''Praeornis'' is an extinct

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 early

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 ...

, possibly an

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

,Agnolin, F.L., Rozadilla, S., and Ismar de Souza Carvalho (2017). ''Praeornis sharovi'' Rautian, 1978 a fossil feather from the early Late Jurassic of Kazakhstan. ''Historical Biology''. from the

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

Karabastau Formation The Karabastau Formation () is a geological formation and lagerstätte in the Karatau Mountains of southern Kazakhstan whose strata date to the Middle to Late Jurassic. It is an important locality for insect fossils that has been studied since ...

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a landlocked country primarily in Central Asia, with a European Kazakhstan, small portion in Eastern Europe. It borders Russia to the Kazakhstan–Russia border, north and west, China to th ...

. Only the type species is known, which is ''P. sharovi''.Rautian, A. S. (1978). "A unique bird feather from Jurassic lake deposits in the Karatau." ''Paleontological Journal'', 4: 520-528.

Discovery and naming

Specimens

The holotype, specimen PIN 2585/32 (a single feather from the

, Aulie,

), was discovered and described in 1971 by

Aleksandr Grigorevich Sharov Aleksandr Grigorevich Sharov (А.Г. Шаров, 1922–1973) was a Soviet palaeoentomologist, paleontologist and expert on Pterosauria. He graduated from Moscow State University. In 1951 he defended Candidate of Science dissertation on the embryo ...

. The specimen was then named as ''Praeornis sharovi'' by Rautian (1978). A second specimen, ZPAL V 32/967, another isolated feather from the Karabatsau Formation, was discovered by Dzik et al. in 2006 and was described by Dzik et al. (2010).Dzik, J., Sulej, T. and Niedzwiedzki, G. (2010). "Possible link connecting reptilian scales with avian feathers from the early Late Jurassic of Kazakstan." ''Historical Biology'', 22(4): 394–402

/ref>

Identity of the specimens

Rautian (1978) initially suggested ''Praeornis'' was a

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

more primitive than ''

Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird'') is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaîos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...

'', however, Bock (1986) argued that the "feather" was in fact the leaf of a

cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...

,Bock (1986). "The arboreal origin of avian flight." Pp. 57-72 in Padian, K. (ed.). ''The Origin of Birds and the Evolution of Flight''. California Academy of Sciences, Memoir 8. with Doludenko et al. (1990) agreed with this assessment, noting that it was similar to the leaves of the cycad species '' Paracycas harrisii''.Doludenko MP, Sakulina GV, Ponomarenko AG. (1990). ''Geologicheskoye stroyenie rayona unikalnogo mestonakhozhdenia posdnejurskoy fauny i flory aule (Karatau, southern Kazakhstan)''. Moskva: Geologicheskiy Institut AN SSSR. Nessov (1992) instead synonymized ''Praeornis sharovi'' with the species '' Cycadites saportae''.Nessov L. A. (1992). Mesozoic and Paleogene birds of the USSR, and their paleoenvironments. In: Campbell KE Jr., editor. Papers on avian Paleontology honouring Pierce Brodkorp. Los Angeles: Natural History Museum of Los Angeles County. Despite this, several different authors have suggested that the holotype did belong to an animal. Glazunova et al. (1991) examined the specimen using an

electron microscope An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing it ...

and found that the microstructure had features in common with the "primitive" feathers of

ratite Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keels and cannot fly. They are mostly large, long-necked, and long-legged, the exception being the kiwi, which is also the only nocturnal ...

birds ince ratites are now known to be secondarily flightless paleognathous birds, their feathers are not primitive but degenerate flight and contour feathers Kurochkin (2001)Kurochkin, E. (2001). "Mesozoic birds of Mongolia and the former USSR." Pp. 533-559 in Benton, Shishkin, Unwin and Kurochkin (eds.). ''The Age of Dinosaurs in Russia and Mongolia.'' and Dzik et al. (2010) also agreed with this assessment; Dzik et al. (2010) conducted a biochemical analysis of a ''Praeornis'' feather and other fossils from the Karabastau Formation, including plants and fish. The analysis showed that the chemical markers of the ''Praeornis'' fossil was more similar to the fish scales than to the plant leaves, supporting the hypothesis that the feathers were animal in origin. Agnolin et al. (2017) suggested that ''Praeornis'' was a member of the

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 ...

after the holotype was compared to a similar feather from 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 ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. The enantiornith found in Brazil was shown to have a pair of

rachis In biology, a rachis (from the [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the ''rachi ...

-dominated tail feathers very similar to the type specimen of ''Praeornis'', making it likely that ''Praeornis'' represents an enantiornith or similar species. If ''Praeornis'' was an enantiornith, it would be the oldest known member of the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

, and the only known member from the

Description

The feathers of ''Praeornis'' likely represent modified tail feathers used for display or balance, similar to those found in some other early avialans. The feathers of ''Praeornis'' are unique as a result of their extremely thick central quill (rachis) and stiffened barbs.

Classification

Rautian (1978) initially assigned ''Praeornis'' to its own subclass (Praeornithes), order (Praeornithiformes) and family (Praeornithidae). Several authors then considered the holotype to belong to the leaf of a cycad, with more recent authors suggesting ''Praeornis'' belonged to

. The family Praeornithidae is also currently accepted as valid, making it a monotypic family containing only the genus ''Praeornis''.

References

{{Taxonbar, from1=Q7237541, from2=Q21078895 Enantiornithes Jurassic birds Fossil taxa described in 1978