Curassows are one of the three major groups of cracid birds. They comprise the largest-bodied species of the cracid family. Three of the four

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

are restricted to tropical

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; a single

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of ''Crax'' ranges north to

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. They form a distinct

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

which is usually classified as the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Cracinae.

Evolution

In line with the other 3 main lineages of cracids ( chachalacas, true guans, and the horned guan), mt and

nDNA Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. It ...

sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is cal ...

data indicates that the curassows diverged from their closest living relatives (probably the guans) at some time during the

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

, or c.35–20 mya (Pereira ''et al.'' 2002). This data must be considered preliminary until corroborated by material (e.g.

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 preserve ...

) evidence however. What appears certain from analysis of the molecular data, calibrated against

geological Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ...

events that would have induced

speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...

, is that there are 2 major lineages of curassows: one containing only ''Crax'', and another made up of ''Mitu'' and ''Pauxi''. The position of the peculiar nocturnal curassow is not well resolved; it might be closer to the latter, but in any case, it diverged around the same time as the split between the two major lineages. All curassow genera appear to have diverged, in fact, during the

Tortonian The Tortonian is in the geologic time scale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma (million years ago). It follows the Serravallian and is followed by the Messinian. The Tort ...

(early Late

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

): the initial split took place some 10–9 mya, and ''Pauxi'' diverged from ''Mitu'' some 8–7.4 mya (but see genus article).(Pereira & Baker 2004) Unlike the other cracids,

biogeography Biogeography is the study of the species distribution, distribution of species and ecosystems in geography, geographic space and through evolutionary history of life, geological time. Organisms and biological community (ecology), communities o ...

and

phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...

indicate that the extant lineages of curassows probably originated in the lowlands of the western/northwestern Amazonas basin, most likely in the general area where the borders of

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

and

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meet. In the two larger genera, vicariant speciation seems to have played a major role.(Pereira ''et al.'' 2002, Pereira & Baker 2004)

References

* Pereira, Sérgio Luiz & Baker, Allan J. (2004): Vicariant speciation of curassows (Aves, Cracidae): a hypothesis based on mitochondrial DNA phylogeny. ''

Auk Auks or alcids are birds of the family Alcidae in the order Charadriiformes. The alcid family includes the Uria, murres, guillemots, Aethia, auklets, puffins, and Brachyramphus, murrelets. The family contains 25 extant or recently extinct speci ...

'' 121(3): 682–694. nglish with Spanish abstract DOI:10.1642/0004-8038(2004)121 682:VSOCAC.0.CO;2HTML abstractHTML fulltext without images
* Pereira, Sérgio Luiz; Baker, Allan J.& Wajntal, Anita (2002): Combined nuclear and mitochondrial DNA sequences resolve generic relationships within the Cracidae (Galliformes, Aves). ''Systematic Biology'' 51(6): 946–958. PDF fulltext
{{Taxonbar, from=Q1037395 * Extant Oligocene first appearances pl:Czubacze