New Scientist, UK: Per Ahlberg, a paleontologist at the University of Uppsala in Sweden, really knows about coprolites. These lumps of fossilised faeces have been known to science for nearly 200 years but were long regarded as the arse end of palaeontology. "They're not the most glamorous of fossils and they were often overlooked," says Ahlberg. But thanks to Grenoble's X-rays, they are now enjoying a golden age.
Coprolites (from the Greek for "dung stones") first came to prominence in the 1820s, when amateur palaeontologist Mary Anning and University of Oxford geologist William Buckland realised the nodules they kept finding in Lyme Regis, UK, were fossilised faeces.
The discovery sparked a brief bout of "copromania" among amateur fossil hunters. However, professional scientists turned their noses up.
In the 1990s, Karen Chin at the University of Colorado, Boulder, revived scientific interest in coprolites with a paper describing a "king-sized" specimen from Canada that she said was probably expelled by a Tyrannosaurus rex. It was 44 centimetres long, 16 centimetres wide, 13 centimetres high and crammed full of pulverised bone that may well have come from a young dinosaur, possibly a triceratops.
Partially digested.
Also Read: The cost of fossil auctions
Since then, coprolites have yielded all kinds of amazing finds, including undigested dinosaur meat, the partial skull of what may be the oldest-known mammal, hair, feathers, insect remains and a lot of intestinal parasites; the early turd catches the worm, after all. In 2009, hominin hair was found in a 200,000-year-old hyena coprolite from South Africa, possibly after it feasted on one of our ancestors.
In a way, it isn't surprising that old crap contains so much treasure. Carnivore faeces are especially ripe for fossilisation because they contain lots of minerals from meat and bone. "They're full of phosphates and that helps them to mineralise early on. It crystallises and binds the whole thing together," says Ahlberg. "That protects the contents, including any soft tissue."
Because faeces preserve so well, coprolites often contain material that wouldn't otherwise fossilise, sometimes in exquisite detail. For this reason, the deposits in which they are found are considered a type of Konservat-Lagerstätte, the scientific name for areas that contain exceptionally well-preserved fossils, especially of soft tissues. This has led to coprolites being compared to amber, fossilised tree resin in which ancient animals can become trapped, though coprolites are less likely to end up as the centrepiece of a necklace.
Also Read: Goodbye to 2020
Like amber, coprolites reveal information about the ecosystem they came from, such as who was eating who, and provide a concentrated snapshot of the whole environment. Insectivores, for example, go round snaffling insects from all over the place and then package them up in a neat little bundle for future palaeontologists to comb through.
"They give you an insight into a functioning, living ecosystem in a way that very few other data sources allow," says Ahlberg. "They are a phenomenal data source, a sausage-shaped Lagerstätte."
Preservation isn't as good as in amber – after all, the contents have usually been chewed and partially digested. But in other ways, coprolites have the edge. Defecation is a great leveller and coprolites are known from all groups of animals, including insects, reptiles, fish, mammals and birds.
And, unlike amber, which opens only occasional windows on the past, when conditions were just right for tree resin to fossilise, the coprolite fossil record is pretty much unbroken. It also happens to be very ancient, going back to at least the time when animals first conquered the land in the Devonian period some 400 million years ago.
Also Read: Buying Guide: Know all about Air Purifiers
The trouble is that coprolites have always been slippery customers. To get at the treasure inside, you had to cut them up, taking thin slices to put under an optical microscope or breaking off bits to view in a more powerful electron microscope. You ended up with hard-to-interpret images and there was always the worry that you might have missed the most interesting stuff. Another approach was to dissolve the whole coprolite, but often that destroyed the delicate contents too.
Ideally, you want to see through coprolites without breaking them up. Which is precisely what an imaging technique called propagation phase-contrast synchrotron microtomography (PPC-SRµCT for short) offers. It works by firing powerful, laser-like X-rays through a sample. These diffract according to the density of the medium, which can reveal the internal contents in fine-grained detail. As the sample rotates, the scanner takes multiple images from all angles before software stitches the data together into a three-dimensional representation.
Also Read: Water bears glow to survive a blast of UV
The first two coprolites Ahlberg and his team imaged in this way were from the rich fossil beds of Krasiejów in Poland, which date to the late Triassic period more than 200 million years ago. The work was just a proof of principle, says Ahlberg, but the scans revealed how useful the new technique would be. They showed that the first specimen contained an almost complete fish, plus pieces of scaly skin, bones and crushed bivalve shells. The team concluded that it was excreted by a large lungfish.
The second number two contained numerous fragments of beetle, including wing cases and legs. It was evidently produced by an insectivorous animal that, judging from the size of the coprolite, was larger than most living insectivorous mammals and lizards. The team later identified its probable source as a dinosaur-like reptile called Silesaurus.
Coprolites are comparable to amber, albeit less likely to end up on a necklace.
Also Read: COVID-19 and death technology sees a rise in Online Memorials
Ahlberg and his colleagues have since imaged many other coprolites. One was from another dinosaur-like predator called Smok wawelski (named after a dragon in Polish folklore) from a different Triassic deposit in Poland. The scans revealed it was a bone crusher like T. rex and prone to swallowing its own teeth.
The researchers also examined the faeces of a pterosaur, a flying reptile, and confirmed that it was a filter-feeder like modern pelicans. "Now we can get a proper view of what coprolites contain, they become enormously informative," says Ahlberg. Chin agrees: "This opens up a whole new perspective on coprolites."
For now, Ahlberg and his team are the only coprolite researchers using PPC-SRµCT, but he says others are keen to get their hands dirty. Scanning a coprolite only takes a few minutes and you can do a big pile at the same time. "We stack them in tall plastic tubes and scan 25 to 30 at once," says Ahlberg.
Creating the final images and analysing them is much more time-consuming. Ahlberg says he could gather a career's worth of data in an afternoon. And there are so many tantalising coprolites, it is hard to decide which ones to look into first. But whichever ones get the nod, there's a treasure to be had. Talk about turning muck into brass.
(c) 2020 New Scientist Ltd.
Distributed by Tribune Content Agency, LLC
Also Read: FDA authorizes vaccine from Moderna and NIH, ramping up fight against COVID-19
