Glaucostegus

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Glaucostegus
Two Glaucostegus granulatus on a fish market in Thailand

Two Glaucostegus granulatus on a fish market in Thailand

Systematics
Subclass : Euselachii
Subclass : Plate gill (Elasmobranchii)
without rank: Stingray (batoidea)
Order : Rhinopristiformes
Family : Glaucostegidae
Genre : Glaucostegus
Scientific name of the  family
Glaucostegidae
Last , Séret & Naylor , 2016
Scientific name of the  genus
Glaucostegus
Bonaparte , 1846

Glaucostegus is a genus of rays and, because of its body shape, belongs to the group of fiddle rays.

features

The Glaucostegus species are medium-sized to large rays with a maximum length of over 3 meters. The shark-like trunk is strongly flattened, the body disc consisting of trunk and pectoral fins is wedge-shaped or shovel-shaped. The skin of the fish is covered with small placoid scales . Small thorns can be found along the center line of the back, near the eyes, on the "shoulders" and sometimes on the muzzle. As a rule, the thorns in young fish are more strongly developed than in older animals. The two similarly shaped dorsal fins are clearly separated and lie behind the end of the pelvic fins. The tail is flattened and has a longitudinal fold of skin in the lower part of both sides. Both folds of skin meet at the base of the poorly developed lower caudal fin lobe. The caudal fin is small. The oblique nostrils are close together and are longer than their distance from one another.

On the back side, the animals are brownish or gray in color. The ventral side is mainly white, black spots are sometimes present on the underside of the snout. The most striking feature of the genus is the different coloration of the rostrum and snout. The rod-shaped cartilage is the same color as the rest of the animal, while the skin to the right and left of the rostral cartilage is light, almost transparent.

species

Systematics

The genus Glaucostegus originally belonged to the family Rhinobatidae , to which it is very similar in its body shape. Since, according to molecular genetic studies, it is the sister group of the sawfish (Pristidae), the Glaucostegidae family was introduced in 2016, with Glaucostegus as the only genus. Synapomorphies that distinguish the genus from the rhinobatids are the large, almost transverse nostrils (small and slightly sloping in the rhinobatids) and other details of the anatomy of the nostrils.

literature

  • Last, PR, Séret, B. & Naylor, GJP (2016): A new species of guitarfish, Rhinobatos borneensis sp. nov. with a redefinition of the family-level classification in the order Rhinopristiformes (Chondrichthyes: Batoidea). Zootaxa , Vol 4117, No 4: 451-475. DOI: 10.11646 / zootaxa.4117.4.1

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