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Fwd: Blocked posting: Keichousaurus dimorphism + polycotylid tooth enamel

Still did not work. I'll fudge with some more misspellings...

---------- Forwarded message ----------
From: Ben Creisler <bcreisler@gmail.com>
Date: Mon, Sep 21, 2015 at 10:41 AM
Subject: Blocked posting: Keichousaurus dimorphism + polycotylid tooth enamel
To: dinosaur@usc.edu

Ben Creisler

I have not been able to get these new papers from last week to post on
the DML despite repeated tries over the past few days. I suspect the
spam filter is keying in
on a certain combination of words in the first paper. I'll try again
with deliberate
misspellings (add spaces to fix).

Ryosuke Motani, Da-yong Jiang, Olivier Rieppel, Yi-fan Xue & Andrea
Tintori (2015)
Adultsexratio, sexual dimorphism and sexual selection in a Mesozoic reptile.
Proceedings of the Royal Society B 2015 282 20151658
DOI: 10.1098/rspb.2015.1658

The evolutionary history of sexual selection in the geologic past is
poorly documented based on quantification, largely because of
difficulty in sexingfossil specimens. Even such essential ecological
parameters as adultsexratio (ASR) and sexual sizedimorphism (SSD) are
rarely quantified, despite their implications for sexual selection. To
enable their estimation, we propose a method for unbiased
sexidentification based on sexual shape dimorphism, using
size-independent principal components of phenotypic data. We applied
the method to test sexual selection in Keichousaurus hui, a Middle
Triassic (about 237 Ma) sauropterygian with an unusually large sample
size for a fossil reptile. Keichousaurus hui exhibitedSSD biased
towards males, as in the majority of extant reptiles, to a minor
degree (sexual dimorphism index −0.087). The ASR is about 60% females,
suggesting higher mortality of males over females. Both values support
sexual selection of males in this species. The method may be applied
to other fossil species. We also used the Gompertz allometric equation
to study the sexualshape dimorphism of K. hui and found that two
sexes had largely homogeneous phenotypes at birth except in the
humeral width, contrary to previous suggestions derived from the
standard allometric equation.


Jason J. Testin (2015)

Scanning electron microscope analysis of enamel microstructure in a
Polycotylid (Plesiosauria) from the Pierre Shale Group, South Dakota,

PeerJ PrePrints 3:e1716

doi: https://dx.doi.org/10.7287/peerj.preprints.1381v1


The teeth of polycotylid plesiosaurs are generally simple, cone
shaped, non-serrated and only slightly recurved without distinct
carinae. The surface of crowns are characterized by a series of
vertical enamel wrinkles that are more highly developed on the lingual
surface of the crown, and decrease in width and number toward the
apex. Some of the most promising research related to fossil dentition,
involves the analysis of surface and internal dental microstructure.
This study, is an attempt to examine and describe polycotylid dental
microstructure. It gives an overview of polycotylid plesiosaur enamel
and dentine microstructures using a scanning electron microscope.
Enamel type and structures vary, based on its position on the surface
of the crown, and its perceived strength requirements. The dentition
layer is “honeycombed” with tubular structure, possibly to provide
nourishment to fast growing crowns. The study of crown microstructures
may lead to a better understanding of polycotylid niche preference in
the late Cretaceous oceans.