Amber is often more than just a pretty jewel; it also offers us a glimpse into the past when dinosaurs roamed the planet. A recent discovery has turned the amphibian family tree upside down: tiny ancestors of amphibians trapped in a nugget of amber.
Science News reports that not only have paleontologists identified these ancient amphibians as a new species, Yaksha perettii, from a 99-million-year-old skull specimen encased in amber, but they also discovered evidence of its slingshot tongue. This finding re-classifies previous fossils first thought to be ancestors of modern-day chameleons and suggests that they hunted in the tree canopy rather than lurking in burrows.
Trapped in Amber
The fame or notoriety of amber may be very familiar to fans of Jurassic Park, but have you ever stopped to think how fossils end up in amber in the first place?
Amber forms from the sticky resinous sap that oozes from trees under stress. As the sap drips down the bark, insects and small animals can be trapped in its flow. Larger animals will also be caught up, but they’re usually strong enough to break free, leaving only hairs or feathers in the goo. Tiny lizards and insects engulfed in the resin are too weak to break free and suffocate as they become entombed, preserved as they fell.
When the droplets fall into a suitable environment, they dry out the contents, preventing decay. While the dry conditions inside the amber nugget don’t preserve DNA (so no cloning dinosaurs), they do keep a near-perfect record of anatomy, showing soft tissue, skin scales and feather detail, for example. Earth Archives describes amber fossils showing individual feather plumes, mites or youngsters on an insect’s back, or even a wasp and spider trapped for eternity in battle.
Non-Destructive Fossil Mapping
Researchers often like to take things completely apart in order to fully understand the anatomy of a specimen. But dissection would mean essentially destroying the amber nugget and its precious load. So, instead of chiseling it apart, the research team “mines” the amber digitally using scans and a synchrotron to peer deep into the specimen.
Y. perettii — which is named after Adolf Peretti, the gemologist who discovered the nugget of amber in Myanmar — is an albanerpetontid. These salamander-like amphibians, nicknamed “albies” by researchers, enjoyed a long existence on the planet, starting around 165 million years ago. An article in The Conversation, written by the senior instrument scientist in the synchrotron team, describes them as outliving the dinosaurs before their own extinction around two-and-a-half million years ago.
High-resolution computed tomography created a holotype of the skull encased in the amber. This 3D digital rendering gave the researchers the first confirmation that the tiny reptile skull was somewhat different from what was expected. Soft tissue remnants showed that what was previously thought as an artifact was actually a long bone attached to the tongue. This elongated median hyoid element was part of the suspensory structure for the tongue and is capable of launching the tongue at great speed out of the mouth. You see this kind of ballistic feeding with chameleons today, and Y. perettii is the earliest example of a slingshot tongue in action.
As with other studies of ancient skeletons, scientists can tell a lot about ancient animals and their behavior from their anatomy. For example, dinosaur fossils (especially their teeth) give valuable clues on diet and the way they ate.
As for Y. perettii, the digital microdissection gave the research team another clue that albies were a little different from modern amphibians. Their cervical spines showed two separate neck joints, giving them a much wider range of flexibility. They also had forward-facing eyes, which gives a clue to their preferred style as predators.
The tiny albie fossil, with a full body size of only 52 mm (around 2 inches) in length minus the tail, helped reclassify a previous specimen as a juvenile Y. perettii and not an early chameleon. The 3D digital model also showed that not only were these ancient amphibians ballistic feeders, but they also probably laid in wait for prey in the tree canopy rather than lurking in burrows as previously thought.
Another case of the fossil record rewriting history for the ancestors of amphibians.