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Dinosaur exaggerated structures + hummingbird taste buds + giant Eocene frog + talking turtles



Ben Creisler
bcreisler@gmail.com


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


Benjamin Borkovic & Anthony Russell (2014)
Sexual selection according to Darwin: A response to Padian and
Horner's interpretation.
Comptes Rendus Palevol (advance online publication)
DOI: 10.1016/j.crpv.2014.06.006
http://www.sciencedirect.com/science/article/pii/S1631068314001250



The interpretation of exaggerated structures in the vertebrate fossil
record has been hampered by disagreement over the definition of sexual
selection and how it relates to sexual dimorphism. Previous assertions
that Darwin placed a requirement of sexual dimorphism on sexual
selection are mistaken. Instead, Darwin describes variation within one
sex and the exertion of a struggle (expressed as intrasexual
competition, intersexual mate choice, or both) as the necessary
components of sexual selection. The use of structures by one sex to
attract mates or repel rivals for mates occurs independently of any
existing sexual differences. Differential mating success is also a
requirement of Darwinian sexual selection. Mutual sexual selection is
a legitimate concept that was described by Darwin. Sexual selection
remains a viable explanatory hypothesis for the presence of
exaggerated structures of extinct organisms and need not be dismissed
summarily, but should not be employed without support as a default
hypothesis.

***

Article by Padian and Horner

Kevin Padian & John R. Horner (2014)
The species recognition hypothesis explains exaggerated structures in
non-avialan dinosaurs better than sexual selection does.
Comptes Rendus Palevol 13(2): 97-107
DOI: 10.1016/j.crpv.2013.10.004
http://www.sciencedirect.com/science/article/pii/S1631068313001541



===



Ryan N. Felice (2014)
Coevolution of caudal skeleton and tail feathers in birds.
Journal of Morphology (advance online publication)
DOI: 10.1002/jmor.20321
http://onlinelibrary.wiley.com/doi/10.1002/jmor.20321/abstract

Birds are capable of a wide range of aerial locomotor behaviors in
part because of the derived structure and function of the avian tail.
The tail apparatus consists of a several mobile (free) caudal
vertebrae, a terminal skeletal element (the pygostyle), and an
articulated fan of tail feathers that may be spread or folded, as well
as muscular and fibroadipose structures that facilitate tail
movements. Morphological variation in both the tail fan and the caudal
skeleton that supports it are well documented. The structure of the
tail feathers and the pygostyle each evolve in response to functional
demands of differing locomotor behaviors. Here, I test whether the
integument and skeleton coevolve in this important locomotor module. I
quantified feather and skeletal morphology in a diverse sample of
waterbirds and shorebirds using a combination of linear and geometric
morphometrics. Covariation between tail fan shape and skeletal
morphology was then tested using phylogenetic comparative methods.
Pygostyle shape is found to be a good predictor of tail fan shape
(e.g., forked, graduated), supporting the hypothesis that the tail fan
and the tail skeleton have coevolved. This statistical relationship is
used to reconstruct feather morphology in an exemplar fossil
waterbird, Limnofregata azygosternon. Based on pygostyle morphology,
this taxon is likely to have exhibited a forked tail fan similar to
that of its extant sister clade Fregata, despite differing in inferred
ecology and other aspects of skeletal anatomy. These methods may be
useful in reconstructing rectricial morphology in other extinct birds
and thus assist in characterizing the evolution of flight control
surfaces in birds.

***



Theropods lacked sweet taste buds--how hummingbirds evolved to taste nectar

Maude W. Baldwin, Yasuka Toda, Tomoya Nakagita, Mary J. O'Connell,
Kirk C. Klasing, Takumi Misaka, Scott V. Edwards & Stephen D. Liberles
(2014)
Evolution of sweet taste perception in hummingbirds by transformation
of the ancestral umami receptor.
Science  345 (6199): 929-933
DOI: 10.1126/science.1255097
http://www.sciencemag.org/content/345/6199/929

Sensory systems define an animal's capacity for perception and can
evolve to promote survival in new environmental niches. We have
uncovered a noncanonical mechanism for sweet taste perception that
evolved in hummingbirds since their divergence from insectivorous
swifts, their closest relatives. We observed the widespread absence in
birds of an essential subunit (T1R2) of the only known vertebrate
sweet receptor, raising questions about how specialized nectar feeders
such as hummingbirds sense sugars. Receptor expression studies
revealed that the ancestral umami receptor (the T1R1-T1R3 heterodimer)
was repurposed in hummingbirds to function as a carbohydrate receptor.
Furthermore, the molecular recognition properties of T1R1-T1R3 guided
taste behavior in captive and wild hummingbirds. We propose that
changing taste receptor function enabled hummingbirds to perceive and
use nectar, facilitating the massive radiation of hummingbird species.


News stories:

http://phys.org/news/2014-08-hummingbirds-evolved-sweetness.html

http://newswatch.nationalgeographic.com/2014/08/21/scientists-solve-mystery-of-how-hummingbirds-taste-sweetness/

==

Giant Eocene frog from Chile (in Spanish)

http://www.latercera.com/noticia/tendencias/2014/08/659-591783-9-rana-mas-grande-del-mundo-vivio-en-magallanes-hace-40-millones-de-anos.shtml


original article:

Rodrigo A. Otero, Paulina Jimenez-Huidobro, Sergio Soto-Acuña &
Roberto E. Yury-Yáñez (2014)
Evidence of a giant helmeted frog (Australobatrachia,
Calyptocephalellidae) from Eocene levels of the Magallanes Basin,
southernmost Chile.
Journal of South American Earth Sciences 55: 133–140
DOI: 10.1016/j.jsames.2014.06.010
http://www.sciencedirect.com/science/article/pii/S0895981114000911

Highlights

Southernmost evidence of a fossil amphibian in the Eocene of South America.

Possibly, one of the largest frogs known to date.

First record of Eocene frogs in high latitudes of the Southern Hemisphere.

Abstract

The fossil record of frogs from South America has improved
dramatically in recent years. Here we describe a distal fragment of a
large-sized humerus recovered from the middle–to–upper Eocene of
southernmost Chile. The large distally located ventral condyle, and
the presence of two epicondyles (radial and ulnar) confirm its
identity as an anuran humerus. Comparisons with humeri from extant and
fossil South American neobatrachians suggest a phylogentic affinity to
calyptocephalellids (Australobatrachia). If correct, the new fossil
represents the first occurrence of this family in high latitudes of
South America and the first amphibian recovered from the Magallanes
(=Austral) Basin. The humerus also represents evidence for one of the
largest frogs known to date from anywhere in the world. Such
exceptional body size may reflect an unusually hot and damp
palaeoenvironment.

====

Turtle communication sounds

news stories:
http://www.pri.org/stories/2014-08-18/it-turns-out-turtles-have-something-say

http://www.calacademy.org/sciencetoday/talking-turtles/5516660/

http://phys.org/news/2014-08-scientists-turtles-brazilian-amazon.html

****
papers:

Camila Rudge Ferrara, Richard C. Vogt, Renata S. Sousa-Lima, Bruno
M.R. Tardio, and Virginia Campos Diniz Bernardes (2014)
Sound Communication and Social Behavior in an Amazonian River Turtle
(Podocnemis expansa).
Herpetologica 70(2):149-156. 2014
doi: http://dx.doi.org/10.1655/HERPETOLOGICA-D-13-00050R2
http://www.bioone.org/doi/abs/10.1655/HERPETOLOGICA-D-13-00050R2?journalCode=herp

The social behavior of turtles during the nesting season can be
attributed to a series of functions such as reducing predation,
increasing hatchling survivorship, and information exchange between
nesting females. However, the mechanism(s) used to remain in a group
during the different phases of nesting behavior has yet to be
explained. The objective of this study is to document the sounds
produced by Giant South American River Turtle, Podocnemis expansa,
during the nesting period, and identify how acoustic mechanisms might
facilitate social behavior and group aggregation during this period.
>From September 2009 to October 2011, the sound repertoire of P.
expansa was identified during the nesting period, which begins with
the migration of the turtles from the flooded forests to the nesting
beaches and terminates when the hatchlings emerge and the females
migrate with the hatchlings to the flooded forests. Sounds were
recorded when the turtles were active in different behavioral patterns
(1) migrating; (2) aggregating in front of the nesting beaches before
basking; (3) nesting at night; (4) waiting in the water without
nesting or after they have nested; and (5) waiting for the arrival of
the hatchlings. We observed six types of sound in the recordings of
turtles made during the nesting period. These data indicate that this
species is social, and that sound plays an important role in the
synchronization of the activities of groups during the nesting season.


***

Camila R. Ferrara, Jeanne A. Mortimer, and Richard C. Vogt (2014)
First Evidence that Hatchlings of Chelonia mydas Emit Sounds.
Copeia 2014(2):245-247
doi: http://dx.doi.org/10.1643/CE-13-087
http://www.bioone.org/doi/abs/10.1643/CE-13-087

Hatchling green turtles (Chelonia mydas) were recorded emitting sounds
at Ascension Island, South Atlantic Ocean, on 19 May 1978. Analysis
revealed that the 70 sounds recorded could be separated into four
sound categories. The sounds were complex and characteristic of a
contact call, and were similar to those recently reported in other
species of aquatic turtles. The relationship between the structure and
frequency of the sounds and levels of predation on turtle eggs and
hatchlings, especially by ghost crabs (Ocypode spp.), warrants further
study.