Planonasus indicus
| Planonasus indicus | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Planonasus indicus | ||||||||||||
| Ebert, Akhilesh and Weigmann , 2018 |
Planonasus indicus is a deep-sea shark from the Pseudotriakidae family that wasfirst described in early 2018. The type specimens werecaught by fishing vesselsat depths of 200 to 1000 meters on the upper continental slope of the southern Indian subcontinent off the coast of the Indian state of Kerala , near Sri Lanka and the northern Maldives .
features
The fish are monochrome dark brown to blackish and show no markings such as spots or stripes. The undersides of the head and torso, the sides of the head and the edges of the fins, which are colored differently in many species of shark, have the same coloring as the back. The specimens caught and examined so far were 49 to 64 cm long. Your body is elongated and soft. In front, between the base of the pectoral fins and the beginning of the first dorsal fin, they are rather stocky. The head is wide and flat, its length is 23 to 24.6% of the total length of the fish. Eyes, injection holes and gill slits are very large. There is no nictitating membrane or it is only rudimentarily developed. The teeth are small and numerous and differ significantly in the upper and lower jaw. In the upper jaw, the teeth have a large central point, flanked by a small point on each side of the tooth. They are there in 118 to 122 rows with 5 to 6 teeth in a row. The teeth in the middle four rows are noticeably smaller than the other teeth in the upper jaw. In the lower jaw, the teeth are in 153 to 156 rows. The teeth of the middle 26 rows are arranged in the shape of a quincunx . They have a large, central point, flanked by two small points on each side of the tooth. The teeth on the sides of the jaw have three or five equally sized tips. Together they form a comb-like structure. The placoid scales on the head and below the snout are teardrop-shaped or have the shape of a diamond, on the sides of the body they have a backward-pointing thorn. They don't overlap. The pectoral fins are medium-sized, triangular and broad and convex at the end. The beginning of their base lies under the fourth gill slot. The pelvic fins are also triangular and convex at the end. The first dorsal fin lies in front of the base of the pelvic fin, is of medium length and has the shape of a low triangle with a rounded upper tip and a sharply pointed rear end. The second dorsal fin lies above or slightly behind the base of the pelvic fin. It is about the same length or only slightly shorter than the first, but significantly higher. There is no interdorsal ridge . The anal fin is low and about half as high as the second dorsal fin. It is opposite the second dorsal fin. The tail stalk is slender and slightly flattened on the sides. The caudal fin is heterocercous with a narrow lobe. The holotype has 132 vertebrae. The spiral casing has 12 turns.
Planonasus indicus can be distinguished from Planonasus parini mainly by the lack of a white color at the tip of the first dorsal fin. The inside of the mouth and the tongue are not covered with papillae, as in Planonasus parini and Planonasus indicus has more rows of teeth in the lower jaw (153–156 vs. 115–120).
Way of life
Since the species is only known from dead specimens caught by fishing boats, little is known about their way of life. In one of the type specimens, a 64 cm long female, numerous white eggs were found, which is why one can assume that the species reproduces oviparously .
supporting documents
- ↑ a b c d Ebert, DA, KV Akhilesh and S. Weigmann (2018): Planonasus indicus sp. n., a new species of pygmy false catshark (Chondrichthyes: Carcharhiniformes: Pseudotriakidae), with a revised diagnosis of the genus and key to the family. Marine Biodiversity, August 2018, DOI: 10.1007 / s12526-018-0915-4