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==Description==
▲ wide head with a blunt snout and prominent [[supraorbital ridge]] is over the eyes. The horn shark's supraorbital ridges are low and terminate abruptly; the space between them on top of the head is deeply concave. Each eye lacks a [[nictating membrane]] and is followed by a tiny [[Spiracle (vertebrates)|spiracle]]. The [[nostril]]s are split into inflow and outflow openings by a long flap that reaches the mouth. The inflow openings are encircled by a groove, while another groove connects the outflow openings to the mouth. The mouth is small and curved, with prominent furrows at the corners. There are 19–26 tooth rows in the upper jaw and 18–29 tooth rows in the lower jaw. The teeth at the front of the jaws are small and pointed, with a central cusp flanked by a pair of lateral cusplets; those at the sides of the jaws are much larger, elongated lengthwise, and molar-like.<ref name="compagno"/><ref name="ebert"/>
The body is cylindrical, with two high, somewhat falcate (sickle-shaped) [[dorsal fin]]s bearing stout spines at the front.<ref name="compagno"/> The fin spines of reef-dwelling horn sharks are shorter than those living in algal habitats, as their spines become worn down on rocks from the sharks' movements.<ref name="ebert"/> The first dorsal fin originates over the bases of the large [[pectoral fin]]s, while the second dorsal fin originates slightly anterior to the free rear tips of the [[pelvic fin]]s. The [[caudal fin]] has a short lower lobe and a long, broad upper lobe with a strong notch near the tip. The horn shark's [[dermal denticle]]s are small and smooth, numbering some 200/cm<sup>2</sup> on the back in adults.<ref name="compagno"/> The dorsal coloration consists of various shades of gray or brown with many small dark spots, though these may be absent in older sharks; the underside is yellowish. There is a dark patch of small spots below the eye.<ref name="compagno"/><ref name="ebert"/> This species may reach a length of {{convert|1.2|m|ft|abbr=on}}, though most individuals do not exceed {{convert|1|m|ft|abbr=on}}.<ref name="buch"/>
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