A giant deep-sea isopod collected off Puerto Rico in the 1980s and stored for decades at the University of Tübingen in Germany under the name of a well-known Gulf of Mexico species has been described as a new species. The animal, now named Bathynomus tuebingoborikensis, is about 32 centimeters (12.7 inches) long, placing it among the largest isopods known, according to a study published Oct. 8 in Scientific Reports.

The specimen had been filed as Bathynomus giganteus, the species most people picture when they see the pill-bug-like "giant isopod," according to Gizmodo. It was re-examined by Benedikt Kästle, a paleontology student at Tübingen, and Ingmar Werneburg, curator of the university's Paleontological Collection.

The find is a reminder that natural history collections still hold undescribed species. It also adds a new deep-sea animal to the waters around a U.S. territory, where scientists know relatively little about life hundreds of meters below the surface.

A Specimen From Puerto Rico's Deep Waters

The isopod was caught in a trap at a depth of about 500 meters (roughly 1,640 feet) off Puerto Rico by German paleontologist Adolf "Dolf" Seilacher, who died in 2014, Gizmodo reported. It is a dried female, catalogued in the Tübingen collection as GPIT-PV-94341, and is the only known specimen of the species.

The name combines Borikén, the Indigenous Taíno name for Puerto Rico, with Tübingen, the city where the animal was rediscovered. The study gives it a maximum body length of 322 millimeters and a maximum width of 129 millimeters.

Giant isopods in the genus Bathynomus are scavengers that live on the seafloor at depths of roughly 70 to 2,500 meters, according to the study. They are relatives of the woodlice found in gardens, but some species grow to more than a foot long.

"The new species is very closely related to another giant species found off the Yucatán Peninsula in Mexico," Kästle said in a statement quoted by Gizmodo. The study names that relative as Bathynomus yucatanensis.

Mouthparts and Spines Set It Apart

Telling giant isopods apart is difficult — many species look broadly similar. The team used micro-computed tomography, a form of 3D X-ray scanning, to image the animal's mouthparts without damaging the specimen.

The scans and close inspection revealed a combination of features the authors say no other species shares. Those include a constricted plate at the front of the head, 11 large spines on part of the mouthparts, seven coupling hooks on another mouthpart, and a prominent ridge running the length of the tail plate. The authors also describe a row of 15 comb-like bristles on one pair of legs that they suggest may help the animal groom its swimming legs.

The researchers built a new dataset of 23 living and four fossil species to examine how the genus evolved. Werneburg said the group likely originated in the Gulf of Mexico during the Miocene, more than 15 million years ago, Gizmodo reported. The study also proposes a new size category, "colossogiant," for species that reach at least 255 millimeters (about 10 inches).

Limits of a Single Dried Specimen

The evidence comes with clear limits — and the authors acknowledge them. The description rests on one dried specimen, and some parts, including portions of the antennae, are missing. The authors did not sequence DNA from the animal, so its separation from close relatives is based on anatomy rather than genetics.

The authors call their evolutionary analyses preliminary. Several fossil species have few features that can be scored, and some placements on the family tree have very weak statistical support. Depth records for the genus are also sparse, so the team's finding that body size does not track living depth is weakly supported.

The paper also contains a small internal inconsistency. Its formal diagnosis lists 11 spines on the tail plate, while the full description counts 10 prominent spines plus one vestigial spine. That does not change the conclusion that the animal differs from known species, but it is the kind of detail other specialists are likely to check.

The study does not assess the species' population or conservation status, and nothing is known yet about how common it is around Puerto Rico. Finding live animals or additional specimens would allow DNA comparisons and a clearer picture of its range.

Collections Keep Yielding Surprises

The discovery fits a pattern in which new species are identified not in the field but in drawers and jars collected decades ago. Older specimens were often assigned to the best-known species of the time, and new imaging tools let researchers revisit them without dissection.

That value is part of why the fate of large natural history collections draws concern. Nature World News recently reported that Philadelphia's Academy of Natural Sciences closed its museum after nearly 200 years, raising questions about the care of some 19 million specimens. The Tübingen isopod shows what can be lost, or found, depending on whether such collections remain accessible to researchers.

For readers, the takeaway is that deep-sea biodiversity close to U.S. waters is still poorly documented. People who find unusual marine animals on beaches or in fishing gear can help scientists by photographing them and contacting a local museum, university or state wildlife agency rather than discarding them.

The bottom line is that a 12.7-inch isopod caught off Puerto Rico about 40 years ago has been recognized as a new species, based on careful anatomy rather than DNA. Confirming its place in the family tree will depend on new specimens from the deep waters where it was first found.

What Readers Want to Know

What is the new species?

It is Bathynomus tuebingoborikensis, a giant deep-sea isopod described Oct. 8 in Scientific Reports from a single specimen collected off Puerto Rico.

How big is it?

The specimen is about 32 centimeters, or 12.7 inches, long and about 13 centimeters wide.

Why was it missed for so long?

It was filed as Bathynomus giganteus, a well-known species, and stored in the University of Tübingen collection for decades until a student and the collection's curator re-examined it.

Where does it live?

The only known specimen was caught at about 500 meters, or roughly 1,640 feet, deep off Puerto Rico.

How did scientists confirm it is new?

They compared its anatomy with other species and used micro-CT scans of its mouthparts. They did not analyze its DNA.

Is the species endangered?

Unknown. The study does not assess its population or conservation status.