Schroederichthys Springer

Ulisses L. Gomes, Gerhard O. Peters, Marcelo R. de Carvalho & Otto B. F. Gadig, 2006, Anatomical investigation of the slender catshark Schroederichthys tenuis Springer, 1966, with notes on intrageneric relationships (Chondrichthyes: Carcharhiniformes: Scyliorhinidae)., Zootaxa 1119, pp. 29-58 : 29-30

[[ Genus Schroederichthys Springer ]]

Sharks of the genus Schroederichthys Springer, 1966 are small to medium-sized catsharks (Scyliorhinidae) restricted to temperate and tropical waters of South and Central America, occurring on the continental shelf and upper slope (Compagno, 1984, 1988). The genus was described for Schroederichthys maculatus (type-species) and S. tenuis , two small and strongly attenuated species that differed from other scyliorhinids in having a greatly elongated postpelvic trunk region and well developed upper and lower labial folds (Springer, 1966). Adults of S. maculatus were abundant but unknown for S. tenuis , for which only two specimens existed for almost 20 years since its original description and Springer’s (1979) subsequent review of the Scyliorhinidae. A third specimen, an immature male 260 mm in total length, was finally collected off Suriname in waters 72 m deep (Uyeno and Sasaki, 1983). Springer’s original specimens measured 230 and 180 mm total length (holotype and paratype, respectively) and were also immature males, captured off the mouth of the Amazon River in 410 m (Springer, 1966).

Springer (1979) expanded Schroederichthys to include the South American Scyllium bivium Smith, 1838 and Scyllium chilense Guichenot, 1848, two species that were previously assigned to either Scyliorhinus Blainville, 1816 (Regan, 1908; Norman, 1937) or the Indo-Pacific genus Halaelurus Gill, 1862 (Garman, 1913; Springer, 1966; Kato et al., 1967; Gosztonyi, 1973; Menni et al., 1979). Springer’s (1979) reallocation of these species was based on the observation that newly hatched individuals of Halaelurus bivius were as attenuated as both species of Schroederichthys . In addition, Springer was informed that an unreported adult specimen of Schroederichthys tenuis from southeastern Brazil in the ISH collection in Hamburg differed from adult S. maculatus in not being attenuated (pers. comm. from the late G Krefft; Springer, 1979), which further corroborated the assignment of H. bivius and H. chilensis to Schroederichthys , and led Compagno (1984) to deduce that the tapered adult body of S. maculatus was neotenic. The ISH/Hamburg Schroederichthys specimen was examined by one of us (MRC) in 1996 and identified as a new species of Schroederichthys , which is now referred to S. saurisqualus Soto, 2003 [1].

New specimens of S. tenuis appeared only in 1991 when one male and two females were collected from off the coast of Amapá State (northern Brazil) at 450 m (Gomes and de Carvalho, 1995; Gadig et al., 1996; Gadig, 2001). These specimens contained in their stomachs small teleosts and benthic invertebrates, and represented the first adult specimens of S. tenuis . One of the females was pregnant and contained a single egg capsule in each uterus (Gomes and de Carvalho, 1995). More importantly, these adults have highly tapered bodies and are as attenuated as juveniles of S. tenuis and juveniles and adults of S. maculatus .

The present study reports nine additional specimens of S. tenuis from off Pará State, northern Brazil, caught during exploratory fisheries surveys of its continental slope by the Brazilian Federal REVIZEE program. Our objectives here are to describe and illustrate the skeleton and other morphological features of this rare species, based on mature and immature individuals, and compare them with congeners. Some comments on species relationships within Schroederichthys are also provided, anticipating results of work still in progress (de Carvalho and Gomes, in prep.).