Pseudancistrus Bleeker

Jonathan W. Armbruster, 2004, Pseudancistrus sidereus, a new species from southern Venezuela (Siluriformes: Loricariidae) with a redescription of Pseudancistrus., Zootaxa 628, pp. 1-15 : 2-3

[[ Pseudancistrus Bleeker ]]

Introduction

Pseudancistrus is a medium-sized genus (14 species) of the Loricariidae and is a member of the tribe Ancistrini of the Hypostominae (Armbruster 2004). Bleeker (1862) described Pseudancistrus and separated it from all other members of his Plecostomiformes (=Hypostominae) except Plecostomus (= Hypostomus ) based on the inability to evert the cheek plates but with the presence of hypertrophied cheek odontodes. Isbrücker (1980) retained Pseudancistrus as close to Hypostomus and placed the two genera in a more restrictive Hypostominae, but Schaefer (1986; 1987) found that Pseudancistrus shared a modified bar- or sickle-shaped opercle with the Ancistrinae (now Ancistrini).

Pseudancistrus is also known for the presence of sometimes extremely hypertrophied odontodes along the snout (Burgess 1989). Male and female Pseudancistrus barbatus were pictured in Darwin (1882), and Darwin stated that the male had very hypertrophied odontodes on the snout and they were barely present in females; however, females do develop hypertrophied odontodes in Pseudancistrus species with hypertrophied snout odontodes (Armbruster and Provenzano 2000), although they may not be as long as in males (pers. obs.). Several species appear to lack hypertrophied snout odontodes ( P. brevispinis , P. megacephalus , and the species described herein as P. sidereus ; pers. obs.), and hypertrophied snout odontodes are also found in numerous members of the Ancistrini ( Dolichancistrus and Lasiancistrus for example) as well as many other members of the Loricariidae. However, the presence of hypertrophied snout odontodes is useful in identifying many Pseudancistrus because they are present in the species that have them regardless of season or sex, and they develop fairly early in ontogeny (pers. obs.).

Isbrücker et al. (1988) described Lithoxancistrus orinoco as a new genus and species based on the derived presence of large papillae located behind each dentary. Isbrücker et al. (2001) described Guyanancistrus for several species that were formerly placed in Lasiancistrus ( Isbrücker 1980; Heitmans et al. 1983). The diagnosis of Guyanancistrus in Isbrücker et al. (2001) was brief, and only stated that the species lack the characteristic odontodes of Lasiancistrus (apparently referring to the whiskerlike odontodes of Armbruster 2004); and no characteristics were given to unite the species of Guyanancistrus . The species of Guyanancistrus further lack other synapomorphies for Lasiancistrus , and are not closely related to Lasiancistrus (Armbruster 2004). Armbruster (2004) found that the species of Pseudancistrus , Lithoxancistrus , Guyanancistrus , Hemiancistrus megacephalus , and the species described herein as P. sidereus form a well-diagnosed (decay index = 5), monophyletic clade. Armbruster (2004) placed Lithoxancistrus and Guyanancistrus into the synonymy of Pseudancistrus and transfered Hemiancistrus megacephalus to Pseudancistrus .

Pseudancistrus sidereus , new species, can be considered a basal member of Pseudancistrus based on its lack of the features of more derived members of the genus such as hypertrophied odontodes along the snout (Fig. 1) and loss of the evertible cheek plates, and its placement was in a basal polytomy with P. brevispinis , P. megacephalus , and the remainder of Pseudancistrus in Armbruster (2004). Pseudancistrus sidereus has a unique ridge on the caudal peduncle formed from the concave dorsal sections of the ventral row plates and a fairly uncommon color pattern of white to gold spots. Pseudancistrus sidereus is found only in the southern Venezuelan state of Amazonas, and is described herein. Pseudancistrus is also diagnosed and redescribed.