(via Giordano Cipriani)
(Also on Sb)
Congratulations to Life Before the Dinosaurs for reaching the one year mark. He’s aged before my eyes — now he’s 8.
He has good taste, too. He lists his favorite fossils, and puts Anomalocaris in first place.
No, dinosaurs did not fart themselves to death. This is what happens when you get your information from Fox News.
Dinosaurs may have farted themselves to extinction, according to a new study from British scientists.
The researchers calculated that the prehistoric beasts pumped out more than 520 million tons (472 million tonnes) of methane a year — enough to warm the planet and hasten their own eventual demise.
Until now, an asteroid strike and volcanic activity around 65 million years ago had seemed the most likely cause of their extinction.
So I read the paper. The researchers didn’t say that at all. There is nothing about extinction in the paper; it would have been ridiculous and I was prepared to dismiss such a claim without even reading the paper (the Jurassic lasted 55 million years, the Cretaceous 80 million, with dinosaurs farting away throughout). But the paper makes no such claim, instead suggesting that the mass of herbivores during the Mesozoic would have made a substantial, but stable, contribution of greenhouse gases to the atmosphere that may have been partially responsible for the warmer, moister climate of the era and the greater primary production.
Take together, our calculations suggest that sauropod dinosaurs could potentially have played a significant role in influencing climate through their methane emissions. Even if our 520 Tg estimate is overstated by a factor of 2, it suggests that global methane emission from Mesozoic sauropods alone was capable of sustaining an atmospheric methane mixing ratio of 1 to 2 ppm. Equally, our estimate may be understated by a similar factor, (i.e. possibly supporting 4 ppm methane). In the warm wet Mesozoic world, wetlands, forest fires, and leaking gasfields may have added around another 4 ppm methane to the air. Thus, a Mesozoic methane mixing ratio of 6–8 ppm seems very plausible.
The Mesozoic trend to sauropod gigantism led to the evolution of immense microbial vats unequalled in modern land animals. Methane was probably important in Mesozoic greenhouse warming. Our simple proof-of-concept model suggests greenhouse warming by sauropod megaherbivores could have been significant in sustaining warm climates. Although dinosaurs are unique in the large body sizes they achieved, there may have been other occasions in the past where animal-produced methane contributed substantially to global environmental gas composition: for example, it has been speculated that the extinction of megafauna coincident with human colonisation of the Americas may be related to a reduction of atmospheric methane levels.
See? A reasonable conclusion, not Fox News sensationalism.
But here’s the information you really wanted to know: they estimate that a medium-sized sauropod would have farted out 2675 liters of gas a day. Happy now? Impressed?
Wilkinson DM, Nisbet EG, Ruxton GD (2012) Could methane produced by sauropod dinosaurs have helped drive Mesozoic climate warmth? Current Biology 22(9):292-293.
Vertebrates are modified segmented worms; that is, their body plan is made up of sequentially repeated units, most apparent in skeletal structures like the vertebrae.
Arthropods are also modified segmented worms. Look at a larval fly, for instance, and you can see they are made up of rings stacked together.
So here’s a simple and obvious question: can we infer that the last common ancestor of vertebrates and arthropods was also a segmented worm? That is, is segmentation a common ancestral trait, or did arthropods and vertebrates invent it independently? At first thought, you might assume they are: it’s a complex trait shared by two taxa, so the simplest assumption is that both groups inherited it from their common ancestor (making it a synapomorphy), but there are also substantial differences in the mechanism of segmentation, so it’s possible that this trait wasn’t present in the common ancestor (making it a homoplasy).