Paraphysornis

The holotype (DGM-1418-R) and only known fossil was discovered by a mining company in the Taubaté Basin (São Paulo State) in a layer of bentonite clay, two or three meters below a layer of Pyrobitumen. These sediments belong to the Late Oligocene to Early Miocene Tremembé Formation. Excavation of the bones took several months between 1977 and 1978, yielding a nearly complete (%75) skeleton only lacking most of the cranium, the pelvis and sternum. The bones were initially studied by Herculano Alvarenga, who first described them in 1982 as a species of Physornis. Following closer examination of various phorusrhacid remains held in institutions across Europe, North America and Argentina; Alvarenga came to the conclusion that his taxon displays enough unique features to warrant a new genus distinct from Physornis, naming it Paraphysornis in a publication in 1993. The name is a combination of the genus name of Physornis and the Greek suffix "para-", in combination meaning "close to Physornis". The species name "brasiliensis", coined in the initial description in 1982, reflects the animal's country of origin. == Description ==

The mandible is well preserved but slightly distorted, with a convex lower margin and a concave cutting surface preserving no signs of a longitudinal crest (as seen in Phorusrhacos). The mandible is also wider and higher than that of Phorusrhacos, with a better developed retroarticular process and more elongated foramina. The mandible is long and high at the base of the mandibular symphysis. Only few elements of the cranium are preserved including the quadrates and their articulation with the mandible as well as the front of the premaxilla, which shows a strongly hooked tip as known from other phorusrhacids. Another estimate by Molina-Pérez & Larramendi puts Paraphysornis weight at up to . ==Classification==

Paraphysornis shares several characteristics with Brontornis including the shortend tarsometatarsus (only half the length of the tibiotarsus) and the morphology of the vertebrae. However the two genera also differ significantly not only in size. The phalanges of Paraphysornis are less flattened and the claws of the toes sharper. The condyles of the tibiotarsus run parallel to the axis of the shaft, while the medial condyle of Brontornis is angled similar to waterfowl. However, the nature of this clade has come into question, with some researchers arguing that Brontornis does in fact not represent a phorusrhacid and may instead be a gastornithiform anserimorph. Although the matter is debated, Agnolin proposed the name Physornithinae for a clade containing both Physornis and Paraphysornis. The following phylogenetic tree shows the internal relationships of Phorusrhacidae under the exclusion of Brontornis as published by Degrange and colleagues in 2015, which recovers Paraphysornis as basal to clade that contains Physornis, Phorusrhacos and Andalgalornis, among others. }} ==Paleoecology==

In birds the ability to run is proportional to the ratio between tarsometatarsus and tibiotarsus length. In Paraphysornis the tarsometatarsus is only half the length of the tibiotarsus. This was used to infer a relatively slow speed, matching the animal's increased bodymass. The method of Storer (1960) works in a similar manner, determining locomotion style according to the lengths of the two bones in addition to femur length (a method highly dependent on preservation). Applying this method likewise gives results suggesting a heavyset graviportal animal, with calculated values being similar to those of moas and elephant birds. Alvarenga has suggested that Paraphysornis heavy stature might mean that Paraphysornis was a scavenger. Thus, it's reasonable to assume that Paraphysornis was an active predator like its relatives, leaning more towards ambushing its prey than running them down. Paraphysornis lived during the Late Oligocene or Early Miocene in the Tremembé Formation, which preserves what's thought to be a shallow lake. Other animals present in the formation include a variety of fish, flamingos, a species of screamer, teratorns and leontiniid notoungulates. == References ==