Andrewsornis is an extinct genus of giant flightless of the family Phorusrhacidae or "terror birds" that lived in Oligocene Argentina. Fossils have been found in the Sarmiento Formation, and possibly the Agua de la Piedra Formation.[ Andrewsornis at Fossilworks.org]
Discovery and naming
Fossils of
Andrewsornis were first discovered on 18 September 1923 by fossil collector John Bernard Abbott in Cabeza Blanca in the province of
Chubut Province,
Patagonia in southern Argentina. Abbott was a member of the Marshall Field Paleontological Expeditions, a series of Field Museum expeditions led by paleontologist Elmer Riggs that explored fossiliferous outcrops in Argentina and Bolivia between 1922 and 1927.
The Marshall Field Paleontological Expeditions unearthed many
Phorusrhacidae fossils, however their description was delayed by World War II.
The remains found consisted of an incomplete
skull, both
Mandible (lower jaws), the proximal (towards body) section of the
coracoid (shoulder bone), and two
Phalanx bone (finger bones) from the second digit. These specimens make up the
holotype (name-bearing) specimen, which was deposited at the Field Museum under specimen number FM-P13417.
The strata of the Cabeza Blanca where the fossils were found corresponds to the Deseado Formation, which comes from the
Deseadan SALMA (South American land mammal age) and the middle-upper
Oligocene.
In 1941, paleontologist Bryan Patterson scientifically described the remains as belonging to a new genus and species of phorusrhacid, which he named Andrewsornis abbotti. The generic name is in honor of Charles William Andrews, a paleontologist who specialized in fossil birds, and the Greek root " ornis" meaning "bird". The specific name abbotti is in honor of John Bernard Abbott, an experienced fossil collector and the discoverer of the specimen.
Description
Andrewsornis is so far the largest member of the subfamily Patagornithinae, though it has also been found to be a Phorusrhacine.
The genus is generally very similar to
Phorusrhacos, but differs in that: the skull is slightly flatter, front edge of the antorbital fenestra is strongly sloping, the lower jaw is 39 cm long and slimmer than
Phorusrhacos.
With a length of 10 cm,
the symphysis mandibulae is more similar to that in
Andalgalornis and
Patagornis. The Fenestrae Mandibulares are longer and larger than in
Patagornis and
Andalgalornis, have an oval shape.
Classification
In 2003 during their redescription of phorusrhacidae, Herculano Alvarenga and Elizabeth Hofling created a new subfamily, Patagornithinae, with
Patagornis as the type genus, that included
Andrewsornis and
Andalgalornis.
Andrewsornis is similar to
Patagornis and
Andalgalornis in that they all are medium-sized phorusrhacids with slender, lightly built bodies, long and narrow mandibular symphyses, and long and slender tibiotarsi and tarsometatarsi.
However, a phylogenetic analysis in 2015 by Degrange
et al found
Andrewsornis in a merged Phorusrhacinae and in polytomy with
Physornis and
Phorusrhacos as well.
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 a clade that contains
Physornis,
Phorusrhacos and
Andalgalornis, among others.
External links
