Bony structure derived from intramembranous ossification
A dermal bone or investing bone or membrane bone is a bony structure derived from
intramembranous ossification forming components of the
vertebrateskeleton, including much of the
skull,
jaws,
gill covers, shoulder girdle,
fin rays (
lepidotrichia), and the shells of
turtles and
armadillos. In contrast to
endochondral bone, dermal bone does not form from cartilage that then calcifies, and it is often ornamented.[1] Dermal bone is formed within the
dermis and grows by accretion only – the outer portion of the bone is deposited by
osteoblasts.
The function of some dermal bone is conserved throughout vertebrates, although there is variation in shape and in the number of bones in the
skull roof and postcranial structures. In
bony fish, dermal bone is found in the fin
rays and scales. A special example of dermal bone is the
clavicle. Some of the dermal bone functions regard biomechanical aspects such as protection against predators.[2][3][4] The dermal bones are also argued to be involved in ecophysiological implications such as the heat transfers between the body and the surrounding environment when basking (seen in crocodilians) [5] as well as in bone respiratory acidosis buffering during prolonged apnea (seen in both crocodilians and turtles).[6][7] These ecophysiological functions rely on the set-up of a blood vessel network within and straight above the dermal bones. [8]
^Clarac, F.; Goussard, F.; de Buffrénil, V.; Sansalone, V. (2019). "The function(s) of bone ornamentation in the crocodylomorph osteoderms: a biomechanical model based on a finite element analysis". Paleobiology. 45 (1): 182–200.
doi:
10.1017/pab.2018.48.
S2CID92499041.
^Jackson, D.C.; Goldberger, Z.; Visuri, J.; Armstrong, R.N. (1999). "Ionic exchanges of turtle shell in vitro and their relevance to shell function in the anoxic turtle". Journal of Experimental Biology. 202 (5): 503–520.
doi:
10.1242/jeb.202.5.513.
PMID9929454.