Key to species of Ancistrus from the Río de La Plata and coastal basins from southern Brazil 1 Maxillary barbel longer and free from the lower lip .................................................................................................... 2 - Maxillary barbel short and not free from the lower lip................................................................................................. 6 2 Male with small pale dots on the head becoming vermiform lines on the trunk; female with very small pale dots all over the body ................................................................. A. claro (upper Rio Paraguai basin, Chapada dos Guimarães) - No distinct color pattern among male and female ........................................................................................................ 3 3 Mandibulary teeth row 12.2 to 15.0% of HL ..................................................... A. cuiabae (upper Rio Paraguai basin) - Mandibulary teeth row more than 15.2% of HL........................................................................................................... 4 4 Occipital depth 17.9 to 18.7% of SL .................................................................. A. cirrhosus (lower Río Paraná basin) - Occipital depth less than 16.7% of SL.......................................................................................................................... 5 5 Pear-liked body shape; supracleithral width 30.3 to 37.0% of SL .................... A. piriformis (lower Río Paraná basin) - Not pear-liked body shape; supracleithral width 26.3 to 31.3% of SL ............. A. pirareta (lower Río Paraguay basin) 6 Orbital diameter 8.3 to 8.7% of HL ............................................................ A. formoso (Rio Formoso basin, cave fish) - Orbital diameter more than 11.7 of HL ........................................................................................................................ 7 7 Mandibulary teeth row 13.4 to 15.5% of HL .......................... A. abilhoai n. sp. (upper and middle Rio Iguaçu basin) - Mandibulary teeth row more than 15.5% of HL........................................................................................................... 8 8 Occipital depth 18.8 to 22.0% of SL ................................................................ A. agostinhoi n. sp. (Rio Jordão basin) - Occipital depth less than 18.8% of SL.......................................................................................................................... 9 9 Interopercular spines 12 to 22 ................................................................... A. mullerae n. sp. (lower Rio Iguaçu basin) - Interopercular spines 22 to 35..................................................................................................................................... 10 10 Postopercular plates 8 to 12; plates between anal and caudal 11 to 12 .............. A. taunay (middle Rio Uruguai basin) - Postopercular plates 5 to 8; plates between anal and caudal 12 to 13 ............................................................................ .......................................................................................................... A. multispinis (coastal basins of southern Brazil)

Published as part of Bifi, Alessandro Gasparetto, Pavanelli, Carla Simone & Zawadzki, Cláudio Henrique, 2009, Three new species of Ancistrus Kner, 1854 (Siluriformes: Loricariidae) from the Rio Iguaçu basin, Paraná State, Brazil, pp. 41-59 in Zootaxa 2275 on page 57, DOI: 10.5281/zenodo.191064