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‘Golden’ fossil of ancient arthropod named after Natural History Museum scientist
The work of one of the Natural History Museum’s researchers has been recognised in the name of a new species.
The 450-million-year-old Lomankus edgecombei reveals that an ancient group of arthropods known as the megacheirans lived on for longer than expected.
A distant relative of spiders and scorpions is the new namesake of a Natural History Museum scientist.
While the fossil of Lomankus edgecombei might be preserved in iron pyrite, or fool’s gold, Dr Greg Edgecombe’s research has been the gold standard in arthropod evolution for many years. He’s been part of research that’s revealed the head of the largest arthropod to ever walk the Earth, named countless species, and revealed new insights into the Cambrian Explosion.
Greg’s fellow scientists have now immortalised his name in Lomankus edgecombei, which lived hundreds of millions of years ago in what is now the State of New York in the USA. In fact, as Lomankus is derived from the Greek for Edgecombe, the fossil has been named after Greg twice.
Dr Luke Parry, the lead author of the study published in Current Biology, says that Greg has had “a tremendous influence” on his career.
“Greg was one of my PhD supervisors and was fundamental in shaping my view of how to do good science,” Luke says. “I am certain that I wouldn’t have got to where I am without him.”
“He is someone who has spent a great deal of time thinking carefully about arthropod evolution and how we can make sense of strange early fossils and how they fit into the puzzle of evolutionary history. As such, naming this new, spectacular arthropod after him just made perfect sense.”
Greg, who has previously named fossils after members of the Sex Pistols, the Ramones and AC/DC, says that he’s “really chuffed” to be on the receiving end this time.
“It’s a wonderful fossil to have named after me,” Greg says. “I’ve had about 10 species given my name now, mostly trilobites, along with centipedes and a fossil horseshoe crab. This is the first megacheiran, and having done some work on the group, it’s an honour to be acknowledged not just in the name of a new species, but a new genus as well.”
Dr Greg Edgecombe, the fossil's namesake, specialises in understanding how arthropods evolved. © The Trustees of the Natural History Museum, London
How did Lomankus edgecombei live?
Lomankus edgecombei is a megacheiran, a group of arthropods which have distinctive ‘great appendages’. These modified legs at the front of the head, which are superficially similar to the limbs of modern mantis shrimps, are thought to have been used to find and catch prey.
“While other arthropods from this period have enlarged, spiny predatory appendages, the great appendage has a characteristic elbow joint and long flagella that sets it apart,” Greg explains. “Most species have three, finger-like extensions beyond the bend, and the flagella emerge from the end of them.”
“In Lomankus edgecombei, however, the flagella come off the base of the appendage without these three spines. That’s one of the key characteristics that allowed the team to recognise this not just as a new species, but a new genus.”
As Lomankus lacks the claw-like structures other megacheirans would have used to catch prey, the researchers have suggested that its great appendage would have had a sensory function instead. As this species appears to have lost its eyes, the appendage would have been one of the main ways of sensing the world around it.
The researchers have suggested that Lomankus lost its eyes because it lived in a dark environment where they weren’t especially useful. A similar change has happened more recently in eyeless cave fish, which have enhanced their other senses to compensate for the loss of their sight.
After being buried, Lomankus edgecombei's soft tissues were gradually replaced by fool's gold, allowing researchers to scan it in high definition. Fossil photograph © Luke Parry and 3D model © Yu Liu, Ruixin Ran
A surprisingly resilient group
While Lomankus’ lack of eyes was already a surprise, the species is also a surprisingly late example of a megacheiran. These animals were diverse and abundant during the Cambrian Period, between 538 and 485 million years ago, but were thought to be largely extinct by the start of the following Ordovician Period.
The new fossil shows that not only were these animals still alive towards the end of the Ordovician, but they were still adapting for different roles in the environment. Greg says that the impression that these animals were dying out is probably due to a bias in which fossils survive.
“These animals are usually only found in Burgess shale-type deposits, which formed when seawater was super saturated with calcium carbonate,” he explains. “This crystallised as calcite caps that sealed animals in the sediment in which they were buried.”
“These deposits are most common in the Early and Mid-Cambrian, with relatively few from the Late Cambrian and Ordovician. I suspect that if we had more of these later sites we would see that more of these animals persisted into the Ordovician, and perhaps even later.”
Discovering more well-preserved arthropods from this period will help to further understanding of how the arthropods evolved and became one of the most dominant forms of life on Earth.
