Almost all fossils indicate these owls were larger than modern great horned owls. Though the extant nilgai females lack horns, historic relatives of the antelope had horned females. Rhinoceros horns, unlike those of other horned mammals, only consist of keratin. Polled livestock are livestock without horns in species which are normally horned. Only males possess horns, though a few females may be horned as well. The prominences above a great horned owl's head are commonly mistaken as its ears. Horned lizards adopt differing defences for specific predators. Some prey killed by great horned owls was estimated to weigh up to . It may be horned or naturally hornless. Of the 22 species of horned lizards, 15 are native to the United States. Reid and Reese were both pitchers for the TCU Horned Frogs. Territory size is similar or occasionally slightly greater than great horned owl&colon; averaging . It may be horned or hornless, and tassels may be present. Unlike those of mainland Greece, the Cyprian centaurs were horned. Both sexes of the horned puffin help to construct their nest.