What Scientists Find 155 Million-Year-old Starfish

Through clonal fragmentation, the creature was able to generate genetically identical progeny by fracturing and regrowing segments of its own body, a process known as fissiparity.According to Science Alert, the unique fossil was unearthed in 2018 from a limestone deposit in Germany that was formerly a deep lagoon with sponge beds and coral meadows. This is the sole specimen of the newly discovered brittle star species, Ophiactis hex, according to the researchers.It is noteworthy because the precise moment at which fissiparity evolved for the first time is unknown to scientists. The fossil, which dates back 155 million years, is so perfectly preserved that the hook-shaped arm spines are clearly visible. It was given that name in honor of the fantastical supercomputer that can conceive the unimaginable, found in one of Terry Pratchett's Discworld books.According to Dr. Thuy and his colleagues' study, "cases of individuals with a regenerating body half are exceedingly rare, while skeletons of ophiuroids with individual arms frozen in the process of regeneration are relatively common in the fossil record."Fissiparity is a feature shared by distantly related lineages of brittle stars and starfish, but its evolutionary history is unclear. What is known is that stars that reproduce in this way today typically have six arms rather than five, which makes sense because it makes for an even split. Ben Thuy, a paleontologist at the Luxembourg National Museum of Natural History, and colleagues write in their paper describing the new find that "while the biology and ecology of clonal fragmentation are comparatively well understood, virtually nothing is known about the evolution and geological history of that phenomenon." The Ophiactis hex fossil, which is 155 million years old and has been preserved to the point where you can see its hook-shaped arm spines.The researchers acknowledge that it is impossible to determine the precise appearance of the species prior to its division and whether or not it was six-armed, given that only one specimen of Ophiactis hex has been discovered to date.