| Thecacera | |
|---|---|
| |
| A live individual of Rudman's Thecacera species 2, head end towards the left | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Order: | Nudibranchia |
| Superfamily: | Polyceroidea |
| Family: | Polyceridae |
| Subfamily: | Polycerinae |
| Genus: | Thecacera Fleming, 1828[1] |
| Type species | |
| Thecacera pennigera (Montagu, 1815)
| |
Thecacera is a genus of sea slugs, specifically nudibranchs, shell-less marine gastropod mollusks in the family Polyceridae.