Some of the following reversals were covered in earlier posts.
Others premiere here. Still others remain overlooked or forgotten for the moment. Come back over time to see additions as they spring to mind.
Reversals are distinct from convergent traits
in that reversals also appear in ancestral taxa (in the LRT) while convergent traits do not.
- Platypus electrosensory bill — sturgeon, paddlefish, shark electrosensory rostrum
- Odontocete simple cone teeth — basal bony fish through pelycosaur simple cone teeth
- Multituberculate reappearance of post-dentary bones — cynodont jaw joint
- Prohalecites gill cover (operculum) — sturgeon, paddlefish, ratfish gill cover
- Minjinia, a disc-head, jawless placoderm — drepanaspid jawless anapsid
- Echinosorex, the moonrat and member of Glires lacks gnawing incisors — tree shrews that are not members of Glires also lack gnawing incisors
- Fins (dorsal, pectoral, pelvic, caudal) in ichthyosaurs, odontocetes, mysticetes, and other tetrapods — Similar fins in basal tetrapods (= fish)
- Loss of hind limbs in snakes, whales, amphisbaenids — lampreys, Birkenia
- Acanthostega radius twice as long as the ulna — as in pre-tetrapod lobefin fish
- Ossified skin (bony plates) in ankylosaurs, glyptodonts, etc. — Ossified scales in basal vertebrates (= fish)
- Flightless birds — flightless pre-bird theropods
- Loss of a flexible neck in mysticetes — basal vertebrates and tetrapods
- Heterodont dentition in Longisquama + pterosaurs and, by convergence in cynodonts —as in Hybodus, a shark basal to bony fish
- New world vulture overall morphology (pigeon sisters) — Old world vultures (hawk sisters)
- Long-legged shore birds (stilts, Himantopus, derived from short-legged Eocypselus) — long-legged basal birds like seriemas (Cariama).
- Atavistic tails in humans — monkeys, lemurs
- Extensible ventral mouth parts in skates — as in pre-gnathostome sturgeons
- Gill openings ventral to pectoral fins in skates and rays — as in osteostracans
- Separation of the gill basket from the neurocranium in sturgeons — as in Birkenia
- Fusion of the gill basket with the neurocranium in osteostracoderms — as in Arandaspis.
- Extended rostrum in pachycormiforms — as in Chondrosteus and sharks.