Article: Growth and form of finspines in hybodont sharks

Hybodontiform finspines have certain diagnostic features. The following are the most important: the longitudinal (axial) ornament is costate apically but tends to break up basally; there are posterior hook-denticles (probably secondarily fused to the spine, because abnormalities include partial non-sequence of denticle rows, also supernumerary denticles); osteodentine of the finspine outer layer is layered anteriorly, and this is interpreted in developmental terms. In common with other finspines, much of the spine was covered by an integument in life, and a certain amount of wound-healing was possible.