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Subclade Archosauria: Crurotarsi to Crocodylia 

Taxon Feedback
Taxon Crurotarsi 
Nominal Author Sereno and Arcucci 1990 
2° Nominal Author  
Taxon Status active

The original intention in defining Crurotarsi was to coin a “stem-based taxon” in place of Pseudosuchia (Sereno 1991:42). The active definition is a second-order revision, because the original definition (Sereno and Arcucci 1990:41) and that in Sereno (1991:27) were node-based in error. As defined here, Crocodylotarsi and Pseudosuchia are potentially synonomous with Crurotarsi. Given the “Pan-” prefix suggested recently as a convention (Joyce et al. 2004), there may eventually be an additional junior synonym (“Pancrocodylia”).

Preference is given to Crurotarsi over Pseudosuchia (or Crocodylotarsi) despite the earlier date of definition of the latter, because of the long historical association of Pseudosuchia (“false crocodiles”) with polyphyletic taxonomic content that excluded crocodylomorphs as well as phytosaurs. In Krebs’ (1976) review, Pseudosuchia includes archosaur outgroups (Euparkeria) and taxa closer to birds (Scleromochlus) but excludes crocodylomorphs and phytosaurs. Abandoning Pseudosuchia for a more recently coined and defined taxon Crurotarsi is done reluctantly. Factors that enter such a decision include the mportance of past use regarding Pseudosuchia as well as the etymology of both taxa. Although taxa such as Dinosauria have successfully accommodated a living crown clade (Aves) that was once excluded, the name of the taxon at hand was not “Pseudoaves” and was not erected specifically for non-birds.

Crocodylotarsi, coined two years prior to Crurotarsi but first defined two years later, would have been another possibility. However, it has been defined as a less inclusive, node-based clade linked to the “crocodile normal” tarsus. Basal relationships within Crurotarsi are not well established, and so a taxon so defined may well prove redundant. Recently Parrish (1997) has abandoned Crocodylotarsi and Crurotarsi, whereas other authors have adopted Crurotarsi (Juu, 1994, Brochu 2001).

Potential Synonomy Pseudosuchia, Crocodylotarsi 

Active Phylogenetic Definition Feedback
Active Definition The most inclusive clade containing Crocodylus niloticus (Laurenti 1768) but not Passer domesticus (Linnaeus 1758). 
Shorthand > Crocodylus niloticus but not Passer domesticus
Definitional Author Sereno 2005 
Definition Status original
textual substitution
first-order revision
second-order revision
Definition Type node
Node-Stem Triplet yes
Other Triplet Taxa Archosauria, Avemetatarsalia 
Specifier A Crocodylus niloticus 
Specifier(s) B  
Specifier(s) C Passer domesticus 
Taxonomic Content stem (entirely extinct)
crown (extant-bounded)
mixed (extant/extinct-bounded)
Publication Year 2005 

Inactive Taxon Status Feedback
Rejection Criteria junior synonym
historically polyphyletic
incomplete definition
no definition

Current Age Range Feedback
Earliest Record Anisian (245 Ma) 
Latest Record Recent 
Range (My) 245 
Basis for Range The earliest record is Ticinosuchus ferox and other basal suchians from Anisian-age deposits in Europe (Krebs 1976, Gower 2000), which may be older than is Gracilisuchus stipanicicorum from the Ladinian-age Chañares Formation of northwestern Argentina (Rogers et al. 2001). The latest records are extant crocodilians. Dates are rounded to the nearest million, the earliest from the beginning of the stage (Gradstein et al. 2004). 

Definitional History #1
Definition 1 Ornithosuchidae, Parasuchia, Aetosauria, Rauisuchia, Crocodylomorpha, and all extinct descendants that are most closely related to these taxa. 
Author Sereno and Arcucci 1990:41 
Type node  stem 
Specifiers Ornithosuchidae, Parasuchia, Aetosauria, Rauisuchia, Crocodylomorpha 

Definitional History #2
Definition 2 Parasuchia, Ornithosuchidae, Prestosuchus, Suchia, and all descendants of their common ancestor. 
Author Sereno 1991:27 
Type node  stem 
Specifiers Parasuchia, Ornithosuchidae, Prestosuchus, Suchia 

Definitional History #3
Definition 3 The last common ancestor of Ornithosuchidae (e.g., Riojasuchus; Fig. 4A) and Crocodylotarsi and all its descendants. 
Author Parrish 1993:291 
Type node  stem 
Specifiers Ornithosuchidae, Crocodylotarsi 

Definitional History #4
Definition 4 Phytosaurs and crocodiles and all descendants of their most recent common ancestor. 
Author Parrish 1997: 
Type node  stem 
Specifiers phytosaurs, crocodiles 

Definitional History #5
Definition 5 Phytosauridae, Ornithosuchidae, Prestosuchus, Suchia, and all descendants of their common ancestor.  
Author Benton 2004:14 
Type node  stem 
Specifiers Phytosauridae, Ornithosuchidae, Prestosuchus, Suchia