HENRY

Said the little Eohippus,
“I am going to be a horse!
And on my middle finger-nails
To run my earthly course!
I’m going to have a flowing tail!
I’m going to have a mane!
I’m going to stand fourteen hands high
On the psychozoic plain!”

The Coryphodon was horrified,
The Dinoceras was shocked;
And they chased young Eohippus,
But he skipped away and mocked.
And they laughed enormous laughter,
And they groaned enormous groans,
And they bade young Eohippus
Go view his father’s bones.
Said they, “You always were as small
And mean as now we see,
And that’s conclusive evidence
That you’re always going to be.
What! Be a great, tall, handsome beast,
With hoofs to gallop on?
Why! You’d have to change your nature!”
Said the Loxolophodon.
They considered him disposed of,
And retired with gait serene;
That was the way they argued
In “the early Eocene.”

— Excerpted from: Similar Cases by Charlotte Perkins Gilman

Today, Nature has a new paper arguing that whales evolved from  Eocene-era artiodactyls in India:

Although the first ten million years of whale evolution are documented by a remarkable series of fossil skeletons, the link to the ancestor of cetaceans has been missing. It was known that whales are related to even-toed ungulates (artiodactyls), but until now no artiodactyls were morphologically close to early whales.

Here we show that the Eocene south Asian raoellid artiodactyls are the sister group to whales. The raoellid Indohyus is similar to whales, and unlike other artiodactyls, in the structure of its ears and premolars, in the density of its limb bones and in the stable-oxygen-isotope composition of its teeth. We also show that a major dietary change occurred during the transition from artiodactyls to whales and that raoellids were aquatic waders. This indicates that aquatic life in this lineage occurred before the origin of the order Cetacea.

Paper:  Whales originated from aquatic artiodactyls in the Eocene epoch of India, related news story

In short: John Scalzi takes a day trip to the Creationism Museum, and mercilessly mocks the stupidity therein. The photos he took are amazing, and includes what may just possibly be the coolest photo ever:

Image © John Scalzi 2007

One of the big debates in evolution has been about the diversification of life on earth and how rapidly this occured. Around 580 million years ago, organisms tended to be quite simple and single-celled. However, shortly afterwards, we start to see a rapid burst of diversification leading to precursors of all the complex organisms we know and love today (rapid, that is, geologically, so around 80 million years).

This “Cambrian explosion” has always been a huge area of debate. Did this explosion really occur, or is it an artifact of the fossil record and the difficulty of finding fossil single-celled organisms? If the explosion did occur, then we need to re-think the idea of gradualistic change which has been central to evolutionary theory since the modern synthesis in the 50s. More importantly what caused this explosion? increase in oxygen levels? development of bodyplan genes like Hox? the end of “Snowball Earth” caused by global warming? Increased ecological specialisation and the spread into niches by the organisms?

In short - we don’t have a clue. However, today in Science a paper provides strong evidence that something unusual did happen during the Cambrian. Mark Webster, in A Cambrian Peak in Morphological Variation Within Trilobite Species (doi:10.1126/science.1142964), compares differences in almost 1,000 species of trilobyte, and shows that prior to the explosion, the variation in trilobites was much greater than after the explosion.

Science Daily says:

(Webster) focused on actively evolving characteristics. The trilobite head alone, for example, displays many such characteristics. These include differences in ornamentation, number and placement of spines, and the shape of head segments. His findings: Overall, approximately 35 percent of the 982 trilobite species exhibited some variation in some aspect of their appearance that was evolving. But more than 70 percent of early and middle Cambrian species exhibited variation, while only 13 percent of later trilobite species did so.

Unfortunately, no explanations of what caused this, but give it time. This is fascinating stuff, I highly recommend keeping an eye on this work, and reading up about the debates. The wikipedia has a nice sampler and Stephen Jay Gould’s Wonderful Life is a must read.

How did Pterosaurs feed? (doi)

 Just because a component of an extinct animal resembles that of a living one does not necessarily imply that both were used for the same task. The lifestyles of pterosaurs, long-extinct flying reptiles that soared ancient skies above the dinosaurs, have long been the subject of debate among palaeontologists. Similarities between the skulls of living birds (black skimmers) that feed by skimming the water surface with their lower bill to catch small fish, and those of some pterosaurs have been used to argue that these ancient reptiles also fed in this way. We have addressed this question by measuring the drag experienced by model bird bills and pterosaur jaws and estimating how the energetic cost of feeding in this way would affect their ability to fly.

Interestingly, we found that the costs of flight while feeding are considerably higher for black skimmers than previously thought, and that feeding in this way would be excessively costly for the majority of pterosaurs. We also examined pterosaur skulls for specialised skimming adaptations like those seen in modern skimmers, but found that pterosaurs have few suitable adaptations for this lifestyle. Our results counter the idea that some pterosaurs commonly used skimming as a foraging method and illustrate the pitfalls involved in extrapolating from living to extinct forms using only their morphology.

It’s commonly accepted that feathers evolved as structures to keep dinosaurs warm, before becoming exapted for flight. However, a new specimen of Sinosauropteryx suggests that these proto-feathers are actually degraded collagen, and were probably the result of decomposed soft tissue surrounding them.

The paper is available here:  A new Chinese specimen indicates that ‘protofeathers’ in the Early Cretaceous theropod dinosaur Sinosauropteryx are degraded collagen fibres (DOI - may not be active yet)

Nature News has more information:

But the discovery does not mean that Sinosauropteryx and its kin were not the forefathers of birds. “There’s no need to panic,” says David Unwin, a dinosaur expert at the University of Leicester, UK. “This doesn’t in any way challenge the idea that dinosaurs had feathers and that dinosaurs gave rise to birds.” The real argument now is when in evolutionary history feathers started to emerge. “Things may be more complex than we thought,” he says.