7) Cynodonichthys fuscolineatus (Bussing, 1980);

Rivulidae .

Arenal Rivulus; Olomina, Alumina, Olomina Saltona, Killi, Saltón, Olomina del Arenal, Killi del Arenal (Fig. 4D).

New record for the Río Frío River basin; previous records of the species in Costa Rican freshwaters were restricted to the San Carlos and Bebedero River basins. New elevational record (731 m. a.s.l.); previous records of the species in Costa Rican freshwaters were restricted to 525– 695 m.a.s.l. Basis of the record: Two specimens were captured in an unnamed stream on the Bijagua-Zapote-El Higuerón road, Bijagua, Upala, Alajuela (10.76306, -85.06727), at 541 m. a.s.l., on May 1, 2021, by Jorge San Gil, Susana Gutiérrez, Pablo Morales, Derick Herrera and Arturo Angulo; additional specimens were captured on the Parque Nacional Volcán Tenorio (10.71147, -84.98826, at 674 m. a.s.l, and 10.70378, -84.99076, at 731 m. a.s.l; one and four, respectively) on the same date and by the same collectors (plus the park ranger Isaac López—SINAC) as above.