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Non-dino papers: Femur microanatomy; feather color and structure; neognath pneumaticity

From: Ben Creisler

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

Sonia Quemeneur, Vivian de Buffrénil & Michel Laurin (2013)
Microanatomy of the amniote femur and inference of lifestyle in limbed
Biological Journal of the Linnean Society (advance online publication)
DOI: 10.1111/bij.12066

The femoral microanatomy of 155 species of extant amniotes (57 species
of mammals, 15 species of turtles, 56 species of lepidosaurs, and 27
species of birds) of known lifestyle is studied to demonstrate a
possible link between some basic parameters of bone structure and
specific lifestyles, as well as phylogenetic relationships between
taxa. Squared change parsimony with random taxon reshuffling and
pairwise comparisons reveal that most compactness and size parameters
exhibit both phylogenetic and ecological signals. A discriminant
analysis produces several inference models, including a ternary model
(aquatic, amphibious, terrestrial) that yield the correct lifestyle in
88% of the cases. These models are used to infer the lifestyle of
three extinct Permian temnospondyls: Eryops megacephalus, Acheloma
dunni, and Trimerorhachis insignis.


Alexandre Roulin, Jule Mangels, Kazumasa Wakamatsu &, Thomas Bachmann (2013)
Sexually dimorphic melanin-based colour polymorphism, feather melanin
content, and wing feather structure in the barn owl (Tyto alba).
Biological Journal of the Linnean Society (advance online publication)
DOI: 10.1111/bij.12078

Feathers confer protection against biophysical agents and determine
flying ability. The geometry and arrangement of the barbs, together
with the keratin and pigments deposited in the feathers, determine the
mechanical stability of the vane, and its stiffness and resistance to
abrasive agents. In colour-polymorphic species, individuals display
alternative colour morphs, which can be associated with different
foraging strategies. Each morph may therefore require specific flying
abilities, and their feathers may be exposed to different abrasive
agents. Feathers of differently coloured individuals may thus have a
specific structure, and colour pigments may help resist abrasive
agents and improve stiffness. We examined these predictions in the
barn owl (Tyto alba), a species for which the ventral body side varies
from white to dark reddish pheomelanic, and in the number and size of
black spots located at the tip of the feathers. White and reddish
birds show different foraging strategies, and the size of black
feather spots is associated with several phenotypic attributes. We
found that birds displaying a darker reddish coloration on the ventral
body side deposit more melanin pigments in their remiges, which also
have fewer barbs. This suggests that wear resistance increases with
darkness, whereas feathers of lighter coloured birds may bend less
easily. Accordingly, individuals displaying a lighter reddish
coloration on the ventral body side, and those displaying larger black
spots, displayed more black transverse bars on their remiges: as
larger-spotted individuals are heavier and longer-winged birds also
have more transverse bars, these bars may reduce feather bending when
flying. We conclude that differently coloured individuals produce wing
feathers of different strengths to adopt alternative behavioural and
life history strategies.


Sarah C. Gutzwiller, Anne Su & Patrick M. O'Connor (2013)
Postcranial pneumaticity and bone structure in two clades of neognath birds.
The Anatomical Record (advance online publication)
DOI: 10.1002/ar.22691

Most living birds exhibit some degree of postcranial skeletal
pneumaticity, aeration of the postcranial skeleton by pulmonary air
sacs and/or directly from the lungs. The extent of pneumaticity varies
greatly, ranging from taxa that are completely apneumatic to those
with air filling most of the postcranial skeleton. This study examined
the influence of skeletal pneumatization on bone structural parameters
in a sample of two size- and foraging-style diverse (e.g., subsurface
diving vs. soaring specialists) clades of neognath birds
(charadriiforms and pelecaniforms). Cortical bone thickness and
trabecular bone volume fraction were assessed in one cervical and one
thoracic vertebra in each of three pelecaniform and four charadriiform
species. Results for pelecaniforms indicate that specialized
subsurface dive foragers (e.g., the apneumatic anhinga) have thicker
cortical bone and a higher trabecular bone volume fraction than their
non-diving clademates. Conversely, the large-bodied, extremely
pneumatic brown pelican (Pelecanus occidentalis) exhibits thinner
cortical bone and a lower trabecular bone volume fraction. Such
patterns in bone structural parameters are here interpreted to pertain
to decreased buoyancy in birds specialized in subsurface dive foraging
and decreased skeletal density (at the whole bone level) in birds of
larger body size. The potential to differentially pneumatize the
postcranial skeleton and alter bone structure may have played a role
in relaxing constraints on body size evolution and/or habitat
exploitation during the course of avian evolution. Notably, similar
patterns were not observed within the equally diverse charadriiforms,
suggesting that the relationship between pneumaticity and bone
structure is variable among different clades of neognath birds.