Phorusrhacos (meaning "bearer of scars" or "bearer of wrinkles") is an extinct genus of phorusrhacid ("terror bird"), an extinct group of predatory, typically large and flightless birds. It lived during the Early to Middle Miocene epoch (18-13 mya) of the Neogene in what is now southern Argentina. The first fossil known to science, an isolated mandible (lower jaw) fragment, was unearthed in 1887. Argentine paleontologist Carlos Ameghino discovered it in sediments of the Santa Cruz Formation in Santa Cruz Province, Argentina. Later that year, Carlos' brother Florentino scientifically described the fossil as a new genus and species, Phorusrhacos longissimus. Florentino stated it was a type of giant, toothless sloth that belonged to its own family, Phorusrhacidae. However, in 1891 Argentine naturalist Francisco Moreno pointed out that the fossil actually came from a bird. Since its 1887 description, Phorusrhacos has become one of the most well-known and common phorusrhacids, with fossils known from sites throughout southern Argentina. Phorusrhacos is estimated to have been 1.4–1.9 meters (4.6–6.2 ft) tall and weighed 93 kilograms (205 lb), making it among the largest phorusrhacids. However, it was more lithe and cursorial (built for running) than the similarly-sized phorusrhacids Kelenken and Devincenzia. Being a phorusrhacid, it has an elongated, tall skull with a sharp beak. In anterior (front) view, the skull is laterally compressed (thin). Its cervical (neck) vertebrae are short, thick, and wide, likely an adaptation for striking prey. Its hindlimbs are long and slender; the tarsometatarsus is about 70% the length of the tibiotarsus (shin bone) and has a thin shaft. During the Miocene, Santa Cruz Province was blanketed in savanna-like grasslands, shrublands, and woodlands. Due to its isolation from other continents, South America developed a unique mammalian, avian, and reptilian fauna before the Great American Interchange. Phorusrhacos was an apex predator in Santacrucian ecosystems, likely preying on mammals including ground sloths, notoungulates, and litopterns.
Discovery and naming
Initial description
The taxonomic history of Phorusrhacos is muddled due to the fragmentary nature of fossils, few of which overlap, and little consensus between scientists. In the 19th century, interest in the rich "Tertiary" (now Neogene) fossil sites of Argentina boomed. This included exploration by two teams of Argentine paleontologists: Florentino and Carlos Ameghino, who operated independently, and Francisco Pascasio Moreno and Alcides Mercerat of the Museo de La Plata (MLP). Their discoveries comprised thousands of fossils from Cenozoic fossil deposits throughout Patagonia and central Argentina. Initially, Moreno hired Florentino and Carlos Ameghino as staff at the MLP in 1887; Florentino operated as a researcher and Deputy Director, while his brother conducted expeditions and assisted with preparation. However, the relationship between Moreno and Florentino Ameghino deteriorated, culminating in the Ameghinos' resignation from the MLP in 1888. Operating independently of any institutions until 1902, the Ameghinos competed with Moreno and the Museo de La Plata to discover and describe as many new fossils as they could. This led to the description of many genera and species based on fragmentary, undiagnostic, or poorly described material.
The first known discovery of Phorusrhacos was made in 1887 by Carlos Ameghino during an expedition to an outcrop of the Miocene-aged Santa Cruz Formation along the Santa Cruz River in Santa Cruz Province, Argentine Patagonia. This formation dates to the Santacrucian South American Land Mammal Age (a series of mammalian fauna-based geologic ages), which lasted from 22 to 16 million years ago, and preserves a diverse array of endemic birds, mammals, reptiles, and more. This trip alone produced hundreds of fossils, which were described as over 120 novel species of fossil mammals in 1887. The descriptions produced by Florentino were short, vague, and sought to establish priority for new taxa before his competitor, Moreno, could. Along the Santa Cruz River, Carlos unearthed an isolated, incomplete edentulous (toothless) mandible (lower jaw), which was later deposited at the MLP. Florentino believed this fossil belonged to a new genus and species of edentate mammal, around the size of Mylodon, which he named Phorusrhacos longissimus. He chose the mandible (specimen number MLP-118) as the holotype (name-bearing) specimen of P. longissimus. The etymology of Phorusrhacos is convoluted. Ameghino did not explain the etymology of the generic name Phorusrhacos or the specific name longissimus. The former is derived from the Greek -φόρος, (-phoros), meaning "bearer" in word combinations, and ῥάκος, (rhakos), "rag" or "wrinkle", probably in reference to the wrinkled jaw surface of the holotype. This creates the literal meaning "wrinkle bearer (jaw)" for Phorusrhacos. When the original derivation was no longer understood, other translations were proposed, such as the literal translation "rag-thief" and "branch-holder" based on mistaken assumption that the name was intended to derive from the Greek rhakis, "branch". The specific name means "very long" in Latin, again in reference to the holotype.
Competition
… excerpt ends here. Continue reading the full article.
