Aquila bullockensis
Encyclopedia
Aquila bullockensis is an extinct species
of large true eagles in the Accipitridae
family. A. bullockensis is related to the living species A. audax
to which it might be ancestral. The species is solely known from the distal end of a right humerus
found in the Middle Miocene
(about 12 Ma), Bullock Creek
deposits in Australia
. A. bullockensis is the oldest confirmed record of the genus Aquila
in Australia, and possibly in the world.
specimen, number QVM:2000:GFV:154
, the distal end of a right humerus
, conserved in the collections housed by the Queen Victoria Museum and Art Gallery
in Launceston, Tasmania
. The specimen was collected from Bullock Creek exposures of the Camfield Fossil Beds, located 550 kilometres (550,000 m) south-southeast of Darwin, Northern Territory
, Australia. The bone was first studied by a pair of researchers from Monash University
in Melbourne, Victoria and led by Priscilla Gaff as part of her master's thesis. Gaff and Walter E. Boles published their 2010 type description in the Records of the Australian Museum. The specific epithet "bullockensis" was chosen by the authors in recognition of the type locality, with the Latin
ensis meaning "belonging to".
s. Within the family Accipitridae
the bone is similar to the genera Hieraaetus
and Aquila
. The two genera are very similar in morphology, and separation of the two is very difficult; they may be merged in the future. However the bone is closer in appearance to the modern species Aquila audax, Aquila chrysaetos and Aquila fasciata though is distinct enough to be considered a separate species. On the fossil the tuberculum supracondylare ventrale is flat unlike that of the modern species.
The humerus is 27.7 millimetres (1.1 in) wide on the distal end, while the shaft is broken off and missing above the fossa m. brachialis but enough bone is present to show that the shaft is curved. A. bullockensis was smaller in size then A. audax, A. chrysaetos and larger than A. fasciata. Though many members of Aquila display sexual dimorphism, the size of humerus is not a distinct feature.
Aquila bullockensis is one of the oldest members of the genus. The two species A. delphinensis and A. pennatoides which are from deposits in Grive-Saint-Alban, France, were described by Claude Gaillard in 1938 and also date to the Middle to Late Miocene. Of the other known Accipitridae bones from the Bullock Creek deposits several may belong to A. bullockensis, but none have been studied in depth to date.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of large true eagles in the Accipitridae
Accipitridae
The Accipitridae, one of the two major families within the order Accipitriformes , are a family of small to large birds with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a...
family. A. bullockensis is related to the living species A. audax
Wedge-tailed Eagle
The Wedge-tailed Eagle , sometimes known as the Eaglehawk in its native range, is the largest bird of prey in Australia, but it is also found in southern New Guinea. It has long, fairly broad wings, fully feathered legs, and an unmistakable wedge-shaped tail...
to which it might be ancestral. The species is solely known from the distal end of a right humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
found in the Middle Miocene
Middle Miocene
The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene....
(about 12 Ma), Bullock Creek
Bullock Creek
The Bullock Creek Fossil site is one of three known vertebrate fossil sites in the Australia's Northern Territory, along with the Alcoota Fossil Beds on Alcoota Station and the Kangaroo Well site on Deep Well Station. It is located about 550km south-southeast of Darwin, on Camfield Station...
deposits in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. A. bullockensis is the oldest confirmed record of the genus Aquila
Aquila (genus)
Aquila is the genus of true eagles. It is often united with the buteos, sea eagles and other more heavyset Accipitridae, but more recently it appears as if they are less distinct from the more slender accipitrine hawks than believed...
in Australia, and possibly in the world.
History and classification
The species is known solely from the holotypeHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen, number QVM:2000:GFV:154
Queen Victoria Museum and Art Gallery
The Queen Victoria Museum and Art Gallery is a museum located in Launceston, Tasmania, Australia. Established in 1891, the Queen Victoria has a strong reputation for its excellent collection, which includes fine exhibitions of colonial art, contemporary craft and design, Tasmanian history and...
, the distal end of a right humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
, conserved in the collections housed by the Queen Victoria Museum and Art Gallery
Queen Victoria Museum and Art Gallery
The Queen Victoria Museum and Art Gallery is a museum located in Launceston, Tasmania, Australia. Established in 1891, the Queen Victoria has a strong reputation for its excellent collection, which includes fine exhibitions of colonial art, contemporary craft and design, Tasmanian history and...
in Launceston, Tasmania
Launceston, Tasmania
Launceston is a city in the north of the state of Tasmania, Australia at the junction of the North Esk and South Esk rivers where they become the Tamar River. Launceston is the second largest city in Tasmania after the state capital Hobart...
. The specimen was collected from Bullock Creek exposures of the Camfield Fossil Beds, located 550 kilometres (550,000 m) south-southeast of Darwin, Northern Territory
Darwin, Northern Territory
Darwin is the capital city of the Northern Territory, Australia. Situated on the Timor Sea, Darwin has a population of 127,500, making it by far the largest and most populated city in the sparsely populated Northern Territory, but the least populous of all Australia's capital cities...
, Australia. The bone was first studied by a pair of researchers from Monash University
Monash University
Monash University is a public university based in Melbourne, Victoria. It was founded in 1958 and is the second oldest university in the state. Monash is a member of Australia's Group of Eight and the ASAIHL....
in Melbourne, Victoria and led by Priscilla Gaff as part of her master's thesis. Gaff and Walter E. Boles published their 2010 type description in the Records of the Australian Museum. The specific epithet "bullockensis" was chosen by the authors in recognition of the type locality, with the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
ensis meaning "belonging to".
Description
Within the possible bird families that the holotype may belong, it is distinguished from the old-world buzzards (Gypinae) and honey-vultures (Gypaetinae) by its shallow fossa m. brachialis, a more bulbous processus flexorius and a broader condylus dorsalis. These features also distinguish the bone from OspreyOsprey
The Osprey , sometimes known as the sea hawk or fish eagle, is a diurnal, fish-eating bird of prey. It is a large raptor, reaching more than in length and across the wings...
s. Within the family Accipitridae
Accipitridae
The Accipitridae, one of the two major families within the order Accipitriformes , are a family of small to large birds with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a...
the bone is similar to the genera Hieraaetus
Hieraaetus
The genus Hieraaetus, sometimes known as hawk-eagles, denoted a group of smallish eagles usually placed in the Buteoninae subfamily of accipitrids....
and Aquila
Aquila (genus)
Aquila is the genus of true eagles. It is often united with the buteos, sea eagles and other more heavyset Accipitridae, but more recently it appears as if they are less distinct from the more slender accipitrine hawks than believed...
. The two genera are very similar in morphology, and separation of the two is very difficult; they may be merged in the future. However the bone is closer in appearance to the modern species Aquila audax, Aquila chrysaetos and Aquila fasciata though is distinct enough to be considered a separate species. On the fossil the tuberculum supracondylare ventrale is flat unlike that of the modern species.
The humerus is 27.7 millimetres (1.1 in) wide on the distal end, while the shaft is broken off and missing above the fossa m. brachialis but enough bone is present to show that the shaft is curved. A. bullockensis was smaller in size then A. audax, A. chrysaetos and larger than A. fasciata. Though many members of Aquila display sexual dimorphism, the size of humerus is not a distinct feature.
Aquila bullockensis is one of the oldest members of the genus. The two species A. delphinensis and A. pennatoides which are from deposits in Grive-Saint-Alban, France, were described by Claude Gaillard in 1938 and also date to the Middle to Late Miocene. Of the other known Accipitridae bones from the Bullock Creek deposits several may belong to A. bullockensis, but none have been studied in depth to date.