Andalgalornis

Source: Wikipedia, the free encyclopedia.

Andalgalornis
Temporal range:
Ma
↓
CT scan of the skull of P 14357, holotype of A. ferox in the collections of the Field Museum of Natural History
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Cariamiformes
Family: †Phorusrhacidae
Subfamily: †
Patagornithinae
Genus: †Andalgalornis
Patterson & Kraglievich, 1960
Species:
†A. steulleti
Binomial name
†Andalgalornis steulleti
(Kraglievich, 1931)
Synonyms
List
  • Phororhacos steulleti Kraglievich, 1931
  • Phororhacos deautieri Kraglievich, 1931
  • Andalgalornis ferox Patterson & Kraglievich, 1960
  • Phorohacos deautieri Kraglievich, 1931

Andalgalornis is a

predatory birds of the extinct family Phorusrhacidae (often called "terror birds") that lived in Argentina. The type and only species
is A. steulleti.

Taxonomy

Andalgalornis is known from an incomplete skeleton and some single bones found from sites in the Entre Ríos and Catamarca Provinces of northeast and northwest Argentina. The fossils were uncovered from the Late Miocene (Huayquerian in the SALMA classification) Ituzaingó Formation of the Paraná Basin.[1]

The following cladogram shows the position of Andalgalornis following a 2015 analysis:[2]

Phorusrhacidae 
 
Mesembriornithinae
 

 

Mesembriornis incertus

 

Mesembriornis milneedwardsi

 

Llallawavis scagliai

 

Procariama simplex

 
Psilopterinae
 

 

Psilopterus affinis

 

Psilopterus bachmanni

 

Psilopterus colzecus

 

Psilopterus lemoinei

 

Kelenken guillermoi

 

Devincenzia pozzi

 

Titanis walleri

 

Phorusrhacos longissimus

 Andalgalornis steulleti

 

Andrewsornis abbotti

 

Patagornis marshi

 

Physornis fortis

 

Paraphysornis brasiliensis

Description

Life restoration

Around 1.4 metres (4.6 ft) tall in height, Andalgalornis is estimated to have weighed around 40 kilograms (88 lb),[3] on the basis of the methodology proposed by Campbell and Marcus (1992).[4] The subfamily to which the genus belonged, the Patagornithinae, contained species that were of quite slender build; it looked much like the larger phorusrhacid Phorusrhacos, but it was more elegant and smaller and had a proportionally higher beak, the most massive in proportion to body size of all phorusrhacids.

Paleobiology

Phorusrhacids are thought to have been ground predators or scavengers, and have often been considered

borhyaenid mammals. Earlier hypotheses of phorusrhacid feeding ecology were mainly based on them possessing large skulls with hooked beaks rather than through detailed hypotheses and biomechanical studies, and such studies of their running and predatory adaptations were only tested from the beginning of the 21st century.[3][5]

Alvarenga and Elizabeth Höfling made some general remarks about phorusrhacid habits in a 2003 article. They were flightless, as evidenced by the proportional size of their wings and body mass, and wing size was more reduced in larger members of the group. They pointed out that the narrowing of the pelvis, upper maxilla, and thorax may have been adaptations for hunting in regions with high vegetation, which would permit greater agility when moving between vertical obstacles. The narrow upper maxilla would also help catching small animals hidden among tree trunks or stones. The large expansions above the eyes formed by the lacrimal bones (similar to what is seen in modern hawks) would have protected the eyes against the sun, and enabled keen eyesight, which indicates they hunted by sight in open, sunlit areas, and not shaded forests.[6]

Stress distribution in bird skulls, including Andalgalornis (left, A–C), and hypothetical upwards-and-downwards range of movement of the neck in the same genus (right)

A 2010 study by Degrange and colleagues of Andalgalornis, based on

intracranial immobility (mobility of skull bones in relation to each other), as was also the case for other large phorusrhacids. These researchers interpreted this loss as an adaptation for enhanced rigidity of the skull, and compared to the modern red-legged seriema and white-tailed eagle, the skull of the phorusrhacid showed relatively high stress under sideways loadings, but low stress where force was applied up and down, and in simulations of "pullback". Due to the relative weakness of the skull at the sides and middle, these researchers considered it unlikely that Andalgalornis engaged in potentially risky behavior that involved using its beak to subdue large, struggling prey. Instead, they suggested that it either fed on smaller prey that could be killed and consumed more safely, by, for example, swallowing it whole, or that when targeting large prey, it used a series of well-targeted repetitive strikes with the beak, in an "attack-and-retreat" strategy. Struggling prey could also be retained with the feet, despite the lack of sharp talons.[3]

A 2012 follow-up study by Tambussi and colleagues analyzed the flexion abilities of the neck of Andalgalornis, based on the morphology of its

plesiomorphic (more similar to the ancestral type), and the "Terror Bird Skull Type", which included Andalgalornis and other large members, that was more specialized, with more rigid and stiff skulls. Despite the differences, studies have shown the two types handled prey similarly, while the more rigid skulls and resulting larger bite force of the "Terror Bird" type would have been an adaptation to handling larger prey.[5]

References
  1. ^ Paraná, Pueblo Brugo to Diamante, Ituzaingó Fm at Fossilworks.org
  2. S2CID 85212917
    .
  3. ^
    PMID 20805872
    .
  4. ^ Campbell, K.E.; Marcus, L. (1992). "The relationship of hindlimb bone dimensions to body weight in birds". Papers in Avian Paleontology Honoring Pierce Brodkorb. 36. Natural History Museum of Los Angeles County, Science Series: 395–412.
  5. ^
    S2CID 234119602
    .
  6. doi:10.1590/S0031-10492003000400001
    .
  7. PMID 22662194
    .

Further reading

  • Kraglievich, Lucas (1931): Contribución al conocimiento de las aves fósiles de la época araucoentrerriana. Physis 10: 304–315. (in Spanish)
  • Patterson, B. & Kraglievich, Lucas (1960): Sistemática y nomenclatura de las aves fororracoideas del Plioceno Argentino. Publicacion del Museo Municipal Ciencias Naturales y Tradicionales de Mar del Plata 1: 1-51. (in Spanish)
Retrieved from "https://en.wikipedia.org/w/index.php?title=Andalgalornis&oldid=1213820286"