Dried teaching specimen in Tübingen turns out to be a new giant isopod species

At 32.2 centimeters, Kästle said, the specimen "falls into the category of 'colossogiants'" ^[14]. The label comes from the team's size classes. Kästle said the genus's spread through the Indian and Pacific oceans "gave rise to the so-called 'giant' isopods that are up to 15 centimeters (5.9 inches) long, and the 'supergiants' with a body length of more than 15 centimeters (5.9 inches)" ^[10]. A later Indo-Pacific group, Werneburg said, "grew to more than 25.2 centimeters (9.9 inches) in length" ^[12]. The Puerto Rico animal is 7 centimeters past that threshold ^[17].

The authors expect the description to help scientists understand the evolution of all deep-sea isopods ^[20]. Their phylogenetic analysis gives the Gulf of Mexico origin as likely ^[8]. "At that time, the Isthmus of Panama was open, leaving a strait between North and South America, and the marine animals were able to spread westward, initially as far as Japan," Werneburg said ^[9]. After diversifying in the Indian and Pacific oceans, the isopods reached Australia, East Africa and, before the Arabian and African plates collided, Europe, where they died out at the end of the Miocene ^[11]. The colossi evolved in the Indo-Pacific as Earth cooled at the Miocene-Pliocene boundary, 5.333 million years ago ^[12]. In the team's account they later spread from Australia via Antarctica to South and Central America, meeting smaller relatives left behind by the first westward expansion ^[13].

On that reconstruction, the Caribbean animal belongs to a group whose ancestors left the Americas heading west and whose descendants came back from the south ^[18]. The team describes the new species as "very closely related to another giant species found off the Yucatán Peninsula in Mexico" ^[15].

The gap between the animal's arrival in Tübingen in the 1980s and the 2026 paper is 37 to 46 years ^[19]. Seilacher, who brought it in, died in 2014 ^[6]. Werneburg argues the find shows the importance of natural history collections as global archives of nature ^[16]. As evidence about museum backlogs, it is a single case, and a single case cannot say how often teaching drawers hold new species.

The species itself rests on one dried animal ^[7]. The press account does not say how many species went into the tree or whether any genetic data were used. One individual cannot show how much a species varies from animal to animal. That variation is what decides how cleanly the Puerto Rico form separates from its Yucatán relative. In my view the name stands on the published anatomy, and the genus-wide route is a dated hypothesis that more specimens, from Puerto Rico and off Yucatán, can test.