Trilobites breathed through their legs

They are among the oldest animals on Earth

Now, thanks to new technologies and an extremely rare, but incredibly well-preserved set of fossils, UC Riverside scientists have shown that the trilobites breathed oxygen and their curious method of doing it, something that helps us to continue completing the puzzle of this animal that had great evolutionary success (In fact, its fossil exoskeletons can be found all over the world).

“Until now, scientists have compared the upper limb of the trilobite with the non-respiratory upper limb in crustaceans, but our paper shows, for the first time, that the upper limb functioned as gills,” says Jin-Bo Hou, PhD student in paleontology at the UCR who directed the research published in the journal Science Advances.

The researchers examined the pyritized remains of two trilobite species: Olenoides serratus from Burgess Shale and Triarthrus eatoni from Beecher’s Beds. Triarthrus eatoni lived approximately 450 million years ago (Ordovician period); Olenoides serratus lived during the Cambrian period, about 500 million years ago.

“They were preserved in pyrite, fool’s gold, but is more important than gold to us, because it is key to understanding these ancient structures, “said Professor Nigel Hughes, a paleontologist in the Department of Earth and Planetary Sciences at the University of California and leader of the work.

A computerized axial tomography scanner was able to read the differences in density between the pyrite and the surrounding rock, which made it possible to create three-dimensional models of these rarely seen gill structuresThus, they did not have to drill and polish the rock that covered the specimens and, therefore, see the fossil without having to damage the preserved structure in the pyrite.

“This way we could get a view that would even be difficult to see with a microscope: really tiny trilobite anatomical structures on the order of 10 to 30 microns wide“, He said. For comparison, a human hair is approximately 100 microns thick.

The researchers pThey could see how blood had seeped through chambers in these delicate leg structures, picking up oxygen on its way as it moved. They closely resemble the gills of modern marine arthropods such as those found in crabs and lobsters.

“In the past, there was some debate about the purpose of these structures because the upper part of the leg does not seem like a good location for the respiratory apparatus,” clarifies. Hopkins. “You’d think it would be easy for those filaments to get clogged with sediment where they are. It is an open question of why they developed the structure in that place of their bodies “, concludes the expert.

An exciting find without a doubt.