Scientists have discovered the fossil remains of a 430-million-year-old crustacean previously unknown to science – a proto-shrimp that they're naming in honor of British naturalist and television personality David Attenborough. The new species, described in Proceedings of the Royal Society B, could shed fresh light on crustacean evolution.
"Our analysis suggests that it is an early representative of the line leading ultimately to modern shrimps, lobsters and crabs," study co-author Derek Briggs, a paleontologist at Yale University, said in an email.
Cascolus ravitis may not sound like the name of the 90-year-old Attenborough, famed for his work on "Life on Earth" and other well-known documentary series, but look closely: Cascolus, a blend of the Latin castrum ("stronghold") and colus ("dwelling in"), is inspired by the naturalist's surname, which has Middle and Old English roots.
The species name, ravitis, is also partly in honor of the University of Leicester campus, where Attenborough grew up while his father served as principal of what was then called University College Leicester. Ravitis is a blend of the Latin Ratae (the Romans' name for Leicester), vita ("life"), and commeatis ("messenger"). The blend appears to allude to the broadcaster, who, in his instantly recognizable voice, has long communicated the wonders of the natural world to the public.
"We thought this would be a way of recognizing his remarkable career creating and presenting natural history programs which have reached millions around the world," Briggs said.
C. ravitis was found in the deposits of volcanic ash that eventually became rock in present day Herefordshire. Given the specimen's extremely high quality, with evidence of multiple limbs and even soft tissue such as eyes and antennae preserved, the researchers were able to construct a "virtual fossil' that allowed them to examine it in three dimensions.
"We ground the fossil away in very thin increments – some 50 for every millimeter – imaging the details at each stage (which are like slices through the specimen) and then combining the images into a three-dimensional reconstruction," Briggs explained. "So the specimen we treated in this way no longer exists but survives as images and a reconstruction that can be provided to any researcher. The nature of these fossils is such that there is no density contrast between fossil and the nodule in which it is found so they cannot be revealed by normal scanning methods."
This proto-shrimp was tiny — the entire specimen is just 8.9 millimeters long; its widest point is its head shield, measuring 1.3 millimeters wide. This little critter had a long, segmented body with several "biramous" (or two-branched) limbs, which are typical of crustaceans today. It featured rows of strange, petal-shaped appendages, which scientists think probably helped it both to swim and to breathe in the ancient sea, some 100 to 200 meters beneath the water.
"Their relatively large surface area would presumably facilitate efficient oxygen uptake," the study authors wrote.
This is actually a pretty normal situation for living shrimp, Briggs said.
"The potential of shrimps and their relatives to diversify their limbs for different modes of feeding and locomotion certainly contributed to their success," he added.
Based on its features, the scientists concluded that C. ravitis is a malacostracan, making it an ancient relative to today's lobsters, crabs and shrimp — one that may help shed light on this part of the crustacean family tree.
"Cascolus provides important clues into the morphological evolution of the sister-taxon of Eumalacostraca and of the Malacostraca, one of the major groups of Crustacea," the study authors wrote.
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8:28 p.m.: This story was updated with quotes and information from paleontologist Derek Briggs.