Editing Archaeopteryx (section)

== Palaeobiology ==

=== Flight ===
[[File:Vog1h.jpg|thumb|upright|left|1880 photo of the Berlin Specimen, showing leg feathers that were removed subsequently, during preparation]]
<!-- <ref name=Lindhe_50:921/> -->As in the wings of modern birds, the flight feathers of ''Archaeopteryx'' were somewhat asymmetrical and the tail feathers were rather broad. This implies that the wings and tail were used for lift generation, but it is unclear whether ''Archaeopteryx'' was capable of flapping flight or simply a glider. The lack of a bony [[Sternum|breastbone]] suggests that ''Archaeopteryx'' was not a very strong flier, but flight muscles might have attached to the thick, boomerang-shaped wishbone, the platelike [[coracoid]]s, or perhaps, to a [[cartilage|cartilaginous]] [[sternum]]. The sideways orientation of the glenoid (shoulder) joint between [[scapula]], coracoid, and [[humerus]]—instead of the dorsally angled arrangement found in modern birds—may indicate that ''Archaeopteryx'' was unable to lift its wings above its back, a requirement for the upstroke found in modern flapping flight. According to a study by [[Philip Senter]] in 2006, ''Archaeopteryx'' was indeed unable to use flapping flight as modern birds do, but it may well have used a downstroke-only flap-assisted gliding technique.<ref name=senter_1/> However, a more recent study solves this issue by suggesting a different flight stroke configuration for non-avian flying theropods.<ref name="Voeten">{{Cite journal |last=Voeten |first=Dennis F.A.E. |display-authors=etal |year=2018 |title=Wing bone geometry reveals active flight in ''Archaeopteryx'' |journal=Nature Communications |volume=9 |issue=1 |page=923 |bibcode=2018NatCo...9..923V |doi=10.1038/s41467-018-03296-8 |pmc=5849612 |pmid=29535376}}</ref>

''Archaeopteryx'' wings were relatively large, which would have resulted in a low stall speed and reduced [[turning radius]]. The short and rounded shape of the wings would have increased drag, but also could have improved its ability to fly through cluttered environments such as trees and brush (similar wing shapes are seen in birds that fly through trees and brush, such as [[crows]] and [[pheasant]]s). The presence of "hind wings", asymmetrical flight feathers stemming from the legs similar to those seen in dromaeosaurids such as ''[[Microraptor]]'', also would have added to the aerial mobility of ''Archaeopteryx''. The first detailed study of the hind wings by Longrich in 2006, suggested that the structures formed up to 12% of the total [[airfoil]]. This would have reduced stall speed by up to 6% and turning radius by up to 12%.<ref name=Longrich_1/>

The feathers of ''Archaeopteryx'' were asymmetrical. This has been interpreted as evidence that it was a flyer, because flightless birds tend to have symmetrical feathers. Some scientists, including Thomson and Speakman, have questioned this. They studied more than 70 families of living birds, and found that some flightless types do have a range of asymmetry in their feathers, and that the feathers of ''Archaeopteryx'' fall into this range.<ref name="speakmanthomson1994">{{Cite journal |last1=Speakman |first1=J. R. |last2=Thomson |first2=S. C. |year=1994 |title=Flight capabilities of ''Archaeopteryx'' |journal=Nature |volume=370 |issue=6490 |pages=336–340 |bibcode=1994Natur.370..514S |doi=10.1038/370514a0 |pmid=28568098 |s2cid=4248184|doi-access=free }}</ref> The degree of asymmetry seen in ''Archaeopteryx'' is more typical for slow flyers than for flightless birds.<ref>{{Cite journal |last=Norberg |first=R. A. |year=1995 |title=Feather asymmetry in ''Archaeopteryx'' |journal=Nature |volume=374 |issue=6519 |page=211 |bibcode=1995Natur.374..211M |doi=10.1038/374211a0 |doi-access=free |s2cid=4352260}}</ref>

[[File:Archaeopteryx bavarica Detail.jpg|thumb|The Munich Specimen]]

In 2010, Robert L. Nudds and Gareth J. Dyke in the journal ''Science'' published a paper in which they analysed the [[rachis]]es of the primary feathers of ''[[Confuciusornis]]'' and ''Archaeopteryx''. The analysis suggested that the rachises on these two genera were thinner and weaker than those of modern birds relative to body mass. The authors determined that ''Archaeopteryx'' and ''Confuciusornis'', were unable to use flapping flight.<ref name="Nudds&Dyke2010">{{Cite journal |last1=Nudds |first1=Robert L. |last2=Dyke |first2=Gareth J. |date=14 May 2010 |title=Narrow Primary Feather Rachises in ''Confuciusornis'' and ''Archaeopteryx'' Suggest Poor Flight Ability |journal=Science |volume=328 |issue=5980 |pages=887–889 |bibcode=2010Sci...328..887N |doi=10.1126/science.1188895 |pmid=20466930 |s2cid=12340187}}</ref> This study was criticized by [[Philip J. Currie]] and Luis Chiappe. Chiappe suggested that it is difficult to measure the rachises of fossilized feathers, and Currie speculated that ''Archaeopteryx'' and ''[[Confuciusornis]]'' must have been able to fly to some degree, as their fossils are preserved in what is believed to have been marine or lake sediments, suggesting that they must have been able to fly over deep water.<ref name="sciencefeatherdebate">Balter, M. (2010). [http://news.sciencemag.org/sciencenow/2010/05/did-first-feathers-prevent-early.html "Did First Feathers Prevent Early Flight?"] {{Webarchive|url=https://web.archive.org/web/20100518072039/http://news.sciencemag.org/sciencenow/2010/05/did-first-feathers-prevent-early.html |date=18 May 2010 }} ''Science Now'', 13 May 2010.</ref> [[Gregory Paul]] also disagreed with the study, arguing in a 2010 response that Nudds and Dyke had overestimated the masses of these early birds, and that more accurate mass estimates allowed powered flight even with relatively narrow rachises. Nudds and Dyke had assumed a mass of {{cvt|250|g}} for the Munich specimen ''Archaeopteryx'', a young juvenile, based on published mass estimates of larger specimens. Paul argued that a more reasonable body mass estimate for the Munich specimen is about {{cvt|140|g}}. Paul also criticized the measurements of the rachises themselves, noting that the feathers in the Munich specimen are poorly preserved. Nudds and Dyke reported a diameter of {{cvt|0.75|mm|+2}} for the longest primary feather, which Paul could not confirm using photographs. Paul measured some of the inner primary feathers, finding rachises {{cvt|1.25–1.4|mm}} across.<ref name="paul2010">{{Cite journal |last=Paul |first=G. S. |date=15 October 2010 |title=Comment on 'Narrow Primary Feather Rachises in ''Confuciusornis'' and ''Archaeopteryx'' Suggest Poor Flight Ability.' |journal=Science |volume=330 |issue=6002 |page=320 |bibcode=2010Sci...330..320P |doi=10.1126/science.1192963 |pmid=20947747 |doi-access=free}}</ref> Despite these criticisms, Nudds and Dyke stood by their original conclusions. They claimed that Paul's statement, that an adult ''Archaeopteryx'' would have been a better flyer than the juvenile Munich specimen, was dubious. This, they reasoned, would require an even thicker rachis, evidence for which has not yet been presented.<ref name="Nudds&Dyke_October2010">{{Cite journal |last1=Dyke |first1=G. J. |last2=Nudds |first2=R. L. |date=15 October 2010 |title=Response to Comments on "Narrow Primary Feather Rachises in Confuciusornis and Archaeopteryx Suggest Poor Flight Ability" |url=http://www.sciencemag.org/cgi/reprint/330/6002/320-d.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.sciencemag.org/cgi/reprint/330/6002/320-d.pdf |archive-date=9 October 2022 |url-status=live |journal=Science |volume=330 |issue=6002 |page=320 |bibcode=2010Sci...330..320N |doi=10.1126/science.1193474 |doi-access=free |s2cid=85044108}}</ref> Another possibility is that they had not achieved true flight, but instead used their wings as aids for extra lift while running over water after the fashion of the [[basilisk lizard]], which could explain their presence in lake and marine deposits (see [[Origin of avian flight]]).<ref>Videler, JJ (2005) Avian Flight. Oxford University Press. {{ISBN|0-19-856603-4}} pages&nbsp;98–117</ref><ref>{{Cite web |last=Videler, John J |date=January 2005 |title=How Archaeopteryx could run over water |url=https://www.researchgate.net/publication/38957284 |website=ResearchGate}}</ref>

[[File:Archaeopteryx lithographica, replica of London specimen, Staatliches Museum für Naturkunde Karlsruhe, Germany - 20100925.jpg|left|upright|thumb|Replica of the London Specimen]]

In 2004, scientists analysing a detailed [[CT scan]] of the [[braincase]] of the London ''Archaeopteryx'' concluded that its brain was significantly larger than that of most dinosaurs, indicating that it possessed the brain size necessary for flying. The overall brain anatomy was reconstructed using the scan. The reconstruction showed that the regions associated with vision took up nearly one-third of the brain. Other well-developed areas involved hearing and muscle coordination.<ref name=Witmer_1/> The skull scan also revealed the structure of its inner ear. The structure more closely resembles that of modern birds than the inner ear of non-avian reptiles. These characteristics taken together suggest that ''Archaeopteryx'' had the keen sense of hearing, balance, spatial perception, and coordination needed to fly.<ref name=Alonso/> ''Archaeopteryx'' had a cerebrum-to-brain-volume ratio 78% of the way to modern birds from the condition of non-[[coelurosaurian]] dinosaurs such as ''[[Carcharodontosaurus]]'' or ''[[Allosaurus]]'', which had a crocodile-like anatomy of the brain and inner ear.<ref name="Larsson2001">Larsson, H. C. E. (2001). "Endocranial anatomy of ''Carcharodontosaurus saharicus'' (Theropoda: Allosauroidea) and its implications for theropod brain evolution". In: Tanke, D. H.; Carpenter, K.; Skrepnick, M. W. (eds.) ''Mesozoic Vertebrate Life''. Indiana University Press. pp.&nbsp;19–33.</ref> Newer research shows that while the ''Archaeopteryx'' brain was more complex than that of more primitive theropods, it had a more generalized brain volume among [[maniraptoran|Maniraptora]] dinosaurs, even smaller than that of other non-avian dinosaurs in several instances, which indicates the neurological development required for flight was already a common trait in the maniraptoran clade.<ref>{{Cite journal |last1=Balanoff |first1=Amy M. |last2=Bever |first2=Gabe S. |last3=Rowe |first3=Timothy B. |last4=Norell |first4=Mark A. |year=2013 |title=Evolutionary origins of the avian brain |journal=Nature |volume=501 |issue=7465 |pages=93–6 |bibcode=2013Natur.501...93B |doi=10.1038/nature12424 |pmid=23903660 |s2cid=4451895}}</ref>

Recent studies of flight feather barb geometry reveal that modern birds possess a larger barb angle in the trailing vane of the feather, whereas ''Archaeopteryx'' lacks this large barb angle, indicating potentially weak flight abilities.<ref>{{Cite journal |last1=Feo |first1=Teresa J. |last2=Field |first2=Daniel J. |last3=Prum |first3=Richard O. |date=22 March 2015 |title=Barb geometry of asymmetrical feathers reveals a transitional morphology in the evolution of avian flight |journal=Proceedings of the Royal Society of London B: Biological Sciences |volume=282 |issue=1803 |page=20142864 |doi=10.1098/rspb.2014.2864 |issn=0962-8452 |pmc=4345455 |pmid=25673687}}</ref>

[[File:Archaeopteryx in flight at AMNH.jpg|thumb|Skeletal reconstruction of ''Archaeopteryx'' in gliding posture, [[American Museum of Natural History]]]]
''Archaeopteryx'' continues to play an important part in scientific debates about the origin and evolution of birds. Some scientists see it as a semi-arboreal climbing animal, following the idea that birds evolved from tree-dwelling gliders (the "trees down" hypothesis for the evolution of flight proposed by [[O. C. Marsh]]). Other scientists see ''Archaeopteryx'' as running quickly along the ground, supporting the idea that birds evolved flight by running (the "ground up" hypothesis proposed by [[Samuel Wendell Williston]]). Still others suggest that ''Archaeopteryx'' might have been at home both in the trees and on the ground, like modern crows, and this latter view is what currently is considered best supported by morphological characters. Altogether, it appears that the species was not particularly specialized for running on the ground or for perching. A scenario outlined by Elżanowski in 2002 suggested that ''Archaeopteryx'' used its wings mainly to escape [[Predation|predators]] by glides punctuated with shallow downstrokes to reach successively higher perches, and alternatively, to cover longer distances (mainly) by gliding down from cliffs or treetops.<ref name=Elzanowski2002/>

In March 2018, scientists reported that ''Archaeopteryx'' was likely capable of a flight stroke cycle morphologically closer to the grabbing motion of [[maniraptorans]] and distinct from that of [[Birds|modern birds]].<ref name="NAT-20180313">{{Cite journal |last=Voeten, Dennis F.A.E. |display-authors=et al |date=13 March 2018 |title=Wing bone geometry reveals active flight in Archaeopteryx |journal=[[Nature Communications]] |volume=9 |pages=923 |bibcode=2018NatCo...9..923V |doi=10.1038/s41467-018-03296-8 |pmc=5849612 |pmid=29535376 |number=923}}</ref><ref name="WP-20180313">{{Cite news |last=Guarino |first=Ben |date=13 March 2018 |title=This feathery dinosaur probably flew, but not like any bird you know |newspaper=[[The Washington Post]] |url=https://www.washingtonpost.com/news/speaking-of-science/wp/2018/03/13/this-feathery-dinosaur-probably-flew-but-not-like-any-bird-you-know/ |access-date=13 March 2018 |archive-date=26 June 2018 |archive-url=https://web.archive.org/web/20180626030303/https://www.washingtonpost.com/news/speaking-of-science/wp/2018/03/13/this-feathery-dinosaur-probably-flew-but-not-like-any-bird-you-know/ |url-status=live }}</ref> This study on ''Archaeopteryx''{{'}}s bone histology identified biomechanical and physiological adaptations exhibited by modern volant birds that perform intermittent flapping, such as [[pheasant]]s and other burst flyers.

Some researchers suggested that the feather sheaths of ''Archaeopteryx'' shows a center-out, flight related [[moulting]] strategy like modern birds. As it was a weak flier, this would have been extremely advantageous in preserving its maximum flight performance.<ref>{{Cite journal|vauthors=Kaye TG, Pittman M, Wahl WR|year=2020|title=''Archaeopteryx'' feather sheaths reveal sequential center-out flight-related molting strategy|journal=Communications Biology|volume=3|issue=1|pages=Article number 745|doi=10.1038/s42003-020-01467-2|pmc=7722847|pmid=33293660}}</ref> Kiat and colleagues reinterpreted this purported moulting evidence to be problematic and equivocal at best, and considered that these structures more likely represents the calami traces of the fully grown feathers,<ref>{{Cite journal|vauthors=Kiat Y, Pyle P, Balaban A, O'Connor JK|year=2021|title=Reinterpretation of purported molting evidence in the Thermopolis ''Archaeopteryx''|journal=Communications Biology|volume=4|issue=1|pages=Article number 837|doi=10.1038/s42003-021-02349-x|pmc=8257594|pmid=34226661|s2cid=235738230}}</ref> though the original authors still remained by their conclusion.<ref>{{Cite journal|vauthors=Kaye TG, Pittman M|year=2021|title=Reply to: Reinterpretation of purported molting evidence in the Thermopolis ''Archaeopteryx''|journal=Communications Biology|volume=4|issue=1|pages=Article number 839|doi=10.1038/s42003-021-02367-9|pmc=8257677|pmid=34226634|s2cid=235738222}}</ref>

=== Growth ===
[[File:Archaeopteryx growth curve.jpg|thumb|upright=1.75|Growth trends compared with other dinosaurs and birds]]

An [[histological]] study by Erickson, Norell, Zhongue, and others in 2009 estimated that ''Archaeopteryx'' grew relatively slowly compared to modern birds, presumably because the outermost portions of ''Archaeopteryx'' bones appear poorly vascularized;<ref name=Erickson_etal_2009/> in living vertebrates, poorly vascularized bone is correlated with slow growth rate. They also assume that all known skeletons of ''Archaeopteryx'' come from juvenile specimens. Because the bones of ''Archaeopteryx'' could not be histologically sectioned in a formal skeletochronological ([[growth ring]]) analysis, Erickson and colleagues used bone vascularity (porosity) to estimate bone growth rate. They assumed that poorly vascularized bone grows at similar rates in all birds and in ''Archaeopteryx''. The poorly vascularized bone of ''Archaeopteryx'' might have grown as slowly as that in a mallard (2.5{{nbsp}}micrometres per day) or as fast as that in an ostrich (4.2{{nbsp}}micrometres per day). Using this range of bone growth rates, they calculated how long it would take to "grow" each specimen of ''Archaeopteryx'' to the observed size; it may have taken at least 970 days (there were 375 days in a Late Jurassic year) to reach an adult size of {{cvt|0.8–1|kg}}. The study also found that the avialans ''[[Jeholornis]]'' and ''[[Sapeornis]]'' grew relatively slowly, as did the dromaeosaurid ''[[Mahakala (dinosaur)|Mahakala]]''. The avialans ''[[Confuciusornis]]'' and ''[[Ichthyornis]]'' grew relatively quickly, following a growth trend similar to that of modern birds.<ref>''EurekAlert!'' (8 October 2009), [http://www.eurekalert.org/pub_releases/2009-10/amon-wn100809.php "''Archaeopteryx'' was not very bird-like"].</ref> One of the few modern birds that exhibit slow growth is the flightless [[Kiwi (bird)|kiwi]], and the authors speculated that ''Archaeopteryx'' and the kiwi had similar [[basal metabolic rate]].<ref name=Erickson_etal_2009/>

=== Daily activity patterns ===
Comparisons between the [[sclerotic ring|scleral ring]]s of ''Archaeopteryx'' and modern birds and reptiles indicate that it may have been [[Diurnality|diurnal]], similar to most modern birds.<ref>{{Cite journal |last1=Schmitz, L. |last2=Motani, R. |year=2011 |title=Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology |journal=Science |volume=332 |issue=6030 |pages=705–8 |bibcode=2011Sci...332..705S |doi=10.1126/science.1200043 |pmid=21493820 |s2cid=33253407}}</ref>