''Jinguofortis'' 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 ...

of primitive

avialan Avialae ("bird wings") is a clade containing the only living dinosaurs, the birds, and their closest relatives. It is usually defined as all theropod dinosaurs more closely related to birds (Aves) than to deinonychosaurs, though alternative defi ...

belonging to the clade

Pygostylia Pygostylia is a group of avialans which includes the Confuciusornithidae and all of the more advanced species, the Ornithothoraces. Definition The group Pygostylia was intended to encompass all avialans with a short, stubby tail, as opposed t ...

that lived during the

Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 137.05 ± 0.2 Ma and 132.6 ± 0.2 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretac ...

stage of the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

. It was found in the

Dabeigou Formation The Dabeigou Formation () is a palaeontological formation located in Hebei, China.China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

, and isotope dating from the samples overlying the bird-bearing horizon is 127 million years ago.

Description

''Jinguofortis'' is notable for having a combination of primitive and advanced traits. Some of these are typical of stemward avialans (further from modern birds) while others occur in crownward avialans (closer to modern birds). The

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

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 ...

bones of the shoulder girdle are fused into a single bone, the

scapulocoracoid The scapulocoracoid is the unit of the pectoral girdle that contains the coracoid and scapula. The coracoid itself is a beak-shaped bone that is commonly found in most vertebrates with a few exceptions. The scapula is commonly known as the ''shoulde ...

. A fused scapulocoracoid is a

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...

(primitive) feature which is not present in modern birds. This plesiomorphic state is found in pterosaurs and non-avian dinosaurs, including coelurosaurian theropods ancestral to birds. However, these bones become unfused in the famed early avialan ''Archaeopteryx'', and in more crownward avian clades. Outside of ''Jinguofortis'' and its closest relatives, the presence of a fused scapulocoracoid is found only in confuciusornithids among other avialans. This is an apparent example of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

, suggesting that these early avialans likely acquired a high rate of

osteogenesis Osteoblasts (from the Greek language, Greek combining forms for "bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cell (biology), cells with a single Cell nucleus, nucleus that synthesize bone. However, in the p ...

(tendency for bone formation) similar to other theropods. Later, separation of the coracoid and scapula becomes evolutionarily “fixed” (with a few exceptions in the crown groups) across more advanced birds in the clade

Ornithothoraces Ornithothoraces is a group of avialan dinosaurs that includes all enantiornithes ("opposite birds") and the euornithes ("true birds"), which includes modern birds and their closest ancestors. The name Ornithothoraces means "bird thoraxes". This r ...

. By this time, the pectoral (shoulder) girdle developed further modifications, including an ossified

sternal The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood ve ...

keel and formation of the triosseal canal. The strong tendency for convergent evolution in early avialans points to high developmental plasticity (various developmental strategies) for anatomical systems in the shoulder region. Other traits are more advanced, such as the highly reduced digits of the hand. ''Jinguofortis'' is morphologically similar to ''

Chongmingia ''Chongmingia'' is a genus of basal Avialae, avialan belonging to Pygostylia that lived during the Aptian. It was found in the Jiufotang Formation in Chaoyang, Liaoning, Chaoyang, China, and was described by Wang ''et al''., 2016. The name comes ...

,'' another early avialan which preserved a fused scapulocoracoid. The two genera were placed in a new family, Jinguofortisidae. However, Jinguofortis could still differentiated from ''Chongmingia'' in several ways. Its

furcula The (Latin for "little fork"; : furculae) or wishbone is a forked bone found in most birds and some species of non-avian dinosaurs, and is either an interclavicle or formed by the fusion of the two clavicles. In birds, its primary function is ...

was less robust, with a smaller angle of 70° between the clavicular branches. Pedal digit I (the first toe) was approximately 70% of the length of digit II (the second toe), which itself was shorter than digit IV (the fourth toe). In addition, these two taxa are separated in time by approximately seven million years.

Etymology

The name ''Jinguofortis'' is a combination of ''jinguo'', from

Mandarin Mandarin or The Mandarin may refer to: Language * Mandarin Chinese, branch of Chinese originally spoken in northern parts of the country ** Standard Chinese or Modern Standard Mandarin, the official language of China ** Taiwanese Mandarin, Stand ...

(巾帼), referring to female warrior, and ''fortis'',

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for brave.

Classification

Wang et al. (2018) recovered ''Jinguofortis'' as a basal pygostylian more derived than Confuciusornithiformes, but more primitive than

Sapeornithiformes Omnivoropterygidae (meaning "omnivorous wings") is a family of primitive avialan dinosaurs known exclusively from the Jiufotang Formation of China, though putative omnivoropterygids are known from the Maevarano Formation of the Maastrichtian of M ...

, and as

sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

to the previously problematic genus ''Chongmingia''. Cladogram of Mesozoic birds Phylogenetic tree from Wang etal PNAS

References

{{Taxonbar, from=Q56751050 Jinguofortisidae Bird genera Valanginian birds Fossil taxa described in 2018 Birds of Asia