A new species of freshwater mussel in the genus Popenaias Frierson, 1927, from the Gulf coastal rivers of central Mexico (Bivalvia: Unionida: Unionidae) with comments on the genus Author Inoue, Kentaro Natural Resources Institute, Texas A & M University, College Station, Texas, USA & Daniel P. Haerther Center for Conservation and Research, John G. Shedd Aquarium, Chicago, IL, USA kinoue @ sheddquarium. org, https: // orcid. org / 0000 - 0001 - 6087 - 3290 Author Cummings, Kevin S. Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, Illinois, USA, kscummin @ illinois. edu, Environmental Science Center, Laredo Community College, Laredo, Texas, USA, tmiller @ laredo. edu, Author Tiemann, Jeremy S. Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, Illinois, USA, kscummin @ illinois. edu, Environmental Science Center, Laredo Community College, Laredo, Texas, USA, tmiller @ laredo. edu, & jtiemann @ illinois. edu, https: // orcid. org / 0000 - 0001 - 7635 - 1403 Author Miller, Thomas D. Author Johnson, Nathan A. Wetland and Aquatic Research Center, U. S. Geological Survey, Gainesville, Florida, USA Author Smith, Chase H. Biology Department, Baylor University, Waco, Texas, USA. Author Randklev, Charles R. Natural Resources Institute, Texas A & M University, College Station, Texas, USA & crandklev @ ag. tamu. edu, https: // orcid. org / 0000 - 0002 - 6755 - 1507 text Zootaxa 2020 2020-07-20 4816 4 457 490 journal article 10.11646/zootaxa.4816.4.3 1175-5326 3954602 7683A3B0-5833-49B6-A7CE-675D116DBC67 Popenaias tehuantepecensis ( Crosse & Fischer, 1893 ) ( Fig. 9D ) Original Combination: Unio tehuantepecensis Crosse & Fischer, 1893 . Diagnoses molluscorum novorum, Republicae Mexicanae incolarum. Journal de Conchyliologie 41:293–297. Page 296. Not figured. Figured in Fischer & Crosse 1894:618 , pl. 65, figs. 3, 3a and 4. Verbatim Type Locality : “prope Santa Efigenia, in isthmo Tehuantepec dicto, provinciae Oajaca, reipublicae Mexicanae” Type locality : Río Novillero (Pacific Ocean), Santa Efigenia , Isthmus of Tehuantepec , Oaxaca , Mexico , [ 16.40387 , -94.216116 ] . Type specimens : Syntypes , MNHN-IM-2000-1799 (n = 11, 2 of which were figured as noted above).