Gracilisuchus stipanicicorum, Romer, 1972

Autapomorphies of G. stipanicicorum

Three autapomorphies are recovered from the optimization of all MPTs. The first is the presence of four premaxillary teeth (6.1), contrasting with Turfanosuchus and Yonghesuchus that possess five (6.2). The condition of Gracilisuchus is not unique and is convergent with that of basal loricatans ( Prestosuchus , Saurosuchus , Fasolasuchus , Batrachotomus ), Rauisuchidae and Crocodylomorpha ( Kayentasuchus , Litargosuchus , Protosuchidae ). A second autapomorphy is the presence of a lacrimal as high as the orbit and contacting the jugal at the level of the ventral margin of the orbit (38.1), contrasting with the low lacrimal present in Turfanosuchus and Yonghesuchus that is significantly lower than the height of the orbit (38.0). Gracilisuchus shares this character state with Tropidosuchus , all Crocodylomorpha that were possible to score ( Hesperosuchus , Dromicosuchus , Sphenosuchus , Junggarsuchus ) as well as in early Theropoda. The last autapomorphy of Gracilisuchus is the presence of a jugal posterior process lying ventral to the anterior process of the quadratojugal (70.1). In Turfanosuchus and Yonghesuchus the process lies dorsal to the anterior process of the quadratojugal (70.0). This autapomorphy is shared convergently with Erpetosuchus , Postosuchus kirkpatricki , Polonosuchus and Crocodylomorpha.

The three character-states obtained as autapomorphies of Gracilisuchus in this phylogenetic analysis are also present in other taxa including Crocodylomorpha. These characters are interpreted as convergences based on the present phylogenetic results, which depict Gracilisuchus as a basal Suchia. The presence of these characters in both Gracilisuchus and Crocodylomorpha, along with the large number of synapomorphies recovered when their monophyly is forced (see above), probably contributed to previous authors interpreting them as derived similarities and postulating the affinities of Gracilisuchus to Crocodylomorpha (e.g. Clark et al., 2000, 2004; Sues et al., 2003; Brusatte et al., 2010; Pol et al., 2012). However, this hypothesis lacks support with the data of the present analysis.