Titanis

Titanis; Temporal range: Early Pliocene-Early Pleistocene (Hemphillian-Blancan); ~
	Reconstructed skeleton, Florida Museum of Natural History
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Cariamiformes
Family:	†Phorusrhacidae
Subfamily:	†Phorusrhacinae
Genus:	†Titanis; Brodkorb, 1963
Type species
	†Titanis walleri; Brodkorb, 1963

Titanis (meaning "Titan" for the mythological Greek Titans) is a genus of phorusrhacid ("terror birds", a group originating in South America), an extinct family of large, predatory birds, in the order Cariamiformes that inhabited the United States during the Pliocene and earliest Pleistocene. The first fossils were unearthed by amateur archaeologists Benjamin Waller and Robert Allen from the Santa Fe River in Florida and were named Titanis walleri by ornithologist Pierce Brodkorb in 1963, the species name honoring Waller. The holotype material is fragmentary, consisting of only an incomplete right tarsometatarsus (lower leg bone) and phalanx (toe bone), but comes from one of the largest phorusrhacid individuals known. In the years following the description, many more isolated elements have been unearthed from sites from other areas of Florida, Texas, and California. It was classified in the subfamily Phorusrhacinae, which includes some of the last and largest phorusrhacids like Devincenzia and Kelenken.

Like all phorusrhacids, Titanis had elongated hind limbs, a thin pelvis, proportionally small wings, and a large skull with a hooked beak. It was one of the largest phorusrhacids, possibly similar in size to Phorusrhacos based on preserved material. More recent estimates placed Titanis at 1.4 to 2 meters (4.6 to 6.6 ft) in height and over 300 kilograms (660 lb) in body mass. Due to the fragmentary fossils, the anatomy is poorly known, but several distinct characters on the tarsometatarsus have been observed. The skull is estimated to have been between 36 centimetres (14 in) and 56 centimetres (22 in) in length, one of the largest known from any bird.

Phorusrhacids are thought to have been ground predators or scavengers, and have often been considered apex predators that dominated Cenozoic South America in the absence of placental mammalian predators, though they did co-exist with some large, carnivorous borhyaenid mammals. Titanis co-existed with many placental predators in North America and was likely one of several apex predators in its ecosystem. The tarsometatarsus was long and slender, like that of its relative Kelenken, which has been suggested to have been agile and capable of running at high speeds. Studies of the related Andalgalornis show that large phorusrhacids had very stiff and stress-resistant skulls; this indicates they may have swallowed small prey whole or targeted larger prey with repetitive strikes of the beak. Titanis is known from the Pliocene deposits of Florida, southern California, and southeastern Texas, regions that had large open savannas and a menagerie of mammalian megafauna. It likely preyed on mammals such as the extinct armadillo relatives Holmesina and Glyptotherium, equids, tapirs, capybaras, and other Pliocene herbivores. Titanis is unique among phorusrhacids in that it is the only one known from North America, crossing over from South America during the Great American Interchange.