Sinopterus

{{Short description|Genus of tapejarid pterosaur}} {{Automatic taxobox | fossil_range = [[Early Cretaceous]], {{fossilrange|120}} | image = Sinopterus dongi NMNS.jpg | image_caption = Fossil specimen of ''S. dongi'', [[National Museum of Natural Science]] | taxon = Sinopterus | authority = Wang & Zhou, 2003 | type_species = {{extinct}}'''''Sinopterus dongi''''' | type_species_authority = Wang & Zhou, 2003 | synonyms = '''Genus synonymy''' *''Huaxiapterus'' Lü & Yuan, 2005 {{collapsible list|bullets = true|title=Species synonymy |''Huaxiapterus atavismus'' Lü ''et al.'', 2016 |''Sinopterus atavismus'' (Lü ''et al.'', 2016) Zhang et al. 2019 |''Sinopterus gui'' Li ''et al.'', 2003 |''Huaxiapterus jii'' Lü & Yuan, 2005 |''Sinopterus jii'' (Lü & Yuan, 2005) Kellner and Campos, 2007 |''Sinopterus lingyuanensis'' Lü ''et al.'', 2016 }} }}

'''''Sinopterus''''' (meaning "Chinese wing") is a [[genus]] of [[Tapejaridae|tapejarid]] [[pterodactyloid]] [[pterosaur]] from the [[Aptian]]-age [[Lower Cretaceous]] [[Jiufotang Formation]] of [[Chaoyang, Liaoning|Chaoyang]], [[Liaoning]], China. It was first described and named by [[Wang Xiaolin]] and [[Zhou Zhonghe]]. Historically, there were multiple species attributed to the genus although only one is considered to be valid. ''Sinopterus'' is known for its proportionally large skull, which has a [[bird]]-like pointed [[beak]] lacking teeth, and a long bony crest that starts with a tall [[premaxilla]] and goes back along the middle of the skull to form a point overhanging the rear of the skull. Direct dietary evidence based on gut contents suggest that ''Sinopterus'' is a [[herbivore]].

==History of discovery== [[File:Sinopterus dongi holotype.png|thumb|left|[[Holotype specimen]] of ''S. dongi'']] ''Sinopterus'' is known from numerous specimens, some of which have been assigned to unique species and even different genera over the years. The type species, ''Sinopterus dongi'', is known from one specimen described in 2003. A second specimen, BPV-077, was also described in 2003 by Li, [[Lü Junchang|Lü]], and Zhang, who classified it in its own species, ''S. gui''. It was said to differ from ''S. dongi'' mainly in its smaller size (only about half the size of ''S. dongi'') and the presence of a [[notarium]],<ref name=LLZ03>{{cite journal | last1 = Li | first1 = J. | last2 = Lü | first2 = J. | last3 = Zhang | first3 = B. | year = 2003 | title = A new Lower Cretaceous sinopterid pterosaur from the Western Liaoning, China | journal = Acta Palaeontologica Sinica | volume = 42 | issue = 3| pages = 442–447 }}</ref> though this was later disproved.<ref name=kellner2007>{{cite journal | last1 = Kellner | first1 = A.W.A. | last2 = Campos | first2 = D.A. | year = 2007 | title = Short note on the ingroup relationships of the Tapejaridae (Pterosauria, Pterodactyloidea) | journal = Boletim do Museu Nacional | volume = 75 | pages = 1–14 }}</ref> Some later studies found ''S. gui'' to simply represent a younger specimen of ''S. dongi'',<ref name=pinheiroetal2011>{{cite journal |last1=Pinheiro |first1=Felipe L. |last2=Fortier |first2=Daniel C. |last3=Schultz |first3=Cesar L. |last4=De Andrade |first4=José Artur F.G. |last5=Bantim |first5=Renan A.M. |title=New information on the pterosaur ''Tupandactylus imperator'', with comments on the relationships of Tapejaridae |journal=Acta Palaeontologica Polonica |date=September 2011 |volume=56 |issue=3 |pages=567–580 |doi=10.4202/app.2010.0057|doi-access=free }}</ref> though one large analysis in 2014 found it to be a more primitive tapejarid.<ref name=kryptodrakon/>

A third specimen was referred to ''Sinopterus'' in 2007, again classified as a new species, this time given the name ''S. jii''. This species was first named by Lü & Yuan in 2005 as the type species of a new genus which they named ''Huaxiapterus''. Two later studies in 2007 and 2011 both showed that ''H. jii'' was in fact more closely related to ''Sinopterus'' than to the two other species also assigned to ''Huaxiapterus'', "''H.''" ''corollatus'' and "''H.''" ''benxiensis''. Both groups of researchers concluded that ''Huaxiapterus jii'' should therefore be reclassified as ''Sinopterus jii'', and that the other two species of "''Huaxiapterus''" require a new genus name.<ref name=kellner2007/><ref name=pinheiroetal2011/> However, a more complete phylogenetic analysis suggested that ''Sinopterus'' may actually be an intermediate step in the grade between ''H. jii'' and the other two ''Huaxiapterus'' species, making ''Sinopterus'' paraphyletic if ''H. jii'' is included.<ref name=kryptodrakon/>

In 2016, another species, ''S. lingyuanensis'', was named. It purportedly differed from the other species in the proportions of its [[antorbital fenestra|nasoantorbital fenestra]], its rostral index, the relative sizes of its femur and tibia, and the relative sizes of the first and second wing digits. In the same paper describing this species, the species ''Huaxiapterus atavismus'' was also named.<ref name="luetal2016">{{cite journal | last1 = Lü | first1 = Junchang | last2 = Teng | first2 = Fangfang | last3 = Sun | first3 = Deyu | last4 = Shen | first4 = Caizhi | last5 = Li | first5 = Guoqing | last6 = Gao | first6 = Xia | last7 = Liu | first7 = Hanfeng | date = 2016 | title = The toothless pterosaurs from China | journal = Acta Geologica Sinica | volume = 90 | issue = 9 | pages = 2513–2525 | url = http://www.geojournals.cn/dzxb/ch/reader/create_pdf.aspx?file_no=2016224&flag=1&journal_id=dzxb&year_id=2016 | access-date = 2016-10-10 | archive-date = 2016-10-11 | archive-url = https://web.archive.org/web/20161011062528/http://www.geojournals.cn/dzxb/ch/reader/create_pdf.aspx?file_no=2016224&flag=1&journal_id=dzxb&year_id=2016 }}</ref> However, [[Xinjun Zhang]] and colleagues in 2019 considered ''Huaxiapterus'' an invalid genus and therefore reassigned ''H. atavismus'' to ''Sinopterus'', which created the new combination ''Sinopterus atavismus''.<ref>{{cite journal |last1=Zhang |first1=Xinjun |last2=Jiang |first2=Shunxing |last3=Cheng |first3=Xin |last4=Wang |first4=Xiaolin |title=New Material of Sinopterus (Pterosauria, Tapejaridae) from the Early Cretaceous Jehol Biota of China |journal=[[Anais da Academia Brasileira de Ciências]] |date=27 June 2019 |volume=91 |issue=suppl 2 |pages=e20180756 |doi=10.1590/0001-376520192018756 |pmid=31271567 |doi-access=free }}</ref>

[[File:Huaxiapterus jii holotype.png|thumb|left|Holotype specimen of ''Huaxiapterus jii'', now considered a synonym of ''S. dongi'']] A 2021 study by Darren Naish and colleagues of variation within pterosaur growth stages noted that numerous species had been classified as ''Sinopterus'' or "''Huaxiapterus''", most based only on a single specimen, and most differentiated from each other by features like wing proportions, skull length, and crest shape and size. Naish ''et al.'' pointed out that all of these features are known to be variable within a single species due to growth, and that there were unlikely to be such a high diversity of extremely similar species in the same ecosystem when their differences are more likely due to variation within a few species. They suggested that a larger study would be needed to untangle the question of how many species of ''Sinopterus''-like pterosaurs actually existed in the Jiufotang ecosystem, and how they are related to each other. In a preliminary opinion, these scientists stated that there is likely only one valid species of ''Sinopterus'', ''S. dongi'', but that "''Huaxiapterus''" ''corollatus'' might be a valid second species based on unique wing and leg proportions.<ref name=Sinopterus_hatchling/>

In 2023, Rubi V. Pêgas et al. reviewed the recent taxonomic histories of the tapejarids. In their article, they made ''S. gui'' and ''S. lingyuanensis'' synonymous with ''S. dongi''. In addition, the genus ''Huaxiapterus'' was synonymized with ''Sinopterus'' as a result of ''H. jii'' and ''H. atavismus'' being reclassified as synonyms of ''S. dongi'' and "''H.''" ''corollatus'' being reclassified to the new genus ''[[Huaxiadraco]]'' from which ''Huaxiapterus benxiensis'' became synonymous with.<ref name=Pegas>{{Cite journal|last1=Pêgas |first1=R. V. |last2=Zhoi |first2=X. |last3=Jin |first3=X. |last4=Wang |first4=K. |last5=Ma |first5=W. |year=2023 |title=A taxonomic revision of the ''Sinopterus'' complex (Pterosauria, Tapejaridae) from the Early Cretaceous Jehol Biota, with the new genus ''Huaxiadraco'' |journal=PeerJ |volume=11 |at=e14829 |doi=10.7717/peerj.14829 |doi-access=free |pmc=9922500 }}</ref>

==Description== [[File:Jiufotang tapejarids.png|thumb|left|[[Life restorations]] of ''Sinopterus'' and ''[[Huaxiadraco]]'' in [[Jiufotang]]]] The [[type species]], ''S. dongi'', is [[holotype|based on]] [[Institute of Vertebrate Paleontology and Paleoanthropology|IVPP V13363]], an articulated, nearly complete skeleton. The skull of this individual was 17 centimeters (6.7 inches) long, and the [[wingspan]] was estimated to be 1.2 meters (3.9 feet). The authors suggested that it was an [[omnivore]], and noted that it was the first record of a [[Tapejaridae|tapejarid]] outside of [[Brazil]], and the earliest and most complete tapejarid.<ref name=WZ03>{{cite journal |last1=Wang |first1=Xiaolin |last2=Zhou |first2=Zhonghe |title=A new pterosaur (Pterodactyloidea, Tapejaridae) from the Early Cretaceous Jiufotang Formation of western Liaoning, China and its implications for biostratigraphy |journal=Chinese Science Bulletin |date=June 2003 |volume=48 |issue=1 |pages=16–23 |doi=10.1007/bf03183326 |bibcode=2003ChSBu..48...16W |s2cid=43993745 }}</ref> The maximum adult wingspan of this pterosaur would have been {{convert|1.9|m|ft}}, and an individual of this size would have weighed {{cvt|2.87|kg|lb}}.<ref name=Sinopterus_hatchling/>

==Classification== [[File:Sinopterus gui holotype.png|thumb|right|Holotype of ''S. gui'', which may be a [[junior synonym]] of ''S. dongi'']] [[File:Huaxiapterus atavismus holotype.png|thumb|right|Holotype of ''H. atavismus'', which may be a junior synonym of ''S. dongi'']] The cladogram below follows the 2014 analysis by Brian Andres and colleagues, showing the placement of two ''Sinopterus'' species ("''S.''" ''gui'' and ''S. dongi'') within the clade [[Tapejaromorpha]].<ref name=kryptodrakon>{{cite journal |last1=Andres |first1=Brian |last2=Clark |first2=James |last3=Xu |first3=Xing|author3-link=Xu_Xing_(paleontologist) |title=The Earliest Pterodactyloid and the Origin of the Group |journal=[[Current Biology]] |date=5 May 2014 |volume=24 |issue=9 |pages=1011–1016 |doi=10.1016/j.cub.2014.03.030 |pmid=24768054 |s2cid=18293296 |doi-access=free }}</ref>

{{clade| style=font-size:100%;line-height:100% |label1=[[Tapejaromorpha]] |1={{clade |1=''[[Bennettazhia oregonensis]]'' |2={{clade |1={{clade |1=''[[Eopteranodon lii]]'' |2={{clade |1="'''''Sinopterus'''''" '''''gui''''' |2=''[[Nemicolopterus crypticus]]'' }} }} |2={{clade |1='''''Huaxiapterus jii''''' |label2=[[Tapejaridae]] |2={{clade |1='''''Sinopterus dongi''''' |label2=[[Tapejarinae]] |2={{clade |1={{clade | 1=''[[Huaxiadraco|"Huaxiapterus" benxiensis]]'' | 2=''[[Huaxiadraco|"Huaxiapterus" corollatus]]'' }} |label2=[[Tapejarini]] |2={{clade |1={{clade |1=''[[Tupandactylus navigans]]'' |2=''[[Tupandactylus imperator]]'' }} |2={{clade |1=''[[Bakonydraco galaczi]]'' |2={{clade |1=''[[Europejara olcadesorum]]'' |2=''[[Tapejara wellnhoferi]]'' }} }} }} }} }} }} }} }} }}

[[File:Sinopterus lingyuanensis holotype.png|thumb|right|Holotype of ''S. lingyuanensis'', which may be a junior synonym of ''S. dongi'']] Based on their reassessment of the ''Sinopterus'' species-complex, Pêgas ''et al.'' modified their working dataset, previously used in the redescription of ''[[Aerotitan]].<ref>{{Cite journal |last=Pêgas |first=Rubi V. |last2=Holgado |first2=Borja |last3=Ortiz David |first3=Leonardo D. |last4=Baiano |first4=Mattia A. |last5=Costa |first5=Fabiana R. |date=January 2022 |title=On the pterosaur ''Aerotitan sudamericanus'' (Neuquén Basin, Upper Cretaceous of Argentina), with comments on azhdarchoid phylogeny and jaw anatomy |journal=Cretaceous Research |volume=129 |article-number=104998 |doi=10.1016/j.cretres.2021.104998 |issn=0195-6671}}</ref>'' Their cladogram is shown below:<ref name="Pegas2">{{Cite journal |last1=Pêgas |first1=R. V. |last2=Zhoi |first2=X. |last3=Jin |first3=X. |last4=Wang |first4=K. |last5=Ma |first5=W. |year=2023 |title=A taxonomic revision of the ''Sinopterus'' complex (Pterosauria, Tapejaridae) from the Early Cretaceous Jehol Biota, with the new genus ''Huaxiadraco'' |journal=PeerJ |volume=11 |at=e14829 |doi=10.7717/peerj.14829 |pmc=9922500 |doi-access=free}}</ref>{{clade|{{clade |1=[[Thalassodromidae]] |label2=[[Tapejaridae]] |2={{clade |label1=[[Caupedactylia]] |1={{clade |1=''[[Caupedactylus ybaka]]'' |2=''[[Aymberedactylus cearensis]]'' }} |label2=[[Eutapejaria]] |2={{clade |label1=[[Tapejarinae]] |1={{clade |1=''[[Europejara olcadesorum]]'' |2={{clade |1={{clade |1=''[[Tupandactylus imperator]]'' |2=''[[Tupandactylus navigans]]'' }} |2={{clade |1=''[[Tapejara wellnhoferi]]'' |2=''[[Caiuajara dobruskii]]'' }} }} }} |label2=[[Sinopterinae]] |2={{clade |1={{clade |1=''[[Huaxiadraco corollatus]]'' |2={{clade |1=''[[Eopteranodon lii]]'' |2='''''Sinopterus dongi''''' }} }} |2={{clade |1=''[[Wightia declivirostris]]'' |2={{clade |1=''[[Afrotapejara zouhrii]]'' |2=''[[Bakonydraco galaczi]]'' }} }} }} }} }} }}|label1=[[Tapejaromorpha]]}}

==Paleobiology== ===Growth=== [[File:Nemicolopterus crypticus holotype.png |thumb|right|Juvenile ''[[Nemicolopterus]]'' specimen IVPP V-14377, which may be ''Sinopterus'']] ''Sinopterus'' is known from several specimens at various stages of growth, which has allowed scientists to study the changes these animals went through during their life histories.

At least one very small juvenile (possibly hatchling) specimen has been attributed to ''Sinopterus''. This specimen was originally classified as a distinct genus in 2008, ''Nemicolopterus crypticus''. The name ''Nemicolopterus'' comes from the Greek words "Nemos" meaning "forest", "ikolos" meaning "dweller", and the Latinised "pteron" meaning "wing". The specific name ''crypticus'' is derived from the Greek "kryptos", meaning "hidden". Thus "''Nemicolopterus crypticus''" means "Hidden flying forest dweller". The type specimen of ''N. crypticus'', catalog number IVPP V-14377, is housed in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China. The fossil was collected from the [[Jiufotang Formation]], like all adult ''Sinopterus'' specimens. It was discovered in the Luzhhouou locality of Yaolugou Town, Jianchang County, Huludao City, western [[Liaoning Province]] in northeastern [[China]]. It has a wingspan of slightly under 25 centimeters (10 in), making it smaller than all but a few specimens of hatchling pterosaurs.<ref>{{cite journal |last1=Wang |first1=Xiaolin |last2=Kellner |first2=Alexander W. A.|author2-link=Alexander_Kellner |last3=Zhou |first3=Zhonge|author3-link=Zhou_Zhonghe |last4=de Almeida Campos |first4=Diogenes |title=Discovery of a rare arboreal forest-dwelling flying reptile (Pterosauria, Pterodactyloidea) from China |journal=[[Proceedings of the National Academy of Sciences]] |date=12 February 2008 |volume=105 |issue=6 |pages=1983–1987 |doi=10.1073/pnas.0707728105 |pmid=18268340 |pmc=2538868 |doi-access=free }}</ref>

[[File:Nemicolopterus.jpg|thumb|left|[[Life restoration]] of two ''Nemicolopterus'']] Wang ''et al.'' (2008), who originally described the specimen, concluded that it was immature, citing the amount of bone fusion and the [[ossification]] of the toes, gastralia, and sternum as indicating that it was a sub-adult rather than a hatchling. However, [[Darren Naish]] argued on his popular weblog that, due to the hypothesis that pterosaurs were highly [[precocial]], bone fusion and ossification could have occurred very early in life, and that ''Nemicolopterus'' might in fact be a hatchling ''Sinopterus''.<ref>{{cite web |title=Tiny pterosaurs and pac-man frogs from hell |url=https://scienceblogs.com/tetrapodzoology/2008/03/19/tiny-pterosaurs-pacman-frogs |last=Naish |first=Darren |author-link=Darren_Naish|website=scienceblogs.com |publisher=Science 2.0 Corp.|access-date=2022-06-10 }}</ref> This identification was formally presented in 2021 study, which found that ''Nemicolopterus'' fit into a growth series as a young juvenile or hatchling ''Sinopterus'' hatchling.<ref name=Sinopterus_hatchling>{{cite journal |last1=Naish |first1=Darren |author1-link=Darren_Naish|last2=Witton |first2=Mark P. |author2-link=Mark_P._Witton|last3=Martin-Silverstone |first3=Elizabeth |title=Powered flight in hatchling pterosaurs: evidence from wing form and bone strength |journal=[[Scientific Reports]] |date=22 July 2021 |volume=11 |issue=1 |page=13130 |doi=10.1038/s41598-021-92499-z |pmid=34294737 |pmc=8298463 |bibcode=2021NatSR..1113130N }}</ref> An analysis of pterosaur relationships by Andres and colleagues in 2014 found the specimen in a sister group relationship with "''Sinopterus''" ''gui''.<ref name=kryptodrakon/>

Based on study of hatchling ''Sinopterus'' skeletons as well as comparison with hatchlings of other pterosaur species, Naish and colleagues (2021) found that the wing proportions and bone strength/flexibility of hatchlings were similar to adults, and concluded that ''Sinopterus'' was capable of powered flight very shortly after hatching. They found that while young juveniles would have been excellent gliders, they would not have been reliant on gliding alone as opposed to true flight. Juveniles also seem to have been more adapted to flight in closed environments, like dense forests, compared to adults. Juveniles therefore probably occupied different ecological niches than adults, transitioning between different niches as they grew.<ref name=Sinopterus_hatchling/>

Osteohistological studies on a late juvenile individual of ''Sinopterus'' demonstrates that this taxon achieved sexual maturity before skeletal maturity, with onset of sexual maturity at approximately 79% adult size. The high number of juvenile ''Sinopterus'' fossils found compared to sexually mature adults suggests migratory habits, with mature adults living in different habitats from juvenile and subadult individuals.<ref>{{cite journal |last1=Zhou |first1=Chang-Fu |last2=Yu |first2=Dongxiang |last3=Zhu |first3=Ziheng |last4=Andres |first4=Brian |year=2022 |title=A new wing skeleton of the Jehol tapejarid ''Sinopterus'' and its implications for ontogeny and paleoecology of the Tapejaridae |journal=Scientific Reports |volume=12 |article-number=10159 |doi=10.1038/s41598-022-14111-2 |doi-access=free |url=https://www.nature.com/articles/s41598-022-14111-2|pmc=9205892 }}</ref>

===Diet===

[[File:Tapejaridae skull comparison.png|thumb|right|Comparison of [[tapejarid]] skulls, ''Sinopterus'' is F]] Tapejarids like ''Sinopterus'' have long been speculated as having been [[frugivore]]s or [[omnivore]]s, based on their parrot-like beaks.<ref>{{cite journal | last1 = Wu | first1 = Wen-Hao | last2 = Zhou | first2 = Chang-Fu | last3 = Andres | first3 = Brian | year = 2017 | title = The toothless pterosaur ''Jidapterus edentus'' (Pterodactyloidea: Azhdarchoidea) from the Early Cretaceous Jehol Biota and its paleoecological implications | journal = PLOS ONE | volume = 12 | issue = 9| article-number = e0185486 | doi = 10.1371/journal.pone.0185486 | pmid = 28950013 | pmc = 5614613 | bibcode = 2017PLoSO..1285486W | doi-access = free }}</ref> In 2025, the palaeontologist Shunxing Jiang and colleagues reported stomach contents from the abdominal cavity of a ''Sinopterus'' specimen. These include [[gastroliths]] (stones used to aid food processing in the [[gizzard]]) and the first evidence of [[phytoliths]] in pterosaurs (minerals found in certain plants which persist after their decomposition), and the first evidence of these co-occurring in a pterosaur. Earlier known pterosaur stomach contents are all from more basal pterosaurs, containing fish remains. The gizzard of the ''Sinopterus'' specimen is similar to that of the bird ''[[Jeholornis]]'', and the pattern and size of their gastroliths are similar; since both belonged to the [[Jehol Biota]], these writers suggested they shared a herbivorous diet such as seeds and grains. Some of the phytoliths of the specimen were identified as the angiosperm family [[Poaceae]] as well as gymnosperms or [[ferns]], indicating ''Sinopterus'' had a diverse diet of plants. While noting that tapejarids and some other pteosaurs had earlier been suggested as herbivorous based on indirect evidence, these researchers considered the gut contents confirmation of herbivory, and excluded a generalist diet for ''Sinopterus'' as for example no undigested bones, scales, or insect [[exoskeletons]] were found. They also stated that [[bite force]] estimations of ''Tapejara'' had suggested a herbivorous diet of fruits, seeds, and more resistant plant matter, and added that the similarity between their skulls indicated similar bite forces, supporting a herbivorous diet for both.<ref>{{cite journal|author1=Jiang, S.|author2=Zhang, X.|author3=Wu, Y.|author4=Zheng, M.|author5=Kellner, A.W.A.|author6=Wang, X.|year=2025|title=First occurrence of phytoliths in pterosaurs—evidence for herbivory|journal=Science Bulletin|volume=70|issue=19|pages=3134–3138|doi=10.1016/j.scib.2025.06.040}}</ref>

==See also== * [[List of pterosaur genera]] * [[Timeline of pterosaur research]]

==References== {{Reflist}} {{Pterosauria|Az.}} {{Taxonbar|from=Q311479}} {{Portal bar|Paleontology|China}}

[[Category:Tapejaridae]] [[Category:Early Cretaceous pterosaurs of Asia]] [[Category:Jiufotang fauna]] [[Category:Fossil taxa described in 2003]] [[Category:Taxa named by Zhou Zhonghe]] [[Category:Pterosaur genera]]