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AW: Cloudy With A Chance of New Papers



> Sepúlveda, J., Wendler, J.E., Summons, R.E., and Hinrichs,
> K.-U. 2009. Rapid resurgence of marine productivity after
> the Cretaceous-Paleogene mass extinction. Sciencce
> 326:129-132. doi: 10.1126/science.1176233.
> 
> ABSTRACT: The course of the biotic recovery after the
> impact-related disruption of photosynthesis and mass
> extinction event at the Cretaceous-Paleogene boundary has
> been intensely debated. The resurgence of marine primary
> production in the aftermath remains poorly constrained
> because of the paucity of fossil records tracing primary
> producers that lack skeletons. Here we present a
> high-resolution record of geochemical variation in the
> remarkably thick Fiskeler (also known as the Fish Clay)
> boundary layer at Kulstirenden, Denmark. Converging evidence
> from the stable isotopes of carbon and nitrogen and
> abundances of algal steranes and bacterial hopanes indicates
> that algal primary productivity was strongly reduced for
> only a brief period of possibly less than a century after
> the impact, followed by a rapid resurgence of carbon
> fixation and ecological reorganization.

That's quite quick indeed. Though a prolonged period of marine unproductivity 
would not have squared well with the fact that about half[*] the neornithine 
lineages that survived into the Pg were marine carnivores.

[*] If you do not believe in a deep-Mesozoic radiation of Neornithes - which is 
really not a very plausible scenario anymore if you're no BANDit. (The 
"deep-Mesozoic" scenario rests almost entirely on molecular data, which by now 
demands also things like a mid-late Cretaceous origin for Passeriformes and is 
really not very compatible with the Neornithes originating significantly 
*after* the Kimmeridgian... apomorphies do not simply establish themselves from 
one day to the next, after all.

The caveat of "almost" is _Gallornis straeleni_ being neornithine and the Lance 
Creek mandibular symphysis being a psittaciform more advanced than 
pseudasturids.)


> Elzanowski, A., and Stidham, T.A. 2009. Morphology of the
> quadrate in the Eocene anseriform Presbyornis and extant
> galloanserine birds. Journal of Morphology. doi:
> 10.1002/jmor.10799.
> 
> ABSTRACT: Despite the notoriety, phylogenetic significance,
> and large number of available specimens of Presbyornis, its
> cranial anatomy has never been studied in detail, and its
> quadrate has been partly misinterpreted. We studied five
> quadrates of Presbyornis that reveal features hitherto
> unknown in the anseriforms but otherwise present in
> galliforms. As a result, we analyzed the variable quadrate
> characters among all extant galloanserine families and
> identified synapomorphies and other morphological variation
> among the major galloanserine clades. In terms of quadrate
> morphology, Presbyornis is more plesiomorphic than any
> extant anseriform (including the Anhimidae) and shares
> ancestral galloanserine characters with the Megapodiidae,
> the earliest branch of extant galliforms. The quadrate's
> morphology is inconsistent with the currently accepted
> anseriform phylogeny that nests Presbyornis within the
> crown-group as a close relative of the Anatidae. The
> presbyornithid quadrates exhibit an unusual variation in the
> presence of a caudomedial pneumatic foramen, which we
> interpret as a result of a discontinuous change in the
> growth path of the pneumatic diverticulum. Another episode
> of morphogenetic imbalance in the growth path of the
> pneumatic diverticulum may have accompanied the
> disappearance of the basiorbital pneumatic foramen (along
> with the pneumatization of the pterygoid) at the origin of
> the crown-group anseriforms. This episode is marked by the
> striking individual variation in the presence and location
> of pneumatic foramina in the mandibular part of the quadrate
> in the Anhimidae.

Heh. Not now, but eventually I'll look this over and compare it with what has 
been published about the quadrate in diatrymas, pseudotooth birds and 
mihirungs. Note that the results are less controversial than they look at first 
glance: morphological conservativeness is no indicator of advanced age. (This 
means I'll probably have to include lithornithids in the comparison too - 
plesiomorphies are phylogenetically informative in the big scheme of things - 
all plesiomorphies started as apomorphies. The question is: "when did they 
start?", i.e. in the present case you need an outgroup which has a 
plesiomorphic condition in respect to _Presbyornis_)


Regards,

Eike