George Poinar Jr., an insect specialist at 7, is peering through a microscope at a 30-million-year-old piece of amber. Then he spots something really special. And it’s something that’s entirely unknown to entomology – the study of insects. So he comes up with a name for these miniscule bugs that have been trapped in amber for all those years: “mold pigs.”
In fact, the name Poinar came up with initially is a Latin one – as is customary in the life sciences. That name is Sialomorpha dominicana and it comes from the ancient Greek sialos meaning fat hog and morphe – or shape. The word dominicana tells us that this piece of amber was discovered in the Dominican Republic.
Quoted in a statement released by Oregon State University in October 2019, Poinar explained that these mold pigs “share characteristics with tardigrades – sometimes referred to as water bears or moss pigs, and mites…” But even though they may resemble mites and moss pigs, it seems that there is no doubt that they are a different type of creature.
As we’ve said, these mold pigs were alive some 30 million years ago. But there is much more to learn about the time scale that the species occupied. Poinar said, “We don’t know when the Sialomorpha lineage originated, how long it lasted, or whether there are descendants living today.” However, there’s much more knowledge about the era they lived in: the mid-Tertiary.
We’ll get back to these weird mold pigs shortly, but first let’s take a look at what the world was like during the mid-Tertiary. This is a period which lasted from 66 million to 2.6 million million years ago. So it makes sense to describe the time when these mold pigs existed – 30 million years ago – as the mid-tertiary.
However, many modern scientists no longer use the term Tertiary. They instead refer to the period around 30 million years ago as the Oligocene epoch – which lasted from 33.9 to 23 million years ago. Heinrich Ernst Beyrich, a German palaeontologist, came up with the term Oligocene in 1854, and it’s a name derived from the ancient Greek language.
Oligis is the Greek word for few and kainos means new. Although it’s not immediately apparent from the term, in his naming of the epoch Beyrich was referring to the fact that there were very few species of mollusk on Earth during the period. That’s a stark contrast to our modern planet – which boasts around 85,000 species of mollusk. These include everything from snails and slugs to octopuses and cuttlefish.
But the world was a very different place during the Oligocene. The continents were not yet in place on the Earth’s surface as we know them today, but they were drifting towards the positions that we are now familiar with. In Europe, the Alps were beginning to rise above the landscape, while mountains were also forming in the west of North America.
Interestingly, fossil species found in both Europe and North America have been very similar. And paleontologists have speculated that in the past, there may have been a land bridge which previously existed between the two land masses during the Oligocene. On the other hand, South America had recently – at least in geological terms – split from Antarctica and was inching towards North America. So even though the modern geography of the planet was slowly coming together, it was still quite markedly different from its future shape.
The Oligocene was a time when changes in flora and fauna were happening across the world – in part responding to an overall decrease in temperatures. Deciduous forests were now appearing and replacing tropical vegetation, and grasslands had begun to take hold as well as deserts. North America saw various species of trees becoming more widespread, while plants like ferns and bulrushes were thriving.
Sea animals were becoming more akin to species we would recognize today and many land animals were increasing in size. In Asia, for example, the largest land mammal ever seen appeared – a kind of giant rhinoceros known as a Paraceratherium. Some animals may have flourished in the niches vacated as other species became extinct.
So this was the world that the microscopic mold pigs lived in – with some of them ending up trapped in amber so that we could study them today. But also alive during this epoch were both tardigrades and mites. And these were creatures that, as Poinar has pointed out, bear some resemblance to the mold pigs. In fact, tardigrades – which are still around today – can be traced back as far as 500 million years ago.
Just like mold pigs, tardigrades are sometimes suspended in amber, and the earliest examples we have were preserved in that way. Johann August Ephraim Goeze, a German zoologist, was the first to describe tardigrades back in 1773. He also gave them the name of “water bears.” And they can indeed swim – using their eight legs to move through water.
It was an Italian biologist called Lazzaro Spallanzani who in 1777 dubbed them Tardigrada – which means slow stepper. They also have an endearing second nickname: “moss piglets.” Attached to their eight legs the creatures have anywhere from three to eight claws. Elsewhere, their tiny mouths can extend outwards to snatch food.
Tardigrades actually live on liquid which they such from lichens, moss and algae. But far and away their most bizarre quality is the ability to enter a state of suspended animation just a tiny step away from complete death. And then they can come back to life.
This Lazarus-like ability is exhibited by Tardigrades when water is absent from their environment. When that is the case they dry out, pull in their legs and heads and end up as tiny waterless lumps known as tuns. This process is called cryptobiosis, and it can be reversed after a period of not just days or weeks but when decades have passed.
This ability to return from near-death was confirmed in 2016. Scientists defrosted a sample of moss that had been collected in Antarctica and stored in a deep freeze at minus-four degrees Fahrenheit for 30 years. The moss included some tardigrades in a state of cryptobiosis. Two of those were revived and not only did they come back to life, they also proceeded to reproduce vigorously.
In fact, tardigrades can even tolerate outer space, and they are the only animal we know about that can pull off that trick without the benefit of a spacesuit or ship. In 2007 some of the tiny animals were taken into orbit around the Earth aboard the Russian robot spacecraft Foton M-3 and exposed to outer space conditions. And incredibly, most of them survived.
There’s even been speculation that there are actually tardigrades living on the Moon. Some of them were aboard an Israeli Moon probe that launched in 2019 but crash landed. The moss piglets had been dehydrated prior to their journey and at least one researcher believed they had probably survived. If so, they’re the first creatures from Earth to colonize an extraterrestrial body.
The extraordinary capabilities of the water bears seem to know no bounds. In 2017 scientists from Oxford and Harvard universities published a paper in which they asserted that tardigrades would likely survive almost any catastrophe that our planet might suffer. Nearby supernova explosions or asteroid impacts might wipe out the Earth’s flora and fauna, but the tardigrades would likely survive. We humans, of course, would not.
The other animal that Poinar compared with the mold pig is the mite. Scientists have studied and described some 48,200 species, but estimates indicate that there may actually be as many as one million types of mite. And some of them have a number of extraordinary qualities.
For example, a mite called Archegozetes longisetosus is credited with being one of the strongest animals in the world – despite being just 0.04 inches long. It’s said to be able to shift an object equivalent to 1,182 times its weight, according to the Journal of Experimental Biology. And they have another fascinating attribute – they’re all females and require no males for reproduction.
Of course, many mites are regarded as pests. There are some which damage plants and others which prey on honey bees. But the most familiar ones are those which thrive in a domestic setting: dust mites. This latter species can cause a variety of unpleasant conditions in humans including eczema, hay fever and asthma. But other types of mites offer benefits by breaking down decomposing organic matter.
We’ll leave behind the mites and tardigrades for now, but before we get back to the mold pig, it’s worth a short detour to return to George Poinar – who we mentioned earlier. He is the individual who discovered our mold pigs preserved in 30-million-year-old amber. And the scientist has made the discovery and analysis of ancient creatures suspended in this tree resin something of a specialty.
In fact, it’s said that one of Poinar’s discoveries inspired Michael Crichton’s 1990 thriller Jurassic Park. And that book was of course the basis for Steven Spielberg’s Hollywood blockbuster of the same name which came out three years later. Crichton is said to have been inspired at least in part by research published by Poinar and others in 1982.
In the aforementioned study, the scientists had investigated a 40-million-year-old fungus gnat that had been preserved in Baltic amber – just like the mold pigs were ten million years later. One scientist suggested at the time that it might be possible to extract DNA from the insect remains. Crichton apparently read the study and wanted to find out more.
In a 2016 article on the website Science Friday, Poinar described what had happened with Crichton. The scientist explained, “From what Michael Crichton said, he had written Jurassic Park, but he hadn’t decided how he was going to get the dinosaur DNA, and when he read the paper [on the fly in Baltic amber], this gave him the idea that he would obtain it from mosquitoes that bit the dinosaurs.” Poinar added, “The next thing we knew, the book was out and then the movie was out.”
Crichton underlined the influence of Poinar by actually acknowledging and thanking him in one edition of Jurassic Park. And the book’s central plot device – that dinosaurs could be reintroduced in modern times from their ancient fossil DNA – is an obvious echo of Poinar’s scientific work. But, sadly for science fiction fans, the idea is not one we should take too literally.
Poinar himself has said that recreating dinosaurs from ancient DNA is a non-starter. And science confirms this to be so. In 2012 experts worked out that the half-life of DNA was 521 years. That means DNA would be completely gone after about 6.8 million years. The dinosaurs, of course, died out some 66 million years ago.
And now let’s get back to the mold pigs. As we heard earlier, both mites and tardigrades have some similarities to the mold pig. But there is a key difference that comes in the categorization of the different animals. There are many different species of both mites and tardigrades but these two types of animals are part of a recognized scientific family of creatures.
Mites are part of the Arthropoda phylum which includes insects, spiders and crustaceans. A phylum is a scientific term for a family of creatures – the level below the Animalia which includes all animals. The over 1,100 species of tardigrades are placed in their own exclusive phylum: Tardigrada. And the fact that they have their own phylum emphasizes the singularity of these minuscule creatures.
But the astonishing thing is that the fossil mold pigs seem to fit into no previously known phylum. This single species is so different to any other that, in splendid isolation, it inhabits its own classification. In the Oregon State University statement, Poinar said, “No claws are present at the end of their legs as they are with tardigrades and mites.” And that feature immediately distinguished the mold pigs from those other creatures that they resembled.
And Poinar continued, “Based on what we know about extant and extinct microinvertebrates, S. dominicana [the mold pig] appears to represent a new phylum. The structure and developmental patterns of these fossils illustrate a time period when certain traits appeared among these types of animals.” And that is dramatic news indeed within the world of science: the discovery of an entirely new phylum.
So these extraordinary mold pigs appear to be unique within the animal kingdom. What’s more, Poinar was able to learn a remarkable amount from these tiny fossilized creatures in their protective coating of Dominican amber. And the mold pigs truly are only 0.004 of an inch long – about the thickness of an average human hair.
Poinar has dubbed these creatures mold pigs because he says they looked somewhat like pigs and because of what the creatures ate. He described the circumstances surrounding the discovery of this previously unknown species, “Every now and then we’ll find small, fragile, previously unknown fossil invertebrates in specialized habitats.”
Poinar continued, “And occasionally, as in the present case, a fragment of the original habitat from millions of years ago is preserved too. The mold pigs can’t be placed in any group of currently existing invertebrates. They share characteristics with both tardigrades, sometimes referred to as water bears or moss pigs, and mites – but [they] clearly belong to neither group.”
In fact, Poinar has discovered several hundred of these microscopic beasts trapped in amber. And, he says, they would have shared their warm and wet environment with a variety of life forms. These included fungi, pseudoscorpions and nematode worms. Their habitat would also have been home to protozoa – single-celled organisms.
Poinar described the insights offered by this abundance of specimens he had discovered. He told Oregon State University, “The large number of fossils provided additional evidence of their biology – including reproductive behavior, developmental stages and food.” Indeed, the amount of knowledge that Poinar extracted from those 30 million-year-old amber fragments is astonishing.
Poinar outlined some of the other facts that he’d been able to learn about the mold pigs. They were equipped with eight legs arranged in pairs, and he described their heads as flexible. They would have increased in size by shedding their exoskeletons and their diet consisted mostly of fungi with the occasional addition of microscopic animals.
And Poinar went on to highlight how unique these animals are. He pointed out that, “There is no extant group that these fossils fit into, and we have no knowledge of any of their descendants living today. This discovery shows that unique lineages were surviving in the mid-Tertiary.” And the discovery of an entirely new life form on our planet is something of genuine wonder.