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Cracidae

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iChachalacas, Guans
Image:Penelope jacquacu - Spix-Guan - Spix's Guan.jpg
Spix's Guan, Penelope jacquacu
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Galliformes
Family: Cracidae
Vigors, 1825
Genera

The chachalacas, guans and curassows are birds in the family Cracidae.

These are species of tropical and subtropical Central and South America. One species, the Plain Chachalaca, just reaches southernmost Texas in the USA. Two species, the Trinidad Piping Guan and the Rufous-vented Chachalaca occur on the islands of Trinidad and Tobago respectively.

These are large birds, similar in general appearance to turkeys. The guans and curassows live in trees, but the smaller chachalacas are found in more open scrubby habitats. They are generally dull-plumaged, but the curassows and some guans have colourful facial ornaments.

These species feed on fruit, insects and worms. The nest is built in a tree, and two to three large white eggs are laid; the female alone incubates.

The Cracidae are an ancient group related to the Australasian Mound-builders.

Contents

[edit] Species

Image:Cascais20.jpg

[edit] Phylogeny and Evolution

Recent research has analyzed DNA sequences and other evidence to study the phylogenetic relationships of cracid birds, namely the relationships among the genera (Pereira et al., 2002), the relationships between the species of curassows (Pereira & Baker, 2004) and between the piping- and Wattled Guans (Grau et al., 2005). The results suggest that the Cracidae originated in the Late Cretaceous, but the authors caution that this cannot be more than a hypothesis at present: as the rate of molecular evolution is neither constant over time nor uniform between genera and even species, dating based on molecular information has a very low accuracy over such long timespans and needs to be corroborated by fossil evidence. The fossil record of cracids is limited to some chachalacas, however:

  • Boreortalis (Hawthorn Early Miocene of Florida, USA; may actually be a junior synonym of Ortalis)
  • Extant genus Ortalis
    • Ortalis tantala (Early Miocene of Nebraska, USA)
    • Ortalis pollicaris (Flint Hill Middle Miocene of South Dakota, USA)
    • Ortalis phengites (Snake Creek Early Pliocene of Sioux County, USA)

The genera Procrax, Palaeonossax and Paleophasianus are often considered cracids, but this is not certain at all; they may belong to a related extinct lineage.

Thus, the assumption that modern genera radiated during the Eocene must also be considered hypothetical given the lack of robust evidence. Still, the "molecular" scenario is entirely possible considering what is known about the evolution and radiation of the Galloanseres. The ichnotaxon Tristraguloolithus cracioides is based on fossil eggshell fragments from the Late Cretaceous Oldman Formation of southern Alberta, Canada which are similar to chachalaca eggs (Zelenitsky et al, 1996), but in the absence of bone material their relationships cannot be determined except that they are apparently not from a dinosaur.

By comparison, speciation within curassows (Crax, Nothocrax, Pauxi and Mitu) and the piping/wattled guans is supported by better evidence. It was usually caused by changes in topography which divided populations (vicariant speciation), mainly due to the uplift of the Andes which led to the establishment of the modern river basins. The distribution of curassow and piping-guan species for the most part follows the layout of these river systems. Another result was that the Wattled Guan belongs to the same genus as the piping-guans, which uses the older name Aburria (Grau et al., 2005).

[edit] References

  • Grau, Erwin T.; Pereira, Sérgio Luiz; Silveira, Luís Fábio; Höfling, Elizabeth & Wanjtal, Anita (2005): Molecular phylogenetics and biogeography of Neotropical piping guans (Aves: Galliformes): Pipile Bonaparte, 1856 is synonym of Aburria Reichenbach, 1853. Molecular Phylogenetics and Evolution 35: 637-645. PDF fulltext
  • Pereira, Sérgio Luiz & Baker, Allan J. (2004): Vicariant speciation of curassows (Aves, Cracidae): a hypothesis based on mitochondrial DNA phylogeny. Auk 121(3): 682-694. DOI:10.1642/0004-8038(2004)121[0682:VSOCAC]2.0.CO;2 HTML abstract
  • 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. DOI:10.1080/10635150290102519 PDF fulltext
  • Zelenitsky, Darla K.; Hills, L. V. & Currie, Philip J. (1996): Parataxonomic classification of ornithoid eggshell fragments from the Oldman Formation (Judith River Group; Upper Cretaceous), Southern Alberta. Canadian Journal of Earth Sciences 33(12): 1655-1667.

[edit] External links

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