Foot of Tyrannosaurus showing the arctometatarsal condition in the middle metatarsus, compared to the foot of Allosaurus.
The arctometatarso is an anatomical term that is used to refer to when the proximal area of an average metatarsus is compressed between the other metatarsals that surround it. This condition appears to be highly homoplastic, and is common in certain types of race-adapted dinosaurs (including tyrannosauroids, ornithomyosaurs and trodonids), to transmit force uniformly to the metatarsals.
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