Colloquially known as the crocodile needlefish (Tylosurus crocodilus), this species can be found in practically all tropical seas. Its characteristic body with extremely elongated and slender shape, has an almost cylindrical section. The color of its body is silvery on the back and a dark blue-green tone at the top. Additionally, it may present one or several dark stripes on the gill cover, but never along its body. Juveniles have a black spot on the back of their dorsal fin, which they gradually lose as they mature.
The fine and elongated mouth of Tylosurus crocodilus is straight, and can reach a length equivalent to 1.5 times the length of the head, which places this species among the species of the needlefish family with the least long mouth. However, Tylosurus crocodilus is the species that reaches a greater total body size, reaching 150 cm in length, although the most common length is 90 cm. The mouth has very sharp conical teeth. In juvenile specimens, these teeth are positioned both in the lower and upper jaw, with a slightly forward orientation.
As for the fins of Tylosurus crocodilus, this species is characterized by having a single dorsal fin formed by between 21 and 23 rays. The anal fin is constituted by between 18 and 22 rays. It should be noted that the front part of both the dorsal and the anal fins have lobes that are higher than the rest of the corresponding fin. The pectoral and pelvic fins are relatively long. The pectoral fins generally have 14 or 15 rays, although we can observe some specimens with 13. The caudal fin is very forked, with the lower lobe longer than the upper one. At the base of the caudal fin, they have a stabilizing peduncle of small size and dark color.
Tylosurus crocodilus is generally a solitary and scary species, although sometimes we can find it forming small groups, always in superficial waters of lagoons or internal reefs. Its diet is predominantly carnivorous, preying mainly on small fish. There is the possibility of confusion with similar species, such as Strongylura timucu which is distinguished by its dark colored head and for having the dorsal fin in a position behind the anal fin. The other species that could lend itself to confusion is Strongylura marina, which is distinguished by its bluish tail.
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