robustus, Rivulus Miller [R. R.] & Hubbs [C. L.] 1974:865, Figs. 1-3 [Copeia 1974 (no. 4); ref. 7523] Pool north of Arroyo Zacatispán, about 5 kilometers south of Papaloapan (now El Hule), Oaxaca, Mexico. Holotype: UMMZ 124278. Paratypes: (107) UF 16212 (4); UMMZ 124231 (5), 124252 (3), 124279 (4), 146156 (1), 188784 (8), 194706 (62, 8 c&s); USNM 212230 [ex UMMZ 194706] (20). Appeared first as nomen nudum (name only) in Gordon 1947:128 [ref. 38365], based on an unpublished revisionary study by Miller & Gordon. •Valid as Rivulus robustus Miller & Hubbs 1974 -- (Huber 1992:382 [ref. 20639], Espinosa Pérez et al. 1993:37 [ref. 22290]). •Valid as Millerichthys robustus (Miller & Hubbs 1974) -- (Costa 1995:19 [ref. 22097], Costa 1998:79 [ref. 23792], Lazara 2001:209 [ref. 25711], Costa in Reis et al. 2003:532 [ref. 27061], Nelson et al. 2004:101 [ref. 27807], Miller 2006:207 [ref. 28615], Scharpf 2007:11 [ref. 30398], Page et al. 2013:103 [ref. 32708], Lozano-Vilano & De la Maza-Benignos 2016:5 [ref. 35401], Page et al. 2023:140 [ref. 40505]). Current status: Valid as Millerichthys robustus (Miller & Hubbs 1974). Rivulidae: Rivulinae. Distribution: Southern North America: Papaloapan and Coatzacoalcos River basins (Mexico). IUCN (2019): Endangered. Habitat: freshwater.