Millions of Years Ago, the Caribbean Flooded the Amazon Rain Forest—Twice

iStock
iStock

Long before the trees of today’s Amazon reached for the sky, scientists say, sharks weaved through salty waters there, and mantis shrimp rattled across the flooded forest floor. The researchers published their findings in the journal Science Advances.

Scientists have known for some time now that an area of the western Amazon basin was underwater millions of years ago. The exact source of that water has been the subject of some dispute. Some researchers have envisioned a wide river sweeping down from the Andes, while others say the inundation must have washed inland from the sea. But neither side had compelling evidence to support their ideas—until now.

The researchers studied two nearly-2000-foot-long sediment cores, one taken by an oil company in eastern Colombia, and the other taken across the border in northwestern Brazil by Brazilian Geological Survey. Each was packed with the natural detritus of millions of years of local life.

The bulk of each core told the story of a world on dry land, but within two thin slices—one from about 18 million years ago, another from about 12 million years ago—a glimmer of the sea appeared. The complete cores contained a total of 933 different types of pollen grains. The thin slices included types of pollen only found in salt water.

Bigger clues were yet to come: The researchers also found a fossilized shark tooth and the remains of a mantis shrimp. “It’s a lost ecosystem,” lead author Carlos Jaramillo, of the Smithsonian Tropical Research Institute, told Lizzie Wade in Science.


Carcharhiniformes indet. tooth from the Saltarin core, Carbonera C2 Formation, early Miocene flooding.
Jorge Carillo


A modern Carcharhinus shark, similar to the fossil shark found in the early Miocene flooding.

Lasting a few hundred thousand to a few million years, each flood period was relatively brief from a geological perspective, Jaramillo says. But they weren't so brief that they didn’t completely alter the landscape.

“The life span of a single Amazonia canopy tree is about 200-400 years,” he tells Mental Floss. “Therefore, for thousands of generations, not a single tree could occupy Amazonia. In other words, the immense forest we see today is geologically young.”

The findings came as a surprise even to Jaramillo and his colleagues. He added, “I was of the opinion that there were no floodings, but it turned out I was mistaken!”

Scientists Find Fossil of 150-Million-Year-Old Flesh-Eating Fish—Plus a Few of Its Prey

M. Ebert and T. Nohl
M. Ebert and T. Nohl

A fossil of an unusual piranha-like fish from the Late Jurassic period has been unearthed by scientists in southern Germany, Australian news outlet the ABC reports. Even more remarkable than the fossil’s age—150 million years old—is the fact that the limestone deposit also contains some of the fish’s victims.

Fish with chunks missing from their fins were found near the predator fish, which has been named Piranhamesodon pinnatomus. Aside from the predator’s razor-sharp teeth, though, it doesn’t look like your usual flesh-eating fish. It belonged to an extinct order of bony fish that lived at the time of the dinosaurs, and until now, scientists didn’t realize there was a species of bony fish that tore into its prey in such a way. This makes it the first flesh-eating bony fish on record, long predating the piranha. 

“Fish as we know them, bony fishes, just did not bite flesh of other fishes at that time,” Dr. Martina Kölbl-Ebert, the paleontologist who found the fish with her husband, Martin Ebert, said in a statement. “Sharks have been able to bite out chunks of flesh, but throughout history bony fishes have either fed on invertebrates or largely swallowed their prey whole. Biting chunks of flesh or fins was something that came much later."

Kölbl-Ebert, the director of the Jura Museum in Eichstätt, Germany, says she was stunned to see the bony fish’s sharp teeth, comparing it to “finding a sheep with a snarl like a wolf.” This cunning disguise made the fish a fearful predator, and scientists believe the fish may have “exploited aggressive mimicry” to ambush unsuspecting fish.

The fossil was discovered in 2016 in southern Germany, but the find has only recently been described in the journal Current Biology. It was found at a quarry where other fossils, like those of the Archaeopteryx dinosaur, have been unearthed in the past.

[h/t the ABC]

Could Leonardo da Vinci's Artistic Genius Be Due to an Eye Condition?

Young John the Baptist, Leonardo da Vinci (1513-16, Louvre, Paris).
Young John the Baptist, Leonardo da Vinci (1513-16, Louvre, Paris).
Christopher Tyler, JAMA Ophthalmology (2018)

Leonardo da Vinci was indisputably a genius, but his singular artistic vision may have been the result of seeing the world differently in more ways than one. A new paper argues that he had strabismus, a vision disorder where the eyes are misaligned and don’t look toward the same place at the same time. This disorder, visual neuroscientist Christopher Tyler argues, may have helped the artist render three-dimensional images on flat canvas with an extra level of skill.

Tyler is a professor at City, University of London who has written a number of studies on optics and art. In this study, published in JAMA Ophthalmology, he examined six different artworks from the period when Leonardo was working, including Young John the Baptist, Vitruvian Man, and a self-portrait by the artist. He also analyzed pieces by other artists that are thought to have used Leonardo as a model, like Andrea del Verrocchio’s Young Warrior sculpture. Leonardo served as the lead assistant in the latter artist’s studio, and likely served as the model for several of his works. Leonardo was also a friend of Benedetto da Maiano, and possibly served as a model for his 1480 sculpture of John the Baptist. Tyler also looked at the recently auctioned Salvator Mundi, a painting that not all experts believe can be attributed to Leonardo. (However, at least one scientific team that examined the painting says it’s legit.)

With strabismus, a person’s eyes appear to point in different directions. Based on the eyes in Leonardo’s own portraits of himself and other artworks modeled after him, it seems likely that he had intermittent strabismus. When he relaxed his eyes, one of his eyes drifted outward, though he was likely able to align his eyes when he focused. The gaze in the portraits and sculptures seems to be misaligned, with the left eye consistently drifting outward at around the same angle.

'Vitruvian Man' with the subject's pupils highlighted
Vitruvian Man, Leonardo da Vinci (~1490, Accademia, Venice)
Christopher Tyler, JAMA Ophthalmology (2018)

“The weight of converging evidence suggests that [Leonardo] had intermittent exotropia—where an eye turns outwards—with a resulting ability to switch to monocular vision, using just one eye,” Tyler explained in a press release. “The condition is rather convenient for a painter, since viewing the world with one eye allows direct comparison with the flat image being drawn or painted.” This would have given him an assist in depicting depth accurately.

Leonardo isn’t the first famous artist whose vision researchers have wondered about. Some have speculated that Degas’s increasingly coarse pastel work in his later years may have been attributed to his degenerating eyes, as the rough edges would have appeared smoother to him because of his blurred vision. Others have suggested that Van Gogh’s “yellow period” and the vibrant colors of Starry Night may have been influenced by yellowing vision caused by his use of digitalis, a medicine he took for epilepsy.

We can never truly know whether a long-dead artist’s work was the result of visual issues or simply a unique artistic vision, but looking at their art through the lens of medicine provides a new way of understanding their process.

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