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Fig. 1. (Top) Schematic of M. californicus vertebral column. Vertebrae
used in these experiments were excised from under the first dorsal fin (boxed)
(A). Neural and hemal arches were removed leaving cylindrical centra for
materials testing. (B) The mineralized double cone structure is highlighted in
this generalized elasmobranch vertebra. Intricate mineralization patterns
branch off the double cone structure and the patterns vary extensively among
elasmobranch species (Ridewood,
1921). (C) Drawings of 3/4 views of two species of shark
vertebrae. The anterior surface is concave, part of the double cone structure,
coming to a point in the middle of the centra. Mako (I. oxyrinchus)
centra have many plates of mineral surrounding the double cone while the silky
shark (C. falciformis) has a crust of mineral extending from the
central double cone. (D) Anterior view radiographs of mako and silky vertebral
centra with excised neural and hemal arches. The mako shark vertebra mineral
is arranged in plates around the centra and relatively unmineralized cartilage
fills the gaps between the plates. The silky shark vertebra has a highly
mineralized sheath around the centra with less mineralized cartilages
appearing where the neural and hemal arches are placed
(Porter et al., 2006).
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