A 48-million-year-old fossil has provided insight into the evolution of a group of lizards that famously run on water.
Officially named Basiliscus, (no, not that basilisk), Jesus lizards use their water running to escape predators. These days, they are restricted to equatorial regions, existing no further north than central Mexico.
However, the oldest fossil of a related species, found in the Bridger Formation of Wyoming, has been described by Dr. Jack Conrad of the American Museum of Natural History. At that time the creature lived, the world was 9°C (16°F) warmer than today.
In PloS One, Conrad named the fossil Babibasiliscus alxi, which means “older male cousin of basilisks” in the language of Wyoming's indigenous Shoshone people. Like modern relatives, it probably ate small snakes, lizards, fish, insects and plants. However, its larger cheekbones suggest it may have tackled more sizable prey than its descendants. Conrad describes the Wyoming of that era as being somewhere Babibasiliscus could take advantage of its adaptability, running on water and climbing trees with equal ease.
It had plenty of reason to run. “The Bridger Formation tells the story of a semi-tropical habitat filled with lakes and rivers,” Conrad told IFLScience. “It's at this time that we're seeing early relatives of cats, dogs, and bears – carnivorans that would like to make a meal out of a lizard. Other potential lizard predators would include raptorial birds and wading birds as well. There were abundant crocodylians and these will usually eat anything they can catch and kill.”
If those creatures were not enough incentive for a lizard to learn to run on water, Conrad said, “There was a small cousin of the Komodo Dragon running around... It would have been a harsh time to be a medium-sized reptile.”
“We have no direct evidence that this animal was actually able to run across the surface of the water,” Conrad told IFLScience. “However, we may infer that it might have because it belongs to a family of lizards (Corytophanidae) that includes several species that are able to do so.”
The best water runners are the Basiliscus, Conrad says, “but the related form Laemanctus can do so also (but not as well).” Babibasiliscus has resemblances to the Basiliscus, but is also a “sister taxon” to Laemanctus. The fossil is now housed in the Burke Museum at the University of Washington.
Conrad was funded from what seems a surprising source: the New York College of Osteopathic medicine. “We have more permanent faculty who study paleontology than most major museums,” he told IFLScience. “Vertebrate paleontologists and evolutionary biologists have to know a lot of anatomy – more than doctors.”
Conrad says this makes paleontologists useful for teaching medicine. Lizards have proven advantageous since some of their venom became a possible weapon against diabetes, and he notes the Corytophanidae habitat closely match malaria hotspots.