Titanoceratops ouranos, a giant horned dinosaur from the late Campanian of New Mexico

At the end of the Cretaceous, 65.5 million years ago, the giant ceratopsids Triceratops and Torosaurus dominated North America’s dinosaur fauna. The origins of these giant ceratopsids, the Triceratopsini, are poorly understood. This paper describes Titanoceratops ouranos, a giant ceratopsid from the late Campanian (73-74 Ma) of New Mexico, and the earliest known triceratopsin. The holotype was previously interpreted as an aberrant and exceptionally large specimen of Pentaceratops sternbergi, but the animal does not show the diagnostic features of Pentaceratops. Instead, cladistic analysis shows that Titanoceratops is the sister taxon of a clade formed by Eotriceratops, Triceratops, and Torosaurus. With an estimated mass of 6.5 tons, Titanoceratops is among the largest dinosaurs known from the Campanian of North America, and rivaled Triceratops in size. The recognition of Titanoceratops suggests that giant chasmosaurines evolved once, among the Triceratopsini, and that the group evolved large size five million years earlier than previously thought. The giant horned dinosaurs probably originated in the southern part of the North American continent during the Campanian but only became widespread during the Maastrichtian.     

A juvenile Edmontosaurus from the late Maastrichtian (Cretaceous) of North America: Implications for ontogeny and phylogenetic inference in saurolophine dinosaurs

The anatomy of an articulated juvenile specimen of the saurolophine hadrosaurid dinosaur Edmontosaurus annectens, LACM 23504, is described in detail. This individual consists of a partial skull and nearly complete articulated postcranium, collected from upper Maastrichtian strata of the Hell Creek Formation of Montana, USA. This study aims to help understand the ontogenetic morphological changes occurring in the cranium and postcranium of saurolophine hadrosaurids using E. annectens as a case study. Emphasis is placed on those morphological attributes that are ontogenetically variable via comparative osteology between the juvenile and the available adult specimens. It is observed that much of the cranial ontogenetic variation relates to the elongation of the skull and mandible. In the postcranium, most of the ontogenetic variation concentrates in the pectoral and pelvic girdles and the stylopodia. Not all the identified patterns of ontogenetic variation may be generalized to all hadrosaurids. The impact of ontogenetic variation on phylogenetically informative characters of saurolophine hadrosaurids is evaluated. It is concluded that, at least for Edmontosaurus annectens (and perhaps other saurolophine hadrosaurids), most characters used in phylogenetic inference of these animals are not affected by ontogeny. Thus, juvenile specimens are still a source of substantial character data suitable for use in phylogenetic analyses of saurolophine relationships. Nevertheless, it is recommended that ontogenetically variable characters are left as missing data in a character–taxon matrix when only juvenile material is available for a given saurolophine taxon. Scoring those characters based solely on juveniles is likely to decrease the accuracy of the phylogenetic inference.     

Juvenile specimens of Pinacosaurus grangeri Gilmore, 1933 (Ornithischia: Ankylosauria) from the Late Cretaceous of China, with comments on the specific taxonomy of Pinacosaurus

Four juvenile specimens referable to Pinacosaurus grangeri (Ankylosauria: Dinosauria) are described from the Campanian (Upper Cretaceous) locality Bayan Mandahu in northern Inner Mongolia Autonomous Region (People’s Republic of China). All the specimens preserve the skulls as well as, in some cases, mandibles, postcrania, and osteoderm. They are not taphonomically deformed by expanding matrix distortion, unlike many Gobi specimens, including the holotype of P. grangeri. Bayan Mandahu is also the type locality for Pinacosaurus mephistocephalus. The proximity in space and time of these two closely related species warrants a generic and specific revision for Pinacosaurus. The distinction of the two species is based on characters of the squamosal dermal elaborations, cranial roof posterior to the orbits, premaxillary notch, and distal margin of the ilium. Although a relatively well-represented ankylosaur taxon, the phylogenetic position of Pinacosaurus has not been unequivocally resolved. A new analysis recovers Pinacosaurus as the most basal member of the Ankylosaurinae.     

Dinosaur eggshell assemblage from Japan reveals unknown diversity of small theropods

The Lower Cretaceous (Albian) Sasayama Group in the Hyogo Prefecture of southwestern Japan has yielded various vertebrate fossils, including skeletal remains of dinosaurs, anurans, lizards, and mammals, and recently eggshell fragments. Here we report on numerous fossil eggshells from the bone-bearing Kamitaki locality in Tamba City, which represents a diverse dinosaur eggshell assemblage. Of the more than 90 eggshell fragments recovered, five different types were identified, including eggshells that likely belong to a variety of theropods (Nipponoolithus ramosus oogen. et oosp. nov., Elongatoolithus sp., Prismatoolithus sp., and Prismatoolithidae indet.) and at least one ornithopod (Spheroolithus sp.). All eggshells are relatively thin, and a new derived estimation method correlating egg mass with eggshell thickness indicates that they are among the smallest (28–135 g) theropod eggs known, likely laid by small bodied forms. The eggshell assemblage from this locality suggests that a diverse small dinosaur fauna, consisting primarily of theropods, nested in the region, a diversity yet to be evidenced from skeletal remains in Japan.     

Pachycephalosaurs (Dinosauria: Ornithischia) from the Upper Cretaceous (upper Campanian) of New Mexico: A reassessment of Stegoceras novomexicanum

Pachycephalosaurs, a group of ornithischian dinosaurs with distinctive cranial ornamentation and skull domes, underwent dramatic changes in cranial morphology during ontogeny. This has caused debate about whether some specimens belong to juveniles or adults, which impacts studies of pachycephalosaur phylogeny and evolution. One such debate concerns a small skull roof specimen from the Campanian (Upper Cretaceous) of New Mexico, NMMNH P-33898, which was originally described as an indeterminate juvenile but later regarded as a mature adult and erected as the holotype of a new small-bodied species, Stegoceras novomexicanum. We restudied NMMNH P-33898 using computed tomography scanning, morphometric and phylogenetic analyses, and comparisons to growth series of other pachycephalosaurs (Stegoceras validum, Pachycephalosaurus wyomingensis). We conclude that two purported paratype specimens of Stegoceras novomexicanum cannot be referred to the same taxon as the holotype, that the holotype and controversial paratypes all belong to immature specimens and not aberrant small-bodied adults, but that current evidence cannot clearly determine whether NMMNH P-33898 is a juvenile belonging to its own diagnostic species (S. novomexicanum) or is a juvenile of Stegoceras validum, Sphaerotholus goodwini, or another known taxon. We review the pachycephalosaur record of New Mexico and demonstrate that pachycephalosaurs were important components of dinosaur faunas in the southern part of Western North America during the ∼15 million years before the end-Cretaceous extinction, just as they were in roughly contemporaneous northern localities.     

The first record of a neonatal ornithopod dinosaur from Gondwana

Discrete post-embryonic teeth and bone fragments have been recovered from the matrix with the holotype skeleton (MPM‐10001) of the ornithopod dinosaur, Talenkauen santacrucensis Novas et al., 2004 (Upper Cretaceous, Argentina). The minute tooth crowns are 1 mm apicobasally tall and 1.7 mm mesodistally wide. The crowns are symmetrical and have a centrally located primary ridge on the lingual surface. Secondary ridges lead to five marginal denticles on both teeth. The tooth morphology is consistent with dentary teeth in euiguanodontids. There is no evidence of transport, suggesting that the material is autochthonous with respect to the adult body block of T. santacrucensis (MPM‐10001). Steeply inclined wear facets on the lingual surface and associated microstriae support the conclusion that the minute teeth were from a post-embryonic euiguanodontid dinosaur rather than early stage replacement teeth. The morphology, size, and wear of the teeth and small bone fragments found in the body block of MPM‐10001 suggest that this material belongs to a neonatal T. santacrucensis. This is the first record of neonatal ornithopod remains from Gondwana.     

Dentary groove morphology does not distinguish ‘Nanotyrannus’ as a valid taxon of tyrannosauroid dinosaur. Comment on: “Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988”

There has been considerable debate about whether the controversial tyrannosauroid dinosaur ‘Nanotyrannus lancensis’ from the uppermost Cretaceous of North America is a valid taxon or a juvenile of the contemporaneous Tyrannosaurus rex. In a recent Cretaceous Research article, Schmerge and Rothschild (2016) brought a new piece of evidence to this discussion: the morphology of the dentary groove, a depression on the lateral surface of the dentary that houses neurovascular foramina. They argued that an alleged ‘Nanotyrannus’ specimen, which possesses a groove, cannot be referable to Tyrannosaurus rex, which they considered as lacking the groove, and they hypothesized that ‘Nanotyrannus’ is closely related to albertosaurine tyrannosauroids, which also are said to possess the groove. However, we show that the groove is a widespread feature of tyrannosauroids that is present in T. rex and many other specimens, and that it is an ontogenetically variable feature that changes from a sharp, deeply-impressed groove to a shallower sulcus as an individual matures. As a result, the presence or absence of a dentary groove does not clarify the validity of ‘Nanotyrannus’ or its phylogenetic position among tyrannosauroids. We consider it most parsimonious that ‘Nanotyrannus’ specimens belong to juvenile T. rex.     

Dinosaur eggshells from the Santonian Milk River Formation of Alberta,Canada

The North American fossil record of dinosaur eggshells for the Cretaceous is primarily restricted to formations of the middle (Albian–Cenomanian) and uppermost (Campanian–Maastrichtian) stages, with a large gap in the record for intermediate stages. Here we describe a dinosaur eggshell assemblage from a formation that represents an intermediate and poorly fossiliferous stage of the Upper Cretaceous, the Santonian Milk River Formation of southern Alberta, Canada. The Milk River eggshell assemblage contains five eggshell taxa: Continuoolithus, Porituberoolithus, Prismatoolithus, Spheroolithus, and Triprismatoolithus. These ootaxa are most similar to those reported from younger Campanian–Maastrichtian formations of the northern Western Interior than they are to ootaxa reported from older middle Cretaceous formations (i.e., predominantly Macroelongatoolithus). Characteristics of the Milk River ootaxa indicate that they are ascribable to at least one ornithopod and four small theropod species. The taxonomic affinity of the eggshell assemblage is consistent with the dinosaur fauna known based on isolated teeth and fragmentary skeletal remains from the formation, although most ornithischians and large theropods are not represented by eggshell. Relative to the Milk River Formation eggshell, similar oospecies occurring in younger Cretaceous deposits tend to be somewhat thicker, which may reflect an increase in body size of various dinosaur lineages during the Late Cretaceous.     

A new ornithomimid dinosaur with North American affinities from the Late Cretaceous Qiupa Formation in Henan Province of China

A partial skeleton of the ornithomimid dinosaur, discovered from the Late Cretaceous Qiupa Formation of Luanchuan County, Tantou Basin, Henan Province, China, is described here and assigned to a new genus and species, Qiupalong henanensis, with unique features (a notch on the lateral surface of the lateral posterior process of the proximal end of tibia and a small pit at the contact between astragalus and calcaneum). A phylogenetic analysis in this study suggests that it is a derived ornithomimid and form a monophyly with North American ornithomimids (Struthiomimus altus and Ornithomimus edmontonicus), sharing two characters (straight pubic shaft and large acute angle between pubic shaft and boot). Some characters (small anterior process of the pubic boot and curved pedal unguals) are seen in basal ornithomimosaurs as well, but these features in Q. henanensis are reversal. Qiupalong is the first definitive ornithomimid from outside of the Gobi Desert and is the southern-most occurrence of Late Cretaceous ornithomimid from eastern Asia, demonstrating southern extension of ornithomimid distribution in Asia.     

Perinates of a new species of Iguanodon (Ornithischia: Ornithopoda) from the lower Barremian of Galve (Teruel,Spain)

Although Iguanodon is one of the most abundant and well-known of Europe's dinosaur genera, fossils of young specimens are very rare. Indeed, the fossil record contains very few examples of the young of any non-hadrosaurid iguanodontian. Here we report the discovery of 13 Iguanodon perinates from the Lower Cretaceous of Galve (Teruel, Spain). The characteristics of an adult and juvenile found nearby show these perinates to belong to a new species: Iguanodon galvensis sp. nov. The histological and osteological features of these young animals indicate them to have been in their first year of life. The taphonomic features of their remains, plus the finding of clearly embryonic vertebrae alongside them, suggest the perinates of this species remained in the vicinity of their nests for some time, possibly congregating in nursery areas.     

A snapshot into the terrestrial ecosystem of an exceptionally well-preserved dinosaur (Hadrosauridae) from the Upper Cretaceous of North Dakota,USA

A palynological investigation of sedimentary rocks enclosing an exceptionally well-preserved fossil dinosaur (Hadrosauridae) discovered in the upper part of the Hell Creek Formation in south western North Dakota was conducted in order to document the immediate paleoenvironment of this dinosaur. The specimen, an Edmontosaurus annectens is remarkable in having exceptional three-dimensional preservation of soft tissue around the skeleton, indicating rapid burial. A well-preserved palynological assemblage dominated by fern and bryophyte spores, with lesser gymnosperm and angiosperm pollen was recovered. Sparse fresh-water algae and marine dinoflagellate cysts were also recorded. The palynofacies is dominated by wood fragments, including charcoal, with little amorphous organic matter. The presence of some typical pollen taxa of the Wodehouseia spinata Assemblage Zone including Striatellipollis striatellus, Tricolpites microreticulatus, Leptopecopites pocockii as well as a diverse suite of Aquilapollenites, is fully consistent with a Late Cretaceous (late Maastrichtian) age. The palynoflora indicates a local vegetation composed of a canopy of conifers dominated by Pinaceae and a minor sub-canopy of Taxodium and cycads, as well as an understory of hydrophilous ferns, mosses and herbaceous angiosperms, indicative of a warm and humid climate – an environment where this specific hadrosaur roamed over 66 million years ago.     

中国东部晚白垩世恐龙化石集群埋藏特征及国内外对比

运用埋藏学与沉积地质学的研究方法与手段,对中国东部晚白垩世具有恐龙化石集群埋藏盆地中恐龙骨骼化石的埋藏地层层序与年代、埋藏骨骼化石特征、骨骼化石埋藏类型及其埋藏成因等进行了分析与总结,并将其产出时代、埋藏相、埋藏特征与国外进行了对比研究。研究认为:中国东部与国外相比,虽然化石产出的具体时期有所差异,但从恐龙种群、埋藏相及沉积地层学等方面均具有相似性,反映了晚白垩世全球古环境、古生态及古气候的相似性。(1)中国晚白垩世恐龙骨骼化石埋藏事件可分为早期与晚期2个阶段:早期的Cenomanian期与晚期的Santonian-Maastrichtian期。而国外晚白垩世恐龙骨骼化石埋藏事件只发生在晚期,在美洲及蒙古国发生在Campanian晚期,在欧洲则为Campanian-Maastrichtian期的过渡时期及Maastrichtian期。(2)中国埋藏骨骼化石种属以鸟脚类鸭嘴龙科与兽脚类恐龙为主,它们埋藏于紫红色地层中,埋藏环境主要为冲积扇与河流环境;美洲以鸭嘴龙科为主,欧洲与蒙古国的种群各地不相同,都埋藏于紫红色岩石地层中,埋藏环境主要为河流—泛滥平原。骨骼在不同沉积相组合地层中埋藏学特征各异,与古地理、古生态及古环境密切相关。(3)结合盆地中的化石埋藏学特征与盆地演化特征,总结了恐龙化石埋藏类型主要有原地埋藏与异地埋藏,盆地古地理格局变动、火山活动、古温度升高及古地震等事件的综合作用是可能的埋藏成因,并提出了恐龙化石的埋藏模式。此研究为揭示中国东部乃至全球晚白垩世的古地理、古气候及古生态环境及恐龙灭绝原因的探讨提供了新的材料与证据。     

Palynoassemblages associated with a theropod dinosaur from the Snow Hill Island Formation (lower Maastrichtian) at the Naze,James Ross Island,Antarctica

The Cape Lamb Member of the Snow Hill Island Formation at The Naze on the northern margin of James Ross Island, east of the Antarctic Peninsula, yielded a theropod dinosaur recovered near the middle of a 90 m thick section that begins at sea level, ends below a basalt sill, and is composed of interbedded green–gray massive and laminated fine-grained sandstones and mudstones. Sixteen palynoassemblages were recovered from this section, which yielded moderately diverse assemblages with a total of 100 relatively well-preserved species. The principal terrestrial groups (32%) are represented by lycophytes (8 species), pteridophytes (15 species), gymnosperms (13 species), angiosperms (21 species) and freshwater chlorococcaleans (3 species). Marine palynomorphs (68%) belong to dinoflagellates (61 species), chlorococcaleans (6 species), and one acritarch. The vertical distribution of selected species allows the distinction of two informal assemblages, the lower Odontochitina porifera assemblage from the base to its disappearance in the lower part of the section, and the remaining section characterized by the Batiacasphaera grandis assemblage. The global stratigraphic ranges of selected palynomorphs suggest an early Maastrichtian age for this section and the entombed dinosaur that is also supported by the presence of the ammonoid Kitchinites darwinii. These assemblages share many species with latest Campanian–early Maastrichtian palynofloras from Vega and Humps Islands, New Zealand, and elsewhere in the Southern Ocean, establishing a good correlation among them. The dominance or frequent presence of dinoflagellates throughout the section supports the general interpretation of a shelf marine depocenter. The consistent presence of terrestrial palynomorphs suggests contributions from littoral/inland environments.     

A new Brachiosauridae Sauropod dinosaur from the lower Cretaceous of Europe (Soria Province,Spain)

A new dinosaur sauropod from the Golmayo Formation (upper Hauterivian-lower Barremian) in Soria province (Spain) is described as Soriatitan golmayensis gen. et sp. nov. The new material consists of one tooth, three dorsal vertebrae with ribs, a partial sacrum, five caudal centra, two caudal vertebral spines, one chevron, a humerus, an ulna, a radius, two partial ilia, two ischia, a fragment of pubis, and a partial femur. Cladistic analysis identified the material as belonging to Brachiosaruidae within Titanosauriformes. Sauropod material from the Golmayo Formation shares a diagnostic feature with Abydosaurus, Cedarosaurus, Tastavinsaurus and Venenosaurus including anteriorly deflected anterior–middle caudal neural spines and with Cedarosaurus a proximodistally straight lateral margin between the proximal head and the shaft of the humerus. Eight characters are potential autapomorphies in the sauropod from Spain, including the presence of a large rectangular ventral ridge below the preacetabular process of the ilium, the same length of the pubic and ischiadic blades in the ischium, and two lateral ridges in the lateral area of the deltopectoral crest of the humerus. The presence of Early Cretaceous brachiosarids in both, North America and Europe, give support to the hypothesis of a connection between the tectonic plates of these continents at some point during the Early Cretaceous.     

The Bristol Dinosaur Project

Dinosaurs have been fascinating to the widest public since the 1840s, and that interest has grown step-wise ever since. Public interest has been harnessed over the years especially by museums in blockbuster exhibitions, and in the form of best-selling books and films. Here we describe a major educational initiative, the Bristol Dinosaur Project, which has run for ten years and has reached tens of thousands of children and adults, supported by substantial funding. The Bristol Dinosaur Project focuses on the fourth dinosaur ever named in the world, Thecodontosaurus, discovered in Bristol in 1834, and named in 1836. The dinosaur is not in itself spectacular, being only 1–2 m long, but its evolutionary role as one of the first plant-eating dinosaurs in the world justifies our current research, and provides a strong theme for the public presentation. Further, the fact that the dinosaur is found as disarticulated bones in ancient tropical cave systems, allows us to develop numerous key themes with all age groups: the geological time scale, continental drift, reconstruction of ancient environments, modern landscape analogues, the rock cycle, evolution, biomechanics, and critical assessment of geological and palaeontological evidence. These themes are of key importance for socio-economic and intellectual reasons, and yet are often poorly understood.     

A new ornithopod (Dinosauria; Ornithischia) from Antarctica

A new ornithopod dinosaur from Antarctica, Trinisaura santamartaensis n. gen. et n. sp. is diagnosed by a unique combination of characters that includes a scapula with a spike-like acromial process with a strong and sharp lateral crest and longer than other ornithopods, a humerus with a rudimentary deltopectoral crest represented as a thickening on the anterolateral margin of the humerus, and shaft strongly bowed laterally, and an ischium gently curved along its entire length. The holotype specimen comprises vertebral and appendicular elements. The presence of axially elongate distal caudal vertebrae, pubis with long prepubic and postpubic processes, as well as a femur with a distinct anterior trochanter, pendant 4th trochanter and shallow anterior intercondylar groove constitute a combination of characters present in the Late Cretaceous Patagonian Gasparinisaura, Anabisetia and Talenkahuen. The materials were found on the surface enclosed in a hard sandstone concretion collected near the Santa Marta Cove, James Ross Island, from the lower levels of the Snow Hill Island Formation (Campanian). This is the first ornithopod taxon identified from this unit, and the second ornithischian dinosaur, after the ankylosaur Antarctopelta oliveroi. However, other ornithopod reports from nearby localities of James Ross and Vega islands in outcrops of the overlying Lopez de Bertodano Formation suggest that this clade was widely represented in the Campanian and Maastrichtian of the James Ross Basin, Antarctic continent.     

Kazaklambia convincens comb. nov., a primitive juvenile lambeosaurine from the Santonian of Kazakhstan

The holotype of ‘Procheneosaurus’ convincens, a juvenile lambeosaurine, is the most complete hadrosaurid known from Kazakhstan. North American species of Procheneosaurus are considered juveniles of Corythosaurus, Hypacrosaurus, and Lambeosaurus, rendering the generic name unusable. A replacement name, Kazaklambia convincens comb. nov., is herein proposed as this specimen is morphologically distinct from other Eurasian taxa and known juvenile lambeosaurines at a similar ontogenetic stage in having a prefrontal process of the postorbital with a dorsal thickening forming a dome lateral to the frontal dome, doming of the nasal anterodorsal to the orbit, and a frontal length/width ratio <1. The juvenile status of Kazaklambia makes phylogenetic placement difficult; however, morphometric and morphological information (particularly in relation to the hollow cranial crest and the length of the frontal) suggest a close affiliation with the basal lambeosaurines Amurosaurus and Tsintaosaurus, and support the hypothesis for an Asian origin for Lambeosaurinae.     

A new sauropod dinosaur (Dinosauria,Sauropoda) from the late Early Cretaceous of the Ruyang Basin (central China)

A new long-necked sauropod dinosaur, Yunmenglong ruyangensis gen. et sp. nov., is erected on the basis of an incomplete skeleton from the late Early Cretaceous Haoling Formation of the Ruyang Basin, Henan Province. The characters of the anterior cervical vertebrae, the shape of the neural canal of the dorsal vertebra and the ball-shaped distal end of the neural spine of caudal vertebrae with coarse surfaces differ from other long-necked sauropod dinosaurs. The new genus has characters in common with both Euhelopus and Erketu; it represents the first long-necked sauropod dinosaur recorded from central China to date. The rod-like, well-developed epipophyses and the pleurocoels on the cervical vertebrae indicate that it may be close to Euhelopus, an observation also confirmed by a phylogenetic analysis, which shows that Erketu, Yunmenglong and Qiaowanlong form a clade, and are more derived than Euhelopus.     

The first lizard fossil (Reptilia: Squamata) from the Mesozoic of South Korea

Upper Cretaceous deposits in Mongolia, Chinese Inner Mongolia, and, more recently, southern China, have yielded individually rich and taxonomically diverser lizard assemblages. Here we describe the remains of a new terrestrial lizard, Asprosaurus bibongriensis gen. et sp. nov., from the Upper Cretaceous of South Korea. It represents the first record of a Mesozoic lizard from the Korean Peninsula and, although incomplete, is exceptional in its very large size. Characters of the mandible support attribution to crown-group Anguimorpha, with the closest similarities being to monstersaurs, the group represented today by the venomous North American Beaded lizard and Gila monster, genus Heloderma. This group is well-represented in the Upper Cretaceous fossil record in of eastern Asia, and the remains of large monstersaurs have been recovered from several dinosaur egg localities, suggesting dietary preferences similar to those of the living genus. The new Korean lizard, recovered from the Boseong Bibong-ri Dinosaur Egg Site, fits the same pattern.     

The longest theropod trackway from East Asia,and a diverse sauropod-, theropod-, and ornithopod-track assemblage from the Lower Cretaceous Jiaguan Formation,southwest China

Here we report a large dinosaur tracksite from an extensive fluvial sandstone surface in the Lower Cretaceous Jiaguan Formation of Sichuan Province, China. The site contains over 250 individual tracks comprising at least 18 recognizable trackways, including the longest theropod trackway (cf. Eubrontes) known from China. This exceptional theropod trackway consists of 81 successive footprints covering a distance of 69 m. The tracks are well-preserved and are expressed both as true tracks on the main “upper” surface and as transmitted undertracks on a locally exposed “lower” bed. Also recorded are six other theropod trackways, including small Grallator-like ichnites, eight sauropod trackways (cf. Brontopodus), and three small ornithopod (cf. Ornithopodichnus) trackways with a parallel orientation, which may indicate gregarious behavior. Several trackways of a larger theropod trackmaker show pes imprints with elongated traces of the metatarsals, suggesting extramorphological (substrate-controlled) variation and/or plantigrade posture, which is here interpreted as indicating a change in gait assumed in response to deep and soft sediment. The assemblage indicates a diverse dinosaur fauna in the Lower Cretaceous Sichuan Basin with variously sized theropods, sauropods, and ornithopods. The late occurrence of footprints of the Grallator-Eubrontes plexus in Lower Cretaceous strata is further evidence of the extended stratigraphic range of this morphotype and the distinct palaeobiogeographic distribution of these trackmakers in East Asia.