Pauxi

The

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

''Pauxi'' consists of the three species of helmeted curassows, terrestrial black

fowl Fowl are birds belonging to one of two biological orders, namely the gamefowl or landfowl (Galliformes) and the waterfowl (Anseriformes). Anatomical and molecular similarities suggest these two groups are close evolutionary relatives; together ...

with ornamental casque on their heads. All are found in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

. This genus contains 3 species As indicated by analysis of 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. I ...

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 called ...

s and calibrated with

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

data, this genus' ancestors probably diverged from those of '' Mitu'', their closest living relatives, in 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 Torto ...

(early

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million years ago) to 5.333 Ma. The ...

), some 8–7.4 mya. How the present distribution in 4 small areas quite distant from each other came to be is not known. Given that helmeted curassows are birds of the foothills and uplands, it might be that the ancestral ''Pauxi'' population became fragmented by the uplift of the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

, which in their area of distribution took place during the Late Miocene, around the ''Pauxi''-''Mitu'' divergence and some time after.(Pereira & Baker 2002, Pereira ''et al.'' 2002). Pereira & Baker (2002) reported an interesting find: in the mtDNA phylogeny, ''Pauxi'' was

paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...

, with ''P. unicornis'' being resolved as the

sister species In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of '' Mitu tuberosa''. This, of course, does not automatically imply that they are closely related or that the genera are invalid. Rather, the authors point out, given the distinct and peculiar morphology of the two genera, incomplete lineage sorting or

hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...

between ancestral individuals of the two species is a more likely explanation. According to their data, there must have been some extent of

gene flow In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent a ...

between ''Mitu tuberosa'' and ''P. unicornis'' around 2 mya. Unfortunately, the authors do not provide subspecific identification of their single ''P. unicornis'' specimen. In any case, they took care to exclude captive hybridization in their choice of samples, as it is frequently known to occur in

curassow 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 are restricted to tropical South America; a single species of ''Crax'' ranges north to Mexico ...

s and would have confounded the analysis. Altogether, what can be said with certainty is that there seems to have been some extent of hybridization between at least one population of the southern helmeted curassow and female

razor-billed curassow The razor-billed curassow (''Mitu tuberosum'') is a species of bird in the family Cracidae, the chachalacas, guans, and curassows. It is found in Bolivia, Brazil, Colombia, and Peru.Remsen, J. V., Jr., J. I. Areta, E. Bonaccorso, S. Claramunt ...

s at the end of the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Auk An auk or alcid is a bird of the family Alcidae in the order Charadriiformes. The alcid family includes the murres, guillemots, auklets, puffins, and murrelets. The word "auk" is derived from Icelandic ''álka'', from Old Norse ''alka'' (a ...

'' 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=Q944496 Bird genera Extant Tortonian first appearances