Biodiversity and systematics of skates (Chondrichthyes: Rajiformes: Rajoidei)

Abstract

Skates (Rajiformes: Rajoidei) are a highly diverse fish group, comprising more valid species than any other group of cartilaginous fishes. The high degree of endemism exhibited by the skates is somewhat enigmatic given their relatively conserved body morphology and apparent restrictive habitat, e.g. soft bottom substrates. Skates are primarily marine benthic dwellers found from the intertidal down to depths in excess of 3,000 m. They are most diverse at higher latitudes and in deepwater, but are replaced in shallower, warm temperate to tropical waters by stingrays (Myliobatodei). The number of valid skate species has increased exponentially, with more species having been described since 1950 (n = 126) than had been described in the previous 200 years (n = 119). Much of the renaissance in skate systematics has largely been through the efforts of a few individuals who through author-coauthor collaboration have accounted for 78 of the 131 species described since 1948 and for nine of 13 genera named since 1950. Furthermore, detailed regional surveys and accounts of skate biodiversity have also contributed to a better understanding of the diversity of the skates. A checklist of the living valid skate species is presented.

Reproductive biology of the skates Sympterygia acuta Garman, 1877 and S. bonapartii Müller & Henle, 1841 (Chondrichthyes: Rajoidei) in south Brazil

“…The genus Sympterygia Müller & Henle, 1837 (Chondrichthyes, Rajiformes) constitutes a taxonomically stable clade within the Suborder Rajoidei and includes four neotropical oviparous skate species: S. lima (Poeppig, 1835), S. brevicaudata (Cope, 1877), S. acuta (Garman, 1877) and S. bonapartii (Müller & Henle, 1841) (McEachran, 1982;Ebert & Compagno, 2007). The latter two are endemic to the shelves of the western South Atlantic Ocean shelves (Figueiredo, 1977;McEachran & Aschliman, 2004) and represent an important economic resource in their whole distribution area (Mabragaña et al, 2002;Menni & Stehmann, 2000;Paesch & Domingo, 2003).…”

Hábitos alimentarios de la raya de cola corta, <i>Bathyraja brachyurops</i> (Chondrichthyes, Rajidae), en el Atlántico Sudoccidental

“…They are a significant link of food webs in benthic communities (Orlov, 1998) and may play influential roles in the food webs of demersal marine communities (Ebert and Bizzarro, 2007). Bathyraja is the most diverse genus of skates (Nelson, 2006;Ebert and Compagno, 2007) with eight species (B. brachyurops, B. macloviana, B. albomaculata, B. magellanica, B. scaphiops, B. multispinis, B griseocauda and B. cousseauae) present on the Argentinean continental shelf (Cousseau et al, 2000;Menni and Stehmann, 2000;Díaz de Astarloa and Mabragaña, 2004). Of these, the broad nose skate Bathyraja brachyurops (Fowler, 1910) is widely distributed in Argentinean waters, from 36º to 55ºS (Menni and López, 1984;Cousseau et al, 2000).…”

Resolving taxonomic uncertainty in vulnerable elasmobranchs: are the Madeira skate (Raja maderensis) and the thornback ray (Raja clavata) distinct species?

“…Skates represent a particularly speciose group constituting nearly a quarter of all known chondrichthyan fishes (Ebert and Compagno 2007). Perhaps somewhat paradoxically, they are extremely morphologically conserved, maintaining a dorso-ventrally flattened body form typical of all batoids and brown-grey coloration.…”

“…In particular the main evolutionary lineages (families Rajidae, Blainville 1816 and Arhynchobatidae, Fowler 1934) were clearly identifiable (Ebert and Compagno 2007). Within Rajidae, clades with strong support were the Amblyrajini, Rajini, and a third containing Raja eglanteria and Rostroraja alba of the Rostrorajini (Chiquillo et al 2014), as well as genera Neoraja and Malacoraja of the Gurgesiellini (McEachran and Dunn 1998).…”