Rhinoceros dolphin

The account derives from a shipboard natural-history observation: Jean René Constant Quoy and Joseph Paul Gaimard reported seeing a pod of dolphins with a frontal, horn‑like dorsal structure on 19 October 1819 during the Uranie voyage; they published the description (binomial Delphinus rhinoceros) in their Voyage Autour du Monde (1824). Later authors have treated the report skeptically, proposing misidentification hypotheses (overlapping silhouettes of mother and calf, confusion with beaked whales, or other taxa) and noting the absence of collected specimens.

Contemporary summaries of Quoy & Gaimard’s description report a generally dark-bodied cetacean with sporadic white blotching along the dorsum that ceased around or soon after the dorsal fin closest to the fluke. The most distinctive reported feature is an anterior dorsal fin or horn‑like projection situated close to the neck. Size was estimated as roughly double a porpoise (Quoy & Gaimard) with an 1856 observer noting individuals up to about 2.4 m; head and beak morphology were not documented in the original account because the animals did not surface sufficiently.

No supernatural abilities are attested in the sources. Reported behaviors are consistent with ordinary cetacean activity: observed in pods, passing close to a ship's prow, and in at least one later report breaching and playing among common dolphins. Subsequent commentators have proposed non‑supernatural interpretive explanations for the unusual silhouette (mother‑and‑calf overlap, misidentified beaked whales, or misidentification with basking sharks in related Mediterranean reports).