To the untrained eye, the traditional brittle star fossil above appears to be like like what you’d count on 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 historic sponges, crinoids, and ammonite coprolites and beaks. When you look intently, you’ll see the three arms on the fossil’s proper facet are thinner and barely shorter than these on its left facet. To the crew’s data, the specimen is simply the second case of a fossil with a regenerating physique half, and the primary during which 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 not starfish; although each sometimes 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 standard ancestor, nonetheless). Although many brittle stars are five-armed, the examine authors word that O. hex “exhibits an everyday six-fold symmetry with none indicators of unintended ray addition, suggesting that the person was hexamerous earlier than fragmentation.” Nevertheless, they word that it’s not potential to say for certain that the animal was frequently six-armed from only one specimen.
Primarily based on its options, together with its small physique dimension and arm spines, the crew concluded that the brittle star had an epizoic life-style: It lived on a number creature, maybe sponges that grew in the identical setting.
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 Exquisite Shark Fossil Actually Is
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