Polyclads (Platyhelminthes) in the southern Gulf of Mexico: unveiling biodiversity and descriptions of two new species.

The order Polycladida (Platyhelminthes) in Mexico has historically received limited attention from researchers, primarily due to challenges associated with its low detectability and the scarcity of specialists. This study addresses part of the gap by conducting a comprehensive assessment of polyclad diversity in the southern Gulf of Mexico. Our investigation revealed a total of 27 distinct species, belonging to 17 genera and 12 families, within the suborders Cotylea and Acotylea. Our findings include the identification of 17 species previously undocumented in the Gulf of Mexico. This represents a significant expansion of the region's known polyclad biodiversity. By revising the polyclad records in the Gulf of Mexico, the known species count has increased from 31 to 50. Furthermore, our research unveiled the presence of two new species, and , also marking the first time a species of the genus has been reported for the Atlantic coast of the Americas.