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Permian extinction acid rain and other non-dino papers

From: Ben Creisler

A number of recent non-dino papers that may be of interest:

Permian-Triassic extinction

Benjamin A. Black, Jean-François Lamarque, Christine A. Shields, Linda
T. Elkins-Tanton and Jeffrey T. Kiehl (2013)
Acid rain and ozone depletion from pulsed Siberian Traps magmatism.
Geology (advance online publication)
doi: 10.1130/G34875.1

The Siberian Traps flood basalts have been invoked as a trigger for
the catastrophic end-Permian mass extinction. Widespread aberrant
plant remains across the Permian-Triassic boundary provide evidence
that atmospheric stress contributed to the collapse in terrestrial
diversity. We used detailed estimates of magmatic degassing from the
Siberian Traps to complete the first three-dimensional global climate
modeling of atmospheric chemistry during eruption of a large igneous
province. Our results show that both strongly acidic rain and global
ozone collapse are possible transient consequences of episodic
pyroclastic volcanism and heating of volatile-rich Siberian country
rocks. We suggest that in conjunction with abrupt warming from
greenhouse gas emissions, these repeated, rapidly applied atmospheric
stresses directly linked Siberian magmatism to end-Permian ecological
failure on land. Our comprehensive modeling supplies the first picture
of the global distribution and severity of acid rain and ozone
depletion, providing testable predictions for the geography of
end-Permian environmental proxies.

News release:



Archosaur tooth development

Olivia Weeks, Bhart-Anjan S. Bhullar & Arhat Abzhanov (2013)
Molecular characterization of dental development in a toothed
archosaur, the American alligator Alligator mississippiensis.
Evolution & Development 15(6): 393–405
DOI: 10.1111/ede.12049

Few skeletal structures are as informative of the adaptive natural
history of vertebrate animals as their teeth. Understanding principles
of tooth development is key to understanding evolution of the
vertebrate dentition in general and emergence of multiple specialized
tooth types in particular. Morphological and phylogenetic
considerations suggest that crocodilians have the most primitive mode
of dentition within extant tetrapods, displaying simple, conical,
socketed, and continuously replaced teeth. Previous histological
studies revealed several dental fates, including functional and
non-functional teeth (rudiments) in the developing alligator embryos.
We analyze expression of key odontogenic regulators and markers to
better characterize the molecular patterning of crocodilian dentition.
Importantly, we demonstrate that the morphologically distinct tooth
types in Alligator mississippiensis are distinguishable by differences
in their developmental programs. We also present evidence showing that
tooth maturation is accompanied by dynamic gene expression in the
epithelial and mesenchymal cells involved in tooth development. Our
data reveal a significant morphological and genetic variation in early
dental fates. We believe that this underlying developmental variation
reflects modularity, or the ability of teeth to develop
semi-autonomously along the alligator jaw. We propose that such
modularity may have been a crucial for adaptive evolution within
Amniota, allowing for the progressive modifications to tooth
replacement, number, and shape.


Mesozoic lissamphibians

James D. Gardner & David G. DeMar Jr. (2013)
Mesozoic and Palaeocene lissamphibian assemblages of North America: a
comprehensive review.
Palaeobiodiversity and Palaeoenvironments (advance online publication)
DOI: 10.1007/s12549-013-0130-z

The Mesozoic and Palaeocene record of lissamphibians (i.e. anurans,
caudates, gymnophionans and albanerpetontids) in North America is
reviewed on the basis of over 400 published and unpublished
occurrences from 61 geological formations. The record is heavily
biased towards isolated bones, although some associated and
articulated skeletons and rare tracks and trackways are known. Most of
the localities are in the Western Interior: in central and southern
Alberta and southern Saskatchewan, Canada, extending southwards
through the USA and into northern Mexico. Outside of that region,
records are limited to one Late Cretaceous age formation in Baja
California and several Late Triassic and Cretaceous age formations in
the eastern USA. Putative lissamphibians have been reported from the
Late Triassic (middle Carnian and early Norian). Unambiguous
lissamphibians are known from the Early Jurassic
(Sinemurian–Pliensbachian), the Late Jurassic (Kimmeridgian–earliest
Tithonian), the basal Cretaceous (late Berriasian–Valanginian) and a
nearly continuous sequence extending from the Aptian through to the
terminal Palaeocene. The Early Jurassic (Sinemurian–Pliensbachian) of
Arizona documents the oldest global occurrences of an anuran (i.e.
crown frog) and a stem caecilian; the latter also is the only North
American fossil occurrence for Gymnophiona prior to the Quaternary.
Late Jurassic (Kimmeridgian–earliest Tithonian) age deposits in
Colorado, Utah and Wyoming contain a moderate diversity of anurans,
urodeles (i.e. crown salamanders) and possibly stem salamanders. A
basal Cretaceous locality (late Berriasian–Valanginian) in South
Dakota contains a urodele and the first North American occurrence for
Albanerpetontidae. Aptian/Albian age localities in Montana, Wyoming,
Texas and Oklahoma contain a mixture of anurans, urodeles and
albanerpetontids—that tripartite lissamphibian composition persists in
North America through the remainder of the Cretaceous and
intermittently through the Palaeocene. Most of the anurans are of
uncertain familial affinities. The urodeles contain a mixture of
extinct families (Scapherpetontidae and Batrachosauroididae) that were
prominent through the Cretaceous into the early Palaeogene, along with
the earliest appearances of several extant families, specifically
sirenids in the Santonian, amphiumids and proteids in the late
Maastrichtian and dicamptodontids and unequivocal cryptobranchids in
the late Palaeocene. The albanerpetontid genus Albanerpeton was
moderately diverse during the Cretaceous and Palaeocene, before
vanishing from the North American record near the end of the
Palaeocene. Temporal richness estimates of North American
lissamphibians were calculated based on taxic and minimum lineage
level occurrence data per 5 million year time interval beginning in
the Early Jurassic and though to the end of the Palaeocene. The
resulting richness curves demonstrate a general pattern of increasing
richness leading up to the Cretaceous-Palaeogene (K-Pg) boundary, with
peak values during the Campanian and Maastrichtian and a decline
thereafter. The latter part of that pattern suggests higher extinction
rates for lissamphibians across the K-Pg boundary compared to previous
estimates, which we attribute to our coarser temporal binning,
taxonomic additions and changes to some earlier taxonomic
identifications. Although the overall richness pattern may at least
partially reflect a true signal, it is heavily influenced by factors
such as taphonomy, temporal gaps, fossil sampling and publication
biases towards particular intervals and taxonomic groups; more
detailed studies of all major lissamphibian clades are needed to
corroborate these findings. This review highlights the strengths and
weaknesses of the Mesozoic and Palaeocene portion of the North
American lissamphibian record and provides a framework for future


Zbynek Rocek (2013)
Mesozoic and Tertiary Anura of Laurasia.
Palaeobiodiversity and Palaeoenvironments (advance online publication)
DOI: 10.1007/s12549-013-0131-y

Anurans of Laurasia have a long history that begins with the earliest
known anuran, Prosalirus, from the Early Jurassic of Arizona, USA. At
that time, western Laurasia (North America) was still connected with
Gondwana, so faunal interchange was still possible between those parts
of the former Pangean supercontinent. The anuran fossil record from
the Jurassic and Cretaceous of Laurasia is mainly represented by
disarticulated skeletal elements similar to those of Prosalirus (e.g.
amphicoelous vertebrae indicating the presence of continuous
notochord; ilia without dorsal crest and dorsal tubercle; small body
size). Because the morphology of the ilium, the most commonly
preserved element of Mesozoic anurans, superficially recalls that of
Recent Alytes, Bombina or Pelobates, Mesozoic anurans often were
assigned to discoglossids and pelobatids. The Cretaceous portion of
the Laurasian anuran record is marked by the appearance of procoelous
and opisthocoelous vertebrae, ilia bearing a dorsal crest and dorsal
tubercle (although such ilia may rarely be found as early as in the
Jurassic) and larger body sizes. Cretaceous anuran assemblages include
a mix of generalised taxa that are comparable to Recent basal anurans
and more specialised taxa lacking clear affinities with any extant
anurans. Some of these forms survived into the Paleocene, but in
general anuran faunas on all Laurasian continents were markedly
depleted in the Paleocene. Major groups of anurans appeared in the
Eocene. The early Miocene is the interval when Eurasian and American
herpetofaunas reached their peak taxonomic diversities. In the
Pliocene, some extant anuran species appeared, but at the same time
taxa that had been dominant throughout the Oligocene and Miocene (e.g.
Eopelobates, palaeobatrachids) became extinct during this interval or
during the subsequent Pleistocene glaciation. The brief
biochronological synopsis presented here is followed by a systematic
review of taxa with their diagnoses and published data on their
stratigraphic and geographic distributions.