Pseudotothyris, BRITSKI & GARAVELLO, 1984

Martins, Fernanda O., Britski, Heraldo A. & Langeani, Francisco, 2014, Systematics of Pseudotothyris (Loricariidae: Hypoptopomatinae), Zoological Journal of the Linnean Society 170 (4), pp. 822-874 : 824-825

PSEUDOTOTHYRIS BRITSKI & GARAVELLO, 1984

Pseudotothyris Britski & Garavello, 1984: 232 ( Otocinclus obtusus Miranda-Ribeiro, 1911 , type species by original designation) (distribution: coastal rivers of south-eastern Brazil, from Rio de Janeiro to Santa Catarina state); Schaefer, 1997: 41 (identification key); Eschmeyer, 1998: 2099 (catalogue); Schaefer, 2003a: 327 (catalogue); Ferraris, 2007: 290 (catalogue).

Diagnosis: Pseudotothyris differs from all other Hypoptopomatinae by having odontodes on anterior region of snout unequal in size, those on dorsal surface well developed, longer and wider than the other on ventral portion, which are more similar to the odontodes on the rest of the head ( Fig. 1B ) (vs. either small or well-developed odontodes on both surfaces of the snout or well-developed odontodes restricted to ventral portion). Additionally, Pseudotothyris can be diagnosed from all hypoptopomatines except Otothyris by having the compound pterotic with an elongate posterior extension, easily distinguished from the main body of the bone, its distal portion surpassing the rib of the sixth vertebra [vs. posterior extension absent, or if present never surpassing the rib of the sixth vertebra ( Fig. 2 )]. Pseudotothyris is readily distinguished from Otothyris by having 14 branched rays on the caudal fin (vs. 12); abdominal plates, when present, numerous and small (vs. abdomen plates always present, few and large); anterior portion of snout with four elongate plates ( Fig. 3C ) [vs. two quadrangular plates ( Fig. 3B )]; canal of the second infraorbital present ( Fig. 4B ) [vs. absent in most specimens ( Fig. 4C )]; and mesethmoid extending beyond the condyle, with the anterior portion rounded and narrow ( Fig. 5B ) [vs. mesethmoid never extending beyond the condyle, the anterior portion truncated and laterally expanded ( Fig. 5A )].

Additionally, Pseudotothyris can be easily distinguished from Schizolecis by having the arrector fossae entirely closed and pectoral girdle often totally exposed, sometimes with a small median area without odontodes, covered only by skin (vs. arrector fossae partially open and pectoral girdle exposed only laterally); a raised tuft of well-developed odontodes on the parietosupraoccipital in adults (vs. absent); and first pelvic-fin ray with a dorsal fleshy flap in males (vs. absent). Finally, Pseudotothyris differs from Otothyropsis by having the anterior portion of snout with four elongate plates (vs. a single plate); iris operculum absent (vs. present); and upper pharyngeal toothplate small and rounded, its length less than 50% of the length of ceratobranchial 5 (vs. upper pharyngeal toothplate relatively large and wedgeshaped, its length more than 50% of the length of ceratobranchial 5).

Distribution: Pseudotothyris occurs in southern and south-eastern Brazilian coastal drainages, from Rio de Janeiro to Santa Catarina state ( Fig. 6 ). The region includes three subareas as defined by Abell et al. (2008): Fluminense (from Rio de Janeiro mountain region, near Macaé, to Santos); Ribeira de Iguape (from Santos to São Paulo and Paraná state limits), and Sudeste Mata Atlântica (from São Paulo and Paraná states’ division to Florianópolis). In the transition between Fluminense and Ribeira de Iguape subareas there is a gap in the genus distribution. This region is known to have low richness ( Sabino & Castro, 1990; Esteves & Lobón-Cerviá, 2001; Ribeiro et al., 2006), not having many species that are common in neighbouring areas. This is probably related to the geographical formation of the area, which is characterized by a reduced coastal plain, with numerous waterfalls and drainage area reduced, which could decreases the habitat for many species of fishes, including Pseudotothyris species.

Figures

Figure 1. Odontodes at anterior margin of snout. A, Otothyris lophophanes, MNRJ 22985, 20.0 mm standard length (SL), female. B, Pseudotothyris obtusa, MCP 31726, 24.2 mm SL, female. Scale bar = 0.5 mm.

Figure 2. Skull in lateral view (left side, dissected). A, Otothyris lophophanes, MNRJ 22985, 20.0 mm standard length (SL), female. B, Pseudotothyris obtusa, MCP 31726, 24.2 mm SL, female. Scale bars = 1 mm.

Figure 3. Skull in dorsal view (specimens dissected on the left). A, Schizolecis guntheri, DZSJRP 6525, 32.9 mm standard length (SL), male. B, Otothyris lophophanes, MNRJ 22958, 20.0 mm SL, sex undetermined. C, Pseudotothyris obtusa, MCP 31726, 24.2 mm SL, female. Abbreviations: CP1, canal-bearing plate 1; F, frontal; IO1−6, infraorbitals 1–6; N, nasal; OP, opercle; PF, prefrontal plate; PN, prenasal plates; POP, preopercle; PR1−4, postrostral plate 1–4; PT-SC, compound pterotic; R, rostral plate(s); SOC, parietosupraoccipital; SOCP, subocular cheek plate; SP, sphenotic. Scale bars = 1 mm.

Figure 4. Infraorbital series, lateral view (left side). A, Isbrueckerichthys duseni, DZSJRP 13670, 48.3 mm standard length (SL), sex undetermined. B, Pseudotothyris obtusa, MCP 31726, 24.2 mm SL, female. C, Otothyris lophophanes, MNRJ 22985, 20.0 mm SL, female. D, Microlepidogaster sp. nov., MZUSP 95291, 38.1 mm SL, female. E, Gymnotocinclus anosteos, UFRGS 11296, 43.7 mm SL, male. Abbreviations: IO1−6, infraorbitals 1–6; LN, lateronasal plate. Scale bars = 1 mm.

Figure 5. Mesethmoid in ventral view. A, Otothyris rostrata, MCN 18943, 23.6 mm standard length (SL), male. B, Pseudotothyris obtusa, MCP 31726, 24.2 mm SL, female. C, Otocinclus affinis, DZSJRP 7610, 31.5 mm SL. D, Rhinolekos britskii, DZSJRP 6983, 36.0 mm SL, female. E, Pareiorhina rudolphi, DZSJRP 13713, unmeasured, sex undetermined. F, Hisonotus notatus, DZSJRP 13852, 31.5 mm SL, female. G, Neoplecostomus microps, DZSJRP 2768, unmeasured, sex undetermined. H, Isbrueckerichthys duseni, DZSJRP 13670, 48.3 mm SL, sex undetermined. Arrows showing the cartilaginous process (D), and process anterior to the condyle (F). Scale bars = 1 mm.

Figure 6. Geographical distribution of Pseudotothyris species in southern and south-eastern Brazilian costal drainages: Pseudotothyris ignota sp. nov. (dots), Pseudotothyris obtusa (squares), and Pseudotothyris janeirensis (triangles). The symbols can represent more than one sampling locality. Open symbols represent type localities.