The maximum locomotor capabilities of theropod dinosaurs have long been a subject of considerable scholarly, primarily due to the lack of contemporary species for direct comparison. Biomechanical modeling and the analysis of dinosaur trackways have yielded significant theoretical insights into this area of research. This study investigates the running speed of a mid-sized theropod dinosaur trackway recently identified in the Otog region of Inner Mongolia, and it juxtaposes these findings with other running theropod trackways from diverse various global locations utilizing standardized inference methodologies. The results indicate that the trackmaker was capable of achieving a running speed of 45 or 41±4.9 km/h, thereby establishing it as the fastest-running theropod trackway documented from the Cretaceous period. Additionally, this paper reviews biomechanical investigations concerning the maximum running speeds of theropod dinosaurs and illustrates that the inferred speed of this mid-sized theropod aligns with the predictions of the majority of biomechanical models, thereby providing compelling new evidence to enhance our understanding of the locomotor capabilities of mid-sized theropods.

Pterosaur remains are rare from the lowermost Cretaceous, hampering our understanding of the taxonomic and morphological diversities of pterosaurs during this period. The Lower Cretaceous Tugulu Group in Wuerho, China is renowned for hosting the Wuerho Pterosaurian Fauna (WPF), which has so far yielded numerous fossil remains of two dsungaripterid pterosaurs, Dsungaripterus weii and Noripterus complicidens. Here we report a partial ornithocheiromorph humerus from the WPF, representing a deeply divergent clade from Dsungaripteridae. The scarcity of ornithocheiromorphs from the WPF might be interpreted by niche partitioning with dsungaripterids. Meanwhile, we also report a U-Pb zircon age of 134.27 ± 0.36 Ma dated by LA-ICP-MS for the tuffaceous layer at the uppermost part of the Shengjinkou Formation, confirming the Valanginian age of the WPF presented by a previous study. The Wuerho region is one of the few localities producing abundant pterosaur fossils and the only one with an earliest Cretaceous age. The new finding here also suggests that Ornithocheiromorpha had rapidly diversified and achieved a global distribution during the earliest Cretaceous, presumably through a series of modifications on the locomotor apparatus including the warped deltopectoral crest of the humerus, which might substantially improve their flight efficiency.

The Wukongopteridae is an important pterosaur clade from the Yanliao Biota, combining features of basal and derived pterosaurs. So far, the Wukongopteridae consists of five species divided into three genera: Wukongopterus lii, Darwinopterus modularis, Darwinopterus linglongtaensis, Darwinopterus robustodens, and Kunpengopterus sinensis. Here we report a new species, Darwinopterus camposi sp. nov., based on an almost complete skeleton (IVPP V 17957). The new species is referred to Darwinopterus due to the presence of an elongated posterior region of the skull and the bony premaxillary crest that starts about the anterior margin of the nasoantorbital fenestra. It differs from all other wukongopterids by having the dorsal margin of the premaxillary crest straight, without an extensive dorsal projection and presenting a smooth lateral surface. Furthermore, D. camposi sp. nov. has eighteen and fourteen teeth on each side of the upper and lower jaws, respectively, and the fourth phalanx of the wing finger shorter than the first. IVPP V 17957 shows some fused postcranial bones, like the extensor tendon process to the first wing finger phalanx, but also has unfused premaxilla and frontal, which provides further information about wukongopterid ontogeny.

The Compsognathidae was originally considered an early-diverging clade of coelurosaur theropods. However, recent study suggests that Compsognathidae is not monophyletic. Here, we describe two new compsognathid-like species, Sinosauropteryx lingyuanensis sp. nov. and Huadanosaurus sinensis gen. et sp. nov. from the Lower Cretaceous Yixian Formation of Dawangzhangzi (Lingyuan, Western Liaoning, China). The phylogenetic results indicate that all compsognathid-like theropods from the Early Cretaceous Jehol Biota form a monophyletic group Sinosauropterygidae nested among early-diverging coelurosaurs. Morphological comparison between various species of sinosauropterygids from the Early Cretaceous of Northeast China, combined with the phylogenetic results, suggests that at least three distinct hunting strategies were present among coeval species. The diversification of theropods should be attributed to the landscape caused by the destruction of the North China craton.

Abundant and diverse pterosaur records have been reported from the Jehol Biota since the end of the last century, including an early reported member, Haopterus gracilis, from the Yixian Formation. The referral of Haopterus gracilis has been a subject of debate since its discovery. Various phylogenetic analyses have suggested different positions for Haopterus gracilis, including the sister taxon of the Ornithocheiroidea or placed differently in the Pteranodontoidea. Recent research has proposed that Haopterus gracilis is the sister-taxon of the Lebanese istiodactyliform Mimodactylus libanensis. Here we redescribe the holotype and only specimen of Haopterus gracilis, a relatively complete skeleton of a juvenile individual in detail using Micro-CL scanning. Haopterus possesses several pteranodontoid features including a stout scapula shorter than the coracoid, a sternum with a constriction posterior to the sternocoracoid articulations, and humeri with trapezoidal deltopectoral crests and constricted mid-shafts. A close affinity between Haopterus and istiodactylids has been suggested by several researchers, whereas some features of Haopterus revealed here distinguish Haopterus from istiodactylids, including the low skull with a long rostrum occupying more than half the skull length anterior to the jaw articulation, and a long tooth row with different tooth morphologies. The phylogenetic position of Haopterus was reevaluated by utilizing a more comprehensive character matrix derived from three previous matrices. The new analysis revealed Haopterus in the Pteranodontoidea and, within this clade, it was an istiodactyliform. The study of Haopterus holds potential significance in enhancing our understanding of the morphology and taxonomy of short-toothed pteranodontoids.

The Istiodactyliformes, a group of short-toothed Cretaceous pterosaurs including istiodactylids and their relatives, have mostly been reported from the Jehol Biota of Northeastern China. Recently, a new specimen of Hongshanopterus lacustris, an istiodactyliform from the Lower Cretaceous Jiufotang Formation, has been unveiled. Here we present a detailed description of a new specimen, which comprises most of the skull, the mandible, several cervical vertebrae, and plenty of isolated teeth, providing additional anatomical information of this taxon. We also present the comprehensive redescription of the holotype of Nurhachius ignaciobritoi, the first reported istiodactylid from China. Most of the previously suggested variances between Nurhachius specimens are here found invalid to separate different taxa, but the holotype has a shorter rostrum compared with others. Additional morphological information revealed by the new specimen and redescription further supports the affinity between Hongshanopterus and istiodactylids, and between istiodactylids and other pteranodontoids, but istiodactylids possess narrower cervical vertebrae compared with anhanguerians.

Pterosaur footprints, crucial for understanding their ecological habits, are rare but have been found abundantly in the Lower Cretaceous of the Junggar Basin, China, establishing it as a significant global site for pterosaur tracks. Detailed examination proposed a new ichnospecies, Pteraichnus junggarensis isp. nov., associated with the trackmaker of Dsungaripterus weii based on comparisons with pedal bone fossils. This correlation is groundbreaking, representing the first accurate linking of local pterosaur skeletal fossils with footprints. Additionally, by analyzing 54 specimens, estimates of pterosaur pes length and hip height were derived for the first time, revealing a distinct difference between non-pterodactyloid and pterodactyloid pterosaurs. Linear equations based on footprint dimensions suggest the hip heights range from 0.10-0.20 m for Noripterus complicidens and 0.28-0.47 m for D. weii. Additionally, based on the ratio of stride length to hip height in the trackways, it is inferred that the trackmakers exhibited a typical walking gait.

Among the least studied portion of the pterosaur skeleton is the palate, which tends to be poorly preserved and commonly only visible from one side (the ventral portion). Even in well-preserved specimens, the bones tend to be fused, with the limits of individual palatal elements obscured. To shed new light on this region, we employed advanced X-ray imaging techniques on the non-pterodactyloid Kunpengopterus (Wukongopteridae), and the pterodactyloids Dsungaripterus (Dsungaripteridae), Hongshanopterus (Istiodactylidae), and Hamipterus (Hamipteridae). Our analyses revealed the presence of sutures between palatal bones in Dsungaripterus and Kunpengopterus, which resulted in different interpretations of the relation between palatine, ectopterygoid, and pterygoid, leading to a new identification of the palatal openings. Furthermore, our study shows six main observations such as the variation of the angle between the palatine rami and the variation in the relative sizes of the palatal openings. We also point out that the presence of a maxillopalatine fenestra (previously identified as postpalatine fenestra), is unique within Diapsida. Although much more work needs to be done, we showed that advanced X-ray imaging techniques open a window for understanding pterosaur cranial anatomy and provide a new perspective for investigating the evolutionary history of these flying reptiles. A study on the palatal region of pterosaurs suggests different bone interpretations and new identification of the palatal openings, pointing out that the maxillopalatine fenestra in pterosaurs is unique within Diapsida.

Ornithocheiroidea was a globally diverse group of pterosaurs during the Cretaceous. However, well-documented ornithocheiroids are highly derived, hampering our understanding on the morphological evolution of this clade. Dsungaripterus weii Young, 1964 from the Lower Cretaceous Tugulu Group (Valanginian) of the Junggar Basin is an iconic early member of Ornithocheiroidea. Dsungaripterus is known from numerous three-dimensionally preserved specimens, ranging from isolated bones to partially articulated individuals. Here we provide a comprehensive description of the postcranium of Dsungaripterus. We find that Dsungaripterus has many autapomorphies in the postcranial skeleton parallelling its unique skull, including the asynchronous fusion between the sacrum and pelvis and a posterodorsal fossa of the humerus with a paper-thin bone wall. Dsungaripterus also displays some plesiomorphic features of Ornithoecheiroidea, for example, limb bones with relatively thick bone walls, variably reduced pneumatic features in cervical vertebrae and appendicular skeletons, absence of spinoprezygapophyseal and spinopostzygapophyseal ridges in middle-series cervical vertebrae, at least one metacarpal articulating with the distal syncarpal, and a distally displaced adductor ridge on the femur. Additionally, Dsungaripterus possesses some unexpected features possibly convergent with other members of Ornithocheiroidea. Although the postcranial skeletons of Dsungaripterus are represented by osteologically mature specimens, notable morphological variation is present. Functional reconstructions of several aspects of the postcranial skeleton of Dsungaripterus are elucidated, including the arrangement of the metacarpophalangeal region during terrestrial locomotion. Niche partitioning between the two dsungaripterids from the Tugulu Group of Wuerho, Dsungaripterus and Noripterus, is supported by their distinct dentitions, neck morphology, and limb proportions.

Recently a new genus and species of istiodactylid pterosaur was named by Hone et al. (2020) based on a very complete skeleton from northern China. Although the possibility that the specimen was a chimera was raised by the authors themselves, checks of the specimen revealed no tampering with the specimen and it was considered genuine. The animal was posited as an unusual member of the clade, but characters from both the head and body supported the general identification as an istiodactylid. However, recent damage to the specimen because of flooding in the museum in which it is housed, has revealed that the rostrum and mandible were in fact added to the back of the skull and rest of the body of a second pterosaur. Here we correct the record on this specimen and suggest that Luchibang xingzhe as a taxon is still valid.

The Tapejaridae is an exquisite toothless pterodactyloid clade of pterosaurs that flourished in the Jehol Biota with well-developed premaxillary and dentary crests, large nasoantorbital fenestra and downward rostrum. Since Sinopterus dongi has been reported from the Jiufotang Formation, most of the Chinese tapejarids were discovered from this geological unity. Eopteranodon lii, the first tapejarid from the Yixian Formation, was formerly referred to the Pteranodontidae and is now assigned to the Tapejaridae. Here, Eopteranodon yixianensis sp. nov. is reported from this latter formation as differing from all other known tapejarids by largest rostral value (10.88); the nasoantorbital fenestra is not as long as that of other tapejarids (accounting for 35% of the skull length). Furthermore, the skull's length/height ratio is ∼5.67; the lower bony crest occupies ∼42% of the total mandibular length; the humerus and the fourth wing phalanx length ratio is ∼2.17 and the downturn rostral angle is ∼17°. New data on the evolution (morphology and geographical origin) of the group is also provided.

The toothed members of Pterosauria display an extremely wide range of tooth morphologies that supported a variety of feeding habits. Histological studies on the teeth of different pterosaur clades are potentially valuable in understanding the development of their tooth diversity. In this study, we used histological sections and scanning electron microscopy to describe and interpret the tooth microstructure of Hamipterus (Pterodactyloidea). Our analysis is based on seven teeth of Hamipterus (six isolated and one from a skull) from the Lower Cretaceous collected in Hami, China. Our results show that the enamel on the tooth crown is thin (~25 μm) in Hamipterus and covers only approximately half of the tooth crown. This thin enamel of the Hamipterus tooth makes it vulnerable and often becomes damaged during taphonomic and diagenetic processes. The radicular pulp inside the conical-shaped root shows a spindle space with a small foramen at the bottom, while the coronal pulp shows a small tunnel (100-140 μm in diameter). We estimate that the small teeth of Hamipterus likely took approximately 80 days to form. Furthermore, the tooth has Andresen lines, which represent 7-15 days period. For stable articulation of the tooth in the alveolus, the thick cellular cementum is concentrated on the lingual side of the root. The acellular cementum (~40 μm thick) layer runs from the root to the partial tooth crown.

As one of the mysteries volant vertebrates, pterosaurs were completely extinct in the K-Pg extinction event, which hampered our understanding of their flight. Recent studies on pterosaur flight usually use birds as analogies, since their shoulder girdle share many features. However, it was also proposed that these two groups may differ in some critical flight mechanisms, such as the primary muscles for the upstroke of the wings. Here, we describe and characterize the detail features of the pectoral girdle morphology and histology in Hamipterus from the Early Cretaceous of Northwest China for the first time. Our research reveals that the scapula and coracoid of Hamipterus form a synostosis joint, representing a distinct pectoral girdle adaption during pterosaur flight evolution, different from that of birds. The residual of the articular cartilage of the glenoid fossa supports the potential for cartilage tissue preservation in this location. The morphology of the acrocoracoid process of Hamipterus indicates it may work as a pulley for M. supracoracoideus as the main power of flight upstroke resembles that of birds. But the saddle type of the shoulder joint of the pterosaur may limit the rotation of the humerus head, suggesting a particular mechanism to control the angle of attack unlike birds. The presence of both the similarity and differences between the flight apparatus of pterosaurs and birds are highlighted in our research, which may be related to the flight mechanism and forelimb functional adaption. The distinctive feature of the flight apparatus of pterosaur should be treated with caution in future research, to better understand the life of this unique extinct volant vertebrate.

The Chaoyangopteridae is a clade of azhdarchoid pterosaurs that stands out in China, particularly in the Jehol Biota, as a Cretaceous group of medium-sized and high-crested pterosaurs. Herein, we describe a new species, Meilifeilong youhao gen. et sp. nov., based on two specimens, one tentatively referred to this taxon. This new species represents the most complete and well-preserved chaoyangopterid recorded to date. Along with a set of characters (low premaxillary crest above the nasoantorbital fenestra extending posteriorly, posterior premaxillary process arched and curving posteriorly, a slightly convex sternal articulation surface of coracoid, and a fibular shaft close to proximal articulation strongly arched posteriorly), this species also provides new information both on the unknown palatal region of this clade, and on the rarely preserved (in place) ear portion with stapes. Moreover, M. youhao sheds light on paleoecological aspects, while also giving new information about the taxonomic diversity of this peculiar group of Jiufotang pterosaurs.

Pterosaurs, an extinct group that ruled Mesozoic skies, flourished during the Cretaceous. Knowledge about their radiation largely comes from several Lagerstätten, especially in China and Brazil. Despite their abundance and diversity in other continents during the latest Early Cretaceous, pterosaurs from East Asia in this period are extremely rare, rendering their evolutionary history still unexplored. Here we redescribe pterosaur remains from the Albian Doushan Formation of Laiyang, Shandong Province, China, to refine such gap. The most completely preserved element, a femur, can be assigned to the Azhdarchoidea, a clade achieving global distribution by the end of the Early Cretaceous, based on combination of derived and plesiomorphic characters including the triangular and anteriorly curved 'greater trochanter', a deep 'intertrochanteric fossa' with a pneumatic foramen, presence of a bulbous ridge and a pulley-like lateral condyle. Moreover, osteological correlates for thigh muscles on the femur are identified here using the Extant Phylogenetic Bracket method. The general pattern of these osteological correlates is conservative when compared with other basal ornithodirans. The pterosaurian 'greater trochanter' is not homologous to the lesser trochanter in other archosaurs as previously suggested. M. femorotibialis internus is subdivided into two parts in some pterosaurs, probably representing a derived trait.

The Huajiying Formation (135.4–128.7 Ma) of the northern Hebei represents the early stage of the Early Cretaceous Jehol Biota in China, yielding many kinds of vertebrates. The only known pterosaur specimen was incomplete and assigned to the Ornithocheiroidea. Here we report a more complete pterosaur specimen, assigned to the Ctenochasmatidae. A new taxon is established on two autapomorphies: a large pneumatic foramen present on the ventral surface of the proximal end of the first wing phalanx; and coracoid lacking an expansion at its contact with the scapula, as well as the following combination of characteristics: subsquare sternal plate; coracoid having an extremely concave articulation with a posterior expansion; humerus without a tubercle on the proximal margin between the deltopectoral crest and the head; humerus slightly longer than the wing metacarpal; and the first and third wing phalanges equal in length. The relative thicknesses of bone walls are investigated among pterosaurs in three ways. The overall distribution of R/t ratios shows that most non-pterodactyloids, archaeopterodactyloids, and dsungaripterids have smaller R/t ratios than other groups. Relatively thick bone walls are not unique for the Dsungaripteridae as previously thought, and the humerus and radius of dsungaripterids have thinner walls than other bones. The feature of small R/t ratios is plesiomorphic and the thin-walled humerus and radius of dsungaripterids were evolved to meet the need of the flight, not for frequent take-off and landing as previously thought.

Laiyangosaurus youngi was erected as a saurolophine hadrosaurid on the basis of several cranial elements from the Jingangkou Formation, Wangshi Group, Upper Cretaceous of Laiyang, Shandong, China. The postcranial elements of this taxon are described in detail here, providing additional postcranial characteristics to L. youngi. The phylogenetic analysis included postcranial elements of L. youngi, indicating that L. youngi still lies in the Edmontosaurini clade and no more supplement of postcranial autapomorphy. However, three new postcranial autapomorphies can help distinguish L. youngi from other members of Edmontosaurini: a poorly expanded deltopectoral crest of the humerus, a brevis shelf at the base of the postacetabular process of the ilium, and a well-defined medioventral ridge on the medial side of the postacetabular process. This study is to increase our knowledge on the anatomy and phylogeny of hadrosaurids of Edmontosaurini and provide new valuable evidence for discussing on the taxonomic position and validity of hadrosauroids in the Laiyang Hadrosauroid Fauna.