Characteristic features of the tyrannosauroid pelvis include a notch at the upper front end of the ilium, a sharply defined vertical ridge on the outside surface of the ilium, extending upwards from the acetabulum (hip socket), and a huge "boot" on the end of the pubis, more than half as long as the shaft of the pubis itself. These features are found in all known tyrannosauroids, including basal members "Guanlong" and "Dilong". The pubis is not known in "Aviatyrannis" or "Stokesosaurus" but both show typical tyrannosauroid characters in the ilium. The hindlimbs of all tyrannosauroids, like most theropods, had four toes, although the first toe (the hallux) did not contact the ground. Tyrannosauroid hindlimbs are longer relative to body size than almost any other theropods, and show proportions characteristic of fast-running animals, including elongated tibiae and metatarsals. These proportions persist even in the largest adult "Tyrannosaurus", despite its probable inability to run. The third metatarsal of tyrannosaurids was pinched at the top between the second and fourth, forming a structure known as the arctometatarsus. The arctometatarsus was also present in "Appalachiosaurus" but it is unclear whether it was found in "Eotyrannus" or "Dryptosaurus". This structure was shared by derived ornithomimids, troodontids and caenagnathids, but was not present in basal tyrannosauroids like "Dilong paradoxus", indicating convergent evolution.