9
The representatives of Placodermi possess a dermal armor consisting of head
armor and a thoracic armor. The thoracic armor is characterized by the foremost
dermal plates which form a complete “ring” around the body. It always includes at
least one median dorsal plate.
The Acanthodii differ from other clades by dermal spines inserted in front of all
fi ns but the caudal one. These animals also possess minute, growing scales with a
special onion-like structure, i.e. the crown consists of overlying dentine or
mesodentine- based layers.
1.2.2.1 Superclass Gnathostomata
Jawed fi shes (99.7 % of all living fi shes) and tetrapods are related to the Superclass
Gnathostomata. These vertebrates possess jaws and usually a set of paired appendages.
The superclass includes all the tetrapods: amphibians, reptiles, birds, and mammals.
Class Chondrichthyes
Cartilaginous fishes (about 1,000 species) possess primitive characters like
cartilaginous endoskeleton, single nostrils, and absence of the gas bladder. Modern
studies suggest that these vertebrates have a terminal position in the piscine tree
(Rasmussen and Arnason 1999a , b ; Botella et al. 2009 ). They fi rst appear in Upper
Silurian, and some fossil record starts in Lower Devonian. Representatives of this
class possess placoid scales, bony teeth of ectodermal and mesodermal origin in
jaws as well as teeth arranged in replacement whorls. Their endoskeleton is partially
covered with prismatically patterned perichondral bone, and their gill septum
extending to lamellar margin. The mosaic calcium carbonate-based granule pattern
is unique to these fi shes. It is known that these mineralized structures on the outside
of the cartilage add strength. Both eggs and embryos of Chondrichthyans are large.
Similar to ray-fi nned fi shes, representatives of this class have also large adults (from
20 cm and 15 g to 12 m and 12,000 kg).
From biological materials point of view, these fi sh possess numerous structures
with high biomimetic potential because of their unique physical, chemical and
material properties (Oeffner and Lauder 2012 ).
Below are listed some of these formations in alphabetical order:
Barbels – From morphological point of view, barbels are long conical paired dermal
lobes on the snouts of sharks. Their function is to locate prey. In contrast to most
sharks which have barbels associated with the nostrils, Sawsharks have barbels
in front of the nostrils.
Claspers – These paired copulatory organs are located on the pelvic fi ns of male
cartilaginous fi shes. Animals use them for internal fertilization of eggs.
Dermal denticle – (or placoid scale) is an example of small tooth-like scale that is
unique to cartilaginous fi sh.
1.2 Part I: Biomaterials of Vertebrate Origin. An Overview
The representatives of Placodermi possess a dermal armor consisting of head
armor and a thoracic armor. The thoracic armor is characterized by the foremost
dermal plates which form a complete “ring” around the body. It always includes at
least one median dorsal plate.
The Acanthodii differ from other clades by dermal spines inserted in front of all
fi ns but the caudal one. These animals also possess minute, growing scales with a
special onion-like structure, i.e. the crown consists of overlying dentine or
mesodentine- based layers.
1.2.2.1 Superclass Gnathostomata
Jawed fi shes (99.7 % of all living fi shes) and tetrapods are related to the Superclass
Gnathostomata. These vertebrates possess jaws and usually a set of paired appendages.
The superclass includes all the tetrapods: amphibians, reptiles, birds, and mammals.
Class Chondrichthyes
Cartilaginous fishes (about 1,000 species) possess primitive characters like
cartilaginous endoskeleton, single nostrils, and absence of the gas bladder. Modern
studies suggest that these vertebrates have a terminal position in the piscine tree
(Rasmussen and Arnason 1999a , b ; Botella et al. 2009 ). They fi rst appear in Upper
Silurian, and some fossil record starts in Lower Devonian. Representatives of this
class possess placoid scales, bony teeth of ectodermal and mesodermal origin in
jaws as well as teeth arranged in replacement whorls. Their endoskeleton is partially
covered with prismatically patterned perichondral bone, and their gill septum
extending to lamellar margin. The mosaic calcium carbonate-based granule pattern
is unique to these fi shes. It is known that these mineralized structures on the outside
of the cartilage add strength. Both eggs and embryos of Chondrichthyans are large.
Similar to ray-fi nned fi shes, representatives of this class have also large adults (from
20 cm and 15 g to 12 m and 12,000 kg).
From biological materials point of view, these fi sh possess numerous structures
with high biomimetic potential because of their unique physical, chemical and
material properties (Oeffner and Lauder 2012 ).
Below are listed some of these formations in alphabetical order:
Barbels – From morphological point of view, barbels are long conical paired dermal
lobes on the snouts of sharks. Their function is to locate prey. In contrast to most
sharks which have barbels associated with the nostrils, Sawsharks have barbels
in front of the nostrils.
Claspers – These paired copulatory organs are located on the pelvic fi ns of male
cartilaginous fi shes. Animals use them for internal fertilization of eggs.
Dermal denticle – (or placoid scale) is an example of small tooth-like scale that is
unique to cartilaginous fi sh.
1.2 Part I: Biomaterials of Vertebrate Origin. An Overview