Photograph of fossil fish from Mafra, Brazil. CP 065. – RODRIGO TINOCO FIGUEROA (UNIVERSITY OF MICHIGAN)
MADRID, June 12. (EUROPA PRESS) –
Late Paleozoic ray-finned fish fossils found in Brazil include a variety of soft tissues, a rarity in paleontology due to the scarcity of the fossil record.
Samples include well preserved brains, and also fragments of the heart and eyes, meninges and gill filaments.
“These fossils not only show extensive soft tissue conservation, but also offer insight into brain evolution in fish that lived more than 290 million years ago“, said it’s a statement Rodrigo Tinoco Figueroa, a Brazilian doctoral student at the University of Michigan, author of the study, which is published in Current Biology. “Fossils like this are the only way to get direct evidence of soft tissue elements from the past. Such information often shatters our expectations about living species.”
Figueroa said that of all the specimens, one called CP 065 is the most surprising.
“In addition to being the first specimen in which I noticed an everted brain, it is also one of the best preserved fossils I have seen,” he said. “Imagine a fossil more than 290 million years old that preserves the brain and its cranial nerves, the delicate meninges that support the brain inside the cranial cavity, gill filaments, fragments of blood vessels, parts of the heart and possibly skeletal muscles. It is certainly a unique find.. “Specimens like this are the best way to bring paleontology closer to biology and vice versa.”
Figueroa works with CT scans of fossil skulls of ray-finned fish, including these specimens he brought to Michigan on loan from the Paleontological Center of the University of Contestado in Mafra, Santa Catarina, Brazil.
“The use of micro-CT of fossils and micro-CT with contrast of current species provides us with new three-dimensional data that can go beyond the results provided in this article, with the incorporation of new fossils and new comparative material of current species“Figueroa said.
In this study, Figueroa scanned eight Mafra specimens and found some degree of soft tissue fossilization in all of them. In most cases, the brain was preserved in detail, showing a morphology similar to that of Coccocephalus, found in previous research.
“After closer examination of all of these brains and the associated osteology of the specimens, I was able to determine that there were two distinct species,” he said. “Given its bone morphology, one seemed to be closely related to younger fossils, closer to the group that includes the 35,000 living species of ray-finned fish.
According to Figueroa, these two taxa show a different brain morphology. “This gives us the first evidence of an everted telencephalon in a ray-finned fossil fish,” she said. “This is found in some specimens, while Coccocephalus, from last year’s work, shows the contrasting condition we call an evaginated telencephalon.”
The Brazilian researcher said the specimens also preserve detailed evidence of meningeal tissues, such as the membranous tissue that supports the brain inside the head and eyes, including lenses, sclera, muscles and retinal tissue.
“Although, at the moment, they are not sufficient to provide a clear picture of the evolution of these structures, they are an indication that such extensive preservation of soft tissues is possible,” Figueroa said. “I think many more discoveries could emerge in the coming years.”
The study is the culmination of five years of research. After discovering the oldest fossil vertebrate brain in 2023, Figueroa wanted to better understand other possible cases of soft tissue preservation in fossils. and how much information this type of preservation can provide.
“I still remember the first time I looked at the CT scan of one of the specimens,” he said. “I was excited to see all the details preserved in the bones and then I realized there was more. It was an eye in almost pristine condition. From that point on, it was an adventure to find more and more preserved soft tissue and compare it to fish alive. It is surprising how much these specimens are preserved.“.
