This contribution describes juvenile specimens of the cienaga wormfish Microdesmus carri (Microdesmidae) collected at the entrance of the estuarine lagoon Ciénaga Grande de Santa Marta on the Colombian Caribbean. This is the first report of M. carri for South American waters and the third of the species since it was originally described from the Caribbean coast of Costa Rica and later reported for Belize and the Gulf of Mexico.
Meristic and morphometric data of the Colombian material are similar to those described for Costa Rica but differences from the Belize and Gulf of Mexico material were found in the fin counts. The species is considered here a southern Caribbean endemic, whose distribution may be explained by geological and oceanographic factors.
