TERROR BIRDS

The generalized term “terror birds” is the focus of this post. It refers to a group of extinct similar looking birds that could be up to 8 or 10 feet tall and weighing 400 pounds. There were several genera/species, and they make up an extinct group of carnivorous flightless birds, referred to as the phorusrhacids. They were the largest apex predators to live in South America during the Cenozoic Era.

One example of this group is genus Phorusrhacos [pronounced For-us-Rah-koss], of middle Miocene age, about 14 million years ago, from Santa Cruz, southern Argentina. Although it superficially resembles an ostrich, it is not one. The skull of Phorusrhacos is very different. Phorusrhacos was 8 feet tall and weight 300 pounds or more. A model of this genus is shown below. 

The geologic time range of “terror birds” is most of the Cenozoic, from late early Paleocene, late Danian Stage [=62 million years], through the early Pleistocene [=1.8 million years]; an interval of approximately 60 million years. Why did they go extinct? Most likely, it was because of changing habitat (related to changing climate during the Pleistocene Ice Age). Also the Panamanian Land Bridge emerged during the Pleistocene, and South America became connected to North America, and large predatory cats and dogs migrated southward into South America for the first time.

It is interesting to mention that the geologically youngest “terror bird” (Titanis walleri = 8 feet tall and 300 pounds), of early Pliocene to early Pleistocene, lived in Texas and Florida. This shows that at least a “terror birds” migrated northward into North America, but their presence there did not last long.

The geologic history of birds, in general, is a complex subject. They originated during the “time of dinosaurs” during the Jurassic Period, but their diversity increased significantly during Cenozoic time. A very generalized cartoon showing the major different groups of Cenozoic birds is shown below. The “story” of bird evolution is still unfolding.  

I encourage you to “Google” the words “terror birds” or Phorusrhacos. There are MANY online colorful renditions of what this animal and its relatives looked like.