Crocodyloidea is one of three superfamilies of

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

ns, the other two being Alligatoroidea and

Gavialoidea Gavialoidea is one of three superfamilies of crocodylians, the other two being Alligatoroidea and Crocodyloidea. Although many extinct species are known, only the gharial ''Gavialis gangeticus'' and the false gharial ''Tomistoma schlegelii'' are ...

, and it includes the crocodiles. Crocodyloidea may also include the extinct Mekosuchinae, native to

Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologica ...

from the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

to the Holocene, although this is disputed.

Classification

Cladistically, it is defined as ''Crocodylus niloticus'' (the

Nile crocodile The Nile crocodile (''Crocodylus niloticus'') is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. It is widely distributed throughout sub-Saharan Africa, occurring mostly in the central, eastern ...

) and all crocodylians more closely related to ''C. niloticus'' than to either ''Alligator mississippiensis'' (the American alligator) or ''Gavialis gangeticus'' (the

gharial The gharial (''Gavialis gangeticus''), also known as gavial or fish-eating crocodile, is a crocodilian in the family Gavialidae and among the longest of all living crocodilians. Mature females are long, and males . Adult males have a distinct b ...

). This is a stem-based definition for crocodiles, and is more inclusive than the

crown group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

Crocodylidae Crocodiles (family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to include all extant mem ...

. As a crown group, Crocodylidae only includes the last common ancestor of all

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

(living) crocodiles and their descendants (living or

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

), whereas Crocodyloidea, as a stem group, also includes more

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

extinct crocodile ancestors that are more closely related to living crocodiles than to alligators or

gavialids Gavialidae is a family of large semiaquatic crocodilians with elongated, narrow snouts. Gavialidae consists of two living species, the gharial (''Gavialis gangeticus'') and the false gharial (''Tomistoma schlegelii''), both occurring in Asia. Man ...

. When considering only living taxa ( neontology), this makes Crocodyloidea and Crocodylidae

synonymous A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

, and only Crocodylidae is used. Thus, Crocodyloidea is only used in the context of

paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

. Traditionally, crocodiles and alligators were considered more closely related and grouped together in the clade

Brevirostres Brevirostres is a paraphyletic group of crocodilians that included alligatoroids and crocodyloids. Brevirostres are crocodilians with small snouts, and are distinguished from the long-snouted gharials. It is defined phylogenetically as the last ...

, to the exclusion of the

s. This classification was based on morphological studies primarily focused on analyzing skeletal traits of living and extinct fossil species. However, recent molecular studies using

DNA sequencing DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. Th ...

have rejected Brevirostres upon finding the crocodiles and gavialids to be more closely related than the alligators. The new clade Longirostres was named by Harshman ''et al.'' in 2003. A 2018 tip dating study by Lee & Yates simultaneously using morphological, molecular (

), and stratigraphic (

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

age) data established the inter-relationships within

Crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

, which was expanded upon in 2021 by Hekkala ''et al.'' using paleogenomics by extracting DNA from the extinct ''

Voay ''Voay'' is an extinct genus of crocodile from Madagascar that lived during the Late Pleistocene to Holocene, containing only one species, ''V. robustus''. Numerous subfossils have been found, including complete skulls, noted for their distinctiv ...

''. The below cladogram shows the results of the latest study, and how Crocodyloidea may only contain one additional

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

beyond Crocodylidae:

References

Crocodilians Extant Campanian first appearances {{archosaur-stub