This discovery was important because the flappy labrum, a kind of upper lip, lies in front of the mouth of most arthropods living today. The finding supports the theory that Leanchoilia and other megacheirans are distant relatives of the living group of arthropods known as chelicerates. They include modern horseshoe crabs, scorpions, and spiders. Until now, the existence of a labrum in megacheirans and its position have been the source of heated debate in the field. It is considered one of the most important features of an arthropod’s head and has prompted very different interpretations about their evolution.
The group published three other papers as part of this work. Two of them were also in Current Biology and BMC Evolutionary Biology, while another was in Geological Magazine.
In the other Current Biology paper in 2019, for instance, the team looked at the Cambrian ancestor of crustaceans to describe the antennae and mandibles on its head in greater detail than previously had been possible.
“Having the additional data that come from the scans, it basically lets you see that much more,” said Joanna M. Wolfe, a research associate in the Ortega-Hernández lab and co-author of that 2019 paper and another. “You can make a more direct comparison of the fossil onto its living relatives.”
The samples the group works with each came from an area in the Yunnan Province in China called the Chengjiang Biota. It’s a popular spot for paleontologists because it’s bustling with diverse and well-preserved Cambrian fossils.
Liu and Ortega-Hernández first connected in 2015 on another project, and have been working together on this one ever since Liu sent Ortega-Hernández micro-CT scans of an ancient fossil.
“I had no idea what I was looking at, but it looked really nice,” Ortega-Hernández said. “It just became a very organic collaboration in that we would have this back and forth between us to refine the interpretation, discuss the broader significance of the discoveries, and simply engage in a very active collaborative effort altogether.”
Most of the scanning work is done in China at Yunnan University, largely to avoid damaging the specimens in travel. It means a lot of the work happens remotely, but Ortega-Hernández and members of his lab are no strangers to visiting Liu’s lab in China to do some analysis. In fact, it goes both ways. Liu has been working at Harvard for the past year as a visiting researcher. He even brought some specimens with him.
“Before COVID-19, we had several face-to-face discussions which were so stimulating and led to some very good ideas as to how some of the scientific problems should be addressed or might be solved,” Liu said. “Our recent Current Biology paper, for instance, was not in the original plan of my visit. It came out naturally after those stimulating discussions.”
Still, the ability to access the data remotely comes in handy, especially in the classroom.
“I would love to be able to showcase fossils from China in my classroom,” Ortega-Hernández said. “But that is not simply not possible … but what I can do is show them amazing 3D models, which are visually stunning and actually have even more data than the fossil itself.”
Ortega-Hernández and Liu say the research isn’t stopping anytime soon.
“We have only really begun to scratch the surface because there are hundreds of species and thousands of specimens in this deposit and we have only used this approach with about a dozen or so,” Ortega-Hernández said, referring to the Chengjiang Biota. “There is a lot of work still to be done.”
