American Museum of Natural History - Mythic Creatures

Saturday, May 26, 2012

The world is full of stories about brave heroes, magical events and fantastic beings. For thousands of years, humans everywhere—sometimes inspired by living animals or even fossils—have brought mythic creatures to life in stories, songs and works of art. Today these creatures, from the powerful dragon to the soaring phoenix, continue to thrill, terrify, entertain and inspire us. We seem to catch glimpses of these creatures all around us: hiding beneath the ocean waves, running silently through the forest and soaring among the clouds. Some symbolize danger. Others, we think, can bring us luck or joy. Together mythic creatures give shape to humankind's greater...


Blasts from the Past: Mosasaurs, Baryonyx, Zeuglodons, and Ichthyosaurs

Artist’s rendering of a Baryonyx, a prehistoric sea predator. (Troy Therrien)

In 1780 a dinosaur jaw was discovered in a mine near the Maas River in the Netherlands. Napoleon had it carted to France in 1795 where it became the object of much discussion for years, as scientists argued whether it was from a toothed whale, alligator, or lizard. Its resemblance to lizards was finally officially recognized in 1822 when it was given the genus name mosasaurus, which means “Maas River lizard.”

Mosasaurs could reach 40 feet or more in length. They looked very similar to Coleman and Huyghe’s drawing of the classic sea serpent” with a long, alligator-like jaw and strong flippers on a mostly tubular body. One artist’s interpretation of the mososaur known as tylosaurus also shows it with a scalloped dorsal (back) fin, which could provide another explanation of the short humps sometimes seen trailing behind a monstrous head. It lived in a sea that once covered the midsection of North America, and it ate diving birds, fish, and other mosasaurs. Tylosaurus was supposed to have died out 65 million years ago. But did it? The state of Utah has become known for sightings of monsters in Bear, Sevier, Fish, Utah, and Great Salt Lakes. Living things can be tenacious. And Natural History magazine has noted several paleontologists maintain that “snakes and mosasaurs are more closely related to each other than either group is to any other group of lizards.” In that case, calling a mosasaur a “sea serpent” does not seem such a stretch.

Baryonyx was another gator-jawed creature whose fossil skeleton was first discovered in 1983 in a clay pit in the United Kingdom. The lizard-like bones were found about three-quarters complete and would have measured 20 feet long. Evidence shows that Baryonyx was a fish-eater and probably used its oversized, deadly claws to hook its prey. The odds may be less likely that this killing machine has survived until the present without detection, since it would probably wreak noticeable havoc wherever it popped up. Baryonyx would surely be termed a “water monster” if encountered by some unwary fisherman today.

Another ancient species that ranks high on the possible relict popularity scale is not a reptile at all. Zeuglodon was a primitive, toothed whale that lived around 25 million years ago and could reach lengths of 70 feet. Zeuglodon did not look much like modern whales; it was originally named Basilosaurus because it resembled a lizard in some ways. But its later placement in the whale category has also been disputed because it has many characteristics of the seal family, or pinnipeds, as well. Author Dr. Roy P. Mackal has proposed that an unknown creature observed snatching a duck from a watery surface near Vancouver in 1934 matched what we know of Zeuglodons perfectly. “Even a casual comparison,” says Mackal, “. . . reveals the striking agreement with the description of the observed animal.”

The observed animal, according to the duck hunters who saw it, was about 40 feet long and two to three feet wide with a tapering body and a three-foot-long head. The head was described as horse-like, though lacking ears or nostrils, and as dark, grayish brown marked with one horizontal, dark stripe. This is a description that could match many water creature sightings from around the world, making Zeuglodon a prime suspect in the relict category.

Zeuglodon was also tapped to explain one of the most famous sea serpent sightings ever—that of the H.M.S Daedalus in August 1848, off St. Helena, a British island in the South Atlantic Ocean. That monster was described by one witness as “a blunt-nosed animal with a neck carried about four feet above the water, which was so long as to present the appearance of a serpent . . . Two or three years after this, on reading the description of a Zeuglodon cetoides . . . it struck me that the animal seen from the Daedalus may have been a descendent of the order to which Zeuglodon belonged; and I have ever since watched with interest for reports of the ‘great sea-serpent.’ ”

While there are probably innumerable prehistoric creatures that resembled traditional sea serpents, with many still possibly undiscovered, one other is often inserted into the lineup of suspected sea monsters: the ichthyosaur, which means “fish-lizard.” The first ichthyosaur skull was found and recognized off Southern England in 1811. Ichthyosaurs varied in size and appearance from three to over 30 feet long, and from early, eel-shaped species to later versions that looked like dolphins with long, sharp beaks full of teeth. Ichthyosaurs, like mosasaurs, were reptiles, and needed to come to the surface to breathe. But they were more ancient than the mosasaurs, making it even less likely that some of them might have survived until present times.

Egg size was dinos ultimate undoing

Wednesday, May 9, 2012

Artist's impression of Massospondylus and babies hatching(Source: Julian Csotonyi/)

The fact that land-bound dinosaurs laid eggs is what sealed their fate of mass extinction 65 millions of years ago, says scientist.
In a new explanation for mammals' evolutionary victory over dinosaurs, researchers claim a mathematical model has shown that infant size was the clincher.
Given physical limitations to egg size, dinosaurs had comparatively small young. Some came out of the egg weighing as little as two to 10 kilograms, yet had to bulk up to a hefty 30 or 50 tonnes.
Growing up, the youngsters had to compete in several size categories with adults of other animal groups for food, says University of Zurich scientist Marcus Clauss.
This meant that all the small and medium animal size categories supported by the natural environment were "occupied", leaving no room for smaller dinosaur species in which to thrive, according to the findings published in Biology Letters.
"There is a lot of room in the ecosystem for small species, but (in such a scenario) that room is taken up by the young ones of the large species," says Clauss.
"That was not a problem for 150 million years but as soon as something happens that takes away all the large species so that only small species remain, if there are no small species to remain you are gone as a whole group."
The catastrophic event that wiped out all larger life forms some 65 million years ago meant the end for terrestrial dinosaurs.

Mammals best equipped

Scientists disagree on whether the scaly reptiles died out before or after a meteorite smashed into Earth in what is known as the Cretaceous-Tertiary impact, causing billions of tonnes of wind-borne ash and dust to filter out light from the Sun and triggering a "nuclear winter" that cooled the planet and withered vegetation.
Mammals did not have the same limitations in size spread, says Clauss, because their young were not born as comparatively small and did not need to compete with other species for food, instead suckling on their mothers.
This meant there were smaller mammal species able to cope with the new post-catastrophe environment and evolve into new species alongside birds, which are also dinosaurs.
"The question that haunted some people including me is ... why did the mammals survive and why did the dinosaurs not. I think we have a very good answer for that," says Clauss.
The researchers says egg size is constricted by upper limits to the thickness of shells, which have to allow oxygen through to the embryo.
The average forty-tonne titanosaur, the largest type of vertebrate that ever lived, was 2500 times heavier than its newborn. A modern-day elephant mother weighs 22 times more than her calf.
Scientists say all animals with a bodyweight of more than about 10 to 25 kilograms died in the mass extinction event.

Some dinos in decline when space rock hit

Tyrannosaurus rex was part of one group of dinosaurs that maintained a stable level of biodiversity leading up to the mass extinction (Source: J Brougham/AMNH)

Large, plant-eating dinosaurs were already in decline by the time a space rock smashed into Earth 65 million years ago and ended their reign, according to a new study.
The findings by scientists in the United States and Germany do not dispute the mass extinction that so dramatically ended the Cretaceous era.
But they suggest the dinosaur kingdom, or at least some of its species, was not struck down in its prime as is often hypothesised. The findings are published in the journal Nature Communications.
"A lot of the time people think of the dinosaurs going extinct: 'oh, you know, an asteroid did it ... the dinosaurs were doing just fine, an asteroid came along and killed them all off'," says Steve Brusatte, a palaeontologist at the American Museum of Natural History.
"I think now we can say it was probably more complicated than that. You had some dinosaurs that were doing just fine, but you had others like these big plant eaters that were maybe in trouble.
"This was a world that was undergoing a lot of changes before the asteroid hit. It wasn't quite such a nice, easy story as we might like to think."

Shrinking diversity

The study compared the skeletal structure of 150 different species of land-bound dinosaurs to see how they changed over time, the idea being to see if a species was up, down or stable in survival terms.
By this benchmark, the large herbivores -- specifically, horned and duckbilled dinosaurs -- were becoming less and less diverse during the last 12 million years of the Cretaceous.
The four-footed giants "were becoming more similar to each other, they were losing variability," says Brusatte. "Usually when you see these big decreases in the anatomy like this, that means that a group is in trouble."
Groups that show an increase in variety boost their chances of survival because they can fill new habitat niches or adapt to changing conditions, he says.

T-rex thriving

But if big herbivores were on the skids towards the end of the Cretaceous, carnivorous dinosaurs and medium-sized herbivores were thriving, say the researchers.
"What we can say for certain now is when the asteroid hit and when these volcanoes began erupting, they didn't hit a world that was totally OK, they didn't hit a static world," says Brusatte.
"At the time, dinosaurs, at least some of them, were undoing major evolutionary changes and at least these plant eaters were declining."
The reason for their downward spiral is unclear but "was probably something ecological," he says.