Lizards locked in amber provide clues to reptile evolution

Some ancient lizards’ bad luck has become a gold mine of information for scientists. 

Reptilian remains in roughly 99-million-year-old amber provide unusually detailed insight into the evolutionary history of lizards, researchers report March 4 in Science Advances.

The 12 chunks of amber, originally collected in Myanmar, contain parts of lizards that got trapped in tree resin during the Cretaceous period. Unlike stone, amber can fossilize small, delicate animals, as well as preserve soft tissues and organs.

Some of the amber specimens contain just a lizard leg; one holds most of a tongue. A translucent layer of scales traces where one lizard’s body once lay (left panel in the image above). In another fossil (middle panel), which contains skin and unusually long claws, sediment snuck into the lizard’s body during fossilization and created a mold of some bones. The researchers used CT scans to observe these internal structures in three dimensions.

Amber-encased toe pads (right panel) identified a few of the lizards as gecko ancestors. One of the preserved lizards may represent an intermediate form between known older relatives and modern geckos, the team says.

The skin and skeleton of a newborn lizard just over a centimeter long (shown in the image below) is the most surprising fossil in the bunch, says study coauthor Juan Daza, a herpetologist at Sam Houston State University in Huntsville, Texas. A stout skull, big eye sockets and a short, curled tail suggest that the young lizard could be the oldest known relative of modern chameleons.