A study led by the Higher Council for Scientific Research (CSIC) with participation of researchers from Spain, the United Kingdom and the United States analyzed the fossil remains of an ancient relative of starfish and sea urchins current, which has provided new insights into the early evolution of a hard skeleton.
According to the article published this Wednesday in the magazine ‘Proceedings of the Royal Society B’, the 510-million-year-old fossil baptized with the name of ‘Yorkicystis haefneri’, unlike its modern relatives, did not have a developed skeleton in most of its body, and only the arms were mineralized. This would have helped protect delicate feeding structures.
The fact of having a partially soft body differentiates it from the rest of hedrioasteroids, the extinct class to which it belongs. This class is characterized by having a disc-shaped body with five arms, a central mouth and a hard calcium carbonate skeleton developed throughout its body.
The absence of a skeleton in ‘Yorkicystis’ is thought to represents a case of evolutionary loss, something that can be difficult to recognize in the fossil record. The lead author of the study, Samuel Zamoraa researcher at the Geological and Mining Institute of Spain (IGME-CSIC) and the Aragosaurus Group at the University of Zaragoza, indicates that “This is a major discovery with important implications for understanding the history of echinoderms.”
‘Yorkicystis’ represents the oldest example of an echinoderm that has secondarily reduced skeleton. We were surprised to see that this had occurred so close to the group’s origins, more than 500 million years ago,” he adds.
‘Yorkicystis’ comes from the Cambrian, a period that covered from about 539 to 485 million years ago. This interval was characterized by a very rapid diversification of animal life, including all the major groups of today. This is what is called the Cambrian explosion.
The doctor imran rahmanco-author of the study and principal investigator of the Natural History Museum Londonnotes that “a key innovation at this time was the evolution of a hard mineralized skeleton, which helped protect early animals from potential predators.” “The reasons Yorkicystis reduced its skeleton at this time are unclear, but it could have helped conserve energy for other metabolic processes,” add.
The study launches the hypothesis that the genes that control the formation of the skeleton they could act independently in the two main parts of echinoderms: the axial part and the extra-axial part. This powerful hypothesis will have to be contrasted by geneticists from current organisms and, if confirmed, would change the current understanding of these organisms.
Named after Chris Haefner
The name of the specimen has been put in honor of the amateur paleontologist Chris Haefner, who ddiscovered the specimen in a York churchyard (Pennsylvania) while searching for more common fossils like trilobites.
Recognizing that the fossil was of scientific importance, he shared the discovery in a social networkwhere Samuel Zamora saw the photographs of the specimen. Haefner kindly agreed to donate the specimen to science and it is now in eThe Natural History Museum in London, after having been studied in Spain.
Chris Haefner, president of the Lancaster County Fossil and Mineral Club has expressed his satisfaction with the find: “I have been digging holes in the grass to locate fossils in the churchyard. When I found ‘Yorkicystis’, I didn’t know its relevance, but I knew it was worth keeping. The City View church site is 90% undiscovered and who knows what is still hiding there.”