[dinosaur] Feather evolution + ostrich leg tendons + tetrapod sesamoid bones

Ben Creisler
[email protected]

Some recent papers:


W. Scott Persons & Philip J. Currie (2019)
Feather evolution exemplifies sexually selected bridges across the adaptive
landscape.
Evolution (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_evo.13795&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3ZivMYqXBsz91334rXBIFdcIdsD94gL0DkaGk2ilwRw&s=f6OxV5_ItgzTgh_S9CcRP2qHaFlNRWQY0NJWkpCDJOw&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1111_evo.13795&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3ZivMYqXBsz91334rXBIFdcIdsD94gL0DkaGk2ilwRw&s=-Fyq_u8VjhBez3n3kndiwlXg7ex-L-cUCYYfQH_e7w0&e= 


Over the last two decades, paleontologists have pieced together the early
evolutionary history of feathers. Simple hair‐like feathers served as
insulating pelage, but the first feathers with complex branching structures
and a plainer form evolved for the purpose of sexual display. The evolution
of these complex display feathers was essential to the later evolution of
flight. Feathers illustrate how sexual selection can generate complex novel
phenotypes, which are then available for natural selection to modify and
direct toward novel functions. In the longstanding metaphor of the adaptive
landscape, sexual selection is a means by which lineages resting on one
adaptive peak may gradually bridge a gap to another peak, without the
landscape itself being first altered by environmental changes.

====

Sarah B. Channon, Iain S. Young, Beckie Cordner & Nicola Swann (2019)
Ontogenetic scaling of pelvic limb muscles, tendons and locomotor economy
in the Ostrich (Struthio camelus).
Journal of Experimental Biology : jeb.182741 (advance online publication)
doi: 10.1242/jeb.182741
https://urldefense.proofpoint.com/v2/url?u=https-3A__jeb.biologists.org_content_early_2019_07_26_jeb.182741&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3ZivMYqXBsz91334rXBIFdcIdsD94gL0DkaGk2ilwRw&s=PFOhSJbvMq7Dcd3pvmWVLAgu91CzyRVTD1VJ92ovDZQ&e= 


In rapidly growing animals there are numerous selective pressures and
developmental constraints underpinning the ontogenetic development of
muscle-tendon morphology and mechanical properties. Muscle force generating
capacity, tendon stiffness, elastic energy storage capacity and efficiency
were calculated from muscle and tendon morphological parameters and
in-vitro tendon mechanical properties, obtained from a growth series of
ostrich cadavers. Ontogenetic scaling relationships were established using
reduced major axis regression analysis. Ostrich pelvic limb muscle mass and
cross-sectional area broadly scaled with positive allometry, indicating
maintained or relatively greater capacity for maximum isometric force
generation in bigger animals. The length of distal limb tendons was found
to scale with positive allometry in several tendons associated with
antigravity support and elastic energy storage during locomotion. Distal
limb tendon stiffness scaled with negative allometry with respect to body
mass, with tendons being relatively more compliant in larger birds. Tendon
material properties also appeared to be size-dependent, suggesting the
relative increased compliance of tendons in larger ostriches is due in part
to compensatory distortions in tendon material properties during maturation
and development, not simply from ontogenetic changes in tendon geometry.
Our results suggest that the previously reported increase in locomotor
economy through ontogeny in the ostrich is likely due to greater potential
for elastic energy storage with increasing body size. In fact, the rate of
this increase may be somewhat greater than the conservative predictions of
previous studies thus illustrating the biological importance of elastic
tendon structures in adult ostriches.

======


Virginia Abdala, Miriam C. Vera, Lucila I. Amador, Gabriela Fontanarrosa,
Jessica Fratani & María L. Ponssa (2019)
Sesamoids in tetrapods: the origin of new skeletal morphologies.
Biological Reviews (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_brv.12546&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3ZivMYqXBsz91334rXBIFdcIdsD94gL0DkaGk2ilwRw&s=GGXe7Tz7iJb1E7Qt-aCk3Ant5lvg_enAUCGksai1bzc&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1111_brv.12546&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3ZivMYqXBsz91334rXBIFdcIdsD94gL0DkaGk2ilwRw&s=NOy74g0B6v6zq1ozR-rYdeU5FzVxN2TucKipTG6RgN0&e= 

Along with supernumerary bones, sesamoids, defined as any organized
intratendinous/intraligamentous structure, including those composed of
fibrocartilage, adjacent to an articulation or joint, have been frequently
considered as enigmatic structures associated with the joints of the
skeletal system of vertebrates. This review allows us to propose a dynamic
model to account for part of skeletal phenotypic diversity: during
evolution, sesamoids can become displaced, attaching to and detaching from
the long bone epiphyses and diaphysis. Epiphyses, apophyses and detached
sesamoids are able to transform into each other, contributing to the
phenotypic variability of the tetrapod skeleton. This dynamic model is a
new paradigm to delineate the contribution of sesamoids to skeletal
diversity. Herein, we first present a historical approach to the study of
sesamoids, discussing the genetic versus epigenetic theories of their
genesis and growth. Second, we construct a dynamic model. Third, we present
a summary of literature on sesamoids of the main groups of tetrapods,
including veterinary and human clinical contributions, which are the
best‐studied aspects of sesamoids in recent decades. Finally, we discuss
the identity of certain structures that have been labelled as sesamoids
despite insufficient formal testing of homology. We also propose a new
definition to help the identification of sesamoids in general. This review
is particularly timely, given the recent increasing interest and research
activity into the developmental biology and mechanics of sesamoids. With
this updated and integrative discussion, we hope to pave the way to improve
the understanding of sesamoid biology and evolution.

===

Free pdf:

Richard T. Bex,  Lisa Lundgren &  Kent J. Crippen (2019)
Scientific Twitter: The flow of paleontological communication across a
topic network
PLoS ONE 14(7): e0219688.
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1371_journal.pone.0219688&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3ZivMYqXBsz91334rXBIFdcIdsD94gL0DkaGk2ilwRw&s=GpjTiTxlIhYT5Uzu526jVdvWtHkVbp9ebG2THCJiLZU&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__journals.plos.org_plosone_article-3Fid-3D10.1371_journal.pone.0219688&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=3ZivMYqXBsz91334rXBIFdcIdsD94gL0DkaGk2ilwRw&s=fxM1zqN7Zq1t8g5pbTLbr16ak8K_7LLxJ7etnpcbeOM&e= 


The field of paleontology, which is based principally on observations of
the natural world, includes an active community that is engaged across
multiple social media platforms, consisting of museums, academic
researchers, amateur fossil collectors, paleontological artists, and
commercial fossil dealers. As such, it represents an ideal environment for
examining the people, interactions, and flow of scientific information.
Using interactions involving the four most popular Twitter hashtags for
paleontology, this embedded mixed methods study defined the members of this
social world and investigated how they influenced and controlled the flow
of information, as well as how their expression of scientific practice was
related to their identity. Results provide further evidence for the
diversity of people and practice involved in this domain of science and
indicate that the magnitude and breadth of the public’s impact may be
larger than previously projected. Certain types of messages were shown to
be effective for different segments of the community, but news posts,
essentially media outlet stories, were ineffective for generating any form
of engagement. This study adds to our understanding of the important
scientific contribution being made by members of the public as they
interact with professional scientists and educators as peers in an open
social media platform that supports a diverse and active community.

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