| Vorombe | |
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| Scientific classification |
Vorombe is one of three genera of elephant birds, an extinct family of large ratite birds endemic to Madagascar. Originally considered to be large Aepyornis specimens, it is now thought Vorombe are the largest and heaviest birds known to have existed. The genus was erected in 2018 after a detailed morphometric analysis.
Taxonomy and naming[]
Vorombe titan was first described by Charles William Andrews as Aepyornis titan in 1894. It was synonymized with the type species of Aepyornis, A. maximus, by American paleontologist Pierce Brodkorb in 1963. In 2018, James Hansford and Samuel Turvey, two researchers from the Zoological Society of London, found that it was sufficiently distinct from Aepyornis and allocated it in the new genus Vorombe. They also recognized Aepyornis ingens as a synonym of Vorombe titan. The study by Hansford and Turvey is the first taxonomic reassessment of elephant birds in over 50 years.
The genus name Vorombe is derived from the Malagasy word vorombe meaning "big bird" while the specific name titan is derived from the Ancient Greek word Τιτάν (Titan), which refers to the Greek gods that preceded the Twelve Olympians.
Tibiotarsus de Vorombe titan
This genus was originally described in 2018 by paleontologist James P. Hansford and British-Finnish zoologist Samuel Thomas Turvey.
Its only species was originally described in 1894 by the British paleontologist Charles William Andrews, with the scientific name of Aepyornis titan.
Type locality
The type locality referred to is: “Itampolo (Itampulu Vé), Madagascar”. This town is in the southwest of the island.
Holotype
The series of syntypes is cataloged as: NHMUK A439 (a femur) and NHMUK A437 (a tibiotarsus). It also has a lectotype: NHMUK A439 (a femur). They are deposited in the Natural History Museum, London.
Etymology
Etymologically, the neutral generic term Vorombe is constructed from words in the Malagasy language, which mean 'large bird'. El epíteto específico titan hace referencia al nombre mitológico homónimo del idioma griego, en alusión al poder y tamaño de esta ave gigantesca.
Attributed age
Samples of two femurs assigned to Vorombe titan (specimens MNHN MAD 364 and NHMUK A2142) were dated; both yielded an antiquity of around 1000 years BP (Holocene).
Taxonomic history
In 1894, the British paleontologist Charles William Andrews described Aepyornis titan, a species that in 1963 the American paleontologist specialist in fossil birds William Pierce Brodkorb synonymized in the type species of the genus Aepyornis, A. maximus, considering it only an unusually large specimen of this species, which had been described in 1851 by the French zoologist Isidore Geoffroy Saint-Hilaire.
En el año 2018, los paleontólogos James P. Hansford y Samuel Thomas Turvey (ambos integrantes de la Sociedad Zoológica de Londres), realizaron la primera revaluación taxonómica de la familia de los epiornítidos luego de 50 años de haberse realizado la última. Se realizó un análisis cuantitativo de los patrones de diversidad morfológica de todos los restos esqueléticos de epiornítidos alojados en las principales colecciones del mundo, se examinaron usando análisis de conglomerados multivariados y el criterio de análisis bayesiano y con la estimación de datos faltantes utilizando algoritmos de imputación múltiple y maximización de expectativas. Como resultado se recuperaron tres morfotipos esqueléticos distintos. Dos de estos morfotipos están asociados a géneros existentes, Mullerornis y Aepyornis, representando ejemplares de cuerpo pequeño y mediano, respectivamente. El tercer morfotipo hallado era el correspondiente al taxón que había sido descrito como Aepyornis titan. Como no había sido reconocido previamente como un género distinto, se procedió a describirlo como un nuevo taxón monotípico de categoría genérica: Vorombe.
El fémur de Vorombe titan
Specimens and features[]
The syntype series of Vorombe titan includes a femur (NHMUK A439) and tibiotarsus (NHMUK A437) found in Itampolo (Itampulu Vé), Madagascar.
The femur of Vorombe is significantly larger than that of Aepyornis and Mullerornis in all measurements. Notable features include enlarged proximal and distal ends, a more acute curvature in the medio-distal margin of the femoral head (caput femoris), the presence of a marked lateral supracondylar ridge, and a medial condyle (condylus medialis) that is expanded medially and flatter than in Aepyornis. The tibiotarsus is extremely large in comparison to Aepyornis and Mullerornis. The proximal and distal ends are enlarged, particularly medio-laterally. It has a more marked narrowing transition into the shaft, which is narrower in proportion to the total length compared to Aepyornis.
The tarsometatarsus is significantly larger and more expanded medio-laterally than in other genera, mainly at the proximal and distal ends. The lateral portion of the proximal articular surface protrudes proximally to the medial portion, creating a prominently angled proximal articular surface similar to that of A. hildebrandti. The tarsometatarsus is larger than Mullerornis in all measurements, and larger than Aepyornis in most measurements.
Comparison of the aepyornthids, Mullerornis (front), Vorombe titan (largest), and Aepyornis (back), of Holocene Madagascar.
Samples from two femora assigned to Vorombe titan (specimens MNHN MAD 364 and NHMUK A2142) were sent for accelerator mass spectrometer carbon-14 dating at the Oxford Radiocarbon Accelerator Unit and calibrated using ShCal13. Both specimens were dated to the Holocene (3,680 to 2,352 BP).
Size[]
Vorombe stood 3 m (9.8 ft) tall and weighed 536 to 732 kg (1,182 to 1,614 lb), with a mean of 642.9 kg (1,417 lb). This is greater than the mass estimates of other extinct Quaternary giant birds such as Dinornis, which was between 61 and 275 kg (134 and 606 lb), and Dromornis stirtoni, between 316.6 and 727.8 kg (698 and 1,605 lb), making it the largest known bird. The largest femur (MNHN MAD 368) measured by Hansford and Turvey could not be formally assigned to a cluster (group) as it was incomplete. The specimen is thought to belong to Vorombe on the basis of its size. It had a least-shaft circumference of 308 mm (12.1 in), which gives a weight estimate of 860 kg (1,900 lb), making it the largest known bird individual ever recorded. This is comparable to or greater than the mass estimates of the smallest (insular dwarf) sauropod dinosaurs: Europasaurus, at 690 kg (1,520 lb); and Magyarosaurus, between 700 and 1,000 kg (1,500 and 2,200 lb).
Ecology[]
Vorombe titan, Aepyornis maximus and Mullerornis modestus were found across much of Madagascar, and were sympatric in the arid spiny forests in the south, succulent woodlands in the southwest, and grassland/subhumid forest mosaic in the Central Highlands. The significant size differences between the three taxa indicates that they exploited different dietary niches and plant interactions. Elephant birds shared the Quaternary ecosystems of Madagascar with dwarf hippos, giant lemurs and giant tortoises.