Recent research has analyzed mt and nDNA sequences, morphological, and biogeographical data 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 traditional groups—chachalacas, guans, and curassows—are verified as distinct clades, but the horned guan represents the sole survivor of a very distinct and ancient lineage.

In addition, the molecular data 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 a single doubtfully distinct genus of chachalaca, Boreortalis (Hawthorn Early Miocene of Florida, USA; may actually be a junior synonym of Ortalis) and some species in the modern genus Ortalis, however.
This does not provide any assistance in evaluating the hypothesis (Pereira et al.,
2002) that the split between the 4 main lineages of our time occurred quite rapidly, approximately in the Oligocene or slightly earlier, somewhere between 40 and 20 mya.

The genera Procrax and Palaeonossax are often considered cracids, but this is not certain at all; they may belong to a related extinct lineage.
It is unfortunate that of these too, few good fossils are known, as they date to about the time when the modern groups presumably diverged.
Should they be cracids, they are not unlikely to represent either some of the last members of the family before guans, chachalacas, etc.
evolved, or very early representatives of these lineages.

Thus, the assumption that the modern diversity started to evolve in the late Paleogene, continuing throughout the Miocene and onwards, 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 Galloanserae, and consistent with the paleogeography of the Americas.
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, and in the latter case, apparently many extinctions of populations in lowland areas (Grau et al.,
2005).
Another result was that the wattled guan belongs to the same genus as the piping-guans, which thus use the older name Aburria (Grau et al.,
2005).

Originally interpreted as a turkey by Othniel Charles Marsh, Meleagris antiquus was referred to as Cracidae in 1964 by Pierce Brodkorb.
It is nowadays considered unambiguously to be a Cariamiformes under Bathornithidae, and indeed a very different animal from cracids, being a 2 meter tall terrestrial predator.
Similarly, Palaeophasianus has been reassigned to Geranoididae, a lineage of large, ostrich-like stem-cranes.
Recent research has analyzed mt and nDNA sequences, morphological, and biogeographical data 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 traditional groups—chachalacas, guans, and curassows—are verified as distinct clades, but the horned guan represents the sole survivor of a very distinct and ancient lineage.
In addition, the molecular data 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 a single doubtfully distinct genus of chachalaca, Boreortalis (Hawthorn Early Miocene of Florida, USA; may actually be a junior synonym of Ortalis) and some species in the modern genus Ortalis, however. This does not provide any assistance in evaluating the hypothesis (Pereira et al., 2002) that the split between the 4 main lineages of our time occurred quite rapidly, approximately in the Oligocene or slightly earlier, somewhere between 40 and 20 mya.
The genera Procrax and Palaeonossax are often considered cracids, but this is not certain at all; they may belong to a related extinct lineage. It is unfortunate that of these too, few good fossils are known, as they date to about the time when the modern groups presumably diverged. Should they be cracids, they are not unlikely to represent either some of the last members of the family before guans, chachalacas, etc. evolved, or very early representatives of these lineages.
Thus, the assumption that the modern diversity started to evolve in the late Paleogene, continuing throughout the Miocene and onwards, 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 Galloanserae, and consistent with the paleogeography of the Americas. 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, and in the latter case, apparently many extinctions of populations in lowland areas (Grau et al., 2005). Another result was that the wattled guan belongs to the same genus as the piping-guans, which thus use the older name Aburria (Grau et al., 2005).
Originally interpreted as a turkey by Othniel Charles Marsh, Meleagris antiquus was referred to as Cracidae in 1964 by Pierce Brodkorb. It is nowadays considered unambiguously to be a Cariamiformes under Bathornithidae, and indeed a very different animal from cracids, being a 2 meter tall terrestrial predator. Similarly, Palaeophasianus has been reassigned to Geranoididae, a lineage of large, ostrich-like stem-cranes.
Cracidae