Ancient ‘Mold Pigs’ Found Trapped In Amber Don’t Fit Into Any Known Animal Group


Ben Taub


Ben Taub

Freelance Writer

Benjamin holds a Master's degree in anthropology from University College London and has worked in the fields of neuroscience research and mental health treatment.

Freelance Writer


The mold pig bears some similarity to tardigrades and mites but is distinct from both. Image: George Poinar Jr/Oregon State University College of Science

Discovering a new species is always a big deal, but finding a creature that doesn’t even fit into any known family within the animal kingdom is earth-shatteringly cool – even if that critter is only about 100 micrometers long. Hence the excitement surrounding the recent discovery of a tiny fossilized invertebrate in a 30-million-year-old piece of amber, which has been dubbed the ‘mold pig’.

Despite its minuscule proportions, this ancient organism is a beast of a discovery, revealing the existence of a previously unknown family, genus, and species of microinvertebrate that lived during the mid-Tertiary period, which began some 65 million years ago and lasted more than 63 million years.

Officially named Sialomorpha dominicana, from the Greek words sialos (meaning fat hog) and morphe (meaning shape), the creature takes its title from its podgy appearance and the fact that it feeds mainly on fungi. The find has been described in a new paper in the journal Invertebrate Biology, with the study authors noting that the mold pig “shares characters with both tardigrades and mites, but clearly belongs to neither group.”

Study co-author George Poinar Jr explained in a statement that “no claws are present at the end of their legs as they are with tardigrades and mites,” adding that “we don't know when the Sialomorpha lineage originated, how long it lasted, or whether there are descendants living today.”

Researchers found hundreds of specimens fossilized in a piece of amber from the Dominican Republic, allowing them to conduct a detailed analysis of various aspects of the mold pigs’ anatomy. The tiny chubsters were observed to have four pairs of legs, flexible heads, and were able to shed their exoskeleton in order to grow.

The amber also contained pseudoscorpions, nematodes, fungi, and protozoa, giving researchers a good idea of the types of animals that mold pigs shared their habitat with. The fact that this newly discovered species is now extinct makes it hard to study them further, although Poinar Jr’s previous work gave birth to the idea of extracting DNA from fossils preserved in amber, inspiring Michael Crichton to write Jurassic Park.

It’s unlikely anyone will be resurrecting the mold pig in a microscopic version of the ill-fated fictional park, although at least if they did you wouldn’t need to worry about getting eaten while on the toilet.


  • tag
  • amber,

  • Tardigrade,

  • mite,

  • jurassic park,

  • species,

  • genus,

  • invertebrate,

  • mold pig,

  • Sialomorpha dominicana