13 October 2011 Fossil Vertebrate of the Month - Terror Bird LA
County Museum's mount of Paraphysornis in the picture at left,
were a group of giant, flightless birds related to living
seriemas, most of which have been uncovered in South America.
Flightless birds are not unusual, as anyone who's seen an
ostrich, emu, or rhea (or fossils of elephant birds, moas, or
mihirungs) can attest. However, phorusrhacids were different in
one key respect: they were carnivorous. Carnivory has been
suggested for some other land birds - chief among them the
Eocene Gastornis, itself a possible terror bird ancestor - but
the huge size, robust build, and raptor-like beaks of
phorusrhacids leave no doubt. In fact, the near absence of large
mammalian carnivores in South America for most of the Cenozoic
indicates that the top predator niche on that continent was
occupied by terror birds (they would have preyed upon one of the
strangest herbivore faunas in the world, composed of, among
other things, meridiungulates, xenarthrans, a