mammals
laelaps | March 29, 2009
The skull of Dorudon, photographed at the National Museum of Natural History.
laelaps | March 28, 2009
The skeleton of a chimpanzee (Pan troglodytes), photographed at the National Museum of Natural History. Notice the bone pathology around the roots of the teeth in the upper jaw.
laelaps | March 27, 2009
A giant anteater (Myrmecophaga tridactyla), photographed at the National Zoo.
laelaps | March 26, 2009
A mother gorilla (Gorilla gorilla) and her child. Photographed at the National Zoo.
It may not be accurate to call our species "the third chimpanzee", but there can be no separation between apes and humans. We are apes. This realization has only come recently. There has been a long tradition of scholars who have tried to find something, anything, to draw an unbreakable line between us and our nearest relatives. As Henry Smith Williams wrote in a 1900 biography of Ernst Haeckel published in Harper's New Monthly Magazine, however, perhaps we have engaged in such efforts because apes are so…
laelaps | March 26, 2009
A mother gorilla (Gorilla gorilla) and her child. Photographed at the National Zoo.
laelaps | March 25, 2009
A cheetah (Acinonyx jubatus) marking its territory. Photographed at the National Zoo.
laelaps | March 24, 2009Last week I wrote about the shuffling and reshuffling of relationships between whales, hippos, pigs, and an extinct group of mammals called raoellids. One aspect of the paper I did not comment on, however, was the problematic placement of the enormous predator Andrewsarchus.
In November of 1924 Henry Fairfield Osborn described the huge skull of a predatory mammal discovered during a American Museum of Natural History expedition to Mongolia. Unfortunately there was little other than the skull left of the great beast, but Osborn thought it belonged to a gigantic omnivore. Osborn named it…
laelaps | March 24, 2009
Tai Shan the giant panda (Ailuropoda melanoleuca), photographed at the National Zoo.
jlynch | March 23, 2009Darren Naish brings an interesting paper to our attention: a claim that over 400 new mammal species have been discovered since 1993. While 60% of these were formerly classified within another species (i.e. were cryptic species), the remainder are apparently brand-spanking-new. Wander on over to Darren's post for further details and discussion.
The paper in question is: Ceballos, G. & Ehrlich, P. R. 2009. Discoveries of new mammal species and their implications for conservation and ecosystem services. Proceedings of the National Academy of Sciences 106, 3841-3846 (link)
edyong | March 21, 2009
Walking on two legs, or bipedalism, immediately sets us apart form other apes. It frees our arms for using tools and weapons and is a key part of our evolutionary success. Scientists have put forward a few theories to explain how our upright gait evolved, but the 'savannah theory' is by far the most prolific.
It's nicely illustrated by this misleading image that has become a mainstay of popular culture. It suggests that our ancestors went from four legs to two via the four-legged knuckle-walking gait of gorillas and chimps. Dwindling forests eventually pushed them from knuckle-walking to a…
laelaps | March 21, 2009
Maiacetus.
I am having a lot of fun visiting the various museums and landmarks in Washington, D.C. this weekend, and while I don't have much time for blogging I wanted to share a photo from my brief stop at the National Museum of Natural History. Even though I spent most of the day talking to paleobiologists behind the scenes (watch Dinosaur Tracking for details) I did have the chance to briefly check out the new ocean gallery. Pictured above is the skull of the suspended mount of Maiacetus on display in that exhibit.
laelaps | March 19, 2009The big news in this week's issue of Nature was the discovery of a small ornithischian dinosaur covered in bristles, but there was another, shorter paper that caught my eye. In December 2007 Nature printed a short communication on Indohyus, a small artiodactyl that seemed like a good candidate for the type of creature that whales evolved from. Paleontologists Hans Thewissen and Lisa Noelle Cooper explain the significance of Indohyus to whale evolution in this video;
There was something that bothered me about the systematic analysis of Indohyus, however. In the paper's phylogenetic tree…
laelaps | March 18, 2009
Sasha the Amur tiger (Panthera tigris altaica), photographed at the Bronx zoo.
laelaps | March 17, 2009
A white-tailed deer (Odocoileus virginianus), photographed in suburban New Jersey.
edyong | March 16, 2009Farmers and herders have known for centuries that herds of cattle have an uncanny ability to all point in the same direction. Last year, a group of German and Czech scientists discovered the reason behind this alignment - unbeknownst to humans for thousands of years of domestication, these animals have a magnetic sense. The team used Google Earth satellite images to rule out alternative explanations like the wind and the sun, and show that cow and deer herds tend to point towards magnetic north like a living, hoofed compass needle.
Now, the same team have found that high-voltage power lines…
laelaps | March 16, 2009
A visual summary of horse evolution published in 1921 (derived from an earlier diagram by W.D. Matthew). From An Introduction to the Study of Fossils.
When Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859 he faced a substantial problem. His evolutionary mechanism predicted that the fossil record would contain finely-graded transitions revealing what G.G. Simpson would later term the "tempo and mode" of evolution, yet such transitional creatures proved elusive. This was a major problem for paleontologists who believed that studies of European geology…