Killer Cave Lured Ancient Carnivores to Their Death
by Tia Ghose
A cavern in Spain may have lured ancient carnivores to their deaths by offering the promise of food and water, new research suggests.
The new study, published today (May 1) in the journal PLOS ONE, may explain how the carcasses of several carnivore species, including saber-toothed cats and “bear dogs,” wound up in an underground cavern millions of years ago.
“Only the carnivores were daring enough to enter,” said study co-author M. Soledad Domingo, a paleontologist at the University of Michigan. “But they were unable to make their way out.”…
(images:1 - illustration of sabertooths with rhino in ancient cave by Mauricio Anton; 2 - photo of Sabertooth skull by Soledad Domingo; 3 - illustration of cave history by Anton, Domingo, Sanchez; 4 - fossil skeleton of ancient “Bear-Dog” by ghedoghedo | Wikimedia)
First Migration from Africa Less Than 95,000 Years Ago: Ancient Hunter-Gatherer DNA Challenges Theory of Early Out-Of-Africa Migrations
by Science Daily staff
Mar. 22, 2013 — Recent measurements of the rate at which children show DNA changes not seen in their parents — the “mutation rate” — have challenged views about major dates in human evolution.
In particular these measurements have made geneticists think again about key dates in human evolution, like when modern non-Africans split from modern Africans. The recent measurements push back the best estimates of these dates by up to a factor of two. Now, however an international team led by researchers at the University of Tübingen and the Max Planck Institute for Evolutionary Anthropology in Leipzig, present results that point again to the more recent dates. The new study is published in Current Biology…
The foot bones of the jerboa are hard to miss. Longer than the animal’s arm, they help the bipedal desert rodent hop quickly away from predators. Now, they have also helped scientists better understand how bones grow to the right length. The finding helps explain some of the factors that affect the shape of skeletons, and they could eventually help to treat bone growth defects.
A growing bone lengthens when cells in its so-called growth plate, a region at the ends of growing bones, multiply and expand. The cells, called chondrocytes, form the cartilage that provides a scaffold for the mature calcified bone that later grows on top of them. Scientists knew that the size of the chondrocytes—not only their number—helped fix how much and how quickly a bone grows. But exactly what drives that cell size growth is a mystery…
How Did the Largest Dinosaurs Grow Such Long Necks?
by Charles Choi
How did the largest of all dinosaurs evolve necks longer than any other creature that has ever lived? One secret: mostly hollow neck bones, researchers say.
The largest creatures to ever walk the Earth were the long-necked, long-tailed dinosaurs known as the sauropods. These vegetarians had by far the longest necks of any known animal. The dinosaurs’ necks reached up to 50 feet (15 meters) in length, six times longer than that of the current world-record holder, the giraffe, and at least five times longer than those of any other animal that has lived on land.
“They were really stupidly, absurdly oversized,” said researcher Michael Taylor, a vertebrate paleontologist at the University of Bristol in England. “In our feeble, modern world, we’re used to thinking of elephants as big, but sauropods reached 10 times the size elephants do. They were the size of walking whales.”
To find out how sauropod necks could get so long, scientists analyzed other long-necked creatures and compared sauropod anatomy with that of the dinosaurs’ nearest living relatives, the birds and crocodilians…
… is an extinct genus of lizard-like reptile. There is only one species, Longisquama insignis, known from a poorly preserved skeleton and several incomplete fossil impressions from the Middle to Late TriassicMadygen Formation in Kyrgyzstan.
Longisquama means “long scales”; the specific name insignis refers to its small size. The Longisquama holotype is notable for a number of long structures that appear to grow from its skin. These structures have been interpreted as either primitive feathers suggesting Longisquama is a close relative of birds, or as feather-like structures that have evolved independently and do not indicate a close relationship with birds.
Longisquama has been used in a heavily publicized debate on of the origin of birds. To some, Longisquama is the gliding, cold-blooded, protobird predicted by Gerhard Heilmann’s hypothetical “Proavis” in 1927, and it proves that birds are not dinosaurs. The current opinion is that Longisquama is an ambiguous diapsid and has no bearing on the origin of birds…
Any idea what this skull is from? A friend of mine found it at a lake in central Oklahoma. I think it is a raccoon but I’m not 100% sure. I have a few more pictures of it if needed. I figured if anyone would know you would.
The Paleo-Diet: Dinosaurs Lose Weight in New Study
by Charles Choi
The fact that bones have curves has now thrown a curveball into calculations of dinosaur weight, researchers say.
New estimates suggest dinosaurs may have been lighter than once thought, scientists explain.
With the rare exceptions of fossilized scraps of skin, feathers, bristles and other relatively soft tissues, all that remains of most extinct creatures are their skeletons. One way that investigators seek to learn more about these lost animals is to deduce their weight from their bones.
Traditionally, researchers would calculate estimates of dinosaur mass using a leg measurement such as the circumference of leg bones, understanding the relationship between body mass and this circumference in modern animals, “and scaling this up to the size of a dinosaur,” said researcher Charlotte Brassey, a biomechanist at the University of Manchester in England…
Entelodonts, sometimes nicknamed “hell pigs” or “terminator pigs”, are an extinct family of pig-like omnivores endemic to forests and plains of North America, Europe, and Asia from the middle Eocene to early Miocene epochs (37.2—16.3 mya), existing for approx 20.9 million years.
The largest were the North American Daeodon shoshonensis, the Entelodon and the Eurasian Paraentelodon intermedium, standing up to 2.1 m (6.9 ft) tall at-shoulder, with brains the size of an orange. A single specimen was recorded for body mass and was estimated to have a weight of 421 kg (930 lb). Their teeth suggest an omnivorous diet, similar to that of modern pigs. Like many other artiodactyls, they had cloven hooves, with two toes touching the ground, and the remaining two being vestigial.
Entelodonts lived in the forests and plains where they were the apex predators of North America’s Early Miocene and Oligocene, consuming carrion and live animals and rounding off their diet with plants and tubers. They would have hunted large animals dispatching them with a blow from their jaws. Some fossil remains of these other animals have been found with the bite marks of entelodonts on them. Like modern day pigs, they were omnivores, eating both meat and plants, but their adaptations show a bias towards live prey and carrion…
(images: T - Elotherium by Heinrich Harder, 1920; ML - skull of Archaeotherium by H. Zell; MR - Archaeotherium by Robert Bruce Horsfall, 1913; BL - Daeodon by Jay Materness, Smithsonian mural, 1964; Daeodon skeleton)
Andrewsarchus mongoliensis was a mammal that lived during the Eocene epoch, roughly 45 - 36 million years ago. It had a long snout with large, sharp teeth and flat cheek teeth that may have been used to crush bones. Because Andrewsarchus is only known from a single skull, whether it was an active predator or a large scavenger is open to debate, as is its exact time range.
Andrewsarchus is named for the famous explorer and fossil hunter Roy Chapman Andrews. It was discovered in June 1923 by Kan Chuen Pao, a member of Andrews’ expedition, at a site in the Gobi Desert in Mongolia known as Irdin Manha on the third Asiatic expedition that was led by Andrews and sponsored by the American Museum of Natural History. The skull is now on display at the American Museum of Natural History in New York; the lower jaw was not found.
It was classified in the clade Mesonychia due to the similarity in structure between its teeth and skull with those of other mesonychid species known from complete skeleton, however, much of this was based only on Osborn’s original publication, and more recent studies have found it to have no special mesonychid affinities, instead grouping with various artiodactyl clades. Indeed one study (Spaulding et al.) has not only found them to be closer to entelodonts (“Hell Pigs”), but as kin to Cetancodonta (cetaceans and hippos)…
Placodus had a stocky body with a long tail, and reached a total length of up to 2 m (6.6 ft). It had a short neck, and a heavy skull. They were specialized for a durophagous diet of shellfish, such as bivalves. Chisel-like incisors protruded from the anterior margin of the snout, and were probably used to pluck hard-shelled benthic prey from the substrate. The back teeth were broad and flattened, and would have helped to crush the prey.Before the animals’ anatomy was known, they were regarded as fishes’ teeth. Similar smaller teeth were present on the palatine bones…
… (meaning “two forward teeth”), sometimes known as the giant wombat or the rhinoceros wombat, is the largest known marsupial ever to have lived. Along with many other members of a group of unusual species collectively called the “Australian megafauna”, it existed from approximately 1.6 million years ago until extinction some 46,000 years ago (through most of the Pleistocene epoch).
Diprotodonfossils have been found in sites across mainland Australia, including complete skulls and skeletons, as well as hair and foot impressions. Female skeletons have been found with babies located where the mother’s pouch would have been. The largest specimens were hippopotamus-sized: about 3 m(10 ft) from nose to tail, standing 2 m (6.6 ft) tall at the shoulder and weighing up to 2,800 kg (6,200 lb). They inhabited open forest, woodlands, and grasslands, possibly staying close to water, and eating leaves, shrubs, and some grasses…
… was an armored, spiked, plant-eating ankylosaur from the early Cretaceous period. Early depictions often gave it a very vague head as it was only known from the rear half of the creature. It lived 130 to 125 million years ago in what is now western Europe. Polacanthus grew to between 4 to 5 m (13 to 16 ft) long. There are not many fossil remains of this creature, and some important anatomical features, such as its skull, are poorly known. Polacanthus had a large sacral shield, a single fused sheet of dermal bone over its hips (sacral area) which was not attached to the underlying bone and decorated with tubercles…