Tiny, spherical fossils have been discovered in southern China by researchers Jesse Broce of Virginia Tech, James Schiffbauer of the University of Missouri and colleagues.
The fossils appear to have belonged to a previously unknown animal, and date back to the Cambrian period, some 540 to 485 million years ago during an explosion of diversity.
Though researchers had originally hoped to come across evidence of ancient worms or other relatively boneless creatures, they found embedded fossils in the local limestone of the Hubei province.These small spheres, covered in polygonal patterns, looked like what once could have been an embryo.
“We found over 140 spherically shaped fossils, some of which include features that are reminiscent of division-stage embryos, essentially frozen in time,” Schiffbauer said, via LiveScience.
Though the researchers initially began to dissolve the fossils out of the limestone from China’s Shuijingtuo formation with acid, this seriously damaged and even destroyed some of the spherical samples. Next, they hand-chiseled the rock into millimeter- or centimeter-sized chunks that exposed the fossil surfaces manually.
The researchers took the fossils from the Shuijingtuo rock formation to a lab where they were examined under a scanning-microscope and through several X-ray techniques.
Though the patterns resemble those seen on fossilized examples of embryos from a worm-like organism known as the Markelia, which lived during the Cambrian period, researchers believe these fossils likely belonged to an undescribed organism. These soft tissue embryos were also much smaller than those typically found during the period.
“My work focuses on those harder-to-find, soft-tissue organisms that weren’t preserved quite as easily and aren’t quite as plentiful,” Schiffbauer added, via LiveScience. “Something obviously went wrong in these fossils.”
“Our Earth has a pretty good way of cleaning up after things die. Here, the cells’ self-destructive mechanisms didn’t happen, and these soft tissues could be preserved.”
While it remains a mystery what these fossilized embryos might have grown up to be, this is not the first time in history for this rarity. A 380-million-year old fish with an embryo inside along with dinosaur embryos still inside their eggs have all been discovered, according to CBS News.