''Bauxitornis'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of avisaurid

enantiornithean The Enantiornithes, also known as enantiornithines or enantiornitheans in literature, are a group of extinct avialans ("birds" in the broad sense), the most abundant and diverse group known from the Mesozoic era. Almost all retained teeth and cla ...

birds which lived in what is now

Hungary Hungary ( hu, Magyarország ) is a landlocked country in Central Europe. Spanning of the Pannonian Basin, Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the ...

during the late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

period (

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. ...

age). Although first mentioned in a 2008 review of Hungarian Cretaceous bird fossils, it was named in a more comprehensive review by Gareth J. Dyke and Attila Ősi in 2010. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

is ''Bauxitornis mindszentyae''. The generic name "''Bauxitornis''" refers to the locality at which it was discovered, a

Bauxite Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO ...

mine. The specific name "''mindszentyae''" honors Andrea Mindszenty, Ősi's advisor.

Description

The holotype of ''Bauxitornis'' is MTV V 2009.31.1 (previously known as MTM Gyn/439), a right tarsometatarsus. At 51 mm (2 inches) in length, this bone indicates that ''Bauxitornis'' was a comparatively large enantiornithean similar to ''Soroavisaurus'' and ''Avisaurus''. In addition, several other traits support the placement of ''Bauxitornis'' as an avisaurid. The inside edge of the trochlea (toe joint) of

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...

III (the middle preserved midfoot bone) possesses a small but noticeable bony tab (known as a plantar projection) which extends towards the underside of the ankle. Although the tarsometatarsus is mostly unfused, the proximal (near) parts of metatarsals II and III have fused together into a flat area that extends about a third the length of their shafts. The proximal end of the tarsometatarsus bends laterally (outwards). However, ''Bauxitornis'' can be distinguished from these other enantiornitheans due to having a shortened metatarsal II (the innermost preserved midfoot bone) without a tubercule (scarred bump) for the M. tibialis cranialis muscle. In addition, ''Bauxitornis'' 's longest metatarsal is metatarsal IV (the outermost midfoot bone) rather than metatarsal III.

Classification

While usually thought to be an avisaurid enantiornithean, one study finds it to be a more basal avialan closely related to ''

Balaur bondoc ''Balaur bondoc'' is a species of theropod dinosaur from the late Cretaceous period, in what is now Romania. It is the type species of the monotypic genus ''Balaur'', after the ''balaur'' (), a dragon of Romanian folklore. The specific name ''b ...

''.

References

Avisaurids Fossil taxa described in 2010 Cretaceous birds of Europe Prehistoric birds of Europe {{paleo-bird-stub