Pyritized trilobite, amirite? MARKUS MARTIN
Scientific American's "The Artful Amoeba" had a piece about trilobite eggs a few years ago. It seems that Markus Martin, an amateur paleontologist, discovered gold, or more specifically trilobite gold. Atlas Obscura has the more personal details of this fossil find. It what was once known as Beecher's Bed, Martin found and then prepared some remarkable trilobite fossils. They were preserved in fool's gold, a mineral called iron pyrite. These golden bugs had a wonderful secret, which was exposed when he prepared the fossils. They held a paleontology first... trilobite eggs, even better golden trilobite eggs. They were golden, because like the fossil animal they were preserved in iron pyrite.
Close-up of suspected trilobite eggs, center. Scale bar 2 mm. Credit: Hegna et al. 2017
Unlike most prospectors who seek their fortune in gold, Markus Martin got lucky on his very first try. He’d come to a desolate patch of forest in upstate New York in hot pursuit of trilobites. It was the early 2000s and Martin’s day job was in finance, but he was far more interested in the treasures of another era: the Ordovician, from 485 to 444 million years ago, when trilobites roamed the sea that covered most of what is now North America. But Martin wasn’t looking for more ordinary trilobite fossils in muddy brown and dull black rocks. He was looking for glittering ones, whose soft tissues had been filled in perfectly with pyrite, the mineral commonly known as fool’s gold.
Martin was no fool. He knew the fossil beds in the area had a reputation for holding these brilliantly preserved arthropods, and he’d spent the hostile New York winter reading up to ascertain the best place to start looking. Martin scoured Microsoft’s TerraServer (this was a world before Google Maps) and picked a hill in an area riddled with slivers of canyons running 200 feet down into the shale, just three miles off a road and close to where he lived in Oneida County. Martin got permission from the landowner to search the area, and as soon as it was warm enough, he drove up with a backpack and a hammer. “I expected this was going nowhere, and that on Monday I’d go back to work with not much to say,” he says. But when he reached the base of the hill, he saw tiny, glittering trilobites sprinkling the forest floor, like flecks of gold in a river. “To say I was surprised is an understatement,” he says. Martin picked up as many as he could carry, around 30 specimens, piled them into his backpack, and lugged it all home.
Beecher’s Bed, teeming with layers of Ordovician shale. MARKUS MARTIN
Martin first found pyritized trilobites in an area now called Martin Quarry (yes, it was named after him), the majority of them come from a deposit called Beecher’s Trilobite Bed. Like Martin Quarry, it was named for the man who discovered its ancient treasures. Charles Emerson Beecher, a paleontologist at the Peabody Museum of Natural History at Yale University, first excavated the site in 1893. Though Beecher never thought to record the site’s location, he did find and prepare more than 500 specimens of the trilobites Trinucleus and Triarthus, each exquisitely preserved in pyrite, until his sudden death in 1904, according to an obituary written by William Healey Dall and read before the National Academy of Sciences. Beecher’s Bed was lost until 1982, when Yale paleontologists found it and set to work on it again. Martin took over the site in 2009, after Yale chose not to renew its lease on the property.
This remarkable discovery was documented in a paper in the Journal Geology. Here is the abstract of the paper.
Despite a plethora of exceptionally preserved trilobites, trilobite reproduction has remained a mystery. No previously described trilobite has unambiguous eggs or genitalia preserved. This study reports the first occurrence of in situ preserved eggs belonging to Triarthrus eatoni (Hall, 1838) trilobites from the Lorraine Group in upstate New York, USA. Like other exceptionally preserved trilobites from the Lorraine Group, the complete exoskeletons are replaced with pyrite. The eggs are spherical to elliptical in shape, nearly 200 μm in size, and are clustered in the genal area of the cephalon. The fact that the eggs are smaller than the earliest-known trilobite ontogenetic (protaspis) stage suggests that trilobites may have had an unmineralized preliminary stage in their ontogeny, and that the protaspis shield formed only after hatching. The eggs are only visible ventrally with no dorsal brood pouch or recognized sexual dimorphism. The location of the eggs is consistent with where modern female horseshoe crabs release their unfertilized eggs from the ovarian network within their head. Trilobites likely released their gametes (eggs and sperm) through a genital pore of as-yet unknown location (likely near the posterior boundary of the head). If the T. eatoni reproductive biology is representative of other trilobites, they spawned with external fertilization, possibly the ancestral mode of reproduction for early arthropods. Because pyritization preferentially preserves the external rather than internal features of fossils, it is suggested that there is likely a bias in the fossil record toward the preservation of arthropods that brood eggs externally: arthropods that brood their eggs internally are unlikely to preserve any evidence of their mode of reproduction.
