The type species,
R. messelensis, is known from many well-preserved specimens from the famous
Lutetian-aged
Messel pit of
Germany. It was initially thought to represent an early relative of
painted-snipes (family Rostratulidae), and was still considered an early
charadriiform for nearly a century, but was identified as an early ibis in 1983. In 2026, a largely complete, articulated
Rhynchaeites specimen from the
Green River Formation of the United States was described as the holotype of a third species,
R. mcfaddeni. The potential leg bone fossils of
Rhynchaeites have also been found in the earliest Ypresian
Fur Formation in
Denmark. It has been hypothesized that the supposed
parrot relative
Mopsitta tanta, known from a single
humerus bone, is the same bird as the leg fossils and thus actually belongs in
Rhynchaeites too. == Morphology ==