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Bird bones cells surface area + next-generation paleornithology + worm lizards and end-Cretaceous mass extinction

Ben Creisler

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

John M. Rensberger , Ricardo N. Martínez
Bone Cells in Birds Show Exceptional Surface Area, a Characteristic
Tracing Back to Saurischian Dinosaurs of the Late Triassic.
PLoS ONE 10(4): e0119083.



Dinosaurs are unique among terrestrial tetrapods in their body sizes,
which range from less than 3 gm in hummingbirds to 70,000 kg or more
in sauropods. Studies of the microstructure of bone tissue have
indicated that large dinosaurs, once believed to be slow growing,
attained maturity at rates comparable to or greater than those of
large mammals. A number of structural criteria in bone tissue have
been used to assess differences in rates of osteogenesis in extinct
taxa, including counts of lines of arrested growth and the density of
vascular canals.

Methodology/Principal Findings

Here, we examine the density of the cytoplasmic surface of
bone-producing cells, a feature which may set an upper limit to the
rate of osteogenesis. Osteocyte lacunae and canaliculi, the cavities
in bone containing osteocytes and their extensions, were measured in
thin-sections of primary (woven and parallel fibered) bone in a
diversity of tetrapods. The results indicate that bone cell surfaces
are more densely organized in the Saurischia (extant birds, extinct
Mesozoic Theropoda and Sauropodomorpha) than in other tetrapods, a
result of denser branching of the cell extensions. The highest
postnatal growth rates among extant tetrapods occur in modern birds,
the only surviving saurischians, and the finding of exceptional
cytoplasmic surface area of the cells that produce bone in this group
suggests a relationship with bone growth rate. In support of this
relationship is finding the lowest cell surface density among the
saurischians examined in Dinornis, a member of a group of ratites that
evolved in New Zealand in isolation from mammalian predators and show
other evidence of lowered maturation rates.


Jamie R. Wood and Vanesa L. De Pietri (2015)
Next-generation paleornithology: Technological and methodological
advances allow new insights into the evolutionary and ecological
histories of living birds.
The Auk 132(2):486-506
doi: http://dx.doi.org/10.1642/AUK-14-257.1

Paleornithology, the study of fossil or ancient bird remains, provides
an important context for understanding the biology, evolutionary
history, and ecology of living birds. Recent technological and
methodological advances in the field of paleornithology have opened up
the potential to extract new pools of information from fossil bird
remains, and hence provide new insights into the histories of living
birds. Here we review some of these advances, covering aspects of
ancient DNA and protein analyses, sedimentary proxies for birds,
stable isotope analyses, coprolite analyses, high-resolution computed
tomography, paleoneurology, finite elements analysis, and
paleohistology. These new advances offer exciting prospects for the
future of paleornithology, but also reaffirm the importance of basic
fieldwork, exploration and the discovery of new fossil specimens,
museum archives in which to curate the specimens, and traditional
morphological approaches to studying the fossil remains.

Nicholas R. Longrich, Jakob Vinther, R. Alexander Pyron, Davide Pisani
& Jacques A. Gauthier (2015)
Biogeography of worm lizards (Amphisbaenia) driven by end-Cretaceous
mass extinction.
Proceedings of the Royal Society B: 2015 282 20143034
DOI: 10.1098/rspb.2014.3034.

Worm lizards (Amphisbaenia) are burrowing squamates that live as
subterranean predators. Their underground existence should limit
dispersal, yet they are widespread throughout the Americas, Europe and
Africa. This pattern was traditionally explained by continental drift,
but molecular clocks suggest a Cenozoic diversification, long after
the break-up of Pangaea, implying dispersal. Here, we describe
primitive amphisbaenians from the North American Palaeocene, including
the oldest known amphisbaenian, and provide new and older molecular
divergence estimates for the clade, showing that worm lizards
originated in North America, then radiated and dispersed in the
Palaeogene following the Cretaceous-Palaeogene (K-Pg) extinction. This
scenario implies at least three trans-oceanic dispersals: from North
America to Europe, from North America to Africa and from Africa to
South America. Amphisbaenians provide a striking case study in
biogeography, suggesting that the role of continental drift in
biogeography may be overstated. Instead, these patterns support Darwin
and Wallace's hypothesis that the geographical ranges of modern clades
result from dispersal, including oceanic rafting. Mass extinctions may
facilitate dispersal events by eliminating competitors and predators
that would otherwise hinder establishment of dispersing populations,
removing biotic barriers to dispersal.


End-Triassic Extinction

Sofie Lindström, Gunver Krarup Pedersen, Bas van de Schootbrugge,
Katrine Hovedskov Hansen, Natascha Kuhlmann, Jean Thein, Leif
Johansson, Henrik Ingermann Petersen, Carl Alwmark, Karen Dybkjær,
Rikke Weibel, Mikael Erlström, Lars Henrik Nielsen, Wolfgang Oschmann,
and Christian Tegner (2015)
Intense and widespread seismicity during the end-Triassic mass
extinction due to emplacement of a large igneous province.
Geology (advance online publication)

Multiple levels of earthquake-induced soft-sediment deformations
(seismites) are concentrated in the end-Triassic mass extinction
interval across Europe. The repetitive nature of the seismites rules
out an origin by an extraterrestrial impact. Instead, this intense
seismic activity is linked to the formation of the Central Atlantic
magmatic province (CAMP). By the earliest Jurassic the seismic
activity had ceased, while extrusive volcanism still continued and
biotic recovery was on its way. This suggests that magmatic intrusions
into sedimentary strata during early stages of CAMP formation caused
emission of gases (SO2, halocarbons, polycyclic aromatic hydrocarbons)
that may have played a major part in the biotic crisis.

Alex H. Kasprak, Julio Sepúlveda, Rosalyn Price-Waldman, Kenneth H.
Williford, Shane D. Schoepfer, James W. Haggart, Peter D. Ward, Roger
E. Summons, and Jessica H. Whiteside (2015)
Episodic photic zone euxinia in the northeastern Panthalassic Ocean
during the end-Triassic extinction.
Geology 43:. 307-310

Severe changes in ocean redox, nutrient cycling, and marine
productivity accompanied most Phanerozoic mass extinctions. However,
evidence for marine photic zone euxinia (PZE) as a globally important
extinction mechanism for the end-Triassic extinction (ETE) is
currently lacking. Fossil molecular (biomarker) and nitrogen isotopic
records from a sedimentary sequence in western Canada provide the
first conclusive evidence of PZE and disrupted biogeochemistry in
neritic waters of the Panthalassic Ocean during the end Triassic.
Increasing water-column stratification and deoxygenation across the
ETE led to PZE in the Early Jurassic, paralleled by a perturbed
nitrogen cycle and ecological turnovers among noncalcifying groups,
including eukaryotic algae and prokaryotic plankton. If such
conditions developed widely in the Panthalassic Ocean, PZE might have
been a potent mechanism for the ETE.