A sunburn for Gorgon

Breaking news from the latest Permian…

The end-Permian mass extinction, apart from being the largest extinction event in history, is one of the earth sciences’ greatest whodunits. Once thought to be a consequence of plate tectonic movement, it is now widely held that the main driver of the extinction was the magmatic event associated with the Siberian Traps large igneous province (but see this study from a couple years ago for an interesting wrinkle).

Now there’s this, from Science Advances; namely, “[in]direct evidence” of elevated UV radiation at the Permo-Triassic (P/Tr) boundary in Tibet. The evidence comes from pollen grains, which show a spike in the prevalence of ultraviolet absorbing compounds near the P/Tr boundary. This, in the words of the abstract, “suggest[s] a close temporal link between large-scale volcanic eruptions, global carbon and mercury cycle perturbations, and ozone layer depletion.” And this in turn supplies another potential cause of the environmental deterioration implicated in the land extinctions.

The article is open access, so you can read the whole thing by following the link, above.

A new addition to the stem bird aviary

An interesting article just appeared in Nature Ecology & Evolution. Here’s the short version. Researchers found a stem bird (a bird occupying an intermediate position in the phylogenetic tree between the oldest bird, Archaeopteryx, and the “true birds”) that helps bridge a large morphological gap in the fossil record. There’s a surface-level irony here given that Archaeopteryx is the OG intermediate form or “missing link.” But whenever you close a morphological gap you also create two new ones…

Anyway, the newly described bird, Cratonavis, is a mosaic of avian and non-avian characters, combining a relatively bird-like body with a more classically theropod-like skull. Don’t believe the news reports describing it as “bizarre”: I’m not even sure you could call it “unexpected.” Still, it is an interesting addition to a rapidly-filling aviary of stem birds. (Here’s a link to a non-technical write-up for anyone blocked by the paywall.)