Otocinclus Cope, 1871

Delapieve, Maria Laura S., A., Pablo Lehmann & Reis, Roberto E., 2017, An appraisal of the phylogenetic relationships of Hypoptopomatini cascudinhos with description of two new genera and three new species (Siluriformes: Loricariidae), Neotropical Ichthyology 15 (4), No. e 170079, pp. 1-38 : 23

Genus Otocinclus Cope, 1871

Otocinclus Cope, 1871: 112 . Type-species: Otocinclus vestitus Cope, 1872 . Type by subsequent monotypy. Gender masculine.

Macrotocinclus Isbrücker, Seidel , in Isbrücker et al., 2001: 20. Type-species: Otocinclus affinis Steindachner, 1877 . Type by original designation. Gender masculine.

Included species. Otocinclus affinis Steindachner, 1877 ; Otocinclus arnoldi Regan, 1909 ; Otocinclus batmani Lehmann, 2006 ; Otocinclus bororo Schaefer, 1997 ; Otocinclus caxarari Schaefer, 1997 ; Otocinclus cocama Reis, 2004 ; Otocinclus flexilis Cope, 1894 ; Otocinclus hasemani Steindachner, 1915 ; Otocinclus hoppei Miranda- Ribeiro, 1939; Otocinclus huaorani Schaefer, 1997 ; Otocinclus juruenae Ribeiro, Lehmann, 2016 ; Otocinclus macrospilus Eigenmann, Allen, 1942 ; Otocinclus mangaba Lehmann, Mayer, Reis, 2010 ; Otocinclus mariae Fowler, 1940 ; Otocinclus mimulus Axenrot, Kullander, 2003 ; Otocinclus mura Schaefer, 1997 ; Otocinclus tapirape Britto, Moreira, 2002 ; Otocinclus vestitus Cope, 1872 ; Otocinclus vittatus Regan, 1904 ; and Otocinclus xakriaba Schaefer, 1997 .

Diagnosis. Otocinclus is diagnosed as monophyletic based on five exclusive synapomorphies: ventral ridge of lateral ethmoid absent (char. 6.2); teeth on pharyngeal jaws reduced and arranged in single series (char. 30.1); dorsal-fin spinelet V-shaped (char. 47.1); esophageal diverticulum expanded into accessory gas bladder (char. 102.2); and contact organ present at base of caudal fin in males (104.1). In addition, there are four non-exclusive synapomorphies: anteroventral surface of mesethmoid with one pair of uncinate processes (char. 1.1); swimbladder capsule enlarged (char. 16.1); anterior portion of basipterygium open, bearing pair of fenestrae (char. 60.0); and possession of gap in pores of canal-bearing median plate series (char. 81.1).

Comparisons. The species of Otocinclus are further distinguished from other hypoptopomatins by having a relatively robust and deep body and head, even though adult body size is moderately small, and its maximum standard length reaches 45 mm. In the species of Otocinclus , the fenestrae in the compound pterotic are progressively larger and irregular towards the posterolateral margin (vs. small and all with same size); and the mesethmoid completely covered by plates (vs. mesethmoid exposed). Otocinclus can be further distinguished by the possession of a V-shaped dorsal-fin spinelet and a functional locking mechanism of the dorsal-fin spine (vs. dorsal-fin spinelet absent); the lateral line not extending to the last plate in the median series (vs. lateral line extending to last plate in the median series); the posterior truncation of the mid-dorsal series, which goes from the compound pterotic to the caudal peduncle (vs. anteriorly truncated, with eight plates or less, not passing the posterior tip of the dorsal fin); and by the posteriorly truncated midventral series which extends to the caudal peduncle (vs. extending to a point between the dorsal and anal fins or even absent). Additionally, Otocinclus is distinguished by the presence of secondary sexual dimorphism in mature males in the form of a contact organ at the base of the caudal fin, composed by a patch of odontodes modified into a swirl (vs. swirl absent).