Chimaerasuchidae
Encyclopedia
Chimaerasuchidae is a family
of mesoeucrocodylia
ns. It was erected as a clade
in 2004 by Carvalho et al and included Chimaerasuchus from the Early Cretaceous
of China
and Simosuchus
from the Late Cretaceous
of Madagascar
. The validity of the clade has been questioned in later studies that found the two genera to be more distantly related.
of small (~1 metre long), possibly herbivorous crocodyliforms from the Cretaceous
. Both had short-snouted heads with multicusped teeth. Carvalho et al placed Chimaerasuchidae within a new clade of mesoeucrocodylians called Gondwanasuchia. It was the sister taxon of Notosuchimorpha, another newly erected clade that contained notosuchia
s, sebecosuchia
ns, and peirosaurids. Below is a modified cladogram
from Carvalho et al (2004):
The Carvalho et al. (2004) paper phylogeny did not include neosuchia
ns in the analysis. Neosuchians and notosuchians are the two major clades of mesoeucrocodylians. When neosuchians are included in analyses with Simosuchus and Chimaerasuchus, the two genera do not appear as sister taxa (Pol 2003; Candeiro & Martinelli 2006). In fact Chimaerasuchus
has been found to be the sister taxon of Sphagesaurus
. Sphagesaurus is often assigned its own family, Sphagesauridae
. If Chimaerasuchus belongs to Shagesauridae, Chimaerasuchidae would be a junior synonym of Sphagesauridae. This is because Sphagesauridae was named before Chimaerasuchidae, and under ICZN
rules, the oldest name has priority.
In a recent contribution, Marinho & Carvalho (2007) did a revision of Sphagesauridae and noticed that Chimaerasuchus does not have any of the synapomorphies of this family that was originally erected by Kuhn (1968). In this new paper, the authors propose an emended diagnosis for the Sphagesauridae, pointing new synapomorphies for this taxon and propose that the Chimaerasuchidae would be a valid family in spite of the poor phylogenetic analysis of Carvalho et al. (2004) paper.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of mesoeucrocodylia
Mesoeucrocodylia
Mesoeucrocodylia is the name of the clade that includes Eusuchia and the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day....
ns. It was erected as a clade
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...
in 2004 by Carvalho et al and included Chimaerasuchus from the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and Simosuchus
Simosuchus
Simosuchus is an extinct genus of notosuchian crocodylomorphs from the Late Cretaceous of Madagascar. It is named for its unusually short skull. Fully grown individuals were about in length. The type species is S. clarki, found from the Maevarano Formation in Mahajanga Province.The teeth of S...
from the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
of Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. The validity of the clade has been questioned in later studies that found the two genera to be more distantly related.
Phylogeny
In the phylogenetic analysis of Carvalho et al, the family contained Chimaerasuchus and Simosuchus, two generaGenus
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...
of small (~1 metre long), possibly herbivorous crocodyliforms from the 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...
. Both had short-snouted heads with multicusped teeth. Carvalho et al placed Chimaerasuchidae within a new clade of mesoeucrocodylians called Gondwanasuchia. It was the sister taxon of Notosuchimorpha, another newly erected clade that contained 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...
s, sebecosuchia
Sebecosuchia
Sebecosuchia is an extinct group of mesoeucrocodylian crocodyliforms that includes the families Sebecidae and Baurusuchidae. The group first appeared in the Late Cretaceous with the baurusuchids and went extinct in the Miocene with the last sebecids. Fossils have been found primarily from South...
ns, and peirosaurids. Below is a modified cladogram
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...
from Carvalho et al (2004):
The Carvalho et al. (2004) paper phylogeny did not include 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...
ns in the analysis. Neosuchians and notosuchians are the two major clades of mesoeucrocodylians. When neosuchians are included in analyses with Simosuchus and Chimaerasuchus, the two genera do not appear as sister taxa (Pol 2003; Candeiro & Martinelli 2006). In fact Chimaerasuchus
Chimaerasuchus
Chimaerasuchus is an extinct genus of Chinese crocodyliform from the Early Cretaceous. The four teeth in the very tip of its short snout gave it a "bucktoothed" appearance. Due its multicusped teeth and marked heterodonty, it is believed to have been an herbivore....
has been found to be the sister taxon of Sphagesaurus
Sphagesaurus
Sphagesaurus is an extinct genus of notosuchian crocodylomorph from the Late Cretaceous of Brazil.-Species and discovery:The type species S. huenei, was discovered in 1950 by Price, with the both the genus and species named from two isolated teeth. More recently a nearly complete skull of S...
. Sphagesaurus is often assigned its own family, Sphagesauridae
Sphagesauridae
Sphagesauridae is a Gondwanan family of mesoeucrocodylians that lived during the Late Cretaceous. It was a clade of terrestrial crocodilians that evolved very mammal-like teeth and jaws. Both Sphagesaurus and Adamantinasuchus are known from the Turonian to Santonian of Brazil....
. If Chimaerasuchus belongs to Shagesauridae, Chimaerasuchidae would be a junior synonym of Sphagesauridae. This is because Sphagesauridae was named before Chimaerasuchidae, and under ICZN
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
rules, the oldest name has priority.
In a recent contribution, Marinho & Carvalho (2007) did a revision of Sphagesauridae and noticed that Chimaerasuchus does not have any of the synapomorphies of this family that was originally erected by Kuhn (1968). In this new paper, the authors propose an emended diagnosis for the Sphagesauridae, pointing new synapomorphies for this taxon and propose that the Chimaerasuchidae would be a valid family in spite of the poor phylogenetic analysis of Carvalho et al. (2004) paper.
External links
- Taxon Feedback http://www.taxonsearch.org/dev/taxon_edit.php?tax_id=399&Action=View
- Science News " Ancient Crocrodile Chomped On Plants"
- Nature "A Pugnosed Crocodyliform from the Late Cretaceous of Madagascar"http://www.nature.com/nature/journal/v405/n6789/full/405941a0.html