Like the cheese, Arizonasaurus stands alone. Almost.
Phylogenetic analysis nests what is known about Arizonasaurus with Yarasuchus and Qianosuchus two sail-less ticinosuchians (not poposaurs, as envisioned by Nesbitt 2011).
We don’t have any fore limbs or hind limbs for Arizonasaurus,
but we do have its pectoral and pelvic girdles.
The pelvic girdle is very deep, compared to the ancestral Vjushkovia, and sister taxa like Yarasuchus, Qianosuchus and Ticinosuchus. In these taxa the femur extends at least as far as the pubis depth and sometimes a little further. If we add such femora to the reconstruction of Arizonasaurus, it becomes essentially bipedal.
The pectoral girdle is quite small and gracile. It would be odd for massive or elongate forelimbs to be attached to such a small pectoral girdle, so here (Fig.1) an appropriate gracile short forelimb is added.
But wait, that’s not all.
That sail adds leverage and strength to the back bone, helping to hold up the elevated anterior half. Moreover, if we add on the deep tail of the related Yarasuchus, we reconstruct a substantial counterbalance (Fig. 1).
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