Alexornis is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of enantiornithine

Enantiornithes

Enantiornithes is an extinct group of primitive birds. They were the most abundant and diverse avialans of the Mesozoic. Almost all retained teeth and clawed fingers on each wing, but otherwise looked much like modern birds externally. Over 50 species of Enantiornithines have been named, but some...

 bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

 from the Late Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 (Campanian

Campanian

The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...

, 84-71 mya) of southwestern North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. The type

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 and only species

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...

 is Alexornis antecedens.

Fragmentary remains containing postcranial elements have been found in the Boca Roja Formation in Baja California

Baja California

Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...

 state, Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

. It was originally described as an early modern bird and a possible ancestor of the order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

s Coraciiformes

Coraciiformes

The Coraciiformes are a group of usually colorful near passerine birds including the kingfishers, the Hoopoe, the bee-eaters, the rollers, and the hornbills...

 and Piciformes

Piciformes

Nine families of largely arboreal birds make up the order Piciformes, the best-known of them being the Picidae, which includes the woodpeckers and close relatives...

. Subsequent analysis showed that it was an enantiornithine. It is sometimes united in a distinct order and family (Alexornithiformes and Alexornithidae, respectively) with the Central Asia

Central Asia

Central Asia is a core region of the Asian continent from the Caspian Sea in the west, China in the east, Afghanistan in the south, and Russia in the north...

n genera Kizylkumavis

Kizylkumavis

Kizylkumavis was an enantiornithine bird. It lived during the Late Cretaceous about 75 mya and is known from fossils found in the Bissekty Formation of the Kyzyl Kum, Uzbekistan....

and Sazavis

Sazavis

Sazavis was an enantiornithine bird from the Late Cretaceous. It might have been related to Alexornis and Kizylkumavis and lived in what is now the Kyzyl Kum of Uzbekistan....

, but this is not usually considered correct and the relationship of these birds - which may or may not form a close-knit group - to other Enantiornithes is unresolved.