A new species of sand-dwelling catfish, with a phylogenetic diagnosis of Pygidianops Myers (Siluriformes: Trichomycteridae: Glanapteryginae)

Abstract

A new species of sand-dwelling catfish genus Pygidianops, P. amphioxus, is described from the Negro and lower Amazon basins. The new species differs from its three congeners in the elongate eel-like body, the short barbels, and the small caudal fin, continuous with the body, among other traits of internal anatomy. The absence of anal fin further distinguishes P. amphioxus from all other Pygidianops species except P. magoi and the presence of eyes from all except P. cuao. The new Pygidianops seems to be the sister species to P. magoi, the two species sharing a unique mesethmoid with a dorsally-bent tip lacking cornua, and a produced articular process in the palatine for the articulation with the neurocranium. Pygidianops amphioxus is a permanent and highly-specialized inhabitant of psammic environments. Additional characters are proposed as synapomorphies of Pygidianops, including a hypertrophied symphyseal joint and associated ligament in the lower jaw; an elongate, laterally-directed, process on the dorsal surface of the premaxilla; and a rotated lower jaw, where the surface normally facing laterally in other glanapterygines is instead directed ventrally. These and other characters are incorporated into a revised phylogenetic diagnosis of Pygidianops.Uma nova espécie do gênero de bagre arenícola Pygidianops, P. amphioxus, é descrita de diferentes localidades na Amazônia brasileira. A nova espécie difere de seus três congêneres pelo corpo alongado e anguiliforme, pelos barbilhões curtos e pela pequena nadadeira caudal, contínua com o corpo, além de outras características da anatomia interna. A ausência de nadadeira anal distingue P. amphioxus de todos os outros Pygidianops exceto P. magoi e a presença de olhos de todos exceto P. cuao. O novo Pygidianops parece ser o grupo-irmão de P. magoi, as duas espécies compartilhando um mesetmóide com a extremidade dobrada dorsalmente, sem cornua, e um processo articular prolongado no palatino para articulação com o neurocrânio. Pygidianops amphioxus é um habitante permanente e altamente especializado de ambientes psâmicos. Caracteres adicionais são propostos como sinapomorfias para Pygidianops, incluindo uma articulação sinfiseana e ligamento associado hipertrofiados na mandíbula; um processo alongado e dirigido lateralmente na superfície dorsal do pré-maxilar; e a mandíbula rotacionada, de forma que a superfície normalmente lateral em outros Glanapteryginae é dirigida ventralmente. Estes e outros caracteres são incorporados em uma diagnose filogenética revisada de Pygidianops.

Multigene phylogeny reveals convergent evolution in small interstitial catfishes from the Amazon and Atlantic forests (Siluriformes: Trichomycteridae)

“…Therefore, the only apomorphic condition shared by Listrura and glanapterygines is the common absence of pelvic fin, although most specimens of G. anguilla and the only known specimen of Glanapteryx niobium de Pinna, have a rudimentary pelvic fin (de Pinna, , ). Abundant morphological evidence has been described corroborating Glanapteryginae monophyly excluding Listrura and sister group relationships between Pygidianops and Typhlobelus (Baskin, ; Costa & Bockmann, ; de Pinna & Kirovsky, ; de Pinna & Zuanon, ), as well as the present study clearly indicates that species of Listrura forms a clade distantly related to Pygidianops amphioxus (Figure ), the only glanapterygine available for the present study, thus supporting exclusion of Listrura from the Glanapteryginae.…”

“…Although a detailed study to test monophyly of the Amazon Sarcoglanidinae is beyond the scope of the present paper, the absence or extreme reduction in opercular teeth described among other features by Baskin () to diagnose a clade containing the Amazon sarcoglanidine genera Malacoglanis and Sarcoglanis and the glanapterygine genera Glanapteryx , Pygidianops and Typhlobelus , may corroborate the Amazon Sarcoglanidinae paraphyly hypothesis indicated in our analysis. Past and recent studies have confirmed that in species of the genera Sarcoglanis , Glanapteryx , Pygidianops and Typhlobelus , opercular odontodes are absent, whereas in Malacoglanis they are rudimentary (Baskin, ; Claeson et al, ; Costa & Bockmann, ; Myers, ; Myers & Weitzman, ; de Pinna, , ; de Pinna & Kirovsky, ; de Pinna & Zuanon, ; Schaefer et al, ), thus contrasting with the robust opercular odontodes in Stauroglanis and Stenolicmus (de Pinna, ; de Pinna & Starnes, ; Figure d). The presence of a long posterior narrow process on the opercular bone, also described to Baskin for that group, is present at least in species of Malacoglanis , Glanapteryx , Pygidianops and Typhlobelus (Baskin, ; de Pinna, ; de Pinna & Kirovsky, ; de Pinna & Zuanon, ), but not in Stauroglanis , Stenolicmus and Ammoglanis (Costa, ; Mattos et al, ; de Pinna, ; de Pinna & Starnes, ; de Pinna & Winemiller, ; Figure d).…”

“…In this paper, the genera Glanapteryx , Pygidianops and Typhlobelus were placed in the new subfamily Glanapteryginae. New records and additional species have been described for all the three genera in recent studies, expanding the distribution of this group to other parts of the Amazon (Costa & Bockmann, ; de Pinna, , ; Sabaj Pérez, ), as well as for the Orinoco River Basin (Nico & de Pinna, ; de Pinna, ; de Pinna & Kirovsky, ; de Pinna & Zuanon, ; Schaefer et al, ). However, whereas species of Pygidianops and Typhlobelus have been reported to live borrowed in sandy substratum, field data suggest that species of Glanapteryx inhabit leaf litter bottom (Schaefer et al, ).…”

“…Sand‐dwelling trichomycterids are similar to many other psammophilic Neotropical fishes in possessing translucent body and small adult size (Zuanon, Bockmann, & Sazima, ). On the other hand, interstitial trichomycterids exhibit uncommon morphology that has convergently occurred in cryptobenthic fishes (Wagner et al, ; Yamada, Sugiyama, Tamaki, Kawakita, & Kato, ), including elongate eel‐shaped body with numerous vertebrae and reduction or absence of eye and fins (Costa & Bockmann, ; de Pinna, ; de Pinna & Kirovsky, ; Schaefer, Provenzano, Pinna, & Baskin, ). Similar adaptations to interstitial life convergently occurred in so different lineages of marine interstitial teleost fishes such as clingfishes (Wagner et al, ) and gobies (Yamada et al, ).…”

Rediscovery, taxonomic and conservation status of the threatened catfish Listrura camposi (Miranda-Ribeiro) (Siluriformes: Trichomycteridae)

“…By contrast, L. camposi displays a putative plesiomorphic condition in comparison to remaining glanapterygines. A fusion between all elements of the caudal skeleton has being considered as a synapomorphic character for Glanapteryginae (e.g., de Pinna, 1988de Pinna, , 1989de Pinna, , 1998. In L.camposi, hypurals 3-5 are separated from hypurals 1-2 (Fig.…”