Ausichicrinites zelenskyyi, the first Jurassic comatulid (feather star) from the African continent, has been named in honor of Volodymyr Zelenskyy, the sixth and current president of Ukraine.
Ausichicrinites zelenskyyi from the upper part of the Antalo Limestone Formation, Ethiopia. Scale bars – 10 mm in (a, c, e, f and g) and 1 mm in (b, d, h and i). Image credit: Salamon et al., doi: 10.1098/rsos.220345.
Feather stars are members of the order Comatulida, the most diversified lineage of crinoids.
Also known as comatulids, they are also the only living crinoid group that is globally distributed in both shallow- and deep-water settings.
They shed their stalks during development and display high mobility (through crawling and swimming), which is regarded as a significant factor related to their success.
The fossil record of feather stars dates back to the Late Triassic epoch. However, their fossils are usually highly incomplete.
“A single isolated element has been the basis for taxonomic description of a vast majority of fossil comatulids,” said lead author Professor Mariusz Salamon from the Institute of Earth Sciences at the University of Silesia and his colleagues from Poland and Ethiopia.
Ausichicrinites zelenskyyi represents one of the most complete fossil feather stars known to date and the oldest one from the African continent.
It lived approximately 145 million years ago during the Tithonian, the latest age of the Late Jurassic epoch.
It possessed 10 massive and uniserial arms and provides a unique insight into the morphology of feather star arms and cirri (grasping ‘legs’).
“Ausichicrinites zelenskyyi shows some similarities with representatives of the Mesozoic Solanocrinitidae but also has close resemblance with the modern family Zygometridae, exclusively known from the Holocene of western Pacific and eastern Indian Oceans,” the paleontologists said.
“This morphologic similarity is considered to be due to convergence.”
The nearly complete specimen of Ausichicrinites zelenskyyi was found in the upper part of the Antalo Limestone Formation in the Blue Nile Basin, central western Ethiopia.
It is currently stored in the Department of Geology at the Adama Science and Technology University in Adama, Ethiopia.
The specimen shows evidence of arm regeneration — the first example of this phenomenon in a fossil feather star.
“Signs of arm regeneration are commonly documented in fossil stalked crinoids,” the researchers said.
“However, this phenomenon has been rarely documented in fossil comatulids probably due to the fact that intact specimens of these crinoids are exceedingly rarely preserved.”
“To date, only a single report has been described, namely a regenerating arm consisting of four tetribrachs in Rautangaroa aotearoa from the Oligocene of New Zeland.”
“Two pinnules of Ausichicrinites zelenskyyi bear clear signs of regeneration,” they added.
“It is clearly recognized by abrupt differences in the size of abutting pinnular plates.”
“Thus, new fossil evidence from Africa constitutes the earliest and the first example of pinnule regeneration in a fossil comatulid.”
“This finding supports the hypothesis about crucial role of predation in the evolutionary history of this group.”
Source: sci.news
