A handful of marine fossil specimens unearthed in northern Portugal that lived between 470 and 459 million years ago is filling a gap in the understanding of evolution during the Middle Ordovician period.
The discovery, explained in a new article just published in The science of nature, details three fossils found in a new "Burgess Shale type deposit". (Burgess Shale is a reservoir in Canada recognized among evolutionary biologists for its excellent conservation of soft-bodied organisms that do not have a biomineralized exoskeleton).
"The document describes the first soft-body fossils preserved as carbonaceous films from Portugal," said lead author Julien Kimmig, collections manager of the Biodiversity Institute at the University of Kansas and the Museum of Natural History. "But what makes this even more important is that it is one of the few deposits that are actually from the Ordovician period, and what is more important, are the Middle Ordovician, a time when very few fossils are known. soft body. "
Kimmig and his colleagues from the KU Institute of Biodiversity, university researcher Wade Leibach and chief curator Bruce Lieberman, along with Helena Couto of the University of Porto in Portugal (who discovered the fossils), describe three marine fossil specimens: a medusoide ( jellyfish), possible wiwaxiid sclerites and an arthropod shell.
"Before this, nothing was found on the Iberian Peninsula in the Ordovician that resembled this," Kimmig said. "They close a gap in time and space, and what is very interesting is the type of fossils, we find Medusozoa, a jellyfish, as well as animals that look like wiwaxiides, which are armored mollusks shaped like slugs that have large spines. Lateral sclerites of animals that were actually believed to have become extinct at the end of the Cambrian.There may be some who survived in the Ordovician in a moroccan deposit, but nothing concrete has been published about them.And here we have evidence of the first In In fact, in the middle of the Ordovician, the range of these animals is incredibly extended ".
Kimmig said the discovery of fossils of rare Wiwaxiides in this time frame suggests that the animals lived on Earth for a much longer period of time than previously understood.
"Especially with animals that are quite rare that we do not have today like the Wiwaxiids, it's nice to see that they lived longer than we ever thought," he said. "Shortly after this deposit, in the Upper Ordovician, we actually have a major extinction event, so it is likely that the Wiwaxiids survived that great extinction event and did not die out earlier due to other circumstances. Whatever it was, it caused the great extinction event of the Ordovician to kill them as well. "
According to the researchers, soft-bodied specimens fill a void in the fossil record for the Middle Ordovician and suggest "many soft-bodied fossils in the Ordovician have not yet been discovered, and a new look at deep-water shales and shales of this period of time is guaranteed. "
"It's very interesting with these discoveries: in fact, we are getting a lot of information about the distribution of animals chronologically and geographically," said Kimmig. "In addition, this gives us a lot of information about how animals adapted to different environments and where they managed to live in. With these soft body deposits, we have a much better idea of how many animals there were and how their environment changed. that applies to modern days, with climate change and water temperature change, because we can see how the animals for long periods of time in the geological record have adapted to these things. "
Co-author Couto discovered fossils in the Valongo Formation in northern Portugal, an area famous for containing trilobites. When the animals were alive, the Valongo Formation was part of a shallow sea on the northern margin of Gondwana, the primordial supercontinent.
"Based on the envelope fossils, the deposit appears to be a fairly common Ordovician community," Kimmig said. "And now we know that, in addition to those common fossils, the jellyfish floated around, we also had mollusks that roamed the ground, and we had larger arthropods, which could have been predatory animals, so in that sense, we're getting an image much better with these soft-bodied fossils of how these communities really looked. "
According to the KU researcher, scientists did not understand until recently that deposits from this period could preserve soft-bodied specimens.
"For a long time, it was simply not known that these types of deposits survived in the Ordovician," Kimmig said. "So, it's likely that these deposits are more common in the Ordovician than we know, it's just that people never looked for them."
Kimmig led the analysis of the fossils in KU's Laboratory of Microscopy and Analytical Imaging to ensure that the fossils were made of organic material. Leibach, the undergraduate researcher at KU, did a lot of the laboratory work.
"We analyze the material and observe the composition because sometimes you can get pseudo fossils, minerals that create something that looks like a fossil," said Kimmig. "We had to make sure that these fossils really had an organic origin, and what we found is that they contain carbon, which was a great indication that they really would be organic."
Rare discovery of fossils & # 39; cone shaped & # 39; 450 million years old
Julien Kimmig et al, soft-bodied fossils of the Upper Valongo Formation (Middle Ordovician: Dapingio-Darriwiliano) from northern Portugal, The science of nature (2019). DOI: 10.1007 / s00114-019-1623-z
Rare fossils provide a more detailed picture of biodiversity during the Middle Ordovician (2019, June 4)
recovered on June 5, 2019
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