Science news tidbits
Researchers working in the western Gobi Desert in Mongolia have discovered the almost complete skeleton of a tyrannosaurid dinosaur that was less than 3 years old when it died, younger and smaller than any previously known. The animal, Tarbosaurus bataar, is the closest relative of Tyrannosaurus rex, the predator that lived at the same time in North America.
In life, the specimen weighed less than 70 pounds, compared with the 6-ton weight of a full-grown T. bataar, the researchers report in The Journal of Vertebrate Paleontology. The researchers were able to determine its age by microscopic examination of one of the leg bones, which reveal periodic pauses in growth, similar to the rings of a tree trunk.
The skulls of adult tyrannosaurids have extremely strong bones, especially those of the jaw, capable of tremendous twisting and bending forces. But the juvenile’s skull bones are more delicate, its teeth much thinner and its jaw much weaker. This suggests that a young T. bataar would be more likely to take its prey by stealth and speed rather than the overwhelming power its parents could use. In other words, T. bataar changed its diet as it matured, unlike some other predatory dinosaurs.
"This is one of the clearest pictures we have of these dinosaurs," said Lawrence M. Witmer, a professor of paleontology at Ohio University and the senior author of the study. "It gives us the best glimpse into the changing lifestyles of these animals as they grew."
IN DIGESTION, LEECHES SHOW SOPHISTICATED SIDE
Some leeches like it cool, but some like it hot. It all depends on whether they are hungry.
Leeches are ectotherms — cold-blooded animals that cannot regulate their own temperature and depend on their environment to do it for them. Blood-sucking species eat large meals and consume significant energy digesting them and excreting waste.
They spend many months between meals, and the faster they process the food, the faster they can use their energy for other activities — growth, reproduction and mobility. Fast digestion, in other words, could provide an evolutionary advantage.
Now researchers report in Biology Letters that well-fed leeches seek out warmth, where chemical processes can move faster, while hungry ones preserve energy by moving to cooler places. This has never before been seen in an invertebrate species.
Researchers used medicinal leeches (yes, leeches are still occasionally used in modern medical practice) in their experiment, placing them in a tube with varying temperatures.
Before feeding, the animals preferred the cooler parts of the tube. Then for the first five days after feeding, they consistently sought out the warmer sections. After 10 days, there was no statistically significant difference from their preference before the meal.
The senior author, David J. Ellerby, an assistant professor of biology at Wellesley College in Massachusetts, said no one expected such sophisticated strategy in a leech.
"That was the really surprising aspect," he said. "If something as simple as a leech can do it, maybe a lot of other invertebrates are also doing it."
BONES INDICATE TASMANIAN TIGER, NOW EXTINCT, AMBUSHED PREY
It was known as the Tasmanian tiger, for its striped coat, or the Tasmanian wolf, for its doglike appearance. But new research indicates the bone structure and hunting habits of Thylacinus cynocephalus may make the "tiger" designation more apt.
Although the now-extinct marsupial was kept in zoos until the 1930s, little is known about its life in the wild. But the shape of its elbows offers some clues to its behavior and calls into question a commonly accepted reason for its extinction, researchers report in the journal Biology Letters.
The authors classified 32 species of mammals into three groups: ambush predators, like tigers; pounce/pursuit predators, like foxes, which engage in a short chase; and pursuit predators, like wolves, which follow their quarry for long distances and may cooperate to bring down larger animals. They found that the groups can be characterized by elbow joints — more flexible for animals that hunt with little running, and more rigid for the distance runners.
The thylacine, with its twistable elbow, was more of an ambusher. Though its nonretractable claws suggest that it did not grapple with its prey, it almost certainly did not run after it like a wolf.
Christine M. Janis, a professor of biology at Brown University in Rhode Island and an author of the study, said the finding made the story of the Tasmanian tiger’s extinction in Australia more complicated.
"People have assumed that the immigration of the doglike dingo was the reason for the extinction," she said. "But the thylacine had a different hunting style from the dingo, and so it was not likely an issue of simple competitive replacement."
In life, the specimen weighed less than 70 pounds, compared with the 6-ton weight of a full-grown T. bataar, the researchers report in The Journal of Vertebrate Paleontology. The researchers were able to determine its age by microscopic examination of one of the leg bones, which reveal periodic pauses in growth, similar to the rings of a tree trunk.
The skulls of adult tyrannosaurids have extremely strong bones, especially those of the jaw, capable of tremendous twisting and bending forces. But the juvenile’s skull bones are more delicate, its teeth much thinner and its jaw much weaker. This suggests that a young T. bataar would be more likely to take its prey by stealth and speed rather than the overwhelming power its parents could use. In other words, T. bataar changed its diet as it matured, unlike some other predatory dinosaurs.
"This is one of the clearest pictures we have of these dinosaurs," said Lawrence M. Witmer, a professor of paleontology at Ohio University and the senior author of the study. "It gives us the best glimpse into the changing lifestyles of these animals as they grew."
IN DIGESTION, LEECHES SHOW SOPHISTICATED SIDE
Some leeches like it cool, but some like it hot. It all depends on whether they are hungry.
Leeches are ectotherms — cold-blooded animals that cannot regulate their own temperature and depend on their environment to do it for them. Blood-sucking species eat large meals and consume significant energy digesting them and excreting waste.
They spend many months between meals, and the faster they process the food, the faster they can use their energy for other activities — growth, reproduction and mobility. Fast digestion, in other words, could provide an evolutionary advantage.
Now researchers report in Biology Letters that well-fed leeches seek out warmth, where chemical processes can move faster, while hungry ones preserve energy by moving to cooler places. This has never before been seen in an invertebrate species.
Researchers used medicinal leeches (yes, leeches are still occasionally used in modern medical practice) in their experiment, placing them in a tube with varying temperatures.
Before feeding, the animals preferred the cooler parts of the tube. Then for the first five days after feeding, they consistently sought out the warmer sections. After 10 days, there was no statistically significant difference from their preference before the meal.
The senior author, David J. Ellerby, an assistant professor of biology at Wellesley College in Massachusetts, said no one expected such sophisticated strategy in a leech.
"That was the really surprising aspect," he said. "If something as simple as a leech can do it, maybe a lot of other invertebrates are also doing it."
BONES INDICATE TASMANIAN TIGER, NOW EXTINCT, AMBUSHED PREY
It was known as the Tasmanian tiger, for its striped coat, or the Tasmanian wolf, for its doglike appearance. But new research indicates the bone structure and hunting habits of Thylacinus cynocephalus may make the "tiger" designation more apt.
Although the now-extinct marsupial was kept in zoos until the 1930s, little is known about its life in the wild. But the shape of its elbows offers some clues to its behavior and calls into question a commonly accepted reason for its extinction, researchers report in the journal Biology Letters.
The authors classified 32 species of mammals into three groups: ambush predators, like tigers; pounce/pursuit predators, like foxes, which engage in a short chase; and pursuit predators, like wolves, which follow their quarry for long distances and may cooperate to bring down larger animals. They found that the groups can be characterized by elbow joints — more flexible for animals that hunt with little running, and more rigid for the distance runners.
The thylacine, with its twistable elbow, was more of an ambusher. Though its nonretractable claws suggest that it did not grapple with its prey, it almost certainly did not run after it like a wolf.
Christine M. Janis, a professor of biology at Brown University in Rhode Island and an author of the study, said the finding made the story of the Tasmanian tiger’s extinction in Australia more complicated.
"People have assumed that the immigration of the doglike dingo was the reason for the extinction," she said. "But the thylacine had a different hunting style from the dingo, and so it was not likely an issue of simple competitive replacement."
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