Oldest fossil brain found in Kansas (Videos)

Mar 02, 2009
Reconstruction of large iniopterygian Sibyrhynchus denisoni. Credit: Philippe Janvier

When Alan Pradel of the Muséum National d'Histoire Naturelle in Paris CAT scanned a 300-million-year-old fossilized iniopterygian from Kansas, he and his colleagues saw a symmetrical blob nestled within the braincase. This turned out to be the oldest brain found in fossil form, a wholly unexpected and rare discovery.

Additional scanning on the synchrotron at the European Synchrotron Radiation Facility in Grenoble, France (and using a new X-Ray approach) yielded detailed information about the structure of brain, the shape of the braincase, and the nerves running between the two features. The new discovery is described with several other intact braincases—the first three-dimensional fossils from this group of extinct marine fishes—in the early online edition of the Proceedings of the National Academy of Sciences.

"For a long time, paleontologists have used the shape of the cranial cavity to research the general morphology of the brain—because soft tissue was not available until today," says Pradel.

This video is not supported by your browser at this time.
A 3-D reconstruction of the iniopterygian braincase viewed from the side after a synchrotron acquisition in absorption contrast (green= braincase; red=endocranial cavity; orange=brain). Credit: Alan Pradel

"Soft tissue has fossilized in the past, but it is usually muscle and organs like kidneys because of phosphate bacteria from the gut that permeates into tissue and preserves its features," says John Maisey, Curator in the Division of Paleontology at the American Museum of Natural History and a co-author of the report. "Fossilized brains are unusual, and this is by far the oldest known example."

Iniopterygians are extinct relatives of modern ratfishes, also known as "ghost sharks" or chimaeras. Chimaeras are obscure relatives of sharks and rays that were extensively described by Museum Curator Bashford Dean in 1906 and number about 40 species. But in the late Paleozoic, relatives of chimaeras were relatively common in the oceans of the world with a huge diversity of shapes and sizes, and iniopterygians were a bizarre part of this radiation. Known at first only from completely flattened fossils (which is partially why the complete braincases described now are so stunning), these fishes had several unusual features: massive skulls with huge eye sockets, shark-like teeth in rows, tails with clubs, enormous pectoral fins that were dorsalized or placed almost on their backs, and bone-like spikes or hooks on the tips of their fins. Most iniopterygians were fairly small, averaging about 6 inches in length.

This video is not supported by your browser at this time.
3-D reconstruction of the braincase in ventral view (green=braincase; red=endocranial cavity; orange=brain). Credit: Alan Pradel

The new research looked at four 3-dimensional braincases of iniopterygians found in shales from Kansas and Oklahoma. The specimens share several features with living ratfishes, which means that these skull features have been conserved in the group for the last 300 million years. Complete reconstructions of these skulls were made with a CAT scan and X-ray synchrotron microtomography, and the imaging of one skull showed a dense, symmetrical object sitting within the large braincase. This was the mineralized brain.

The specimen that included the brain was imaged as a holtomography by Paul Tafforeau and colleagues at the European Synchrotron Radiation Facility. This more powerful scan brought the brain to light in great detail. It is a tiny (about 1.5mm by 7 mm in size), symmetrical shape that sits within a large braincase; as in many lower vertebrates, the brains of these fish ceased to grow as their skulls continued to expand. The brain has a large lobe for vision and an optic nerve that stretches to the correct place on the braincase; both of these features correlate well with the large eye sockets. The auditory section of the brain is reduced, and this information reflects observations of the inner ear in iniopterygians. Unlike typical ear canals that regulate orientation and balance with three big loops, the ear canals in this extinct group are all pulled into a horizontal plane. This means that the fish could detect side to side movements, but not up and down.

"There is nothing like this known today; it is really bizarre," says Maisey. "But now that we know that brains might be preserved in such ancient fossils, we can start looking for others. We are limited in information about early vertebrate brains, and the evolution of the brain lies at the core of vertebrate history."

Pradel agrees and will next look for possible brains of spiny rayed fish found in the same fossil beds from Kansas, Oklahoma, and Texas. "This fossilized brain allows for real paleo-neuroanatomical studies of fossil vertebrates," he says. "Now that we have fossilized soft tissue in addition to bone, we can see that there is no general correspondence between the morphology of the brain and that of the endocranial cavity and that past paleo-neuroanatomical studies must be taken with caution."

Source: American Museum of Natural History

Explore further: T. rex gets new home in Smithsonian dinosaur hall

add to favorites email to friend print save as pdf

Related Stories

More male fish "feminized" by pollution on the Basque coast

Mar 28, 2014

The UPV/EHU's Cell Biology in Environmental Toxicology group has conducted research using thick-lipped grey mullet and has analysed specimens in six zones: Arriluze and Gernika in 2007 and 2008, and since then, Santurtzi, ...

What's so hard about counting craters? (w/ video)

Mar 26, 2014

(Phys.org) —Providing a rare glimpse of the trade secrets of planetary scientists, the journal Icarus published a study this month that compared lunar crater counts by eight professionals with crowdsourced ...

Startup scene flourishes in US capital

Mar 20, 2014

In a large warehouse-type office, software coders work on apps, as "angel" investors and mentors help budding entrepreneurs figure out strategy for their startups.

Recommended for you

Clippers and coiners in 16th-century England

Apr 14, 2014

In 2017 a new £1 coin will appear in our pockets with a design extremely difficult to forge. In the mid-16th century, Elizabeth I's government came up with a series of measures to deter "divers evil persons" ...

Serbia experts use heavy machinery to move mammoth

Apr 11, 2014

Serbian archaeologists on Friday used heavy machinery to move a female mammoth skeleton—believed to be one million years old—from an open mine pit where it was unearthed nearly five years ago.

User comments : 0

More news stories

Online reviews: When do negative opinions boost sales?

When purchasing items online, reading customer reviews is a convenient way to get a real-world account of other people's opinions of the product. According to a new study in the Journal of Consumer Research, negative review ...

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.