Gracilisuchus colorized

Updated January 14, 2015 with new tracings of the Gracilisuchus skull identifying the postfrontals and the addition of the dinosaur lineage image. 

Until recently
I only had Romer’s version of Gracilisuchus, a basal crocodylomorph. The only problem is no other crocodylomorph has an unfused frontal/postfrontal. Another look at a hi-rez Gracilisuchus (Butler et al. 2014) provided the answer (Fig. 1). Recent phylogenetic analysis places it outside of the croc/dino split. both clades fuse the postfrontal, one to the frontal, the other to the postorbital.

Figure 1. Gracilisuchus colorized. Note the separate frontals and postfrontals, distinct from all other  crocodylomorphs.

Figure 1. Gracilisuchus colorized. Note the separate frontals and postfrontals, distinct from all other crocodylomorphs.

Contra Butler et al. 2014, 
Gracilisuchus nests in the large reptile tree with Scleromochlus and Saltopus, not with Yonghesuchus, yet as in Butler et al. 2014, Gracilisuchus was indeed derived from a sister to Turfanosuchus. (Fig. 2).

Figure 1. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

References
Butler RJ et al. 2014. New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and the biogeography of the archosaur radiation. Evolutionary Bioloty 14:128.
Romer AS 1972. 
The Chañares (Argentina) Triassic reptile fauna. An early ornithosuchid pseudosuchian, Gracilisuchus stipanicicorum, gen. et sp. nov. Breviora 389:1-24.

 

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