The scientists who identified a new giant deep-sea isopod from Puerto Rico have now laid out how they think the whole group spread around the planet, and the story begins in waters off the southern United States. In an account released by the University of Tübingen on Oct. 15, researchers Ingmar Werneburg and Benedikt Kästle said the genus Bathynomus likely arose in what is now the Gulf of Mexico more than 15 million years ago.

From there, they propose, the animals moved west through a sea passage that no longer exists. Werneburg explained that at the time "the Isthmus of Panama was open, leaving a strait between North and South America." That route let the crustaceans spread as far as Japan.

The proposal connects a single dried specimen in a German drawer to the movement of continents and a cooling planet. It also suggests the Caribbean and Gulf of Mexico, waters bordering Puerto Rico and the Gulf Coast states, played an outsized role in the early history of these deep-sea giants.

Update Note: This article reports new information involving the evolutionary history proposed for the giant isopod Bathynomus tuebingoborikensis following Nature World News' earlier coverage. The latest verified information comes from the University of Tübingen's account of the study, published Oct. 15, 2026, and the underlying paper in Scientific Reports, published Oct. 8, 2026.

A Deep-Sea Family Shaped by Moving Continents

Giant isopods are ocean-dwelling relatives of the woodlice found in damp basements and gardens. Members of Bathynomus live in oceans worldwide at depths of up to 2,500 meters (about 8,200 feet), scavenging the seafloor. Some grow to 50 centimeters (nearly 20 inches) and weigh several kilograms, placing them among the largest invertebrates.

According to the Tübingen account, the isopods diversified as they spread through the Indian and Pacific oceans. That produced "giants" up to 15 centimeters (about 6 inches) long and "supergiants" longer than that. Their range reached Australia, East Africa and Europe, where they disappeared at the end of the Miocene, before the Arabian and African plates collided.

A third group emerged in the Indo-Pacific as Earth cooled around the boundary between the Miocene and Pliocene epochs, about 5.3 million years ago. The researchers call these "colossogiants." They propose this larger group later spread from Australia by way of Antarctica to South and Central America, where it met smaller relatives whose ancestors had stayed behind. The Puerto Rico animal belongs to that returning group, and its closest known relative lives off Mexico's Yucatán Peninsula.

Since Nature World News First Reported the Specimen

Nature World News previously reported that a giant isopod stored for about 40 years in a German collection had been filed under a well-known Gulf of Mexico species and turned out to be new to science. That report focused on the mislabeling, the anatomy that sets Bathynomus tuebingoborikensis apart, and the limits of a single specimen.

The new development is the authors' detailed dispersal history, which explains how the Puerto Rico animal fits into a global family tree. It is a proposed route, not a confirmed one.

One detail differs between sources — the Tübingen account describes colossogiants as longer than 25.2 centimeters, while Nature World News' earlier review of the paper reported a threshold of 255 millimeters. Both put the cutoff at roughly 10 inches. The specimen itself measures 32.2 centimeters, or about 12.7 inches.

A Single Dried Specimen Carries the Weight

The evidence behind the route is limited, and that matters for how the claim should be read. This is a peer-reviewed taxonomic description and phylogenetic analysis published in Scientific Reports, based on one dried female specimen collected off Puerto Rico in the 1980s. The researchers compared anatomy across living and fossil species but did not sequence DNA.

The authors describe their evolutionary analyses as preliminary, and some branches of the family tree have weak statistical support. Fossil isopods are scarce and often incomplete. The finding suggests a plausible route shaped by ocean gateways and climate. It does not prove the animals traveled that path, and new fossils or genetic data could revise it.

The species' population size and conservation status are unknown. The study does not suggest any threat to people, fisheries, or coastal communities.

U.S. Waters, Museum Drawers and the Next Specimens

The most direct way to test the idea is to find more animals. Live specimens or tissue from the deep waters around Puerto Rico would allow DNA comparisons with the Yucatán species and with Bathynomus giganteus, the familiar giant isopod of the Gulf of Mexico. The waters around Puerto Rico fall within U.S. jurisdiction, yet deep-sea life there remains poorly documented.

The discovery also fits a trend of new species emerging from old collections rather than new expeditions. The specimen was acquired in Puerto Rico by Tübingen paleontologist Dolf Seilacher and sat in storage for decades. Werneburg has pointed to the find as evidence that natural history collections work as global archives of nature. Nature World News recently reported a similar case: a skull fragment stored since 1924 that revealed a new dinosaur.

Readers can help in a small way — people who find unusual marine animals in fishing gear or washed ashore can photograph them and contact a local museum, university or state wildlife agency rather than discarding them.

The bottom line is that the team behind Puerto Rico's new giant isopod proposes that the group began in the Gulf of Mexico, escaped through a long-gone Panama seaway, and later returned via Antarctica. The route is a hypothesis built on one specimen, and the next step is finding more of these animals in the deep Caribbean.

What Readers Want to Know

What is the new species?

Bathynomus tuebingoborikensis is a giant deep-sea isopod described from a single specimen collected off Puerto Rico in the 1980s.

What is new in this update?

The researchers detailed a proposed history in which the genus began in the Gulf of Mexico, spread west through an open Panama seaway, and later returned to the Americas via Antarctica.

Is that history confirmed?

No. The authors call their analysis preliminary. It is based on anatomy, not DNA, and relies on limited fossils.

How big is the Puerto Rico specimen?

It is about 32.2 centimeters, or 12.7 inches, long, placing it in the "colossogiant" size group.

Are giant isopods dangerous to people?

No. They are deep-sea scavengers that live far below where people swim or dive recreationally.

How can the public help?

Photograph unusual marine animals found in fishing gear or on beaches and report them to a local museum, university, or state wildlife agency.