''Enantiornis'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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

. The

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

and only currently accepted species ''E. leali'' is from the Late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

Lecho Formation The Lecho Formation is a geological Formation (geology), formation in the Salta Basin of the provinces Jujuy Province, Jujuy and Salta Province, Salta of northwestern Argentina. Its strata date back to the Maastrichtian, Early Maastrichtian, and i ...

at El Brete,

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. It was described from specimen PVL-4035, a

coracoid A coracoid is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is present as part of the scapula, but this is n ...

, proximal

scapula The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

and proximal

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

found close to each other and suspected to represent the left shoulder of a single individual.

Description

The genus and the larger group it belongs to, get their name from the reversed scapula-coracoid connection they possess compared to modern birds and the hesperornithids that were their contemporaries: Enanti "opposite", ornis is "bird". Another left shoulder and wing, almost complete and found associated in one lump of rock, as well as a few isolated bones were also assigned to this species mainly based on size. It is among the largest enantiornithines discovered to date, with a length in life of around , hip height of , weight of , and wingspan comparable to

herring gull Herring gull is a common name for several birds in the genus ''Larus'', all formerly treated as a single species. Three species are still combined in some taxonomies: * American herring gull (''Larus smithsonianus'') - North America * European h ...

s, around . Its

ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of Resource (biology), resources an ...

resembled that of a mid-sized

vulture A vulture is a bird of prey that scavenges on carrion. There are 23 extant species of vulture (including condors). Old World vultures include 16 living species native to Europe, Africa, and Asia; New World vultures are restricted to Nort ...

eagle Eagle is the common name for the golden eagle, bald eagle, and other birds of prey in the family of the Accipitridae. Eagles belong to several groups of Genus, genera, some of which are closely related. True eagles comprise the genus ''Aquila ( ...

Taxonomy and phylogeny

''E. leali'' was possibly fairly closely related to ''

Avisaurus ''Avisaurus'' (meaning "bird lizard") is a genus of enantiornithine avialan from the Late Cretaceous of North America. Discovery ''Avisaurus archibaldi'' was discovered in the Late Cretaceous Hell Creek Formation of North America (Maastrichtian, ...

'', another genus of probably carnivorous enantiornithines, though its exact relationship is unclear. It was placed in a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of its own, Enantiornithidae. Other species from

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

that were previously placed in this genus are now split off. The former ''Enantiornis martini'' is now placed in '' Incolornis'', while the former ''Enantiornis walkeri'' is now tentatively assigned to '' Explorornis''. The reason for this is that these species were described when the diversity of enantiornithines was underestimated. As no hindlimb elements are known from ''Enantiornis'', it might include one of the El Brete enantiornithines known only from leg bones, namely '' Lectavis'', '' Soroavisaurus'' or '' Yungavolucris''. However, these apparently were all smaller than ''Enantiornis''. Hindlimb material tentatively assigned to '' Martinavis'' and '' Elbretornis'' seems somewhat and a lot too small, respectively, to represent ''Enantiornis''. The cladogram below is from Wang ''et al.'', 2022: Key to letters: ''b'' = '' Boluochia''
''c'' = ''

Cathayornis ''Cathayornis'' is a genus of enantiornithean birds from the Jiufotang Formation of Liaoning, People's Republic of China. It is known definitively from only one species, ''Cathayornis yandica'', one of the first Enantiornithes found in China. Se ...

''
''e'' = '' Enantiophoenix''
''f'' = '' Houornis''
''h'' = '' Longipteryx''
''i'' = '' Parabohaiornis''
''j'' = '' Pterygornis''
''l'' = '' Vorona''
''m'' = ''

Yuanjiawaornis ''Yuanjiawaornis'' is an extinct genus of large Enantiornithes, enantiornithean bird known from the early Cretaceous of present-day China. It is monotypic, with only type species ''Y. virisosus'' named.Dongyu Hu, Ying Liu, Jinhua Li, Xing Xu & Li ...

''
''n'' = '' Yungavolucris''

References

{{Taxonbar, from=Q1084949 Enantiornithes Maastrichtian life Cretaceous birds of South America Cretaceous Argentina Fossils of Argentina Lecho Formation Fossil taxa described in 1981