''Jinguofortis'' is a genus of primitive avialan (bird) belonging to the clade Pygostylia that lived during the Valanginian stage of the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

. 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. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

, 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 and coracoid bones of the shoulder girdle are fused into a single bone, the scapulocoracoid. 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, and ...

(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 Confuciusornithidae is an extinct family of pygostylian avialans known from the Early Cretaceous, found in northern China. They are commonly placed as a sister group to Ornithothoraces, a group that contains all extant birds along with their clos ...

among other avialans. This is an apparent example of convergent evolution, suggesting that these early avialans likely acquired a high rate of osteogenesis (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 avialans 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 refers to ...

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

sternal The sternum 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 vessels from injury. Sh ...

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 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 for brave.

Classification

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

Confuciusornithiformes Confuciusornithidae is an extinct family of pygostylian avialans known from the Early Cretaceous, found in northern China. They are commonly placed as a sister group to Ornithothoraces, a group that contains all extant birds along with their close ...

, but more primitive than Sapeornithiformes, and as sister to the previously problematic genus ''Chongmingia''. Cladogram of Mesozoic birds Phylogenetic tree from Wang etal PNAS

References

{{Taxonbar, from=Q56751050 Early Cretaceous birds of Asia Fossil taxa described in 2018 Valanginian genera Prehistoric avialans