The Phaethontiformes are an order of birds. They contain one extant family, the
tropicbirds (Phaethontidae), and one extinct family
Prophaethontidae from the early Cenozoic. Several fossil genera have been described.
The tropicbirds were traditionally grouped in the
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
Pelecaniformes, which contained the
pelican
Pelicans (genus ''Pelecanus'') are a genus of large water birds that make up the family Pelecanidae. They are characterized by a long beak and a large throat pouch used for catching prey and draining water from the scooped-up contents before s ...
s,
cormorants and shags,
darters
The darters, anhingas, or snakebirds are mainly tropical waterbirds in the family Anhingidae, which contains a single genus, ''Anhinga''. There are four living species, three of which are very common and widespread while the fourth is rarer a ...
,
gannets and boobies and
frigatebirds; in the
Sibley-Ahlquist taxonomy, the Pelecaniformes were united with other groups into a large "Ciconiiformes". More recently this grouping has been found to be massively
paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
(missing closer relatives of its distantly related groups) and split again.
Microscopic analysis of eggshell structure by Konstantin Mikhailov in 1995 found that the eggshells of tropicbirds lacked the covering of thick microglobular material of other Pelecaniformes.
Some early studies in the last decade suggested Phaethontiformes were distantly related to
Procellariiformes,
but since 2004 they have been placed in
Metaves, or in a lineage with no affinities with Procellariiformes, by the results of most recent molecular studies.
[Naish, D. (2012). "Birds." Pp. 379-423 in Brett-Surman, M.K., Holtz, T.R., and Farlow, J. O. (eds.), ''The Complete Dinosaur (Second Edition)''. Indiana University Press (Bloomington & Indianapolis).]
Jarvis, ''et al''.'s 2014 paper "Whole-genome analyses resolve early branches in the tree of life of modern birds" aligns the Phaethontiformes most closely with the
sunbittern and the
kagu of the
Eurypygiformes, with these two clades forming the sister group of the "core water birds", the
Aequornithes
Aequornithes (, from Latin ''aequor'', expanse of water + Greek ''ornithes'', birds), or core water birds are defined as "the least inclusive clade containing Gaviidae and Phalacrocoracidae".
The monophyly of the group is currently supported b ...
, and the Metaves hypothesis abandoned.
References
{{Taxonbar, from=Q12765692
Bird orders
Seabirds