Dermal bone

{{Short description|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 vertebrate skeleton, 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.{{cite journal| last1=de Buffrénil |first1=V. | last2=Clarac |first2=F.| last3=Fau |first3=M.| last4=Martin | first4=S.| last5=Martin |first5=B.| last6=Pellé |first6=E.|last7=Laurin |first7=M.|year=2015 |title=Differentiation and growth of bone ornamentation in vertebrates: a comparative histological study among the Crocodylomorpha |journal=Journal of Morphology |volume=276 |issue=4 |pages=425–445 | doi=10.1002/jmor.20351|pmid=25488816 |s2cid=10809084 |doi-access=free }} 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.{{cite journal| last1=Chen |first1=I.H. | last2=Kiang |first2=J.H.| last3=Correa |first3=V.| last4=Lopeza | first4=M.I.| last5=Chen |first5=P.Y.| last6=McKittrick |first6=J.|last7=Meyers |first7=M.A.|year=2011 |title=Armadillo armor: mechanical testing and micro-structural evaluation.|journal=Journal of Animal Ecology|volume=4|issue=5 |pages=713–722 |doi= 10.1016/j.jmbbm.2010.12.013|pmid=21565719 }}{{cite journal| last1=Broeckhoven|first1=Chris | last2=Diedericks |first2=G.| last3=Mouton |first3=P. le Fras N.| year=2015 |title=What doesn't kill you might make you stronger: functional basis for variation in body armour |journal=Journal of Animal Ecology |volume=84|issue=5 |pages=1213–1221|doi=10.1111/1365-2656.12414 | pmid=26104546|doi-access=free }}{{cite journal| last1=Clarac |first1=F. | last2=Goussard |first2=F.| last3=de Buffrénil |first3=V.| last4=Sansalone| first4=V.|year=2019 |title=The function(s) of bone ornamentation in the crocodylomorph osteoderms: a biomechanical model based on a finite element analysis |journal=Paleobiology |volume=45 |issue=1 |pages=182–200 | doi=10.1017/pab.2018.48|s2cid=92499041 }} 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) {{cite journal| last1=Clarac |first1=F. | last2= Quilhac |first2= A.|year=2019 |title= reptile The crocodylia skull and osteoderms: A functional exaptation to ectothermy?|journal=Zoology |volume=132|pages=31–40 | doi=10.1016/j.zool.2018.12.001|pmid=30736927 |s2cid=73427451 |doi-access=free }} as well as in bone respiratory acidosis buffering during prolonged apnea (seen in both crocodilians and turtles).{{cite journal| last1=Jackson |first1=D.C. | last2= Goldberger |first2=Z.| last3= Visuri |first3=J.| last4= Armstrong | first4=R.N.|year=1999 |title= Ionic exchanges of turtle shell in vitro and their relevance to shell function in the anoxic turtle|journal=Journal of Experimental Biology |volume=202|issue=5 |pages=503–520|doi=10.1242/jeb.202.5.513 |pmid=9929454 }}{{cite journal| last1=Jackson |first1=DC. | last2= Andrade |first2=D.| last3= Abe |first3=AS.|year=2003 |title= Lactate sequestration by osteoderms of the broad-nose caiman, Caiman latirostris, following capture and forced submergence |journal=Journal of Experimental Biology |volume=206|issue=20 |pages=3601–3606 | doi=10.1242/jeb.00611|pmid=12966051 |doi-access=free }} These ecophysiological functions rely on the set-up of a blood vessel network within and straight above the dermal bones. {{cite journal| last1=Clarac |first1=F. | last2= de Buffrénil |first2=V.| last3= Cubo|first3=J.| last4=Quilhac| first4=A.|year=2018 |title= Vascularization in ornamentedosteoderms: physiological implications in ectothermy and amphibious lifestyle in the crocodylomorphs? |journal=Anatomical Record |volume=301|issue=1 |pages=175–183 | doi=10.1002/ar.23695|pmid=29024422 |doi-access=free}}