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Sinopterus
Temporal range: Early Cretaceous, 120 Ma
↓
Fossil specimen of S. dongi, National Museum of Natural Science
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: †Pterosauria
Suborder: †Pterodactyloidea
Clade: †Azhdarchoidea
Family: †Tapejaridae
Subfamily: †Sinopterinae
Genus: †Sinopterus
Wang & Zhou, 2003
Type species
†Sinopterus dongi
Wang & Zhou, 2003
Synonyms

Genus synonymy

  • Huaxiapterus
    Lü & Yuan, 2005
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 tapejarid pterodactyloid pterosaur from the Aptian-age Lower Cretaceous Jiufotang Formation of 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.

Description

[edit]
Life restorations of S. dongi and Huaxiadraco in Jiufotang

The type species, S. dongi, is based on 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 tapejarid outside of Brazil, and the earliest and most complete tapejarid.[1] The maximum adult wingspan of this pterosaur would have been 1.9 metres (6.2 ft), and an individual of this size would have weighed 2.87 kg (6.3 lb).[2]

History of discovery

[edit]
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, 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,[3] though this was later disproved.[4] Some later studies found S. gui to simply represent a younger specimen of S. dongi,[5] though one large analysis in 2014 found it to be a more primitive tapejarid.[6]

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.[4][5] 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.[6]

In 2016, another species, S. lingyuanensis, was named. It purportedly differed from the other species in the proportions of its 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.[7] 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.[8]

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.[2]

In 2023, Rodrigo 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.[9]

Classification

[edit]
Holotype of S. gui, 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.[6]

Tapejaromorpha
Comparison of tapejarid skulls, Sinopterus is F

Based on their reassessment of the Sinopterus species-complex, Pêgas et al. modified their working dataset, previously used in the redescription of Aerotitan.[10] Their cladogram is shown below:[11]

Tapejaromorpha

Paleobiology

[edit]

Growth

[edit]
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.[12] 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.[13] 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.[2] An analysis of pterosaur relationships by Andres and colleagues in 2014 found the specimen in a sister group relationship with "Sinopterus" gui.[6]

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.[2]

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.[14]

Diet

[edit]

Tapejarids like Sinopterus have long been speculated as having been frugivores or omnivores, based on their parrot-like beaks.[15] Direct evidence for herbivory is known in a Sinopterus specimen that preserves phytoliths and gastroliths in the abdominal cavity.[16]

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Sinopterus

View on Grokipedia
from Grokipedia
Sinopterus is a genus of edentulous tapejarid pterodactyloid pterosaur known from the Early Cretaceous Jiufotang Formation of Liaoning Province, China, characterized by a slender rostrum, low sagittal cranial crest, and a large nasoantorbital fenestra comprising about two-and-a-half times the height in length. The type and only valid species, S. dongi, was described in 2003 from a well-preserved near-complete skeleton with a wingspan of approximately 1.2 meters, though later juvenile and adult specimens indicate ontogenetic variation in size up to around 2 meters. These flying reptiles, part of the diverse Jehol Biota, likely inhabited lacustrine or forested environments and had a herbivorous diet, as evidenced by phytoliths and gastroliths in the stomach contents of a specimen, in addition to inferences from their toothless beaks, with robust pedal claws suggesting possible arboreal habits. The Sinopterus was established by Wang and Zhou based on the IVPP V 13363 from the Lamagou locality near Chaoyang, representing the earliest and one of the most complete tapejarid skeletons outside . Subsequent discoveries, including multiple postcranial elements and cranial material from the Dapingfang and other sites in the Jiufotang Formation ( stage, approximately 120 million years ago), have expanded knowledge of its anatomy, such as elongated mid-cervical vertebrae, a subrectangular deltopectoral crest on the , and curved phalanges. A 2023 taxonomic revision by Pêgas et al. confirmed S. dongi as the sole valid within Sinopterus, reassigning or invalidating other nominal taxa like S. gui and formerly in Huaxiapterus (e.g., H. jii, H. benxiensis) as synonyms, immature individuals, or to the new Huaxiadraco corollatus, based on morphometric analyses excluding crest variation. This revision highlights the challenges of taxonomy in the Jehol Biota due to ontogenetic and intraspecific variation, while underscoring Sinopterus as a key for understanding tapejarid evolution and the biostratigraphic correlations between Asian and Gondwanan faunas.

History of Research

Initial Discovery and Naming

The holotype specimen of Sinopterus dongi, cataloged as IVPP V 13363, was discovered in the Jiufotang Formation near Chaoyang in Province, northeastern . This nearly complete and articulated represents a small pterodactyloid from the stage of the , approximately 120 million years ago. The was collected from finely laminated volcanic ash deposits characteristic of the , a renowned for its exceptional preservation of soft tissues and detailed skeletal elements due to rapid burial in low-oxygen, lacustrine environments influenced by volcanic activity. In 2003, paleontologists Xiaolin Wang and Zhonghe Zhou formally described and named the genus and species Sinopterus dongi based on this specimen, published in Chinese Science Bulletin. The generic name Sinopterus combines "Sino-" (referring to ) with the Greek "pteron" (wing), reflecting its origin in Chinese deposits, while the specific epithet dongi honors the prominent Chinese paleontologist Zhiming Dong for his contributions to vertebrate paleontology. The description emphasized the specimen's well-preserved , including a long bony crest and edentulous beak, assigning it to the family Tapejaridae within . This initial find marked the first discovery of a tapejarid outside of , where the family was previously known only from Brazilian Cretaceous formations, thereby expanding the known geographic and temporal range of Tapejaridae into during the . The estimated of the , derived from measurements of the (approximately 50 mm long) and associated wing elements, is about 1.2 meters, indicating a relatively small-bodied comparable in size to some modern . This discovery underscored the biodiversity of pterosaurs in the and highlighted the biostratigraphic value of the Jiufotang Formation for correlating faunas across continents.

Subsequent Specimens and Taxonomic Revisions

Following the initial description of Sinopterus dongi in 2003, additional specimens from the Jiufotang Formation began to accumulate, leading to the proposal of several new species within the genus. In 2005, a partial skull exhibiting a prominent cranial crest was described as Huaxiapterus jii, later referred to Sinopterus jii based on shared tapejarid features such as an elongate skull and reduced dentition. This referral highlighted early taxonomic overlap with S. dongi. In 2006, a nearly complete skeleton from near Lingyuan was named Huaxiapterus corollatus, distinguished by features including a prominent cranial crest and postcranial proportions such as a relatively long humerus relative to the femur. Also in 2006, additional postcranial material referred to Sinopterus dongi was described from the Jiufotang Formation, including elements that reinforced the genus's anatomy and presence in the Jehol Biota. In 2016, another nearly complete skeleton from Lingyuan was named Sinopterus lingyuanensis. Further referrals continued through the early 2010s. In 2008, a specimen with a well-preserved wing was initially assigned to "Sinopterus" gui, but subsequent analyses synonymized it with S. dongi due to matching metacarpal and phalanx ratios. By 2019, a juvenile specimen (IVPP V 23388) with exceptional preservation, including soft tissue outlines around the wings and body, was described as Sinopterus atavismus, based on its small size and proportional similarities to adult Sinopterus material. These discoveries, all from the Jiufotang Formation in Liaoning Province, China, expanded the known specimen count to over 20 by 2025, predominantly from sites near Chaoyang and Lingyuan. Taxonomic revisions intensified in the 2020s, addressing the proliferation of names within the Sinopterus complex. The Huaxiapterus (erected in 2005) was fully synonymized with Sinopterus by 2023, as its diagnostic crests were deemed ontogenetic variants rather than generic traits. Similarly, "Sinopterus" gui (2008) was folded into S. dongi. A comprehensive 2023 study by Pêgas et al. reappraised the Sinopterus complex, confirming S. dongi as the sole valid species of Sinopterus by synonymizing S. jii, S. lingyuanensis, S. gui, H. jii, and H. benxiensis with it; reassigning S. atavismus to the new Huaxiadraco atavismus; and designating the former H. corollatus as the Huaxiadraco corollatus, based on morphometric analyses emphasizing postcranial metrics over variable cranial crests. This revision stabilized the amid ongoing debates about tapejarid diversity in the . In 2025, re-examination of the of the former S. atavismus (now Huaxiadraco atavismus; IVPP V 23388) via CT scanning revealed preserved contents consisting of phytoliths from woody and flowering , alongside gastroliths, providing of herbivory at the level without proposing new taxa or altering existing synonymies. This analysis confirmed the specimen's dietary habits aligned with broader Sinopterus , further solidifying the taxonomic framework established in prior revisions.

Anatomy

Cranial Features

The of Sinopterus is notably elongated, characterized by a slender rostrum comprising approximately 36–44% of the and a large nasoantorbital with a -to-height ratio of 2.8–3.2, making it a dominant feature of the cranium. The and are edentulous, with the anterior portions forming a pointed, robust adapted for non-predatory feeding behaviors typical of tapejarids. This toothless condition extends across the rostrum, distinguishing Sinopterus from toothed pterosaurs and aligning it with other azhdarchoid relatives. A prominent premaxillary crest originates anteriorly on the , exhibiting a rounded, parabolic profile that can reach up to 10 cm in height in adult specimens; this structure is low and incipient in S. dongi but varies in prominence due to , being reduced or absent in some juvenile specimens. Some specimens also preserve a along the skull roof, formed by posterior processes of the premaxillae and frontoparietals that curve upwards, contributing to the overall cranial ornamentation. These crests show ontogenetic variation, with juveniles displaying reduced or absent formations compared to adults. The orbits are subquadrangular in shape, positioned to provide a degree of forward-facing orientation that may have facilitated , with their height roughly equal to their length in S. dongi and other specimens. The palate features elongated, fused vomers and a slight lateral expansion beneath the nasoantorbital in certain specimens, supporting a broad internal structure. Across specimens of S. dongi, cranial variations are evident and largely attributable to , such as larger, more developed premaxillary crests in larger individuals compared to smaller, triangular crests in juveniles, reflecting intraspecific differences.

Postcranial Skeleton

The postcranial of Sinopterus exhibits adaptations typical of tapejarid pterosaurs, with a lightweight construction supporting powered flight, as evidenced by articulated specimens from the Jiufotang Formation of the . The torso is robust yet pneumatized for weight reduction, comprising a series of cervical, dorsal, sacral, and caudal vertebrae, along with reduced that provide minimal ventral support to the abdominal region. In the juvenile specimen IVPP V 23388 (referred to S. dongi), at least seven are preserved, with lengths up to 30.80 mm for the third cervical, followed by a minimum of 14 dorsal vertebrae showing no evidence of fusion into a notarium; four displaced V-shaped elements are also present, indicating a reduced but functional set. Another juvenile specimen, SDUST-V1012 (referred to S. dongi), preserves the last three (seventh cervical 18 mm long), 15 dorsal vertebrae (each approximately 4 mm long and 10 mm high with unfused neural arches and centra), and two or more sacral vertebrae, further highlighting the axial skeleton's elongation and lightness without extensive ossification. The of Sinopterus is notably short and stiff, consistent with azhdarchoid pterosaurs adapted for aerial efficiency rather than maneuverability on the ground. In SDUST-V1012, nine caudal vertebrae form a reduced totaling 9 mm in length (about 16% of femur length), with the first caudal centrum longer than tall and its neural arch 1.5 times the centrum height, contributing to overall rigidity. Specimen IVPP V 23388 similarly shows at least six procoelous caudal vertebrae with smooth centra, totaling around 12.09 mm, underscoring the 's abbreviated structure across individuals. The pectoral girdle and forelimbs form the primary flight apparatus, with elongated wings supported by an extended manual digit IV and a well-developed wing membrane. Metacarpals I-III are reduced and slender, bearing digits with phalangeal formulae of 2-3-4 and sharp, curved claws for grasping; in contrast, metacarpal IV is greatly elongated and pneumatized, as seen in SDUST-V1012 (76 mm long, 162% of humerus length) and IVPP V 23388 (127.49 mm left, 125.39 mm right). The humerus varies by ontogenetic stage, measuring 47 mm in the small juvenile SDUST-V1012 (with a subrectangular deltopectoral crest), 73 mm in the immature SDUST-V1014, and up to 81.01 mm in IVPP V 23388, featuring a pneumatic foramen and plate-like crest for muscle attachment. Wing phalanges of digit IV are successively shortened, with the first phalanx reaching 158.87 mm in IVPP V 23388 and 134 mm in SDUST-V1014; the wing membrane includes a cruropatagium extending from the hindlimbs to the tail, anchored by the femur and a small calcar element for stability during flight. In specimens of S. dongi, wingspans range from approximately 1.13 m in small juveniles like the holotype (humerus 58 mm) to 1.5–1.6 m in larger individuals such as IVPP V 23388, reflecting ontogenetic variation. Hindlimbs are diminutive relative to the forelimbs, reflecting a high intermembral index of around 200%, which emphasizes flight over and supports a quadrupedal stance on the ground with the wings folded back. The is elongated with a hemispherical head and distinct , measuring 56 mm in SDUST-V1012 and 100.97 mm in IVPP V 23388; tibiae and fibulae are proportionally shorter, with pedal claws reduced in size and curvature compared to manual claws, suited for perching rather than scratching. The pelvic girdle and are delicately constructed to minimize mass while maintaining structural integrity for flight muscle anchorage, as detailed in articulated material. In IVPP V 23388, the comprises three unfused vertebrae (first sacral 7.80 mm long), and the features a left ilium 64.03 mm long with a closed acetabular cavity formed by pubis, , and prepubis; the is medium-sized, and the prepubic is rod-like. SDUST-V1012 shows a similar lightweight , with the ilium 39 mm long (preacetabular process 24 mm, or 61.5% of ilium length; postacetabular process hatchet-like with a 9 mm terminus subequal to the acetabulum) and a kidney-shaped prepubic , confirming the girdle's efficiency in distributing aerodynamic forces.

Classification

Phylogenetic Position

Sinopterus is classified within the family Tapejaridae, a of edentulous pterosaurs belonging to the superfamily and the suborder . This positioning is primarily supported by diagnostic synapomorphies including a large with a length-to-height ratio approximately three times greater than in other pterodactyloids, prominent neural crests on the and forming elaborate head crests, and completely toothless jaws adapted for specialized feeding. These features distinguish Tapejaridae from other azhdarchoids like azhdarchids, which exhibit more elongated and rostra. Early cladistic analyses, such as that of Lü et al. (2007), recovered Sinopterus as a basal member of Tapejaridae based on specimens from the Jiufotang Formation, emphasizing shared cranial morphology with South American tapejarids like Tapejara. Subsequent revisions, including Pêgas et al. (2023), refined this placement by validating Sinopterus dongi as the type species and erecting the subfamily Sinopterinae for Asian Jiufotang tapejarids, with S. dongi as sister taxon to Eopteranodon lii. In broader analyses, Tapejarinae (including Tapejara wellnhoferi) forms the sister group to Sinopterinae, supporting a monophyletic Tapejaridae within Azhdarchoidea. The subfamily also includes the closely related Huaxiadraco corollatus, a taxon erected in the same revision for specimens formerly assigned to Huaxiapterus. The phylogenetic position of Sinopterus highlights the (Aptian) diversification of toothless pterosaurs in eastern , as evidenced by the Jiufotang Formation's tapejarid assemblage. This Asian radiation parallels contemporaneous tapejarid evolution in , suggesting biogeographic connections or convergent adaptations among edentulous azhdarchoids, potentially facilitating the global spread of specialized skull morphologies in . Recent specimens continue to reinforce these azhdarchoid affinities without shifting the core cladistic relationships.

Valid Species and Synonyms

The genus Sinopterus contains a single valid , S. dongi, recovered from the Jiufotang Formation of the in Province, . Named in 2003 based on IVPP V13363, it encompasses specimens previously referred to other nominal species, which have been synonymized following a 2023 taxonomic revision. These include S. gui (2008, BPV-077), S. jii (2005, originally Huaxiapterus jii, GMN-03-11-001), S. lingyuanensis (2006, JPM-2014-005), S. maooi (2011), and S. atavismus (2019, originally Huaxiapterus atavismus, XHPM 1009), all considered junior synonyms or nomina dubia based on morphometric analyses that account for ontogenetic and intraspecific variation in features like cranial crests. The of S. dongi varies ontogenetically from approximately 1.2 m in juveniles to 2.0–2.3 m in adults. The 2023 revision also addressed taxa formerly in Huaxiapterus: H. corollatus (2006, ZMNH M813) was reassigned to the new Huaxiadraco corollatus, with H. benxiensis (2006, BXGM V0011) as its junior synonym; these form a distinct closely related to but separate from S. dongi. Ontogenetic variation, supported by histological studies of growth, explains much of the morphological diversity previously interpreted as multiple . No new Sinopterus species have been formally proposed since the 2023 revision, maintaining S. dongi as the sole valid . Phylogenetic analyses affirm the of Sinopterus within Tapejaridae, supported by synapomorphies like elongated .

Paleobiology

Ontogeny and Growth

Sinopterus exhibited rapid growth characteristic of pterosaurs, with juveniles displaying unfused skeletal elements such as epiphyses, indicating ongoing . Specimens reach adult sizes, with wingspans up to approximately 2 meters, within 2–3 years through accelerated osteogenesis marked by highly vascularized fibro-lamellar tissue. This fast early growth phase transitions to slower deposition of parallel-fibred near maturity, allowing individuals to achieve substantial size shortly after . Histological analysis of thin-sections from wing bones, such as the and metacarpal IV of a Sinopterus dongi specimen (SDUST-V1014), reveals zonal bone microstructure with a single line of arrested growth (LAG), suggesting the individual was over one year old at death and experienced seasonal interruptions in growth. These LAGs align with the temperate climate of the , where periodic environmental changes likely influenced deposition rates in the highly vascularized cortex. The absence of an external fundamental system further confirms subadult status, with endosteal lamellae indicating stabilization of marrow cavity expansion. Ontogenetic changes in Sinopterus include post-hatching development of the premaxillary crest, which is absent or minimal in small juveniles (humerus length <60 mm) but becomes prominent in larger subadults ( 62–86 mm). Variations in crest size and shape among specimens have led to hypotheses of , though this remains unconfirmed and may instead reflect individual or ontogenetic variation. Compared to other tapejarids like Tapejara, Sinopterus shows similar growth trajectories, with occurring at approximately 80% of maximum adult size. Isolated juvenile fossils suggest precocial independence, enabling early flight and foraging, though direct evidence for is lacking.

Diet and Feeding Ecology

Prior to the 2025 discovery, the diet of Sinopterus was inferred to be omnivorous or primarily insectivorous based on its toothless jaws and elongated , which were thought suitable for grasping small prey or a mixed diet including seeds and fruits, while the prominent cranial crest was interpreted as a display structure unrelated to feeding. A landmark specimen of S. dongi (IVPP V 23388, previously referred to as S. atavismus), a nearly complete juvenile from the Jiufotang Formation of the (~120 million years ago), provided the first direct evidence of herbivory through exceptional preservation of contents. Over 320 phytoliths—microscopic silica bodies from plant tissues—were extracted from the abdominal cavity, representing diverse forms such as polyhedral, fusiform, bilobate, and elongate shapes indicative of consumption from multiple plant groups, including ferns, gymnosperms like cycads, and early angiosperms. Accompanying gastroliths, including crystals up to 3 mm in size concentrated in the posterior region, suggest these stones aided in grinding tough, fibrous vegetation, further supporting a . The absence of any animal remains, such as bones, scales, or insect exoskeletons, in the gut contents rules out carnivory, omnivory, or insectivory, shifting interpretations toward Sinopterus as a primary engaged in folivory—leaf-eating—targeting low-lying in its lacustrine . Unlike coprolites, which are rare and ambiguous in pterosaurs, the articulated preservation of this specimen's gut contents offers unambiguous confirmation of a purely herbivorous diet. The morphology, with its robust, toothless structure similar to that of the related , was likely adapted for cropping and shearing plant material rather than grasping mobile prey. In the diverse , Sinopterus occupied a herbivorous niche alongside early birds such as confuciusornithids, potentially reducing competition through differences in height or preferences, with its diet of nutrient-rich ferns and cycads possibly supporting rapid growth rates observed in tapejarid .

Habitat and Locomotion

lived in the Jiufotang Formation of western Province, northeastern , part of the renowned , which represented a diverse lacustrine-forest dominated by coniferous forests surrounding ancient lakes and rivers. This environment featured a warm with sub-humid conditions, supporting a rich biota that included feathered theropod dinosaurs such as and primitive birds like Confuciusornis, alongside other pterosaurs, fishes, and insects preserved in fine-grained sediments indicative of low-energy depositional settings. As a tapejarid pterosaur, Sinopterus exhibited aerial proficiency suited to its forested-lacustrine , with elongated wings characterized by high aspect ratios (around 6–7 in juveniles, increasing in adults) that facilitated efficient and soaring over short to moderate distances in lowland woodlands. On the ground, it employed a quadrupedal , supported by robust s and reduced hindlimbs that limited terrestrial but may have allowed wading in shallow waters near lakeshores, potentially aiding access to . pneumaticity, evident in hollow limb elements with thin cortical walls, contributed to a lightweight skeleton essential for flight, enabling powered launches from trees or the ground via forelimb thrusts and sustained with ratios of 10–13 in early ontogenetic stages. Paleoecological interactions within the suggest Sinopterus occupied a niche among flying vertebrates, potentially competing for and resources with contemporaneous ornithocheirid pterosaurs like Guidraco, which shared similar coastal-inland habitats.

References

  1. https://www.researchgate.net/publication/226699713_A_new_pterosaur_Pterodactyloidea_Tapejaridae_from_the_Early_Cretaceous_Jiufotang_Formation_of_Western_Liaoning_China_and_its_implications_for_biostratigraphy
  2. https://pmc.ncbi.nlm.nih.gov/articles/PMC8559606/
  3. https://doi.org/10.1016/j.scib.2025.06.040
  4. https://peerj.com/articles/14829/
  5. https://doi.org/10.1007/BF03183326
  6. https://academic.oup.com/nsr/article/1/4/543/1508504
  7. https://onlinelibrary.wiley.com/doi/10.1111/j.1755-6724.2005.tb00911.x
  8. https://www.researchgate.net/publication/229669585_A_New_Species_of_Huaxiapterus_Pterosauria_Pterodactyloidea_from_the_Lower_Cretaceous_of_Western_Liaoning_China_with_Comments_on_the_Systematics_of_Tapejarid_Pterosaurs
  9. https://onlinelibrary.wiley.com/doi/10.1111/j.1755-6724.2006.tb00302.x
  10. https://pmc.ncbi.nlm.nih.gov/articles/PMC9922500/
  11. https://www.scielo.br/j/aabc/a/cS5WgnyGcdsrFhxgFrNhP8v/
  12. https://www.science.org/content/article/pterosaur-died-belly-full-plants-fossil-first
  13. https://pmc.ncbi.nlm.nih.gov/articles/PMC9754175/
  14. https://doi.org/10.1080/08912963.2022.2042811
  15. https://doi.org/10.1038/s41598-022-14111-2
  16. https://doi.org/10.7717/peerj.14829
  17. https://doi.org/10.1111/j.1755-6724.2007.tb00992.x
  18. https://www.nature.com/articles/s41598-022-14111-2
  19. https://biosoil.ru/storage/entities/publication/22442/f834d139-dc9d-425b-81a0-5d912675791a.pdf
  20. http://www.ivpp.cas.cn/sourcedb/zw/rck/jcqn/202209/P020120601559256800085.pdf
  21. https://www.nature.com/articles/s41598-021-92499-z
  22. https://pmc.ncbi.nlm.nih.gov/articles/PMC4016242/
  23. https://www.researchgate.net/publication/227805105_A_New_Ornithocheirid_from_the_Early_Cretaceous_of_Liaoning_Province_China
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