Pauxi
Encyclopedia
The genus
Pauxi consist of the two species of helmeted curassow
s, terrestrial black fowl
with ornamental casque on their heads. Both are found in South America
.
This genus contains only 2 species, namely
As indicated by analysis of mt and nDNA sequence
s and calibrated with geological data, this genus' ancestors probably diverged from those of Mitu
, their closest living relatives, in the Tortonian
(early Late Miocene
), 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
, 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, with P. unicornis being resolved as the sister species 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 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
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 curassows 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
s at the end of the Pliocene
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Pauxi consist of the two species of helmeted curassow
Curassow
Curassows are one of the three major groups of cracid birds. Three of the four genera are restricted to tropical South America; a single species of Crax ranges north to Mexico...
s, terrestrial black fowl
Fowl
Fowl is a word for birds in general but usually refers to birds belonging to one of two biological orders, namely the gamefowl or landfowl and the waterfowl...
with ornamental casque on their heads. Both are found in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
.
This genus contains only 2 species, namely
- Helmeted CurassowHelmeted CurassowThe Helmeted Curassow or Northern Helmeted Curassow, is a large terrestrial black curassow with a small head, large bluish grey casque on forehead, red bill, white-tipped tail feathers, greenish glossed mantle and breast feathers, and white below. Both sexes are similar...
or Northern Helmeted Curassow, Pauxi pauxi - Horned Curassow or Southern Helmeted Curassow, Pauxi unicornis
As indicated by analysis of mt and nDNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
s and calibrated with geological data, this genus' ancestors probably diverged from those of Mitu
Mitu (bird)
Mitu is a genus of curassows, large birds in the family Cracidae. They are found in humid tropical forests in South America. Their plumage is iridescent black with a white or rufous crissum and tail-tip, and their legs and bills are red...
, their closest living relatives, in the Tortonian
Tortonian
The Tortonian is in the geologic timescale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma . It follows the Serravallian and is followed by the Messinian....
(early Late Miocene
Late Miocene
The Late 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....
), 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
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
, 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, with P. unicornis being resolved as the sister species 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
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
of the two genera, incomplete lineage sorting or hybridization 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
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
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 curassows 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
Razor-billed Curassow
The Razor-billed Curassow is a species of bird in the Cracidae family. It is found throughout a large part of the Amazon Rainforest, though largely restricted to regions south of the Amazon River. Unlike other members of the genus Mitu, its crissum is deep chestnut and the tail-tip is white...
s at the end of the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
.