''Hongshanornis'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of
ornithuromorph
Euornithes (from Greek ' meaning "true birds") is a natural group which includes the most recent common ancestor of all avialans closer to modern birds than to ''Sinornis''.
Description
Clarke ''et al''. (2006) found that the most primitive know ...
birds known from early
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
lake deposits of the
Yixian Formation
The Yixian Formation (; formerly transcribed as Yihsien Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the late Barremian and early Aptian stages of the Early Cretaceous. It is known for its exq ...
,
Inner Mongolia
Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a ...
,
China. The holotype specimen, recovered in 2005, is currently held by the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. It was found in the Jianshangou fossil beds, dated to 124.6 million years ago.
Three additional specimens have been reported, though only one of those has been definitively identified as belonging to ''Hongshanornis''.
This latter specimen was found in the Dawangzhangzi fossil beds, which are about 122 million years old.
''Hongshanornis'' is a member of the group
Hongshanornithidae, to which it lent its name. It is closely related to ''
Longicrusavis
''Longicrusavis'' (meaning "long shin bird" in Latin) is an extinct genus of basal ornithuromorph bird found only at Dawangzhangzi village in Liaoning Province, China. ''Longicrusavis'' was a ground dwelling carnivore, a wader, and part of bio ...
'', which existed alongside ''Hongshanornis'' in the Dawangzhangzi ecosystem, and is very similar to the later ''
Parahongshanornis'' from the
Jiufotang Formation
The Jiufotang Formation ( Chinese: 九佛堂组, pinyin: ''jiǔfótáng zǔ'') is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms (see ...
.
[
]
Description
''Hongshanornis longicresta'' was a small species, especially compared to other early ornithuromorphs (birds with a modern tail anatomy), about the size of a thrush, and adult specimens are estimated to have weighed about in life, with a wingspan of about .[
]
The skull in all known specimens is poorly preserved, but in general appears to have had a narrow snout compared to the closely related ''Longicrusavis
''Longicrusavis'' (meaning "long shin bird" in Latin) is an extinct genus of basal ornithuromorph bird found only at Dawangzhangzi village in Liaoning Province, China. ''Longicrusavis'' was a ground dwelling carnivore, a wader, and part of bio ...
''.[ The teeth were very small and are poorly preserved in all known specimens. At first, this led scientists to conclude that the teeth were absent in both the upper and lower jaws, probably replaced with a beak. However, later study of the type specimen showed that tooth sockets were present in the preserved parts of the jaw, and comparison with related forms showed that it did have teeth.] The discovery of a more well preserved specimen confirmed the presence of teeth in at least the maxilla
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...
(middle of the upper jaw) and dentary
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
(lower jaw). The snout appears to have lacked feathers, though whether it was only covered in skin or some parts bore a beak
The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for eating, preening, manipulating objects, killing prey, fighting, probing for foo ...
is currently unknown. The describers of ''Hongshanornis'' noted a unique bone in the end of the lower jaw which they equated with the beak-bearing "predentary
Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...
bone" similar to the one found in ornithischian dinosaurs. Such bones have also been found in more advanced birds like ''Hesperornis
''Hesperornis'' (meaning "western bird") is a genus of cormorant-like bird that spanned the first half of the Campanian age of the Late Cretaceous period (83.5–78 mya). One of the lesser-known discoveries of the paleontologist O. C. Marsh i ...
''.
Supporting Information
/ref> However, other scientists have pointed out that the "predentary" (or, technically, ''mandibular symphysial ossification'') of ''Hongshanornis'' lacks the characteristic pits and grooves associated with the beak in early beaked birds like '' Archaeorhynchus'', and that the presence or absence of any beak is unclear.[
The original describers of ''Hongshanornis'' noted the apparent presence of a large feathered crest on the head,] though the feather traces are extremely poor quality and it may be an artifact of preservation.[ A second specimen from different fossil beds did not have long feathers on the head, but rather showed feathers which became shorter closer to the snout.][
The wings were long and broad, but tapered and pointed at the tips. The first few primary flight feathers were much shorter than the rest. The total wing area was 0.016 square meters. The wing digits bore small claws, with the claw on the first finger (the alular digit) much larger than that of the second finger (major digit).][ ''Hongshanornis'' is characterized by very long legs, with the lower leg (''tibiotarsus'') more than one and a half times longer than the upper leg (''femur''). The toes were long and thin, with small claws. The first toe (''hallux'') was very small, and the second toe was much shorter than the fourth. The third toe was longest.][
]
The bones of the tail have not been preserved in any known specimen, but comparison with related species suggest it was short with a small, plowshare
In agriculture, a plowshare ( US) or ploughshare ( UK; ) is a component of a plow (or plough). It is the cutting or leading edge of a moldboard which closely follows the coulter (one or more ground-breaking spikes) when plowing.
The plowsh ...
-shaped pygostyle
Pygostyle describes a skeletal condition in which the final few caudal vertebrae are fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these. The pygostyle is the main compone ...
bone, to which the tail feathers anchored. A mass of muscles, called the rectorial bulb, probably was present to control the fanning of the trail feathers. The tail feathers were long, with symmetrical vanes. There were at least 10 tail feathers (''rectrices''), more than in other primitive fan-tailed birds. The overall shape of the tail was rounded and wedge-shaped when viewed from above; due to the symmetrical feathers, the sides of the tail were probably not held fully fanned into the wind but swept back, forming a partially fanned wedge, as in some modern birds like accipiter
''Accipiter'' is a genus of birds of prey in the family Accipitridae. With 51 recognized species it is the most diverse genus in its family. Most species are called goshawks or sparrowhawks, although almost all New World species (excepting th ...
s, tyrant flycatcher
The tyrant flycatchers (Tyrannidae) are a family of passerine birds which occur throughout North and South America. They are considered the largest family of birds known to exist in the world, with more than 400 species. They are the most dive ...
s and sunbittern
The sunbittern (''Eurypyga helias'') is a bittern-like bird of tropical regions of the Americas, and the sole member of the family Eurypygidae (sometimes spelled Eurypigidae) and genus ''Eurypyga''. It is found in Central and South America, and ...
s.[
]
Biology
Diet and ecology
Due to the assumption of toothlessness, hongshanornithids were originally interpreted as having a very specialized diet and ecology, perhaps as waders or shorebirds due to their slim snouts and long legs. However, the confirmation that they did in fact have teeth in both jaws has led to a re-interpretation of their ecological niche. Though still considered probably wading birds, they probably had a more generalized diet than previously assumed, with the different snout shapes present in different members of the group indicating niche portioning within a general wading ecology (''Hongshanornis'' lived alongside the closely related ''Longicrusavis'', and both were very similar to each other except for the shape of the snout).[ One specimen of ''Hongshanornis'' preserved several gizzard stones (]gastrolith
A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In oth ...
s) of various sizes, which is usually an indication of an herbivorous diet.[ Another specimen originally assigned to the genus ''Hongshanornis'' preserved fossilized seeds in the ]crop
A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydropon ...
;[ however, this specimen was subsequently transferred to a distinct taxon '']Eogranivora
''Eogranivora'' is a bird genus, belonging to the Ornithuromorpha, that lived in the area of present-day China during the Early Cretaceous. Its type species is ''Eogranivora edentulata''.Zheng X., O’Connor J.K., Wang X., Wang Y., Zhou Z. 2018 ...
edentulata''.
Flight
The wings of ''H. longicresta'' were broad and tapered, with an average wing area and wing loading compared to modern birds in the same size range.[ The presence or absence of slotting at the wing tips cannot be determined with known specimens, but modern birds with similar size and wing shape tend to lack wing slotting. The absence of wing slotting would suggest that ''Hongshanornis'' tended to fly mainly at relatively high speeds. Given the overall wing shape and comparison to modern birds, ''Hongshanornis'' probably flapped continuously when flying at lower speeds, and switched to bounding flight (rapid flapping alternating with periods of ballistic forward motion with the wings partly folded) at higher speeds. Overall, the wing and tail anatomy, and therefore probably flight style, of ''Hongshanornis'' was similar to many medium-sized ]passerine
A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by th ...
birds.[
]
References
External links
Information and photograph of the type specimen, Palaeocritti
{{Taxonbar, from=Q3029892
Early Cretaceous birds of Asia
Yixian fauna
Hongshanornithids
Fossil taxa described in 2005