mammals
laelaps | April 26, 2009
A cheetah (Acinonyx jubatus) breaking into a run, photographed at the National Zoo.
laelaps | April 25, 2009
Rokan the Sumatran tiger (Panthera tigris sumatrae), photographed at the National Zoo.
laelaps | April 24, 2009
A giant anteater (Myrmecophaga tridactyla), photographed at the National Zoo.
laelaps | April 22, 2009Of all the evolutionary transitions that have ever taken place few have received as much attention as the origin of whales. (See here, here, here, here,and here for a few of my posts on the subject.) The story of how terrestrial hoofed mammals gave rise to the exclusively aquatic leviathans has been highlighted in headlines over and over again, but other marine mammals have not received the same amount of public attention. In the case of pinnipeds (seals, sea lions, and walruses) this may be at least partially due to the fact that their origins have been difficult to tease out.
It has long…
edyong | April 22, 2009
Seals and sea-lions gracefully careen through today's oceans with the help of legs that have become wide, flat flippers. But it was not always this way. Seals evolved from carnivorous ancestors that walked on land with sturdy legs; only later did these evolve into the flippers that the family is known for. Now, a beautifully new fossil called Puijila illustrates just what such early steps in seal evolution looked like. With four legs and a long tail, it must have resembled a large otter but it was, in fact, a walking seal.
Natalia Rybczynski unearthed the new animal at Devon Island, Canada…
laelaps | April 20, 2009
A giraffe, photographed at the Bronx zoo.
Why do giraffes have long necks? We know that modern giraffes must have evolved gradually, but figuring out what selection pressures influenced giraffe evolution is another story altogether. One of the most popular recent explanations is that giraffes have long necks as a result of sexual selection.
The "necks for sex" hypothesis is primarily inspired by the contests between male giraffes. In these duels the males stand side by side and whack each other with their necks and ossicones ("horns"). This can be seen in the video below;
What does this…
laelaps | April 19, 2009A few photos from yesterday afternoon;
A raccoon skull I found on a hike yesterday. It is now a part of my bone collection.
A white-tailed deer leg found on the same hike. It was a little gooey still so I decided to leave it alone.
Hayley, an Australian cattle dog belonging to my in-laws.
I do not know what kind they were, but there was an explosion of these flowers along the trail.
Three new foster kittens. Caption this one as you like.
laelaps | April 15, 2009
A somewhat thrown-together illustration about camel evolution. The series should be read C-D-E-F for the evolution of the forelimb and G-H-I-J for the hind limb. Compare this to more famous diagrams of horse evolution, like this one. From A text-book of geology for universities.
For more than a century fossil horses have stood as some of the most iconic examples of evolutionary change. From about 1870 onward it seemed that the ancestry of modern horses was represented by a nearly complete fossil series, but this is not to say that we have always perfectly understood these remains. Even…
laelaps | April 15, 2009
Rokan the Sumatran tiger (Panthera tigris sumatrae). photographed at the National Zoo.
laelaps | April 14, 2009Evolutionary anthropology is a subject that has traditionally been dominated by a focus on males, or at least "masculine" behaviors like hunting. The most popular images of our own ancestors have often been of a group of males setting out for a hunt or crouched over a freshly-killed carcass. It is as if our evolution was driven by male ambition. Such tendencies have triggered some backlash, from the relatively absurd (i.e. the aquatic ape hypothesis) to more reasoned critiques (i.e. Woman the Gatherer), but it is clear that our understanding of our own history is most certainly biased by…
laelaps | April 14, 2009
The skeletons of a few apes (from the right: Pan troglodytes, Gorilla gorilla, and Homo sapiens), photographed at the National Museum of Natural History.
laelaps | April 12, 2009Ah, Easter. The holiday when many people ask "Wait, bunnies don't lay eggs. What gives?" Not everyone is a fan of the Easter Bunny, though. In Australia rabbits are a major pest and some have attempted to raise awareness of a local, endangered marsupial called the bilby by offering it as an alternative Easter mascot.
A greater bilby (Macrotis lagotis).
Personally, I think another Australian mammal is a better fit as an Easter mascot. The platypus (Ornithorhynchus anatinus) is a monotreme, or one of the few mammals in the world that lays eggs. I would much prefer an Easter platypus to an…