Ardei is a suborder of order
Pelecaniformes
The Pelecaniformes are an order of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all birds that have feet with all four toes webbed. Hence, they were formerly also known by such n ...
that include the families
Ardeidae (herons, egrets, and bitterns) and
Threskiornithidae (ibises and spoonbills).
Traditionally the ardeids and threskiornithids were classified in the order
Ciconiiformes
Storks are large, long-legged, long-necked wading birds with long, stout bills. They belong to the family called Ciconiidae, and make up the order Ciconiiformes . Ciconiiformes previously included a number of other families, such as herons an ...
along with
Ciconiidae (storks),
Phoenicopteridae (flamingos),
Scopidae (hamerkop),
Balaenicipitidae (shoebill), and even
Cathartidae (New World vultures and condors).
However, there were some
osteological
Osteology () is the scientific study of bones, practised by osteologists. A subdiscipline of anatomy, anthropology, and paleontology, osteology is the detailed study of the structure of bones, skeletal elements, teeth, microbone morphology, func ...
studies that have questioned the
monophyly
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...
of Ciconiiformes, suggesting that the ardeids and threskiornithids originated from early
gruiforms, with the latter being a transitionary taxon to order
Charadriiformes
Charadriiformes (, from '' Charadrius'', the type genus of family Charadriidae) is a diverse order of small to medium-large birds. It includes about 390 species and has members in all parts of the world. Most charadriiform birds live near water ...
.
The polyphyly nature of Ciconiiformes is supported by recent genomic studies that have found support threskiornithids, ardeids, scopids and balaenicipitids being closely related to
Pelecanidae (pelicans).
[
The exact relationship between ardeids, threskiornithids and suborder Pelcani is still being investigated with two hypotheses. One hypothesis is ardeids and threskiornithids are each other's sister taxon in suborder Ardei (as presented here).][ The other hypothesis is the ardeids are the sister taxon to the pelecanid-related clade, with threskiornithids the basal most group. This hypothesis is supported from some morphological and the earliest representations of non-threskiornithid pelecaniforms come from the ]Oligocene
The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but ...
deposits in Africa, while threskiornithids have been found in Eocene
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...
deposits of North America and Europe.
References
{{pelecaniformes-stub