Hidden in plain sight: A century-old museum specimen turns out to be a landmark in evolution
Harvard University, Department of Organismic and Evolutionary Biology
image:
Artistic environmental reconstruction of the Montceau-les-Mines Lagerstätte (one of the two sites Palaeocampa is found) with Palaeocampa anthrax. A large Palaeocampa anthrax is depicted at the edge of a shallow inland streambed, shadowed by the lush vegetation and mist of a coal forest, flanked by several euthycarcinoids, Sottyxerxes multiplex, and a pair of freshwater xiphosurans, Alanops magnificus.
view moreCredit: Original artwork by Christian McCall
In a twist worthy of a detective novel, a long-misidentified fossil at Harvard’s Museum of Comparative Zoology (MCZ) has emerged as a key discovery in early animal evolution. Originally described in 1865 as a caterpillar, Palaeocampa anthrax shuffled between classifications—worm, millipede, and eventually a marine polychaete—until 130 years later, when researchers realized its true identity: the first-known nonmarine lobopodian and the earliest one ever discovered.
Lobopodians are extinct, soft-bodied creatures that bridge the evolutionary gap between a primitive worm-like ancestor and modern arthropods like insects and crustaceans. Known mostly from Cambrian marine deposits such as Canada’s Burgess Shale, they include iconic fossils like Hallucigenia and Aysheaia pedunculata discovered in 1911, and were thought to be exclusively marine—until now.
A new study published in Communications Biology led by Richard Knecht, a former graduate student (PhD ’25) in Harvard's Department of Organismic and Evolutionary Biology (OEB), redescribes Palaeocampa anthrax as the first nonmarine and youngest lobopodian discovered; predating the famous Burgess Shale lobopodians by nearly fifty years.
“Lobopodians were likely a common sight on Paleozoic sea beds,” said Knecht, “but apart from microscopic tardigrades and terrestrial velvet worms, we thought they were confined to the ocean.”
Knecht, currently a postdoctoral fellow at the University of Michigan and an associate of the MCZ, discovered Palaeocampa while examining fossil millipedes in the MCZ collection. He noted legs on every trunk —ruling out caterpillar or worm—and recognized it as a lobopodian.
To confirm this, the team analyzed 43 specimens from two Carboniferous Lagerstätten—Mazon Creek (USA) and Montceau-les-Mines (France) —using advanced imaging, including backscatter scanning electron microscopy (SEM) and energy-dispersive spectroscopy. They revealed exquisite anatomical features—most notably, nearly 1,000 bristle-like spines covering the body.
Co-author Nanfang Yu, associate professor of physics at Columbia University, used Fourier-transform infrared spectroscopy (FTIR) to detect chemical residues at the spine tips—suggesting the spines secreted toxins to deter predators in its swampy habitat.
"What amazed me is that fragments of biomacromolecules could be exceptionally preserved or altered to geomacromolecules in fossils,” Yu said. “ I’m thrilled this technique possessed the sensitivity and specificity to differentiate fossilized remains from the rocky substrate.”
Palaeocampa’s closest relative is Hadranax, a Cambrian lobopodian from Greenland, nearly 200 million years older. Both had ten pairs of legs, no claws and were blind. But while Hadranax was unarmored and navigated the deep sea using elongated frontal appendages, Palaeocampa, at just four centimeters long, bore a dense coat of spines—arranged above each pair of legs, giving it a fuzzy caterpillar-like appearance—and inhabited freshwater, possibly amphibious, environments.
Palaeocampa’s discovery also resolves the mystery of France’s Montceau-les-Mines fossil site, once considered as marine. “Mazon Creek is a mix of terrestrial, freshwater, and marine animals,” Knecht explained. “But, Montceau-les-Mines, where half of the specimens come from, was hundreds of kilometers inland, with no ocean present.” Its reclassification confirms the site’s nonmarine setting, offering a rare glimpse into ancient freshwater ecosystems.
This discovery broadens our understanding of lobopodian diversity and raises new evolutionary questions: How many others made the leap from marine to freshwater and could more be hiding, misidentified, in museum drawers?
“The conditions required to fossilize soft-bodied creatures like lobopodians are rare,” Knecht noted. “Most of our insights come from Cambrian Lagerstätten, but the Carboniferous period—when Palaeocampa lived—offers far fewer such windows, making every new find incredibly valuable.”
This breakthrough came from reexamining century-old specimens from museums including the MCZ, Yale Peabody Museum, the Smithsonian National Museum of Natural History, France’s Muséum d’histoire naturelle d’Autun, the Chicago Field Museum, and the University of Illinois Urbana-Champaign—highlighting the ongoing scientific value of museum collections.
Ironically, Palaeocampa sat for decades in a drawer just feet from the office of Stephen Jay Gould’s office—MCZ curator and author who popularized the Cambrian oddities in Wonderful Life. “It was literally hiding in plain sight,” Knecht said. “Sometimes, the biggest discoveries are the ones waiting to be looked at again.”
Neotype of Palaeocampa anthrax from the Mazon Creek Lagerstätte and rediscovered in the Invertebrate Paleontology collection of the MCZ. The faint red and blue grid lines from a wax pencil can still be seen across the specimen, made by the nineteenth century artist Katherine Pierson who illustrated this specimen for Samuel Scudder in 1884.
Credit
Richard J. Knecht
Journal
Communications Biology
Article Title
Palaeocampa anthrax, an armored freshwater lobopodian with chemical defenses from the Carboniferous. Communications Biology
A fossil’s 150-year journey from misidentification to evolutionary insight
University of Michigan
A fossil specimen misidentified since its discovery during the Civil War and correctly identified by a University of Michigan researcher reveals an evolutionary leap: It marks the first time this line of sea creatures is known to have left the ocean.
U-M postdoctoral fellow Richard J. Knecht found that the specimen, identified as a seaworm for well over a century, is actually a kind of invertebrate called a lobopod. Lobopods are soft-bodied invertebrates that closely resemble a "worm with legs," according to Knecht, who led the work as a researcher at Harvard University.
Lobopods are considered the ancestor to all arthropods—all insects, spiders and crustaceans—and scientists have long thought that lobopods, which first appeared in the fossil record more than 500 million years ago, only lived in marine environments.
Now, Knecht suggests that the specimen, named Palaeocampa anthrax, likely lived in a freshwater environment. Knecht also found the specimen likely had chemical defenses that suggest it may have spent at least part of its time on land. The study, which was supported by the National Science Foundation, was published in Communications Biology.
"This is the first evidence that we have that this group actually did leave the ocean. Transitioning from a saltwater environment, even to a freshwater environment, is a major evolutionary step," Knecht said. "Any time you find a group that made this transition, it's not just insightful, it's really important evolutionarily to try to understand how this happened."
Knecht says his study also shows the importance of revisiting fossil collections, even fossils that have been previously identified, with fresh perspectives and updated techniques. Since its discovery, this specimen has been variously misidentified as a caterpillar, a marine worm, and a millipede—organisms from very different evolutionary lineages. Even recent studies cited photographs of the fossil without recognizing its true identity.
"When the specimen was first discovered, lobopods didn't even exist as a group. This is an example of why revisiting older specimens can be of real value," said Knecht, a researcher in the U-M Department of Ecology and Evolutionary Biology and Museum of Paleontology. "Even specimens that are iconic and super well known—provide an opportunity to make big discoveries just by viewing them with new techniques and fresh perspectives."
Palaeocampa anthrax and new techniques
Knecht first encountered the specimen while looking at a collection of millipedes in the Invertebrate Paleontology Department of the Museum of Comparative Zoology at Harvard University. He immediately recognized it as a species of lobopod—not a millipede as it was labeled in the drawer.
Paleozoic lobopods can be difficult to pin down, Knecht said. This species looks superficially like woolly bear caterpillars, with papillae and bristles of spikes growing off the trunks of their bodies. Some lobopods from this era had plates of armor, some had forward-facing arms prodruding from their heads. One species' body is absent of features and just looks like a straw with smooth straw-like legs.
But when Knecht looked at the Palaeocampa specimen, he noticed several noticeable differences from other lobopodian species. For example, most lobopodian spines exhibit a cone-in-cone growth pattern like a stack of traffic cones coming to a point at the tip. Instead, Palaeocampa's spines look like a series of rigatoni growing out of its trunk, each segmented like bamboo, with a top that looks like a castle turret, Knecht said.
Then, the research team noticed orange halos at the tips of the preserved spines. The team wondered if there was a fluid or chemical that the lobopod may have emitted from the tips of its spines.
To investigate this, Knecht worked with Nanfang Yu, a physicist at Columbia University. Yu used a technique called FTIR spectroscopy and infrared light to determine that there were fossilized molecules present at the tips of the specimen's spines that weren't present anywhere else along the spine or in the rock. This suggests, Knecht says, that there was a chemical specifically emanating from the tip of the spine.
This characteristic is the most significant evidence indicating that the lobopod was likely amphibious, Knecht said. Most marine or aquatic organisms that have spines with chemical defense systems have spikes that they can use to inject predators. If their defense systems emanated from an open tip, their chemical defense would be less effective and simply dilute in the water.
"If I were to place a chip on the table, I'd say this organism was probably more terrestrial or amphibious, specifically because of that tip. It makes more sense in an aerial rather than a subaqueous environment," he said.
Statistical miracles
Lobopodians are rare in the fossil record especially after the Cambrian Period, Knecht said. Because invertebrates have no bones, their soft bodies degrade very quickly after death. An unusual set of circumstances has to exist in order for them to fossilize: They have to die and then quickly be buried before scavengers or decomposition takes hold, often in aquatic environments with fine grains or mud and little oxygen.
All known lobopodians come from Lagerstätten—extraordinary fossil sites with the rare geological conditions needed to preserve soft-bodied organisms in exceptional detail and abundance. Palaeocampa anthrax was discovered both at Mazon Creek, Illinois, and Montceau-les-Mines, France, both Lagerstätten renowned for their fossils.
This specimen is one of two lobopodians from the Carboniferous, the last period within the Paleozoic—and represents the youngest fossil lobopodian species yet discovered. It's also a transition fossil, an example of a species that represents an evolutionary leap.
Trying to find transition fossils is extraordinarily difficult, Knecht said. They often occur during a small snapshot of time, geologically speaking. It's even more difficult to discover transition fossils of invertebrates; their lack of bones means they don't preserve well in the fossil record. Finding one is a stroke of luck. To capture the Palaeocampa fossil in such detail, recording chemicals emanating from its tips, its preservation must have been almost instantaneous, Knecht said. It likely was buried alive in the mud.
"It's like winning the lottery not once, but three times. First, that the site existed at all; second, to have this level of preservation; and third, to then find it over 300 million years later," he said. "It's a series of statistical miracles."
Study: Palaeocampa anthrax, an armored freshwater lobopodian with chemical defenses from the Carboniferous. DOI: doi.org/10.1038/s42003-025-08483-0
Journal
Communications Biology
No comments:
Post a Comment