Diversity and distribution of species of the planktonic dinoflagellate genus Alexandrium (Dinophyta) from the tropical and subtropical Mexican Pacific Ocean Author Hernández-Becerril, David U. Author Pichardo-Velarde, Jorge G. Author Alonso-Rodríguez, Rosalba Author Maciel-Baltazar, Ebodio Author Morquecho, Lourdes Author Esqueda-Lara, Karina Author Barón-Campis, Sofía A. Author Quiroz-González, Nataly text Botanica Marina 2023 Warsaw, Poland 2023-11-06 66 6 539 557 http://dx.doi.org/10.1515/bot-2023-0037 journal article 10.1515/bot-2023-0037 1437-4323 11000291 3.1.2 Alexandrium gaarderae Nguyen-Ngoc et Larsen ( Figures 9–11 ) References: Nguyen and Larsen 2004 , 90, pl. 6, figs 1–8; Menezes et al. 2018 , 4. Synonyms = Goniodoma concavum Gaarder , Gonyaulax concava (Gaarder) Balech , Alexandrium concavum (Gaarder) Balech. Reference: Balech 1995 , 60, pl. XVII, figs 24–29. A very characteristic species with solitary and large cells, pentagonal in shape ( Figure 9 ). Epitheca irregularly conical with somewhat sinuous margins, hypotheca more rounded, flattened at the posterior margin, wide and excavated cingulum, and wide and deep sulcus ( Figures 9 and 10 ). Apical pore (Po) large and conspicuous ( Figure 11 ). Measurements: 58–68 μm L, 48–55 μm W (Table 1). Toxicity: this species is not considered to be toxic ( Long et al. 2021 ). Distribution: in the Gulf of Tehuantepec.