231
4.4 Conclusion
Scales originated as a natural consequence of biological evolution. Many animals
and some plants grow them as a form of external protection, and they occur in
nature in many shapes and sizes. The arrangement of scales on an animal’s body,
called its squamation, varies from species to species (Landreneau 2011 ). Different
scale located biocomposites has been developed during the long history of animal
evolution. For example, “the scale-like elements of pteraspidomorphs (Ordovician
to Devonian; ∼480–360 Ma) are characterized by a stratifi ed combination of superfi cial enameloid overlying tubular dentine (orthodentine), set on a basal plate of
acellular bone (aspidin),” (Vickaryous and Sire 2009 ). However, the integumentary
elements of anapsids, which were distributed Silurian to Early Devonian (∼443–
400 Ma), contain only aspidin. In contrast, such biological materials as cellular
bone, mesodentine and orthodentine represented the main structural components of
integumentary elements in osteostracans (mid Silurian to Carboniferous; ∼430–
300 Ma). These data are used also for diagnostic aims. Today, it is well established
(Donoghue et al. 2006 ; Sire et al. 2009 ) that the ability of vertebrates to mineralize
the integument in such different mineralized tissue-types as bone, dentine and
enamel/enamelod and their derivatives dates back at least to the Early Ordovician.
Independent of chemical composition, most types of scales are oriented in a
certain direction. The reasons for this directionality are many. Fish benefi t from
improved laminar fl ow from scales directing the fl ow of water around their bodies.
Both the shape and orientation vary depending on the fl ow of water, habits of the
fi sh, and other environmental factors. Scale orientations also infl uence fl exibility.
While the segmented nature of scales provides more fl exibility than rigid armor,
certain movements are restricted based on orientation of the scale. For example,
highly concave deformations may be restricted due to scales being fl attened against
each other or bunched together, creating restricting layers (Landreneau 2011 ).
The next chapter is dedicated to material and mechanical properties of fi sh scales,
as well as to the unique armored constructs developed by extinct and recent fi sh taxa.
References
Agassiz L (1833–1844) Recherches sur les poissonsfossiles. Imprimerie Petitpierre, Neuchatel
(Suisse)
Baudelot ME (1873) Recherches sur la structure et le developpement des ecailles des poisons
osseux. Arch Zool Exp Gen 2:87–244; 429–480
Baume LJ (1980) The biology of pulp and dentine: a historic, terminologic–taxonomic, histologic–
biochemical, embryonic and clinical survey. In: Myers HM (ed) Monographs in oral science,
vol 8. Karger, Basel
Bemis WE, Findeis EK, Grande L (1997) An overview of Acipenseriformes . Environ Biol Fish
48:25–71
Bendix–Almgreen SE (1983) Carcharodon megalodon from the upper Miocene of Denmark, with
comments on elasmobranch tooth enameloid: coronoiin. Bull Geol Soc Denmark 32:1–32
References
4.4 Conclusion
Scales originated as a natural consequence of biological evolution. Many animals
and some plants grow them as a form of external protection, and they occur in
nature in many shapes and sizes. The arrangement of scales on an animal’s body,
called its squamation, varies from species to species (Landreneau 2011 ). Different
scale located biocomposites has been developed during the long history of animal
evolution. For example, “the scale-like elements of pteraspidomorphs (Ordovician
to Devonian; ∼480–360 Ma) are characterized by a stratifi ed combination of superfi cial enameloid overlying tubular dentine (orthodentine), set on a basal plate of
acellular bone (aspidin),” (Vickaryous and Sire 2009 ). However, the integumentary
elements of anapsids, which were distributed Silurian to Early Devonian (∼443–
400 Ma), contain only aspidin. In contrast, such biological materials as cellular
bone, mesodentine and orthodentine represented the main structural components of
integumentary elements in osteostracans (mid Silurian to Carboniferous; ∼430–
300 Ma). These data are used also for diagnostic aims. Today, it is well established
(Donoghue et al. 2006 ; Sire et al. 2009 ) that the ability of vertebrates to mineralize
the integument in such different mineralized tissue-types as bone, dentine and
enamel/enamelod and their derivatives dates back at least to the Early Ordovician.
Independent of chemical composition, most types of scales are oriented in a
certain direction. The reasons for this directionality are many. Fish benefi t from
improved laminar fl ow from scales directing the fl ow of water around their bodies.
Both the shape and orientation vary depending on the fl ow of water, habits of the
fi sh, and other environmental factors. Scale orientations also infl uence fl exibility.
While the segmented nature of scales provides more fl exibility than rigid armor,
certain movements are restricted based on orientation of the scale. For example,
highly concave deformations may be restricted due to scales being fl attened against
each other or bunched together, creating restricting layers (Landreneau 2011 ).
The next chapter is dedicated to material and mechanical properties of fi sh scales,
as well as to the unique armored constructs developed by extinct and recent fi sh taxa.
References
Agassiz L (1833–1844) Recherches sur les poissonsfossiles. Imprimerie Petitpierre, Neuchatel
(Suisse)
Baudelot ME (1873) Recherches sur la structure et le developpement des ecailles des poisons
osseux. Arch Zool Exp Gen 2:87–244; 429–480
Baume LJ (1980) The biology of pulp and dentine: a historic, terminologic–taxonomic, histologic–
biochemical, embryonic and clinical survey. In: Myers HM (ed) Monographs in oral science,
vol 8. Karger, Basel
Bemis WE, Findeis EK, Grande L (1997) An overview of Acipenseriformes . Environ Biol Fish
48:25–71
Bendix–Almgreen SE (1983) Carcharodon megalodon from the upper Miocene of Denmark, with
comments on elasmobranch tooth enameloid: coronoiin. Bull Geol Soc Denmark 32:1–32
References