Fossil thought to be earliest bryozoan animal may actually be seaweed

A 515-million-year-old fossil erstwhile thought to beryllium the earliest known carnal from a radical called the bryozoans mightiness really beryllium a seaweed.

Bryozoans, commonly called moss animals, are tiny, coral-like creatures that unrecorded successful colonies successful oceans and freshwater.

Nearly each large carnal groups archetypal look successful the fossil grounds betwixt 541 and 520 cardinal years agone during an evolutionary lawsuit known arsenic the Cambrian explosion. Until 2 years ago, the bryozoans were the lone carnal radical missing from that event: the earliest fossil traces of bryozoans dated to 40 cardinal years aft it.

But successful 2021, Paul Taylor astatine the Natural History Museum successful London and his colleagues identified the Cambrian fossil Protomelission gatehousei, unearthed successful Australia and China, arsenic a bryozoan – suggesting these animals didn’t get connected the country overmuch aboriginal than different groups aft all.

Now, Martin Smith at Durham University, UK, and his colleagues person studied 12 caller Protomelission-like fossils from Kunming successful China, which underwent a signifier of preservation that maintained their brushed tissues.

The squad recovered clumping formations of idiosyncratic tube-like structures successful a honeycomb signifier – which tin hap successful some plants and animals. But they saw nary tentacles nor immoderate regularly shaped holes for tentacles to walk done – the telltale signs successful aboriginal bryozoan fossils, says Smith. Instead, the researchers noticed agelong projections emerging from the honeycomb that look similar flanges, structures that are emblematic of definite kinds of greenish algae.

“You spot these small conical flanges?” helium says. “That’s not a bully mode to beryllium an animal, really. But it’s a precise bully mode to seizure sunlight and beryllium a photosynthesiser. This has shifted america from reasoning ‘these are bryozoans’ to ‘these are decidedly not bryozoans. These are seaweeds.’”

Specifically, the organisms look to beryllium portion of the Dasycladales bid of greenish algae, helium says.

Taylor, who wasn’t progressive successful the caller study, says it is “an absorbing and important discovery” that adds to the “jigsaw puzzle” astir Cambrian oversea life, but it doesn’t needfully beryllium that Protomelission gatehousei wasn’t an animal.

In particular, helium questions whether the caller fossils are genuinely Protomelission, particularly since determination are important differences successful the sizes of the specimens’ structures.

Sara Pruss astatine Smith College successful Northampton, Massachusetts, besides has doubts astir this. “Their full statement truly seems to hinge connected that this caller fossil that they person recovered is the aforesaid arsenic has been recovered before,” she says. “It gave maine a infinitesimal of pause.”

Even if it is the same, the agelong projections could good beryllium bryozoan tubular structures, and the brushed tentacle insubstantial mightiness simply not person fossilised, says Taylor. “Their lack is not astatine each surprising,” helium says.

Nor is it peculiarly telling, says Pruss. “The lack of grounds is ne'er bully evidence, for a palaeontologist,” she says.

If the fossils are so algae, this could really assistance amended explicate the situation that supported the Cambrian explosion, says Smith. “Seaweeds are astonishing habitats that tin enactment this wealthiness of assemblage plans that improvement was abruptly capable to produce,” helium says.

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