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  • Writer's pictureThe San Juan Daily Star

News and notes about science

In an undated image provided by Sergei Krasinski, a life reconstruction of Tyrannosaurus mcraeensis, which appears in the fossil record about six million or seven million years before its larger, more famous cousin. Researchers say the species they named Tyrannosaurus mcraeensis predated the dinosaur era’s great predator. (Sergei Krasinski via The New York Times)

What came before Tyrannosaurus rex

Researchers have announced the discovery of a new species of Tyrannosaurus from New Mexico, one that appeared in the fossil record 5 million to 7 million years before the familiar tyrant lizard. Their research, published in Scientific Reports, suggests a new chapter could be added to the origin story of Tyrannosaurus rex.

When staff members from the New Mexico Museum of Natural History and Science collected the partial skull of a large adult tyrannosaurus from the Elephant Butte Reservoir in the state in the 1980s, they assumed the fossils belonged to T. rex. But when paleontologist Sebastian Dalman began working on the specimen in 2013, he noticed subtle differences between it and other T. rex skulls.

Rather than the deep bone-crushing jaws of an adult T. rex, the lower jaw of the reservoir specimen looked more slender. Its teeth were different, and the animal lacked the prominent ridge of bone found behind T. rex’s eye, Dalman said. The animal was about 39 feet long, around the same length as an adult T. rex.

T. rex fossils are believed to be 66 million to 68 million years old, the period recorded in the Hell Creek Formation of the Plains states, said Spencer Lucas, paleontology curator at the museum and an author on the paper. When the fossil was initially discovered, researchers initially assumed the rock layers that produced it — the McRae Formation of New Mexico — belonged to the same period. But the team’s dating of the rocks now suggests that the McRae Formation was 5 million to 7 million years older than Hell Creek, and that the specimen they found came from an earlier relative.

The researchers say this is enough to conclude that the skull belongs to a distinct species, which they’ve named Tyrannosaurus mcraeensis after the formation where the specimen was found. — ASHER ELBEIN

The largest ape ever, but not too big to fail

Standing nearly as tall as a basketball hoop and weighing as much as a grizzly bear, Gigantopithecus blacki was the greatest ape to ever live. For more than 1 million years during the Pleistocene, Gigantopithecus roamed southern China. But by the time ancient humans reached the region, Gigantopithecus had vanished.

To determine why these prodigious primates died out, a team of scientists recently analyzed clues preserved in Gigantopithecus teeth and cave sediment. Their findings, published in the journal Nature, reveal that these nearly 10-foot-tall apes were most likely doomed by their specialized diet and an inability to adapt to a changing environment.

Paleontologists first discovered Gigantopithecus in the mid-1930s in a Hong Kong apothecary where the ape’s unusually large molars were being hawked as “dragon teeth.” The animal was named to honor Davidson Black, the Canadian scientist who studied the early human ancestor known as Peking man. In the decades since, scientists have unearthed about 2,000 Gigantopithecus teeth and a handful of fossil jawbones from caves throughout southern China.

The dearth of fossilized bones makes reconstructing Gigantopithecus difficult; paleoartists depict the ancient ape as looking like an orangutan (its closest living relative) crossed with a silverback gorilla, but bigger. Nevertheless, the very great ape’s teeth, which are encased in a thick layer of enamel, preserve a wealth of clues to how these enigmatic primates lived and potentially why they died out.

Yingqi Zhang, a paleontologist from the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing and an author on the new paper, has studied Gigantopithecus fossils for more than a decade. To determine what drove them to extinction, Zhang needed to nail down exactly when Gigantopithecus disappeared. He teamed up with Kira Westaway, a geochronologist at Macquarie University in Australia.

The team collected and dated material from 22 caves across southern China. To fine-tune the ages of the fossils and the cave sediments, the researchers applied six dating techniques. They also analyzed isotopes and pollen in the samples to recreate what the environment was like around the time Gigantopithecus disappeared. Finally, they compared wear patterns in the oversized teeth with fossilized teeth from Pongo weidenreichi, an orangutan that lived alongside Gigantopithecus.

Gigantopithecus, they say, went extinct between 295,000 and 215,000 years ago.

The pollen samples revealed that before that extinction window, the local environment was dominated by evergreen trees that created closed-canopy forests. Gigantopithecus appeared to be well suited to those environments. Analysis of isotopes in Gigantopithecus teeth from that period revealed that the apes were eating fibrous plants, fruits and flowers.

Beginning around 600,000 years ago, the region’s climate began to change with the seasons as dense forests gave way to a patchwork of open forests and grasslands. That led to “dry periods when fruits were difficult to find,” Westaway said. Gigantopithecus switched to less nutritious alternatives like bark and twigs.

As the environment became unfavorable, Gigantopithecus’s size began to work against it. Unlike spry orangutans, who could travel greater distances through the canopy to forage, Gigantopithecus were most likely restricted to shrinking patches of forest. — JACK TAMISIEA

From ancient fossil, a skin-deep discovery

Dry, scaly skin may be one of the least fun parts of winter. But in the broad scheme of things, a tough, watertight hide is part of what enabled the ancestors of modern reptiles, birds and mammals to move inland while their thin-skinned amphibian cousins remained close to water.

In a study published in the journal Current Biology, scientists announced the discovery of the oldest-known piece of fossilized skin. The pebbly scrap, which is no larger than a human fingernail, most likely belonged to an ancient reptile and provides rare insight into the evolution of skin.

The piece of skin is one of countless traces of prehistoric life preserved in the Richards Spur limestone cave system near an oil seep in southwestern Oklahoma. When animals fell into the caves 289 million years ago, the conditions were ideal for preservation: fine clay sediments rapidly buried the bodies, low levels of oxygen in the groundwater slowed the decay process, and hydrocarbons from the oil permeated the tissues and made them less hospitable to bacteria. The tar seeped into the fossils, staining them.

In 2018, Bill May, a retired forensic analyst, shared some tiny flakes from the Richards Spur that he couldn’t identify with Robert Reisz, a paleontologist at the University of Toronto Mississauga.

“We got very excited by what we saw under the microscope,” said Reisz, an author of the paper.

“The texture of the skin is quite unique and interesting,” said Ethan Mooney, a graduate student who worked with Reisz on the paper. “It really stands out from other fossil material. It’s obviously not bone.” If anything, the fossilized tissue bore a striking resemblance to the scaly skin of a crocodile. — KATE GOLEMBIEWSKI

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