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Clade
Subclade

Taxon
Taxon
Avemetatarsalia
Nominal Author
Benton 1999
2nd Nominal Author
Taxon Status ACTIVE
Comments

This stem-based taxon was coined and defined by Benton (1999) to include all archosaurs closer to dinosaurs than crocodiles, including Scleromochlus, pterosaurs, Lagerpeton, and Marasuchus. This clade intentionally identifies the same stem-based clade as Ornithosuchia (first defined by Gauthier 1986) and Panaves (defined recently by de Queiroz and Gauthier 2001). Ornithodira, as shown in this compilation, has always been associated with a node-based definition. Using Avemetatarsalia as a stem-based taxon in a node-stem triplet at the base of Archosauria (= Crurotarsi + Avematatarsalia) is viewed here as the best option. The active definition presented here is a first-order revision of Benton’s initial definition.

Introducing a new taxon Panaves on the basis of a new “Pan-” convention is not regarded here as productive. It ignores taxonomic history in the service of slightly reducing the number of etymologically novel taxa in taxonomy. The other option is using Ornithodira, as it has been the most familiar taxon associated with the current taxonomic content of Avemetatarsalia. Drawbacks to this option include: (1) Gauthier did not apply Ornithodira in this manner (as a stem-based taxon) but rather used another taxon in this regard (Ornithosuchia); (2) previous definitions of Ornithodira are node-based (Sereno 1991; Benton 2004) rather than stem-based, so to alter the definition requires a second-order revision; (3) the node-based definitions of Orrnithodira have always cited pterosaurs for inclusion, although this is the taxon most likely to be excluded, given its basal position and unknown early history; and (4) the apomorphies that are potentially the most robust are located in the pes rather than in the neck, fitting Avemetatarsalia better than Ornithodira.

In the event that pterosaurs are positioned outside Archosauria, two stem-based taxa in this compilation would apply to the clade that includes all archosaurs more closely related to birds than to crocodilians: Avemetatarsalia and Dinosauromorpha. The latter, Dinosauromorpha, would have precedence, as it was first defined in this manner (Sereno 1991; Arcucci 1997; see Dinosauromorpha for further discussion).

Potential Synonomy
Ornithosuchia, Panaves

Active Phylogenetic Definition
Active Definition
The most inclusive clade containing Passer domesticus (Linnaeus 1758) but not Crocodylus niloticus (Laurenti 1768).
Shorthand
> Passer domesticus but not Crocodylus niloticus.
Definitional Author
Sereno 2005
Definition Status checked
Definition Type STEM
Node-Stem Triplet STEM
Other Triplet Taxa
Archosauria, Crurotarsi
Specifiers
Specifier(s) A
Passer domesticus
Specifier(s) B
Specifier(s) C
Crocodylus niloticus
Qualifiers
+Taxon
-Taxon
Datum
Taxonomic Content
Publication Year Unknown
Unknown
Unknown
1999

Inactive Taxon Status
Rejection Criteria
Critique
 

Definitional History #1
Earliest Record
All avesuchians closer to Dinosauria than to Crocodylia.
Latest Record
Benton 1999:1440
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Dinosauria, Crocodylia
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