A new species of Sturisoma (Loricariidae: Loricariinae) from the Madre de Dios River basin, Peru, with a key to all congeners and comments on the type series of Sturisoma rostratum

Abstract

A new species of the genus Sturisoma from the Madre de Dios River, upper Madeira, Peru, is described. The new species can be differentiated from its congeners by the following characteristics: dorsolateral stripe reaching to less than half, or only half length of caudal peduncle (v. absence of dorsolateral stripe or, if present, spanning more than half caudal-peduncle length); premaxillary teeth longer than dentary teeth (v. dentary teeth longer); sexually mature adult males having well-developed odontodes on the sides of the head and a broader snout (v. adult males lacking well-developed hypertrophied odontodes or, if present, rostrum is same width as females' or immature males'); by having the ventral portion of the rostrum conspicuously darker than ventral surface of the body (v. rostrum light, with same colour as ventral portion of body, except in Sturisoma barbatum); by lacking the lateral process of the sphenotic (v. lateral process of sphenotic well-developed, except in Sturisoma tenuirostre); a dark spot on the first three branched pectoral-fin rays (v. brown spot absent, except in S. barbatum); and the frontal bone contributing less than half of dorsal border of the orbital ridge (v. extensive participation of the frontal, except in Sturisoma guentheri). Furthermore, the new species has 18-20 plates in the median series, which differentiates it from Sturisoma rostratum (21-22), and Sturisoma monopelte (21); and 14-15 coalescent plates, which differentiates it from S. tenuirostre (16-17). It is further differentiated from Sturisoma brevirostre by presence of an enlarged rostrum (v. rostrum not enlarged). A discussion regarding status of the type series and geographic distribution of Sturisoma rostratum is offered, and an identification key for all Sturisoma species is presented.

A new species of Sturisoma Swainson, 1838 (Loricariidae: Loricariinae), from the Madeira River basin, with a discussion of historical biogeography of western Amazonas and Paraguay River basins

“…Captured individuals were anaesthetized and killed by immersion in eugenol, fixed in 10% formalin solution and later preserved in 70% ethanol. Measurements and counts follow Londoño‐Burbano (2018). Measurements were taken point to point using digital callipers (0.1 mm) and were included in tables as percentages of standard length ( L s ) or head length ( L H ); holotype measurements were included as millimetres (mm), not as percentages.…”

“…The last taxonomic addition to Sturisoma was the description of Sturisoma graffini Londoño-Burbano, 2018, from the Madre de Dios River basin, with a revision of the type series and a discussion of the status of the type species of the genus, Sturisoma rostratum. To date, 10 species are recognized as valid for the genus, following Londoño-Burbano (2018) and Fricke et al (2022). Nonetheless, the delimitation of species within the genus remains problematic.…”

“…After a 60 year hiatus, Ghazzi (2005) described Sturisoma kneri , later found to pertain to the genus Sturisomatichthys Isbrücker & Nijssen 1979 (Covain et al ., 2016; Londoño‐Burbano & Reis, 2019, 2021). The last taxonomic addition to Sturisoma was the description of Sturisoma graffini Londoño‐Burbano, 2018, from the Madre de Dios River basin, with a revision of the type series and a discussion of the status of the type species of the genus, Sturisoma rostratum . To date, 10 species are recognized as valid for the genus, following Londoño‐Burbano (2018) and Fricke et al .…”

Taxonomic revision of Sturisoma Swainson, 1838 (Loricariidae: Loricariinae), with descriptions of four new species

“…Measurements and counts follow Londoño‐Burbano (2018). Measurements were taken point to point using digital calipers (0.1 mm) and were included in tables as percentage of standard length (LS) or head length (LH).…”

“…Ghazzi (2005) described S. kneri , later found to be in Sturisomatichthys (Covain et al, 2016; Londoño‐Burbano & Reis, 2019, 2021). S. graffini was described by Londoño‐Burbano (2018) from the Madre de Dios River basin, Peru, with a revision of the type series and a discussion of the status of the type species of the genus, S . rostratum .…”