Metasuchia
Encyclopedia
Metasuchia is a major clade
within the superorder Crocodylomorpha
. It is split into two main groups, Notosuchia
and Neosuchia
. Notosuchia is an extinct group that contains primarily small-bodied Cretaceous
taxa with heterodont
dentitions. Neosuchia includes extant crocodylians and basal
taxa such as peirosaurids
and pholidosaurids
. It is phylogenetically
defined by Sereno et al. (2001) as a clade containing Notosuchus terrestris, Crocodylus niloticus, and all descendants of their common ancestor.
by Larsson and Sues (2007) to include peirosaurids in the clade. Previously, peirosaurids were placed outside of Notosuchia. Larsson and Sues (2007) also suggested that Sebecosuchia (containing the families Baurusuchidae
and Sebecidae
) was polyphyletic, as Baurusuchus
was placed outside of Sebecia, which itself was placed outside of Notosuchia. However, more recent phylogenetic studies have placed Baurusuchus
within Notosuchia once again, although it is still not considered to be a sebecosuchian.
Cladogram
after Sereno et al., 2001:
Cladogram after Sereno et al., 2003:
Cladogram after Sereno and Larsson, 2009:
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
within the superorder Crocodylomorpha
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
. It is split into two main groups, Notosuchia
Notosuchia
Notosuchia is a suborder of primarily Gondwanan mesoeucrocodylian crocodylomorphs that lived during the Cretaceous. Fossils have been found from South America, Africa, and Asia...
and Neosuchia
Neosuchia
Neosuchia is an unranked clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to Crocodylus niloticus than to Notosuchus terrestris...
. Notosuchia is an extinct group that contains primarily small-bodied Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
taxa with heterodont
Heterodont
The anatomical term heterodont refers to animals which possess more than a single tooth morphology. For example, members of the Synapsida generally possess incisors, canines , premolars, and molars. The presence of heterodont dentition is evidence of some degree of feeding/hunting specialization...
dentitions. Neosuchia includes extant crocodylians and basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
taxa such as peirosaurids
Peirosauridae
Peirosauridae is a Gondwanan family of mesoeucrocodylians that lived during the Cretaceous period. It was a clade of terrestrial crocodyliforms that evolved a rather dog-like form, and were terrestrial carnivores. It was phylogenetically defined in 2004 as the most recent common ancestor of...
and pholidosaurids
Pholidosauridae
Pholidosauridae is an extinct family of mesoeucrocodylian crocodylomorphs. Fossils have been found in the United States, Canada, China, Kyrgyzstan, Africa and Spain...
. It is phylogenetically
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
defined by Sereno et al. (2001) as a clade containing Notosuchus terrestris, Crocodylus niloticus, and all descendants of their common ancestor.
Phylogenetics
The phylogeny of basal metasuchians has experienced many revisions in recent years. The phylogeny of notosuchians has been particularly revised, with the construction of SebeciaSebecia
Sebecia is an extinct clade of mesoeucrocodylian crocodyliforms that includes peirosaurids and sebecids. It was first constructed in 2007 to include Hamadasuchus, Peirosauridae, and Sebecus. It was initially considered to be the sister taxon of the clade Neosuchia, which includes living...
by Larsson and Sues (2007) to include peirosaurids in the clade. Previously, peirosaurids were placed outside of Notosuchia. Larsson and Sues (2007) also suggested that Sebecosuchia (containing the families Baurusuchidae
Baurusuchidae
Baurusuchidae is a Gondwanan family of mesoeucrocodylians that lived during the Late Cretaceous. It is a group of terrestrial hypercarnivorous crocodilians from South America and possibly Pakistan. Baurusuchidae has been defined as a clade containing the most recent common ancestor of Baurusuchus...
and Sebecidae
Sebecidae
Sebecidae is an extinct family of prehistoric crocodylomorphs. They lived mostly in Argentina.This group included many medium and large - sized genera, from Sebecus to a giant indeterminate unnamed species from the Miocene.-Phylogeny:...
) was polyphyletic, as Baurusuchus
Baurusuchus
Baurusuchus is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Brazil. It was a terrestrial predator and scavenger, about 3.5 to 4 meters long. Baurusuchus lived during the Turonian to Santonian stages of the Late Cretaceous Period, in Adamantina Formation, Brazil...
was placed outside of Sebecia, which itself was placed outside of Notosuchia. However, more recent phylogenetic studies have placed Baurusuchus
Baurusuchus
Baurusuchus is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Brazil. It was a terrestrial predator and scavenger, about 3.5 to 4 meters long. Baurusuchus lived during the Turonian to Santonian stages of the Late Cretaceous Period, in Adamantina Formation, Brazil...
within Notosuchia once again, although it is still not considered to be a sebecosuchian.
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
after Sereno et al., 2001:
Cladogram after Sereno et al., 2003:
Cladogram after Sereno and Larsson, 2009:
External links
- Metasuchia in the Paleobiology DatabasePaleobiology Database' is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms.-History:The Paleobiology Database was founded in 2000. It has been funded by the National Science Foundation and the Australian Research Council...
- Cladogram of Metasuchia in Mikko's Phylogeny ArchiveMikko's Phylogeny ArchiveMikko's Phylogeny Archive is an amateur paleontology website maintained by Mikko Haaramo, a student at the University of Helsinki's Department of Geology, Division of Geology and Palaeontology....