A new species of ‘ghost shark’ has been discovered off the coast of Costa Rica

The species was described in the journal *Zootaxa* on the basis of three adult males collected off the coast of Costa Rica between 2000 and 2023.

Despite its name, it is not a true shark. ‘Ghost sharks’ is the colloquial name for chimaeras, an ancient group of cartilaginous fish related to sharks and rays. These animals live at great depths and are rarely encountered by scientists, which is why their diversity remains poorly understood.

Details

The new species was described by a team of researchers from the University of Costa Rica, the Costa Rican Institute of Fisheries and Aquaculture, and the Federal University of Pará in Brazil. The lead author of the paper is Naideli Valeria Vidaurre-Quesada, a biology student at the University of Costa Rica.

The specimens were found off the Pacific coast of the province of Puntarenas: one near Caño Island, and the other two near Cabo Blanco. The fish were collected at depths ranging from 390 to 787 metres, that is, in a zone where almost no light penetrates and where research is technically challenging and costly.

The species is described on the basis of three males measuring between 775 and 830 mm in length. The first specimen was collected back in 2000 near Caño Island, whilst the other two were collected in 2023 off Cabo Blanco during deep-sea research operations. The specimens were transferred to the scientific collection of the Zoological Museum at the University of Costa Rica.

To determine whether this is indeed a new species, the scientists compared the fish they found with already known members of the genus Rhinochimaera. They took 49 morphometric measurements — that is, they measured various parts of the body — and compared these with data from 90 specimens of the three previously known species of this genus.

Rhinochimaera costaricana is distinguished by a combination of characteristics: a shorter snout, a larger and taller spine on the first dorsal fin, a taller first dorsal fin, a wider gap between the dorsal fins, and fewer tubercles on the caudal region of the body.

Genetic analysis has also confirmed that this is a distinct species. Analysis of COI sequences from two specimens revealed divergences from other Rhinochimaera species: 3.9 per cent from R. africana, 4.5 per cent from R. atlantica and 4.7 per cent from R. pacifica. Species differentiation methods also supported the recognition of the new form as a separate taxon.

Put simply, the scientists did not limit themselves to external similarities or differences. They used two approaches simultaneously: they carefully compared body structure and analysed the DNA. It is precisely this combination that allows them to state with greater certainty that they are dealing not merely with an unusual individual, but with a new species.

What is this ‘ghost shark’?

‘Ghost sharks’ look unusual: many of them have elongated snouts, large eyes, soft body contours and a deep-sea lifestyle. But from a scientific point of view, these are not sharks, but chimeras — a separate branch of cartilaginous fish.

Cartilaginous fish are a group that includes sharks, rays and chimeras. Unlike bony fish, their skeletons are made of cartilage rather than bone. Chimaeras have their own ancient evolutionary lineage, which is why they are of particular interest to biologists.

The genus Rhinochimaera previously comprised three recognised species: Rhinochimaera africana, Rhinochimaera atlantica and Rhinochimaera pacifica. The new species from Costa Rica adds to this list and helps us better understand the distribution of such deep-sea fish in the eastern Pacific Ocean.

Why this is important

Deep-sea ecosystems remain one of the least studied parts of the planet. At depths of hundreds of metres, conditions differ drastically from those in familiar coastal waters: it is dark, cold, high-pressure, with little food and oxygen. Yet it is precisely there that species live about which scientists often know very little.

The description of Rhinochimaera costaricana suggests that the biodiversity of such areas may be underestimated. Every new species helps us to understand more precisely who inhabits the deep waters, how rare animals are distributed, and which areas require protection.

This is particularly important before deep-sea areas begin to be exploited more intensively by humans. According to the researchers, such ecosystems face growing challenges — from climate change to potential extractive activities. To protect the marine environment, we first need to know which species live there.

Background

An interesting detail of this story is that the discovery did not happen overnight. The first specimen entered the University of Costa Rica’s collection back in 2000 following exploratory work to assess the potential for deep-sea shrimp fishing. Two further specimens were collected in 2023 during further research off the Pacific coast.

It was these scientific collections that made the description of the species possible. When specimens are preserved in museums and universities, they can be revisited years later, compared with new finds and subjected to genetic analysis.

For now, scientists suspect that the range of this new chimera may extend beyond the waters of Costa Rica. Similar specimens have previously been found off the coasts of Peru and Chile, so experts are continuing to compare the specimens to clarify the species’ distribution along the Pacific coast of Central and South America.

Source

Study: Naidely Valeria Vidaurre-Quesada, Alexander Salas-Jimenez, José Miguel Carvajal-Rodríguez, Nixon Lara-Quesada, Simoni Santos, Juliana Araripe, Arturo Angulo, “A new species of Rhinochimaera Garman 1901 (Holocephali: Chimaeriformes: Rhinochimaeridae) from the Eastern Pacific Ocean”, Zootaxa, 2026.