''Kompsornis'' (meaning "elegant bird") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

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 ...

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 ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s that lived during the

Early Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican d ...

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

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 ...

. 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 known

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

is ''Kompsornis longicaudus''; the specific name means "long-tailed". It is known from only a single

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

specimen from the

Jiufotang Formation The Jiufotang Formation () is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms (see Jehol Biota). It is a member of the Jehol group. T ...

. ''Kompsornis'' was closely related to the well-known ''

Jeholornis ''Jeholornis'' (meaning "Jehol bird") is a genus of avialan dinosaurs that lived between approximately 122 and 120 million years ago during the early Cretaceous Period in China. Fossil ''Jeholornis'' were first discovered in the Jiufotang Formati ...

'', another long-tailed avialan from China, but differs from it in features of its skeleton, particularly the fusion and growth rate of its bones. Like other jeholornithiforms, ''Kompsornis'' was a long-tailed avialan with long

wing A wing is a type of fin that produces both Lift (force), lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform (aeronautics), planform. Wing efficiency is expressed as lift-to-d ...

s and possessed little or no teeth, with none identified in the single specimen of ''Kompsornis''.

Classification

''Kompsornis'' was described and named by Wang and colleagues in 2020 from the sole specimen AGB-6997, an articulated complete skeleton preserved on a single slab, and was recognised as a jeholornithiform avialan. Their description included a comprehensive comparison between ''Kompsornis'' and the

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

s of other named jeholornithiform species, including all species of ''Jeholornis'', '' Shenzhouraptor sinensis'', '' Dalianraptor cuhe'' and the possible euavialan '' Jixiangornis orientalis''. They concluded that ''Kompsornis'' was a distinct species from all other jeholornithiform species, and that they all represented valid species except for ''Dalianraptor'', which was determined to be an artificial forgery of different specimens and lacking any diagnostic characteristics. A

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

supported this conclusion, which recovered ''Kompsornis'' as a jeholornithiform most closely related to ''Jeholornis prima'' and ''J. curvipes'' (''Jeholornis'' 'sensu stricto'), and more derived than ''Shenzhouraptor'', ''J. palmapenis'' and ''Jixiangornis'': ''Kompsornis'' is distinguished from other jeholornithiform species by traits such as a more posteriorly directed pubis, especially elongated

caudal vertebrae Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx. In many reptiles, some of the caud ...

in the tail, extreme tail length, longer forelimbs, and features of the

sternum 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 bl ...

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 ...

in the shoulder. The

hip In vertebrate anatomy, the hip, or coxaLatin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) (: ''coxae'') in medical terminology, refers to either an anatomical region or a joint on t ...

and sternum are also more extensively fused than in other jeholornithiforms, despite its immaturity, and the skeleton overall has more bird-like growth patterns than in other sampled jeholornithiforms.

Palaeobiology

The growth rate of ''Kompsornis'' was sampled from a cross-section of a rib bone and compared to those of ''Jeholornis'' sp. The specimen was determined to be at least four years old and approaching maturity, but was not yet fully grown. ''Kompsornis'' possessed a different growth strategy to ''Jeholornis'', particularly in the fusion of the sternum and hips prior to skeletal maturity, which often remain unfused even in larger and older specimens of ''Jeholornis''. Such differences in growth patterns may be evidence that jeholornithiforms evolved distinct growth strategies to adopt different ecologies in the same environment. The sternum is completely fused, and possesses a well-developed

keel The keel is the bottom-most longitudinal structural element of a watercraft, important for stability. On some sailboats, it may have a fluid dynamics, hydrodynamic and counterbalancing purpose as well. The keel laying, laying of the keel is often ...

and a robust

xiphoid process The xiphoid process (), also referred to as the ensiform process, xiphisternum, or metasternum, constitutes a small cartilaginous process (extension) located in the inferior segment of the sternum, typically ossified in adult humans. Both the Gr ...

, suggesting that ''Kompsornis'' was a powerful flier.

References

{{Taxonbar, from=Q95344729 Jeholornithidae Bird genera Aptian birds Jiufotang Formation Fossil taxa described in 2020 Birds of Asia