David Bridges
To the untrained eye, the traditional brittle star fossil above seems to be like what you’d anticipate of a now-especially-brittle echinoderm. However the fossil is kind of uncommon: It captures the second at which the brittle star was cloning itself, regenerating three of its arms because it died.
The specimen was an opportunity discover throughout a 2018 dig in a limestone deposit west of Nusplingen, Germany. The identical fossil mattress yielded historical sponges, crinoids, and ammonite coprolites and beaks. Should you look carefully, you’ll see the three arms on the fossil’s proper aspect are thinner and barely shorter than these on its left aspect. To the staff’s information, the specimen is simply the second case of a fossil with a regenerating physique half, and the primary wherein its regeneration seems related to the animal’s six-fold symmetry and clonal fragmentation.
The newly outlined species—Ophiactis Hex—dates to the Late Jurassic, about 150 million years in the past. Brittle stars are usually not starfish; although each usually have 5 arms, they represent completely different courses of echinoderms, the identical invertebrate group that features sea cucumbers (brittle stars and starfish do share a typical ancestor, nonetheless). Although many brittle stars are five-armed, the research authors notice that O. hex “exhibits an everyday six-fold symmetry with none indicators of unintentional ray addition, suggesting that the person was hexamerous earlier than fragmentation.” Nevertheless, they notice that it isn’t attainable to say for certain that the animal was often six-armed from only one specimen.
Primarily based on its options, together with its small physique measurement and arm spines, the staff concluded that the brittle star had an epizoic life-style: It lived on a number creature, maybe sponges that grew in the identical surroundings. The new paper seems in Royal Proceedings of the Royal Society B.
No matter different conclusions is perhaps drawn from the fossil—about brittle star evolution, or cloning in evolutionary historical past—what is obvious is that the fossil is fairly freakin’ cool.
Extra: Paleontologists Disagree About What This Beautiful Shark Fossil Truly Is
Daniel Mercer
