Ammonis cornua

Ammonis is a dubious genus of extinct ammonite known from fossils found near Pompeii in Ancient Rome. The only known species, Ammonis cornua, was named by Pliny the Elder in A.D. 79. Its fossils were found in the same Pompeiian aged rocks as which "Scipionyx" was discovered in, which were about 110 million years old.
The name "Ammonis cornua", from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble tightly coiled rams' horns. Pliny the Elder (d. 79 AD near Pompeii) called fossils of these animals "ammonis cornua" ("horns of Ammon") because the Egyptian god Ammon (Amun) was typically depicted wearing ram's horns. Often the name of an ammonite genus ends in -"ceras", which is Greek (κέρας) for "horn".
All known specimens of "Ammonis cornua" were destroyed in A.D. 79 when Mount Vesuvius destroyed Pompeii.