The Terror of the Pampas
Even ostriches act like chickens against them: The largest terror birds could look over the shoulder of Asian elephants and weighed as much as some cows. But perhaps they were light on their feet when hunting.
A very peculiar bestiary roamed this land long before our time-in the Miocene of Patagonia: giant sloths, larger and heavier than African elephants, roamed the plains of the La Plata Depression, grazing alongside Glyptodon the Giant armadillos in VW bus format. They were ambushed by Thylacosmilus, a marsupial similar to today's leopard, whose long saber-shaped fangs grew out.
But the rulers of the Pampas were feathered animals with the significant name of terror birds (Phorusrhacidae), early relatives of the modern cranes. They could not fly and foraged on foot, much like the African secretary (Sagittarius serpentarius) still does. Compared to the prehistoric hunters, this bird of prey is more of a linnet, because Brontornis burmeisteri, for example, towered up to three meters and weighed half a ton. And where the slender modern griffin is satisfied with snakes or mice, the terror of the Miocene probably even kicked down animals such as the tapir-like Astrapotherium magnum.
How the terror birds pursued their prey is lost in the murmur of contemporary history: Were they persevering hunters who killed their food after lengthy pursuit races? Or did they prefer ambush attacks with an element of surprise that left the victim little chance of escaping? That probably depended on the species, according to the previous profane answer. The smaller species like Patagornis marshi were agile sprinters, agile like cheetahs and at high speed, putting the targeted rodent on the run. Brontornis burmeisteri or Phorusrhacos longissimus, on the other hand, paid tribute to their enormous size and body mass: The resulting restricted mobility should degrade them to at best opportunistic predators.
Because well-preserved material from large species is rare, such interpretations by paleontologists were based on extrapolated values from well-preserved fossils of the smaller relatives. However, a skull analysis by Luis Chiappe and Sara Bertelli of the Natural History Museum in Los Angeles could now change the conventional view of the terror birds. For the first time, an almost completely preserved, fossilized head of a large phorusrhacid has been excavated - with a diameter of 716 millimeters from the tip of the beak to the base of the neck, BAR 3877-11, the working name of the fossil, offers the largest bird skull known to date.
BAR 3877-11 also roamed Patagonia in the mid-Miocene, and its beak was obviously a formidable weapon, as it alone takes up half of the skull. This biting tool was moved by extensive, strong muscles, which left correspondingly strong scar-like marks on the bone. However, the beak and the rest of the skull are less massive than a comparative but fragmentary head of Devincenzia pozzi - a similarly large species of terror bird, whose head also exceeded 600 millimeters in length.
At the same time, the researchers also tracked down some of the animal's phalanges and metatarsal bone, which they used to calculate the size of the bearer of BAR 3877-11. It surpassed Brontornis burmeisteri and Phorusrhacos longissimus by at least ten percent, which was originally the inspiration for the name "terror bird". In contrast to these two, however, the new member of the family seemed to have been significantly slimmer, because his metatarsal bone is not only long, but also very narrow for this dimension, so that according to Chiappe and Bertelli he could not carry too much weight.
So the probably new species not only had the most impressive beak of any bird ever known, but was also very agile and manoeuvrable - not a pleasant prospect for the potential prey, but quite worthy of a ruler of the Pampas.