Harttiella crassicauda is the only species of the monotypic genus Harttiella, a genus of the family Loricariidae of catfish (order Siluriformes). The phylogenetic position of Harttiella remains uncertain.
This species is only known from its type locality, in the Marowijne River drainage in Suriname. It has been found in a little forest creek over sandy and rocky bottoms.. This fish was previously thought to be extinct after not being sighted for 50 years; however, this fish has since been re-discovered. This fish is not currently on the IUCN Red List.
This species reaches a length of about 5 centimetres (2 in) SL. Sexual dimorphism is similar to that of Harttia, in which mature males develop hypertrophied odontodes on the pectoral spines, along the margin of the snout, and on the entire body except for the abdominal region.