Monday Science Links

This week's sciency goodness:

• Brian at Laelaps looks at horse evolution: As I have mentioned previously many late 19th and early 20th century paleontologists were reluctant to accept natural selection as the primary mechanism of evolution. Competing mechanisms like neo-Lamarckism and orthogenesis were more popular. This was at least partially due to the sparse nature of the fossil record; there were gaps between groups that seemed to require some sort of jump or mechanism more able to produce rapid change than selection on variation. These competing mechanisms were also more easily squared with religious views, for evolution seemed less threatening if it had a direction (i.e. fore-ordained end points various lineages were striving towards).


• Darren at Tetrapod Zoology ends his month of dinosaurs with a look at pterosaurs and birds: It has often been suggested that pterosaur disparity was correlated with the rise of birds. Perhaps, as birds began moving into habitats previously occupied by pterosaurs, pterosaurs were forced to adapt or die. Unwin (2006) proposed that, during the Cretaceous, the niches left vacant as pterosaur species went extinct were not occupied by new pterosaur species, as they were before, but (opportunistically) by birds instead: 'Ultimately, the effect of this process was to leave pterosaurs adapted to a relatively narrow range of specialist lifestyles' (Unwin 2006, p. 264)... Dyke et al. (2009) set out to test this model of waning pterosaur diversity. They report that Cretaceous pterosaurs are more morphologically disparate than older forms, not less so. This suggests, they conclude, that Cretaceous pterosaur evolution was not constrained by birds, and that new morphologies were appearing among pterosaurs during this time.


• PZ at Pharyngula posts on some stunning octopods from the Cretaceous: Several new and spectacular cephalopod fossils from 95 million years ago have been found in Lebanon. "Spectacular" is not hyperbole — these specimens have wonderfully well-preserved soft parts, mineralized in fine-grained calcium phosphate, and you can see…well, take a look. The arms (all eight of them) are intact, right down to the suckers; muscles and gills are preserved; the animal has an ink sac; there is a shell gland a chitinous chunk of vestigial shell called the gladius. In some of the specimens, even membranous fins can be found on the mantle. This stuff is amazing — I've seen some other fossil cephalopods before, but usually they're a squid-shaped smudge of a dark smear on rock. These are detailed.


• Brian at Laelaps again (it's a good week for him) on a hyptothesis that spiny-backs showed dinosaurs were on the way out (?): Perhaps the concept of evolutionary senescence was attractive because it appeared to be useful in identifying patterns of evolution and extinction in the fossil record. As a summary of the "Decline and Senescence of Groups" in the 1911 edition of the Encyclopedia Britannica noted "Periods of gradual evolution and of efflorescence may be followed by stationary or senescent conditions." Why should this be so? Why did fossil groups seem to undergo quick periods of evolution but then undergo little change or fail to generate further disparity in form? Evolutionary senescence appeared to be as good an explanation as any, even if its mechanism was impossible to know for certain .


• An underwater volcano erupts near Tonga, and the Big Picture has it: Scientists sailed out to have a closer look at the eruptions of an undersea volcano off the coast of Tonga in the South Pacific Ocean today. Tonga's head geologist, Kelepi Mafi, said there was no apparent danger to residents of Nuku'alofa and others living on the main island of Tongatapu. Officials also said it may be related to a quake with a magnitude of 4.4 which struck last March 13 around 35 kilometers from the capital at a depth of nearly 150 kilometres. (I know this is an off-day posting, but really, thought the images were worth it.

Enjoy!