[dinosaur] Dinosaur paleohistology + emu skeleton bone laminarity (free pdfs)

Ben Creisler
[email protected]

New papers with free pdfs:


Alida M. Bailleul, Jingmai O'Connor & Mary H. Schweitzer (2019)
Dinosaur paleohistology: review, trends and new avenues of investigation.
PeerJ 7:e7764
doi:  https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.7717_peerj.7764&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=94WqfslbsxGGZ1PxEbC6KCqsLXSCkNb4Mj72AB6vTs4&s=Yj3GlcG-3H-ZkB0k-13c-DlXfFb-Y4zyrvAjPRKxNN4&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__peerj.com_articles_7764_&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=94WqfslbsxGGZ1PxEbC6KCqsLXSCkNb4Mj72AB6vTs4&s=0rG12gYL8NXN6kObNsX5knk2c7iXNqaYMr3WbMHJjmw&e= 
From pdf:
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In the mid-19th century, the discovery that bone microstructure in fossils
could be preserved with fidelity provided a new avenue for understanding
the evolution, function, and physiology of long extinct organisms. This
resulted in the establishment of paleohistology as a subdiscipline of
vertebrate paleontology, which has contributed greatly to our current
understanding of dinosaurs as living organisms. Dinosaurs are part of a
larger group of reptiles, the Archosauria, of which there are only two
surviving lineages, crocodilians and birds. The goal of this review is to
document progress in the field of archosaur paleohistology, focusing in
particular on the Dinosauria. We briefly review the "growth age" of
dinosaur histology, which has encompassed new and varied directions since
its emergence in the 1950s, resulting in a shift in the scientific
perception of non-avian dinosaurs from "sluggish" reptiles to fast-growing
animals with relatively high metabolic rates. However, fundamental changes
in growth occurred within the sister clade Aves, and we discuss this major
evolutionary transition as elucidated by histology. We then review recent
innovations in the field, demonstrating how paleohistology has changed and
expanded to address a diversity of non-growth related questions. For
example, dinosaur skull histology has elucidated the formation of curious
cranial tissues (e.g., "metaplastic" tissues), and helped to clarify the
evolution and function of oral adaptations, such as the dental batteries of
duck-billed dinosaurs. Lastly, we discuss the development of novel
techniques with which to investigate not only the skeletal tissues of
dinosaurs, but also less-studied soft-tissues, through molecular
paleontology and paleohistochemistry--recently developed branches of
paleohistology--and the future potential of these methods to further
explore fossilized tissues. We suggest that the combination of histological
and molecular methods holds great potential for examining the preserved
tissues of dinosaurs, basal birds, and their extant relatives. This review
demonstrates the importance of traditional bone paleohistology, but also
highlights the need for innovation and new analytical directions to improve
and broaden the utility of paleohistology, in the pursuit of more diverse,
highly specific, and sensitive methods with which to further investigate
important paleontological questions.

===


Amanda L. Kuehn, Andrew H. Lee, Russell P. Main & Erin L.R. Simons (2019)
The effects of growth rate and biomechanical loading on bone laminarity
within the emu skeleton.
PeerJ 7:e7616
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.7717_peerj.7616&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=94WqfslbsxGGZ1PxEbC6KCqsLXSCkNb4Mj72AB6vTs4&s=YFneyW5Kceoy0o_vAxBmL5K1VY10-a-m6dwoXdUz6AU&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__peerj.com_articles_7616_&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=94WqfslbsxGGZ1PxEbC6KCqsLXSCkNb4Mj72AB6vTs4&s=dPW_p9eJRiLikcv61ChbMiXlWPFq_m5TbXiIHXhLWeQ&e= 
Free pdf:
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The orientation of vascular canals in primary bone may reflect differences
in growth rate and/or adaptation to biomechanical loads. Previous studies
link specific canal orientations to bone growth rates, but results between
different taxa are contradictory. Circumferential vascular canals (forming
laminar bone) have been hypothesized to reflect either (or both) rapid
growth rate or locomotion-induced torsional loading. Previous work on the
hindlimb biomechanics in the emu shows that the femur and tibiotarsus
experience large shear strains, likely resulting from torsional loads that
increase through ontogeny. Here, we test how growth rate and biomechanical
loading affect bone laminarity in wing and hindlimb elements from growing
emu (2–60 wks). If laminar bone is an adaptation to torsion-induced shear
strains, it should increase from juveniles to adults. Alternatively, if
bone laminarity reflects rapid growth, as has been shown previously in emu,
it should be abundant in fast-growing juveniles and decrease with age.
Transverse mid-shaft histological sections from the limb bones (femur,
tibiotarsus, humerus, ulna, and radius) were prepared and imaged. Growth
rates were measured using fluorescent bone labels. Vascular canal
orientation was quantified using laminarity index (proportion of
circumferential canals). Principal components analysis was performed to
convert highly correlated variables (i.e., mass, age, growth rate, and
shear strain) into principal components. Random-intercept beta regression
modeling determined which principal components best explained laminarity.
The fastest growth rates were found in young individuals for all five
skeletal elements. Maximum growth rate did not coincide with peak
laminarity. Instead, in the femur and tibiotarsus, elevated laminarity is
strongly correlated with adult features such as large size, old age, and
modest growth rate. This result is contrary to predictions made based on a
previous study of emu but is consistent with results observed in some other
avian species (penguin, chicken). Shear strain in the caudal octant of the
femur and tibiotarsus is positively correlated with laminarity but has a
weaker effect on laminarity relative to mass, age, and growth rate.
Laminarity in the wing elements is variable and does not correlate with
ontogenetic factors (including mass, age, and growth rate). Its presence
may relate to relaxed developmental canalization or a retained ancestral
feature. In conclusion, ontogeny (including growth rate) is the dominant
influence on vascular canal orientation at least in the hindlimb of the emu.

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