Pachyosteosclerosis (bone density in aquatics)

[wet]

POS pachy-osteo-sclerosis (Enlarged & thick bones for buoyancy/ballast control, mostly in seawater)


An Analysis of Vertebral "Pachyostosis" In Carentonosaurus Mineaui
(Mosasauroidea, Squamata) from the Cenomanian (Early Late Cretaceous) of
France, with Comments on its Phylogenetic and Functional Significance
Alexandra Houssaye, Vivian De Buffrenil, Jean-Claude Rage & Nathalie Bardet
2008 Journal of Vertebrate Paleontology 28:685-691
doi 10.1671/0272-4634(2008)28[685:AAOVPI]2.0.CO;2

The study of the so-called vertebral "pachyostosis" of Carentonosaurus
mineaui (plesiopedal mosasauroid sensu Bell & Polcyn, Cenomanian (Late
Cretaceous), Charente-Maritime, W-France) has revealed that it actually
corresponds to pachyosteosclerosis resulting from the combination of
cortical hyperplasy with bone compaction, due to an inhibition of
chondroclastic & osteoclastic activities.
This characteristic also occurs in other Cretaceous squamates, eg,
Pachyvaranus crassispondylus & Simoliophis rochebrunei, but it is absent in
extant squamates.
On the contrary, vertebrae of the latter display a very strong porosity due
to intense bone remodelling during growth.
The phylogenetic significance of pachyosteosclerosis in squamates is thus
discussed.
The peculiar structure of the vertebrae of Carentonosaurus may be regarded
as the result of a heterochronic process, more specifically neoteny.
Its association with an adaptation to shallow marine environment is
consistent with the inferred ecology of C.mineaui.
Moreover, the histological features of the periosteal bone of
Carentonosaurus vertebrae provide information about its growth pattern
(asymmetry, rate, cyclicity) which may be compared to the ones of
Pachyvaranus & Simoliophis.

________


"Pachyostosis" in aquatic amniotes: a review
Alexandra HOUSSAYE 2009 DOI 10.1111/j.1749-4877.2009.00146.x
Integrative Zoology 4:325*340
<http://onlinelibrary.wiley.com/doi/10.1111/inz.2009.4.issue-4/issuetoc>

During the course of amniote evolution, numerous taxa secondarily adapted to
an aquatic life. It appears that many of these taxa primitively display
"pachyostosis", an osseous specialization characterized by an increase in
bone compactness &/or volume.
The term "pachyostosis" is used in morphological & histological descriptions
to describe what in fact corresponds to different patterns.
The aim of this paper is to present the current state of knowledge relative
to this adaptation among aquatic amniotes.

All the taxa that have returned to an aquatic environment are listed.
Moreover,
- their degree of adaptation to the marine environment,
- their life environment &
- the nature of their "pachyostotic" pattern (when present)
are described.
This inventory
- enables the evaluation of the current quality of the data relative to this
specialization&
- provides an indication of the work that remains to be done.
The functional consequences of "pachyostosis" & notably its importance for
buoyancy control in the context of hydrostatic regulation of the body trim,
are discussed, and opposed to the requirement of improved swimming abilities
in the case of a hydrodynamic mode of trim regulation.
Questions are posed about the signification of the polymorphism displayed by
this specialization between different taxa, different specimens of the same
taxon & different bones of the same specimen & the problem of quantification
of pachyostosis is discussed.

_______


Evolution of Sirenian Pachyosteosclerosis, a Model-case for the Study of
Bone Structure in Aquatic Tetrapods
Vivian de Buffrénil, Aurore Canoville, Ruggero D¹Anastasio & Daryl P.
Domning 2010 Journal of Mammalian Evolution 17:101-120
DOI 10.1007/s10914-010-9130-1

Osteosclerosis (inner bone compaction) & pachyostosis (outer hyperplasy of
bone cortices, swollen bones) are typical features of tetrapods secondarily
adapted to life in water.
These peculiarities are spectacularly exemplified by the ribs of extant &
extinct Sirenia. Sea cows are thus the best model for studying this kind of
bone structural specializations.
In order to document how these features differentiated during sirenian
evolution, the ribs of 15 spp (from the most basal form Pezosiren portelli
up to extant taxa) were studied & compared to those of other mammalian spp
from both & and histological points of view.
- Pachyostosis was the first of these 2 specializations to occur, by the
middle of the Eocene, and is a basal feature of the Sirenia.
However, it subsequently regressed in some taxa that do not exhibit
hyperplasic rib cortices.
- Osteosclerosis was only incipient in P.portelli. Its full development
occurred later, by the end of the Eocene.
These 2 structural specializations of bone are variably pronounced in
extinct & extant sirenians, and rel.independent from each other, although
frequently associated.
They are possibly due to similar heterochronic mechanisms bearing on the
timing of osteoblast activity. These results are discussed with respect to
the functional constraints of locomotion in water.

 

[wet]

V de Buffrénil 2010 Journal of Mammalian Evolution 17:101-120
"Evolution of Sirenian Pachyosteosclerosis, a Model-case for the Study of
Bone Structure in Aquatic Tetrapods"
... All authors consider that osteosclerosis &/or pachyostosis have a
hydrostatic role, and contribute, as ballast, to regulating buoyancy & trim
in tetrapods incipiently adapting to life in water, or specialized in
feeding on fixed or slow-moving prey in shallow waters ...
-
Archaic hominins had variable bone density and cortical thickness, those near coasts typically had more bone mass. Since the development of boats, nets, advanced projectile technology, fire; this correlation no longer fits the anthropplogical data, parsimoniously due to reduction of dive-foraging and replacement by other procurement strategies (mass herd hunting, mass netting (pygmy net hunting, Khoisan traps etc.).

 

[wet]

Nature 261, 101 - 108 (13 May 1976); doi:10.1038/261101a0

Evolution of type C viral genes: evidence for an Asian origin of man

Raoul E. Benveniste & George J. Todaro

Viral Leukemia and Lymphoma Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20014

Old World monkeys and apes, including man, possess, as a normal component of their cellular DNA, gene sequences (virogenes) related to the RNA of a vims isolated from baboons. A comparison of the viral gene sequences and the other cellular sequences distinguishes those Old World monkeys and apes that have evolved in Africa from those that have evolved in Asia. Among the apes, only gorilla and chimpanzee seem by these criteria to be African, whereas gibbon, orang-utan and man are identified as Asian, leading us to conclude that most of man's evolution has occurred outside Africa.
-
About 6,000,000 years ago the Mediterranean Sea dried out, leaving only freshwater basins at river deltas (Nile) and shallow hypersaline seas in the Med. & Red Sea basins. That is when the last common ancestor of man and Pan (chimps) began the genomic lineage divergence, though wetland foraging of floating plants already existed (air sacs for buoyancy common in all hominids/pongids). Chimp ancestors always remained in Africa, while archaic humans in this deep vast basin initiated a more aquatic phase collecting food underwater, gradually distributed outwards along coasts throughout the Old World, including returning to Africa later. Humans have the 'Asian' version of the retrovirus due to being outside Africa during the period of transmission, like gibbons and orangutans, unlike chimps and gorillas.