[dinosaur] Avian chondroid bone in rapid growth + Paleocene mammal neurosensory system + squamate quadrate

Ben Creisler
[email protected]

Some new non-dino papers in Journal of Anatomy that may be of interest


Edina Prondvai,  P. Eckhard Witten,  Anick Abourachid,  Ann Huysseune  &
Dominique Adriaens (2019)
Extensive chondroid bone in juvenile duck limbs hints at accelerated growth
mechanism in avian skeletogenesis.
Journal of Anatomy (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_joa.13109&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=J9o_4X_hH94MJlBQppwPCtg_sv-dsXcZzYzr_Qli2lg&s=ot2zGmgLd95MBFo5ef5AG2JyziWJDnNMbkssF-3rZgs&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_pdf_10.1111_joa.13109&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=J9o_4X_hH94MJlBQppwPCtg_sv-dsXcZzYzr_Qli2lg&s=CywSLPlyXPO8-_IPV9lQC45MqCpP-vMe9DrvKZq-o_U&e= 

Modern altricial birds are the fastest growing vertebrates, whereas various
degrees of precocity (functional maturity) result in slower growth.
Diaphyseal osteohistology, the best proxy for inferring relative growth
rates in fossils, suggests that in the earliest birds, posthatching growth
rates were more variable than in modern representatives, with some showing
considerably slow growth that was attributed to their assumed precocial
flight abilities. For finding clues how precocial or altricial
skeletogenesis and related growth acceleration could be traced in avian
evolution, as a case study we investigated the growing limb diaphyseal
histology in an ontogenetic series of ducks which, among several other
avian taxa, show a combination of altricial wing and precocial leg
development. Here we report the unexpected discovery that chondroid bone, a
skeletal tissue family intermediate between cartilage and bone, extensively
contributes to the development of limb bone shaft in ducks up to at least
30 days posthatching age. To our knowledge, chondroid bone has never been
reported in such quantities and with an ontogenetically extended deposition
period in post‐embryonic, non‐pathological periosteal bone formation of any
tetrapod limb. It shows transitional cellular/lacunar morphologies and
matrix staining properties between cartilage and woven bone and takes a
significant part in the diametric growth of the limb bone shaft. Its amount
and distribution through duckling ontogeny seems to be associated with the
disparate functional and growth trajectories of the altricial wings vs.
precocial legs characteristic of duck limb development. The presence of
isogenous cell groups in the periosteal chondroid bone implies that
cartilage‐like interstitial growth took place before matrix mineralization
complementing appositional bone growth. Based on these characteristics and
on its fast formation rate in all previously reported normal as well as
pathological cases, we suggest that chondroid bone in ducks significantly
accelerates diametric limb bone growth. Related to this growth
acceleration, we hypothesize that chondroid bone may be generally present
in the growing limb bones of modern birds and hence may have key
skeletogenic importance in achieving extreme avian growth rates and placing
birds among the fastest growing vertebrates. Thus, we encourage future
studies to test this hypothesis by investigating the occurrence of
chondroid bone in a variety of precocial and altricial bird species, and to
explore the presence of similar tissues in the growing limbs of other
extant and extinct tetrapods in order to understand the evolutionary
significance of chondroid bone in accelerated appendicular skeletogenesis.

====

Of interest based on the recent "archaic ungulate" question...

Ornella C. Bertrand, Sarah L. Shelley, John R. Wible, Thomas E. Williamson,
Luke T. Holbrook, Stephen G.B. Chester, Ian B. Butler &  Stephen L.
Brusatte (2019)
Virtual endocranial and inner ear endocasts of the Paleocene 'condylarth'
Chriacus: new insight into the neurosensory system and evolution of early
placental mammals.
Journal of Anatomy (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_joa.13084&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=J9o_4X_hH94MJlBQppwPCtg_sv-dsXcZzYzr_Qli2lg&s=KJ9pAuB37UH7fVFRigTWvpY42-yHAhN6HDjX29Yg6JA&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1111_joa.13084&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=J9o_4X_hH94MJlBQppwPCtg_sv-dsXcZzYzr_Qli2lg&s=Xe4_0KgfkqKOJF1lVSuanTApK7IRM_jOgIdKet14_5A&e= 



The end‐Cretaceous mass extinction allowed placental mammals to diversify
ecologically and taxonomically as they filled ecological niches once
occupied by non‐avian dinosaurs and more basal mammals. Little is known,
however, about how the neurosensory systems of mammals changed after the
extinction, and what role these systems played in mammalian
diversification. We here use high‐resolution computed tomography (CT)
scanning to describe the endocranial and inner ear endocasts of two
species, Chriacus pelvidens and Chriacus baldwini, which belong to a
cluster of 'archaic' placental mammals called ‘arctocyonid condylarths’
that thrived during the ca. 10 million years after the extinction (the
Paleocene Epoch), but whose relationships to extant placentals are poorly
understood. The endocasts provide new insight into the paleobiology of the
long‐mysterious 'arctocyonids', and suggest that Chriacus was an animal
with an encephalization quotient (EQ) range of 0.12–0.41, which probably
relied more on its sense of smell than vision, because the olfactory bulbs
are proportionally large but the neocortex and petrosal lobules are less
developed. Agility scores, estimated from the dimensions of the
semicircular canals of the inner ear, indicate that Chriacus was slow to
moderately agile, and its hearing capabilities, estimated from cochlear
dimensions, suggest similarities with the extant aardvark. Chriacus shares
many brain features with other Paleocene mammals, such as a small
lissencephalic brain, large olfactory bulbs and small petrosal lobules,
which are likely plesiomorphic for Placentalia. The inner ear of Chriacus
also shares derived characteristics of the elliptical and spherical
recesses with extinct species that belong to Euungulata, the extant
placental group that includes artiodactyls and perissodactyls. This lends
key evidence to the hypothesized close relationship between Chriacus and
the extant ungulate groups, and demonstrates that neurosensory features can
provide important insight into both the paleobiology and relationships of
early placental mammals.

===

Alessandro Palci,  Michael W. Caldwel,l  Mark N. Hutchinson,  Takuya
Konishi & Michael S. Y. Lee (2019)
The morphological diversity of the quadrate bone in squamate reptiles as
revealed by high‐resolution computed tomography and geometric morphometrics.
Journal of Anatomy (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_joa.13102&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=J9o_4X_hH94MJlBQppwPCtg_sv-dsXcZzYzr_Qli2lg&s=fToueA7KODP602Xk-IT9hEHamBijC3LKyzwbzqwd4cg&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1111_joa.13102&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=J9o_4X_hH94MJlBQppwPCtg_sv-dsXcZzYzr_Qli2lg&s=A8Z8gc5XXanjI_2Ydls534tBU4Ga0r_nzT-MPrBATp0&e= 


We examined the morphological diversity of the quadrate bone in squamate
reptiles (i.e. lizards, snakes, amphisbaenians). The quadrate is the
principal splanchnocranial element involved in suspending the lower jaw
from the skull, and its shape is of particular interest because it is
potentially affected by several factors, such as phylogenetic history,
allometry, ecology, skull kinesis and hearing capabilities (e.g. presence
or absence of a tympanic ear). Due to its complexity, the quadrate bone is
also considered one of the most diagnostic elements in fragmentary fossil
taxa. We describe quadrates from 38 species spread across all major
squamate clades, using qualitative and quantitative (e.g. geometric
morphometrics) methods. We test for possible correlations between shape
variation and factors such as phylogeny, size, ecology and presence/absence
of a tympanum. Our results show that the shape of the quadrate is highly
evolutionarily plastic, with very little of the diversity explained by
phylogenetic history. Size variation (allometric scaling) is similarly
unable to explain much shape diversity in the squamate quadrate. Ecology
(terrestrial/fossorial/aquatic) and presence of a tympanic ear are more
significant, but together explain only about 20% of the diversity observed.
Other unexplored and more analytically complex factors, such as skull
biomechanics, likely play additional major roles in shaping the quadrates
of lizards and snakes.


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