A team of Costa Rican and Brazilian researchers has identified a new species of deep-sea fish in the Pacific Ocean off the coast of Costa Rica, adding to the country's known marine biodiversity and highlighting how much of its deep-water ecosystems remain unexplored.
The newly described species, Rhinochimaera costaricana, belongs to a group of cartilaginous fishes known as long-nosed chimaeras, or ghost sharks. Although they are related to sharks and rays, chimaeras represent a separate evolutionary lineage that has existed for hundreds of millions of years.
Discovery published in scientific journal
The findings were published this month in the scientific journal Zootaxa by researchers from the Costa Rica Fisheries and Aquaculture Institute, the University of Costa Rica and the Federal University of Pará.
The new species was described using three male specimens measuring between 775 and 830 millimetres in total length. The specimens were collected from Costa Rica's Pacific waters between 2000 and 2023 at depths ranging from 390 to 787 metres.
Researchers said the first specimen was discovered near Isla del Caño in 2000, while the other two were recovered in 2023 off Cabo Blanco in the province of Puntarenas.
The fish were found far below the depths typically reached by recreational divers.
Distinct physical and genetic characteristics identified
To determine whether the specimens represented a previously unknown species, researchers compared 49 body measurements with data from more than 90 individuals belonging to the three recognised species of the Rhinochimaera genus.
The analysis revealed a unique combination of features in the Costa Rican specimens, including a shorter snout, a taller first dorsal fin and spine, a wider separation between dorsal fins and fewer tubercles along the tail.
DNA testing further supported the findings. Genetic comparisons showed clear differences between the Costa Rican fish and other known members of the genus, confirming its status as a distinct species.
Discovery highlights unexplored marine biodiversity
Researchers said the discovery underscores how little is still known about deep Pacific ecosystems beyond the continental shelf.
They noted that advances in technology and genetic analysis are enabling scientists to identify species that may previously have been mistaken for already known animals.
The newly identified species was named Rhinochimaera costaricana in recognition of Costa Rica, where the specimens were collected.
