Cetacean Palaeobiology The archaeocetes are a paraphyletic group of primitive cetaceans that include the earliest, terrestrial 'whales'. The group consists of six families: Pakicetidae, Ambulocetidae, Remingtonocetidae, Protocetidae, Basilosauridae and Dorudontidae, although some scientists include the latter two in one single family Basilosauridae. The graph below shows, how these families are related to each other. Cetacean Evolution In order to understand the biology of the archaeocetes, it is important to first consider what sort of terrestrial animals cetaceans originally evolved from. The relations of early whales (archaeocetes) to artiodactyls and the two extant groups, odontoceti and mysticeti. But in 1994, Dan Graur and Desmond Higgins, two scientists working on cetacean gene sequences dropped a bombshell. Astragali of the Eocene protocetids Rodhocetus balochistanensis (left) and Artiocetus clavis (right), as compared to that of the pronghorn Antilocapra americana (centre). Protocetidae (Stromer 1908)
Cretaceous Birds Survived Mass Extinction By Eating Seeds Variations in teeth shape – what’s called dental disparity – is a proxy for ecological stability. Decreases in variation would indicate ecosystem decline, but if differences between teeth were maintained over time, that would suggest a rich, stable ecosystem. To understand what bird-like dinosaurs were up to at the end-Cretaceous boundary, a team led by Derek Larson from the University of Toronto analyzed 3,104 maniraptoran teeth unearthed throughout western North America. These fossils represent four maniraptoran groups spanning 18 million years of the Cretaceous. Representative teeth from the four groups of bird-like dinosaurs, with enlarged images of tooth serrations. Tooth shape disparity showed no major decline leading up to the mass extinction event within any of the groups studied, but this prolonged period of ecological stability was followed by the sudden extinction of many bird-like dinosaurs. Photo Gallery
"Evolution is Fact" When Did Dino's Sprout Wings? Dinosaurs still walk—and fly—among us: We call them birds. Most paleontologists think birds descended from a group of winged dinosaurs, and thus dinos never went completely extinct. But where did the wings come from? New discoveries from Canada suggest that both wings and feathers arose earlier in dinosaur evolution than previously thought, possibly to attract members of the opposite sex or to protect hatching baby dinos. Although many details of the origins of birds and winged flight are fiercely debated, researchers generally agree that birds belong to a group of dinosaurs called maniraptorans, some of which had feathers and wings and could probably fly.Microraptor, discovered in China, is a leading example of such a dino flyer. But the restriction of these discoveries to such a limited geographical area has left a gap in the fossil record, leaving paleontologists to wonder whether wings and feathers might have evolved in dinosaur groups older than the maniraptorans.
A New Thermodynamics Theory of the Origin of Life Why does life exist? Popular hypotheses credit a primordial soup, a bolt of lightning and a colossal stroke of luck. But if a provocative new theory is correct, luck may have little to do with it. Instead, according to the physicist proposing the idea, the origin and subsequent evolution of life follow from the fundamental laws of nature and “should be as unsurprising as rocks rolling downhill.” From the standpoint of physics, there is one essential difference between living things and inanimate clumps of carbon atoms: The former tend to be much better at capturing energy from their environment and dissipating that energy as heat. Kristian Peters Cells from the moss Plagiomnium affine with visible chloroplasts, organelles that conduct photosynthesis by capturing sunlight. “You start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant,” England said. England’s theoretical results are generally considered valid.
How Dinosaurs Shrank and Became Birds From Quanta Magazine (find original story here). Modern birds descended from a group of two-legged dinosaurs known as theropods, whose members include the towering Tyrannosaurus rex and the smaller velociraptors. The theropods most closely related to avians generally weighed between 100 and 500 pounds — giants compared to most modern birds — and they had large snouts, big teeth, and not much between the ears. For decades, paleontologists’ only fossil link between birds and dinosaurs was archaeopteryx, a hybrid creature with feathered wings but with the teeth and long bony tail of a dinosaur. To explain this miraculous metamorphosis, scientists evoked a theory often referred to as “hopeful monsters.” But it has become increasingly clear that the story of how dinosaurs begat birds is much more subtle. A Phantom Leap In the 1990s, an influx of new dinosaur fossils from China revealed a feathery surprise. Yet once those avian features were in place, birds took off.
Sea anemone: genetically ½ animal, ½ plant A team led by evolutionary and developmental biologist Ulrich Technau at the University of Vienna has discovered that sea anemones display a genomic landscape with a complexity of regulatory elements similar to that of fruit flies or other animal model systems. This suggests that this principle of gene regulation is already 600 million years old and dates back to the common ancestor of human, fly and sea anemone. On the other hand, sea anemones are more similar to plants rather to vertebrates or insects in their regulation of gene expression by short regulatory RNAs called microRNAs. These surprising evolutionary findings are published in two articles in the journal Genome Research. Our appearance, the shape we have and how our body works is, in addition to environmental influences, largely the result of the action of our genes. Simple organism with complex gene content Gene regulation comparable to higher animal model systems MicroRNAs are important for developmental processes in human…
"Dawn" bird oldest found bird A prehistoric beast the size of a pheasant has become a contender for the title of oldest bird to stalk the Earth. The small, feathered "Dawn" bird lived around 160m years ago, about 10m years before Archaeopteryx, which holds the official title of the earliest bird known to science. The new species, which scientists have named Aurornis xui, had claws and a long tail, with front and hind legs similar to those of Archaeopteryx, but some features of its bones were more primitive. It measured 50cm from its beak to the tip of its tail. Encased in sedimentary rock, the fossil preserved traces of downy feathers along the animal's tail, neck and chest, but the absence of larger feathers suggests it was not able to fly. When scientists reconstructed the evolutionary tree of similar beasts using measurements from their skeletons, A xui appeared on the bird lineage, but closer to the base of the tree than Archaeopteryx. Archaeopteryx holds a prized position in evolutionary history.