The head, foot, and eye stalk of a tiny land snail were recently found fossilized in a piece of 99-million-year-old amber. Though the specimen measures less than 0.2 inches across, it offers incredible visibility into the lives of these inconspicuous creatures from the time of the dinosaurs.
The snail was contained in a small chunk of amber from northern Myanmar, also known as Burma. It was purchased from a private fossil collector in 2016 and includes the shell of a second, less well-preserved snail.
Whereas the vast majority of snail fossils retain only the shell, this find is the oldest-ever example of snail soft tissues preserved in amber, say the authors of a paper published this week in the journal Cretaceous Research.
The work was led by National Geographic Explorer Lida Xing of the China University of Geosciences in Beijing, whose team has also been behind recent discoveries of baby birds, rain forest frogs, a baby snake, and even a feathered dinosaur tail in Burmese amber.
This nearly whole, deep-black skull belongs to the most complete specimen of Tyrannosaurus rex on display in Europe, an individual nicknamed Tristan Otto. With 170 of its 300-odd bones preserved, this scientifically important but privately owned skeleton is currently at the Museum für Naturkunde in Berlin, Germany. Discovered in 2010 in Montana’s famed Hell Creek Formation of the late Cretaceous, the 40-foot-long fossil took four years to excavate and prepare.
A rare beauty
Snails entombed in amber are rare, “let alone extraordinary snail specimens that have soft parts,” says coauthor Jeffrey Stilwell, a paleontologist at Monash University in Melbourne, Australia.
“Ancient tree resin has exceptional preservation potential, capturing the finest of details of fossil organisms millions of years old in perfect 3-D space—so much so that they appear as though they just became trapped in the resin yesterday,” he says.
Snails with soft tissues have occasionally been found in amber elsewhere, but the new specimen is at least 70 million years older than the previous record holder. It provides important new data about the rich biodiversity of tropical forest life in the Cretaceous period.
The snail, now in the collection of the Dexu Institute of Palaeontology in Chaozhou, China, is likely related to modern cyclophoroidean land snails found in tropical and subtropical environments. This snail superfamily is known for its hard operculum, which functions as a lid or trapdoor when the snail retreats into its shell. However, the fact that the specimen is tiny and a juvenile has made it difficult to definitively confirm its identity, the authors say.
“Recognizing structures such as an eye stalk or a possible operculum is particularly noteworthy,” says Ricardo Pérez-de la Fuente, a paleoentomologist at the Oxford University Museum of Natural History in the U.K., who coauthored a paper last year on ticks found in Burmese amber.
“Findings like these are very valuable to complete the reconstructions of the Cretaceous amber forests and open a rare window into the 3-D preservation of soft tissues.”
A better fossil record
The authors hypothesize that the incredible specimen was formed when a snail fell into tree resin. The snail’s shell would have quickly been smothered in the sticky stuff, preventing the animal from retracting into it. The snail, they figure, would then have stretched its fleshy body forward trying to free itself, before becoming completely engulfed.
George Poinar, a paleobiologist at Oregon State University in Corvallis, calls the find fascinating but offers an alternative explanation as to how the entire snail could have been preserved.
Poinar has described 20- to 30-million-year-old snails with soft tissues found in amber from the Dominican Republic. He argues that the distended shape of the soft parts instead suggests “that the snail was attacked by a predator that tore its flesh and then by accident dropped it into the resin, where it was left,” he says. “No predator wants resin on its dinner.”
Regardless of how this snail met its demise, the unique find adds to the growing collection of animals and plants described from Burmese amber. Most of these resin-preserved species, which now number more than a thousand, were discovered in the past decade, says study coauthor Andrew Ross at the National Museum of Scotland in Edinburgh.
“The diversity in Burmese amber is truly phenomenal and … contains a mixture of primitive extinct forms and forms that are similar to living relatives,” he says. “It is providing a wealth of information about animals that were previously only known from fossils in rock.”