An analysis of the 30-million-year-old amber has led to the discovery of a previously unknown microscopic creature from the Cenozoic period. Bearing a resemblance to tardigrades (aka water bears), these now-extinct “mold pigs,” as they have been dubbed, are unlike anything seen before.
Introducing Sialomorpha dominicana, a newly discovered microinvertebrate found locked in amber from the Dominican Republic. Its discoverers, paleobiologist George Poinar Jr. from Oregon State University and invertebrate zoologist Diane Nelson from East Tennessee State University have dubbed the creature a "mold pig" in honor of its porcine, porcine appearance and its diet, which consisted primarily of fungi. Details of the discovery were recently published in Invertebrate Biology.
The 83-year-old Poinar is no stranger to working with fossils trapped in amber. His 1982 research paper gave sci-fi author Michael Crichton the idea of extracting dinosaur DNA from insects trapped in amber, as portrayed in the film Jurassic Park.
Poinar has made a career working with amber, finding fossilised flies, bees, bats and ancient flowers.
This time around, however, Poinar, along with Nelson, discovered a creature invisible to the human eye – a microinvertebrate measuring no more than 100 micrometres long.
“It took me many days, weeks, and months to examine [the specimens], and then under the compound microscope, ”Poinar wrote in an email to Gizmodo. “They are as small as the smallest tardigrades, and they have eight legs like tardigrades. However they have mandibles but no claws, whereas tardigrades have claws and stylet mouthparts, ”meaning a sharp, piercing mouthpiece.
The amber fossil analyzed by Poinar and Nelson literally contains hundreds of mold pig specimens, allowing them to study a host of different biological aspects, including their anatomy, reproductive behavior, growth, development, and diet. For example, the mold pigs featured flexible heads and they grew by molting their exoskeleton.
The researchers also discovered other creatures locked inside the amber, including pseudoscorpions, nematode worms, fungi and various protozoa. Mold pigs are preferred warm, moist environments where they feed on fungi and sometimes other small invertebrates, the researchers found.
Because nothing comparable exists in the scientific record, whether extinct or extant, the mold pigs were assigned to an entirely new family, genus, and species. The "fossil shares features with both tardigrades and mites, but clearly belongs to neither group," wrote the authors in their paper. Its major distinguishing features "are its mouthparts in combination with a lack of claws, four pairs of legs, terminal anus, and reproductive openings," Poinar told Gizmodo.
Researchers know when this invertebrate family originated, how long it lasted, or if any descendants are still around today. The discovery shows that extremely tiny animals were able to live in Cenozoic microhabitats, and that these creatures could use the fungi as a food source, according to Poinar.
Tardigrades, nicknamed water bears, are known for their extreme resilience as being able to survive long-term deep-freezing and vacuum of space. We can only guess as to whether these mold pigs would possess similar powers.