12
Batoidea include skates, electric rays, stingrays, guitarfi sh, and sawfi sh (see for
review Daniel 1922 ). They have fi ve or six pairs of ventral gill slits and are characterized by a dorsoventrally fl attened body. Their pectoral fi ns are fused to the head.
There are four orders and ca. 470 species of batoids.
Selachians include all species of sharks. These animals are characterized by a
fusiform body and fi ve to seven pairs of lateral gill slits. Today, 8 orders and about
355 species of selachians are described. The diversity of elasmobranchs is well
described in the literature (see for review Thiel et al. 2009 ; Neumann 2006 ; Howe
and Springer 1993 ; Pollerspöck 2012 ).
Order Cladoselachiformes
Cladoselachidae (frilled sharks) is an extinct family of cartilaginous fi sh and among
the earliest predecessors of recent sharks. As the only members of the order
Cladoselachiformes, these animals were characterized by having an elongated body
with a spine in each of the two dorsal fi ns. According to Martin ( 2012 ), Cladoselache
specimens exhibited a combination of ancestral and derived characteristics. Their
jaw joints are weaker in comparison to modern-day sharks. However, they possess
very strong jaw-closing muscles. Its teeth were smooth-edged and multi-cusped,
making them ideal for grasping, but not tearing or chewing. It is suggested that
Cladoselache only seized prey by the tail and swallowed it whole. Unlike all
modern and most ancient sharks, frilled sharks swam the seas virtually naked.
Cladoselache’ s skin seems to have been almost devoid of the tooth-like scales with
exception of small, multi-cusped structures along the edges of their fi ns, in the
mouth cavity, and around the eye.
Cladoselache’ s scales serve as more than simple armor against injury. These
animals strengthen the skin to provide fi rmer attachments for their swimming
muscles. Their fi n spines were odd, too.
Being short and blade-like, composed of a porous bony material, and located
some distance anterior to the origin of each dorsal fi n, their spine fi ns were very
unusual. In contrast to other sharks with denser, more spike-like fi n spines, that of
Cladoselache may have been lighter and sturdier. These structures may have reduced
swimming effort yet provided solid discouragement to would-be predators.
Order Xenacanthiformes
Xenacanthiforms are known from the Lower Carboniferous up to the Triassic
(Ginter 2004 ; Fischer et al. 2011 ). Their characteristics include articulated skeletons
and diplodont teeth, i.e. teeth with two lateral cusps evidently larger than the median
ones. For example, the recently discovered taxon Reginaselache morrisi is
identifi ed by its teeth. These robust teeth possess multicristate cusps, as well as
prominent rounded coronal button, and a horseshoe-shaped labial boss. This shark
was about 1 m long, and probably fed on smaller paleoniscoid, invertebrates and
fi sh (Turner and Burrow 2011 ).
1 Introduction
Batoidea include skates, electric rays, stingrays, guitarfi sh, and sawfi sh (see for
review Daniel 1922 ). They have fi ve or six pairs of ventral gill slits and are characterized by a dorsoventrally fl attened body. Their pectoral fi ns are fused to the head.
There are four orders and ca. 470 species of batoids.
Selachians include all species of sharks. These animals are characterized by a
fusiform body and fi ve to seven pairs of lateral gill slits. Today, 8 orders and about
355 species of selachians are described. The diversity of elasmobranchs is well
described in the literature (see for review Thiel et al. 2009 ; Neumann 2006 ; Howe
and Springer 1993 ; Pollerspöck 2012 ).
Order Cladoselachiformes
Cladoselachidae (frilled sharks) is an extinct family of cartilaginous fi sh and among
the earliest predecessors of recent sharks. As the only members of the order
Cladoselachiformes, these animals were characterized by having an elongated body
with a spine in each of the two dorsal fi ns. According to Martin ( 2012 ), Cladoselache
specimens exhibited a combination of ancestral and derived characteristics. Their
jaw joints are weaker in comparison to modern-day sharks. However, they possess
very strong jaw-closing muscles. Its teeth were smooth-edged and multi-cusped,
making them ideal for grasping, but not tearing or chewing. It is suggested that
Cladoselache only seized prey by the tail and swallowed it whole. Unlike all
modern and most ancient sharks, frilled sharks swam the seas virtually naked.
Cladoselache’ s skin seems to have been almost devoid of the tooth-like scales with
exception of small, multi-cusped structures along the edges of their fi ns, in the
mouth cavity, and around the eye.
Cladoselache’ s scales serve as more than simple armor against injury. These
animals strengthen the skin to provide fi rmer attachments for their swimming
muscles. Their fi n spines were odd, too.
Being short and blade-like, composed of a porous bony material, and located
some distance anterior to the origin of each dorsal fi n, their spine fi ns were very
unusual. In contrast to other sharks with denser, more spike-like fi n spines, that of
Cladoselache may have been lighter and sturdier. These structures may have reduced
swimming effort yet provided solid discouragement to would-be predators.
Order Xenacanthiformes
Xenacanthiforms are known from the Lower Carboniferous up to the Triassic
(Ginter 2004 ; Fischer et al. 2011 ). Their characteristics include articulated skeletons
and diplodont teeth, i.e. teeth with two lateral cusps evidently larger than the median
ones. For example, the recently discovered taxon Reginaselache morrisi is
identifi ed by its teeth. These robust teeth possess multicristate cusps, as well as
prominent rounded coronal button, and a horseshoe-shaped labial boss. This shark
was about 1 m long, and probably fed on smaller paleoniscoid, invertebrates and
fi sh (Turner and Burrow 2011 ).
1 Introduction