The genus
Eudocimus appears to be most closely related to (but more primitive than)
Plegadis, the latter distinguished anatomically by the conformation of the
tarsometatarsus. The fossil record is poor, but the Early
Miocene fossil species
Plegadis paganus has some intermediate features. It has two
foramina in the intertrochlear groove of its distal tarsometatarsus, as do
Plegadis in contrast to the single foramen of
Eudocimus and many other bird species. The derived nature of this species indicates ibises belonging to
Eudocimus were already in existence at this time. A 2010 study of
mitochondrial DNA of the spoonbills by Chesser and colleagues, which included
E. ruber,
Nipponia nippon and
Threskiornis aethiopicus found that
E. ruber was an early offshoot and not closely related to a clade containing the spoonbills and Old World ibises. Remains similar to
E. albus have been found in Middle
Pliocene deposits of the Bone Valley formation in central Florida, and Lower Pliocene deposits of the Yorktown Formation at Lee Creek in North Carolina.
Species There are just two extant species in this genus, The two species hybridize, and are sometimes considered
conspecific. ==Description==