Re: Phorusrhacids killing large mammals in National Geographic Channel

[Augusto Haro <augustoharo@gmail.com>]

It seems to be that the claws of some phorusrhacids are laterally
compressed instead of wide and blunt as in Ratites, so they are
supposed to use their legs to kick small prey. As far as I know, the
beak is tall and laterally compressed in at least some phorusrhacids.
I suppose perhaps the pointed tip was used more as a canine to kill
with a bite, which would serve for itself against small prey, but not
with prey closer to their size. Unless phorusrhacids shake their heads
to the sides like crocs and dogs, then they may easily kill animals
half their size, but I do not know of birds which do so. Also, the
long pointing tip of the upper jaw and the dorsoventrally tall beak
seems to better suggest resistance to orthal (biting) forces than to
lateral (shaking) forces (the wider snout of crocodylians better
resist lateral forces).

It seems that if the head was used as in the secretary bird or
seriemas, the proportionally larger size of the head and beak in
phorusrhacids suggest they killed proportionally larger prey when
compared to the Recent birds previously mentioned.