Why aren't the Phorusrhacidae better known? Everyone swoons over sabretoothed tigers and velociraptors, everyone likes giants and monsters and weird things. Let's hear it for the Phorusrhacidae, a family of giant carnivorous birds that ruled South America for millions of years. Yes, birds. In appearance a bit like an ostrich wearing an eagle Halloween mask, with the table manners of Tyrannosaurus rex. They even have two ready-made popular names, "terror birds" and "thunderbirds".

Despite the ratite (wingless running bird) appearance, they were actually members of the order Gruiformes, which today contains cranes and the humble coot and moorhen. After the extinction of the dinosaurs, South America drifted off as an island continent, and a certain ambitious proto crane, coot, or moorhen started exercising regularly and tucking into bodybuilder birdseed, and expanded into a race of giants. Their leg bone ratios show they were capable of great speed, and their beaks were formidable. They would have been able to outrun anything in South America and tear it apart. Okay, we think South America, we think sloths and armadillos, so outrunning is probably not that difficult.

The other thing is it had none of the present competition, just its relatives and a marsupial sabretooth called Thylacosmilus. There were no jaguars or ocelots there yet. Then near the end of the Pliocene the Isthmus of Panama closed up, joining South with North America. This caused the so-called Great American Interchange. The Pliocene equivalent of Coca-Cola and Michael Jackson swarmed into the South, and phorusrhacids were out-competed by the giant cats. One species, Titanis walleri, did manage to make it north and survive for a while; fossils have been found in Florida.

Phorusrhacus longissimus stood 2 to 2.5 m tall, and had a skull 65 cm long, which is big by anyone's standards, but especially big for a bird.

The main genus is Phorusrhacus. The names seem to have gone through several alternative spellings. A 2003 study by Alvarenga and Höfling established five subfamilies, thirteen genera, and seventeen species:

  • Phorusrhacidae
    • Brontornithinae
      • Brontornis burmeisteri
      • Physornis fortis
      • Paraphysornis brasiliensis
    • Phorusrhacinae
      • Phorusrhacus longissimus
      • Devincenzia pozzi
      • Titanis walleri
    • Patagornithinae
      • Patagornis marshi
      • Andrewsornis abbotti
      • Andalgalornis steulleti
    • Psilopterinae
      • Psilopterus bachmanni
      • Psilopterus lemoinei
      • Psilopterus affinis
      • Psilopterus colzecus
      • Procariama simplex
      • Parapsilopterus itaboraiensis
    • Mesembriornithinae
      • Mesembriornis milneedwardsi
      • Mesembriornis incertus

In the 1980s two phorusrhacid-like species were discovered in Europe, Aenigmavis sapea and Ameghinornis minor. It has recently been shown that these ought to be classed as genus Strigogyps, and that they lack features to qualify them as Phorusrhacidae.

References. There's disappointingly little about these creatures on the Web. A bit of classification, a few pictures, a couple of abstracts, but nothing very substantial.