The title above is not mine. It belongs to Hasegawa and Kajihara, the Hokkaido University taxonomists who formally described the skeleton panda sea squirt in 2024, and it may be the best title in the recent history of systematic zoology. Their subject is one of two marine invertebrates that have gone viral for looking like something they are not. The other is the sea pig. Neither animal is trying to look like anything. Both are minding their own business at their respective depths while primate visual cortex does the rest.

They make a useful pair because they trip two different wires in our heads. The sea pig triggers the baby schema: plump body, stubby legs, no face required. The skeleton panda triggers face detection: two eye spots and a nose spot on a white patch, and the pattern-matching machinery declares a panda. Same "aww," different circuitry. What follows is a side-by-side comparison, plus the two facts that earn this piece its place: what happens if something bites the panda's face off, and which of these animals is your relative.

The panda face sits on the thorax: the siphons, the gill basket, the white "ribs." It is also the most exposed and most expendable part of the animal. In Clavelina, the genus this species belongs to, thorax loss is not an emergency. It is a Tuesday.

The classic work here is on the European congener Clavelina lepadiformis, a laboratory regeneration model for a century. Remove the thorax and the abdomen regrows it. Paul Brien showed in 1932 that even an isolated fragment of esophagus can rebuild a functioning thorax, and sometimes overshoots and builds two, a condition politely termed bithoracic heteromorphosis. The same genus can dissolve its zooids into dormant tissue nubs over winter and regenerate entire animals from them in spring, and can bud whole new zooids from the vascular stolons at its base. The body plan is less a fixed anatomy than a set of instructions that any sufficient piece of tissue can execute.

The honest caveat: nobody has run these experiments on C. ossipandae itself. The regeneration literature is built on its relatives. But the machinery is a genus-level and family-level trait, and a fish that bites the face off a skeleton panda has most likely purchased a temporary cosmetic change, not a kill.

Sea cucumbers have their own famous trick: many shallow-water species eviscerate, expelling their internal organs at predators and regrowing the entire gut in a few weeks. Whether Scotoplanes does this four kilometers down is not documented. Very little about Scotoplanes at four kilometers is documented, which is part of its charm.

Here is the part worth keeping. The skeleton panda's tadpole larva has a notochord and a dorsal nerve cord. Those are chordate credentials, the same ones your embryo presented. Molecular phylogenetics puts tunicates closer to vertebrates than any other invertebrate group. The animal wearing a counterfeit mammal face is, evolutionarily speaking, family.

The sea pig, the one we named after a mammal, is an echinoderm. Its nearest relatives are sea urchins and sea stars. It has no face, no brain to speak of, and no meaningful claim on the name we gave it.

Both were sorted into our affections by machinery that evolved for human infants and human faces, applied without review to a tunicate at 15 meters and a holothurian at 4,000. The detector does not check credentials. In one case it accidentally got the family tree right.