Fossils of Andrewsornis were first discovered on 18 September 1923 by fossil collector John Bernard Abbott in Cabeza Blanca in the province of Chubut, 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.[2][3] The Marshall Field Paleontological Expeditions unearthed many phorusrhacid fossils, however their description was delayed by World War II.[3] The remains found consisted of an incomplete skull, both mandibles (lower jaws), the proximal (towards body) section of the coracoid (shoulder bone), and two ungual phalanges (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.[3][4] The strata of the Cabeza Blanca where the fossils were found corresponds to the Deseado Formation, which comes from the DeseadanSALMA (South American land mammal age) and the middle-upper Oligocene.[4][5]
In 1941, paleontologist Bryan Pattersonscientifically 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.[3] Since its initial description, few academic studies of the Andrewsornis have been made. In 2003, a study by paleontologists Herculano Alvarenga and Elizabeth Höfling referred a mandibular symphysis (part of the mandible where the two jaws fuse) and a left femur (thighbone) to Andrewsornis based on its origin and size. Additionally, the study stated that Aucornis solidus, a species described in 1898 by paleontologist Florentino Ameghino on the basis of a single phalanx.[6] Alvarenga and Höfling stated that they are likely synonyms, but this cannot be proven due to the lack of diagnostic traits for phalanges. They instead stated that Aucornis solidus is simply a species inquirenda.[4]
Description
Andrewsornis is so far the largest member of the subfamily Patagornithinae, though it has also been found to be a Phorusrhacine.[4] 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's.[4][3] With a length of 10 cm,[3] 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.[4][3]
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.[4] 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.[7] 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.[8]
↑ Ameghino, Florentino (1898). "Sinopsis geológico-paleontológica de la Argentina" [Synopsis of the geology and paleontology of Argentina]. Segundo Censo de la República Argentina (in Spanish). 1: 112–255.
↑ Degrange, Federico J.; Tambussi, Claudia P.; Taglioretti, Matías L.; Dondas, Alejandro; Scaglia, Fernando (2015-03-04). "A new Mesembriornithinae (Aves, Phorusrhacidae) provides new insights into the phylogeny and sensory capabilities of terror birds". Journal of Vertebrate Paleontology. 35 (2) e912656. Bibcode:2015JVPal..35E2656D. doi:10.1080/02724634.2014.912656. hdl:11336/38650. ISSN0272-4634. S2CID85212917.
↑ Degrange, F.J.; Tambussi, C.P.; Taglioretti, M.L.; Dondas, A.; Scaglia, F. (2015). "A new Mesembriornithinae (Aves, Phorusrhacidae) provides new insights into the phylogeny and sensory capabilities of terror birds". Journal of Vertebrate Paleontology. 35 (2) e912656. Bibcode:2015JVPal..35E2656D. doi:10.1080/02724634.2014.912656. hdl:11336/38650. S2CID85212917.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
