Topic
Scymnodon
About: Scymnodon is a research topic. Over the lifetime, 3 publications have been published within this topic receiving 39 citations.
Papers
TL;DR: The new species S. ichiharai is described here on the basis of 14 specimens caught in Suruga Bay and adjacent waters and is clearly discriminated from the closely related S. plunketi and S. ringens.
Abstract: Scymnodon in Japan is represented by two species, S. squamulosus and S. ichiharai sp. nov. The new species differs from other species of the genus by the shape of 1st dorsal fin, dermal denticles and lower teeth, the head length, and the interspace between the pelvic and caudal fins. S. squamulosus is redescribed from 12 specimens. S. obscurus is regarded as a junior synonym of S. squamulosus® A key to the species of Scymnodon is given. Scymnodon is closely related to Centroscymnus. The deep sea shark genus Scymnodon, belonging to the family Squalidae, can be distinguished from related genera by : its upper teeth being much longer midway along each side of jaw than either toward the center of the mouth or toward its outer corner; broadly rounded inner corners of the pectoral fins ; and no concave crown-like dermal denticles. Bocage and Capello (1864) established Scymnodon as a new genus, and described S. ringens from Portugal. From the seas around Japan, Giinther (1877) described a species, S. squamulosus, which he originally placed in the genus Centrophorus. Jordan and Fowler (1903) proposed a new genus Zameus for C. squamulosus but Regan (1906) referred squamulosus to Scymnodon. Garman (1913) included in Scymnodon the species S. ringens, S. squamulosus, S. macracanthus (Regan, 1906), from Magellan, S. plunketi (Waite, 1910), from New Zealand, and treated Centroscymnus obscurus Vaillant, 1888, off the coast of northwestern Africa, as a synonym of S. ringens. Archey (1921) described a new species, S. sherwoodi which Garrick (1956) later placed in a new genus Scymnodalatias within the Dalatiidae. Fowler (1933) proposed for S. plunketi a new subgenus Proscymnodon which Whitley (1934) regarded as a genus. Fowler (1940), also, referred S. squamulosus and S. sherwoodi to a subgenus Zameus, S. ringens to a subgenus Scymnodon, and S. plunketi to a subgenus Proscymnodon. Bigelow and Schroeder (1954) reported that S. melas Bigelow, Schroeder et Springer, 1953 was a juvenile stage in the growth of Centroscymnus coelolepis. Bigelow and Schroeder (1957) referred S. ringens, S. squamulosus and S. obscurus to Scymnodon but placed S. plunketi and S. macracanthus in Centroscymnus. Garrick (1959b) identified C. plunketi as a species of Scymnodon. S. plunketi and C. macracanthus have been variously placed in Centrophorus, Centroscymnus and Scymnodon by several authors. Recently, the genus Scymnodon was stated as including four species : S. ringens, S. squamulosus, S. obscurus and S. plunketi (Cadenat and Blache, 1981). The new species S. ichiharai is described here on the basis of 14 specimens caught in Suruga Bay and adjacent waters. It is clearly discriminated from the closely related S. plunketi and S. ringens. The denticles of the trunk of S. squamulosus as pictured by Gunther (1887) show no trace of transverse ridges. Bigelow and Schroeder (1957), and Cadenat and Blache (1981) used the absence (squamulosus) or the presence (obscurus) of transverse ridges on the denticles as the main difference between these species. But our reexamination of the dermal denticles of the holotype of S. squamulosus from the British Museum revealed that transverse ridges are present in that species just as they are in S. obscurus. Materials and methods The Japanese specimens used for this study were caught with bottom longlines and bottom drop lines, which were set at depths between 400 m and 1,500 m. These localities are shown
20 citations
TL;DR: Scymnodalatias albicauda sp.
Abstract: Scymnodalatias albicauda sp. nov. is described from two specimens taken at high latitudes (45°S and 49°S). It is distinguished fromS. sherwoodi, only known species of the genus, by having white markings on the caudal fin, the second dorsal posterior tip almost reaching the upper caudal fin, shorter snout and head, smaller eye and larger fins. Relationships ofScymnodalatias to the generaScymnodon, Centroscymnus, andZameus are discussed, based chiefly on dermal denticle structure.Scymnodalatias andZameus uniquely share transverse ridges on their dermal denticles, and on this character they are treated as sister-groups. Comments on the above genera,Z. squamulosus and some species ofScymnodon are made to clarify their systematic status. As a result, it is proposed thatScymnodon includesichiharai, macracanthus, plunketi, andringens, thatCentroscymnus includescoelolepis, crepidater, crypt acanthus, andowstonii, and thatZameus includessquamulosus.
19 citations
1 Feb 2020
TL;DR: Stereo-Baited Remote Underwater Videos were deployed to collect ecological data from New Zealand deep-sea sharks and revealed that alternative non-destructive methods can be effective for ecological studies ofDeep-sea marine fauna.
Abstract: Currently the ecology of deep-water sharks is poorly documented, especially in situ information for these elusive species are lacking. In this study, stereo-Baited Remote Underwater Videos (stereo-BRUVs) were deployed to collect ecological data from New Zealand deep-sea sharks. The results showed differences in abundance between species, with Etmopterus granulosus (Etmopteridae) found in greatest numbers. Moreover, the known depth range increased for Scymnodon macracanthus (Centrophiridae). Deep-sea shark species were generally found to swim at slower cruise speeds (0.36 ± 0.04 m s−1) than their shallow-water counterparts (0.63 ± 0.05 m s−1). However, the swimming speed of deep-sea sharks was clearly not uniform, with some species displaying higher cruise swimming speeds than others. The fastest sharks (Centrophorus harrissoni, Etmopterus granulosus and Etmopterus molleri) had swimming abilities comparable to benthic shallow water sharks (0.48 ± 0.02 m s−1). The higher cruise swimming speed in the family Etmopteridae could be an advantage for these luminous sharks if they follow isolumes to match their ventral light intensity with the down-welling light of their environment. This study revealed that alternative non-destructive methods can be effective for ecological studies of deep-sea marine fauna.
14 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2020 | 1 |
| 1986 | 1 |
| 1984 | 1 |