Checklist, new records, and taxonomic annotations of freshwater thecate dinoflagellate (Dinophyceae) in Colombia Author Bustamante-Gil, Carolina Grupo de Limnología Básica y Experimental y Biología y Taxonomía Marina, Instituto de Biología, Universidad de Antioquia, Medellín, Colombia. Author Boltovskoy, Andrés Facultad de Ciencias Naturales y Museo, (UNLP) / CIC-BA, La Plata, Argentina. Author Rengefors, Karin Aquatic Ecology, Department of Biology, Ecology Building, Lund University, Sweden. Author Tavera, Rosaluz 0000-0003-3921-1326 Laboratorio Algas Continentales, Ecología y Taxonomía. Facultad de Ciencias, Universidad Nacional Autónoma de México. r _ tavera @ ciencias. unam. mx; https: // orcid. org / 0000 - 0003 - 3921 - 1326 r_tavera@ciencias.unam.mx Author Amat, Eduardo Grupo de Investigación Bioforense, Facultad de Derecho y Ciencias Forenses, Tecnológico de Antioquia Institución Universitaria, Medellín, Colombia. Author Ramírez-Restrepo, Jhon J. 0000-0001-7644-9494 Grupo de Limnología Básica y Experimental y Biología y Taxonomía Marina, Instituto de Biología, Universidad de Antioquia, Medellín, Colombia. & johnra 77 @ gmail. com; https: // orcid. org / 0000 - 0001 - 7644 - 9494 johnra77@gmail.com text Phytotaxa 2021 2021-06-29 509 2 135 167 http://dx.doi.org/10.11646/phytotaxa.509.2.1 journal article 10.11646/phytotaxa.509.2.1 1179-3163 5426087 Peridiniopsis quadridens (F.Stein) Bourrelly (1968: 9) . Figure 11 Basionym: Peridinium quadridens Stein (1883: 11) Synonym: Glenodinium quadridens in J. Schiller (1935: 117) Cell shape: Pentagonal, slightly compressed dorsoventrally, with bilateral symmetry in apical view. Thecal characteristics: Tabulation, Po, 5ʹ, 1a, 7ʹʹ, 6C, 5S, 5ʹʹʹ, 2ʹʹʹʹ. Conical epitheca, longer than the hypotheca. The only anterior intercalary plate symmetrically located in the dorsal side ( Fig. 11B ). Rounded hypotheca, with spines. FIGURE 11. Peridiniopsis quadridens . A. Epitheca plates, ventral view. B. Epitheca plates, dorsal view. Cingulum and sulcus: Cingulum slightly displaced, descendent. The sulcus penetrates slightly in the epitheca ( Fig. 11A ). Locality: Guatapé reservoir North-west Colombia . Comments: This is the first record of the species in Colombia . Measurements and detailed diagnostic characters were not possible to perform, due to the low number of specimens found. Identification was based on the presence of five apical plates and a single anterior intercalary plate in one empty theca. World distribution: Europe, USA , and New Zealand ( Moestrup & Calado 2018 ).