies by two different teams, it must be stressed, but each an intriguing addition to our knowledge of the natural world. And the common theme is CT scanning.

Fish first. Researchers from the US and Thailand have analysed the bone structure of nearly 30 species of hillstream loach (Balitoridae), describing for the first time three categories of pelvic shapes.

What’s exciting, they say, is that 10 species share the unusually hefty pelvic girdle of the cave angel fish (aka Cryptotora thamicola), the only living fish species reportedly caught in the act of walking.

Its salamander-like wiggle, powered by enlarged ribs bolstered with stabilising muscle attachments, was described in the journal Scientific Reports in 2016.

“What’s really cool about this [new] paper is that it shows with high detail that robust pelvic girdles are more common than we thought in the hillstream loach family,” says Zachary Randall from the Florida Museum of Natural History, a co-author of the study published in the Journal of Morphology.

The team used CT scanning and DNA analysis to trace the evolutionary history of the hillstream loach and found that, rather than evolving from a single origin, a robust pelvic region appeared several times across the family.

“These loaches have converged on a structural requirement to support terrestrial walking not seen in other fishes,” says lead author Callie Crawford, from New Jersey Institute of Technology.

Pinpointing exactly which species of fish have walking capabilities can help scientists piece together how the first land-walking vertebrates might have come to be, the researchers say.

As for the ape, US and Indian researchers believe it is the earliest known ancestor of the modern-day gibbon and can provide important new evidence about when these ancestors migrated to Asia from Africa.

200910 ramnagar
The field site in Ramnagar, India. Credit: Christopher Gilbert

The 13-million-year-old fossilised tooth was found, quite by chance, at the famous Ramnagar fossil site in northern India.

“We knew immediately it was a primate tooth, but it did not look like the tooth of any of the primates previously found in the area,” says Christopher Gilbert from City University of New York, US, lead author of a paper in the journal Proceedings of the Royal Society B

“From the shape and size of the molar, our initial guess was that it might be from a gibbon ancestor, but that seemed too good to be true, given that the fossil record of lesser apes is virtually non-existent.”

Five years of detailed analysis proved that it was, indeed, true. The molar was photographed and CT-scanned, and comparative samples of living and extinct ape teeth were examined to highlight important similarities and differences in dental anatomy.

In addition to determining that the new ape represents the earliest known fossil gibbon, the researchers say, its age is contemporaneous with well-known great ape fossils, providing evidence that the migration of great apes and lesser apes from Africa to Asia happened around the same time and through the same places.

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