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A New Ceratopsian from the Upper Jurassic Houcheng Formation of Hebei, China
Abstract
Abstract A new ceratopsian taxon Xuanhuaceratops niei gen. et sp. nov. is erected based on four fragmentary specimens collected from the Late Jurassic Houcheng Formation, Hebei Province, China. Xuanhuaceratops shares a number of derived features with, and is closely related to, another probable Late Juarassic ceratopsian Chaoyangsaurus youngi, from which it differs in only possessing a single premaxillary tooth as well as in details of quadrate and scapular morphology. We hypothesize that these two taxa represent a primitive lineage of Ceratopsia that is basal to the psittacosaurid-neoceratopsian diversity, and propose the name Chaoyangsauridae for it.
... The pattern of progressively smaller diameter sacral centra with increasing sacral vertebral number in the series is also seen in Protoceratops (Brown and Schlaikjer, 1940). The sacral centra of the chaoyangsaurid Xuanhuaceratops have a ventral sulcus (Zhao et al., 2006) rather than the ventral crest seen in Auroraceratops. The caudal inclination of the first sacral process and the origin of sacral processes on more than one vertebra have also been noted in Archaeoceratops (You and Dodson, 2003) and Psittacosaurus (Sereno, 1987). ...
... The caudal flaring of the scapular blade is more pronounced in Auroraceratops than in many ceratopsians, including the chaoyangsaurid Xuanhuaceratops (Zhao et al., 2006), the leptoceratopsids Cerasinops, Montanoceratops, and Leptoceratops (Brown, 1914;Chinnery and Weishampel, 1998;Chinnery and Horner, 2007), the coronosaurian Protoceratops (Brown and Schlaikjer, 1940), and ceratopsids (Hatcher et al., 1907). Psittacosaurus xinjiangensis is like Auroraceratops in having more strongly developed flaring of the caudal scapula, but the flaring seen on Auroraceratops is more asymmetrical than that of Psittacosaurus. ...
... The caudal notch is curved in Xuanhuaceratops, Psittacosaurus, Leptoceratops, and Protoceratops. The curvature of the notch in Auroraceratops is gentler than in Protoceratops or Leptoceratops, but not as gentle as the curvature in Psittacosaurus (Averianov et al., 2006) or Xuanhuaceratops (Zhao et al., 2006), indicating that the caudoventral projection is relatively further from the glenoid than in the former two genera and relatively closer to the glenoid than in the latter two genera. The distinctive groove on the border of the caudal notch in Xuanhuaceratops (Zhao et al., 2006) is not found in Auroraceratops. ...
The species Auroraceratops rugosus was originally described based upon a single skull. With the recovery of over 80 individuals, a complete description of the postcranial skeleton is presented. Auroraceratops is currently the most complete exemplar we have of ceratopsian postcranial anatomy between Psittacosaurus and Leptoceratops. Adult Auroraceratops had a length of approximately 125 cm and an approximate hip height of 44 cm. Osteological correlates of stance in the fore- and hind limb unequivocally indicate a bipedal gait. The phylogenetically corrected quadrupedal mass-estimation equation modified for mass estimation of bipedal terrestrial vertebrates estimates an average mass of Auroraceratops at 15.5 kg. It has the phylogenetically and temporally earliest documentation of the syncervical in Ceratopsia. The mid-caudal neural spines are elongate and erect, a feature previously only known in Leptoceratopsidae and Protoceratopsidae. Despite being longer than in most ceratopsians, the mid-caudal neural spines are not as tall as in some leptoceratopsids. Most of the phylogenetically relevant characters of the postcranial skeleton in Auroraceratops are a mosaic of features plesiomorphic to Neoceratopsia and features previously considered to be unique to later diverging clades, such as Leptoceratopsidae and Protoceratopsidae.
Citation for this article: Morschhauser, E. M., H. You, D. Li, and P. Dodson. 2019. Postcranial morphology of the basal neoceratopsian (Ornithischia: Ceratopsia) Auroraceratops rugosus from the Early Cretaceous (Aptian–Albian) of northwestern Gansu Province, China; pp. 75–116 in Hailu You, Peter Dodson, and Eric Morschhauser (eds.), Auroraceratops rugosus (Ornithischia, Ceratopsia) from the Early Cretaceous of northwestern Gansu Province, China. Society of Vertebrate Paleontology Memoir 18. Journal of Vertebrate Paleontology 38(Supplement). DOI: 10.1080/02724634.2017.1524383.
... The frontals of Archaeoceratops contribute much less to the orbital margin than do the frontals of Auroraceratops (You and Dodson, 2003). Xuanhuaceratops has a flat skull table (Zhao et al., 2006), in contrast to the inclined skull table of Auroraceratops and most basal ceratopsians and neoceratopsians (Sternberg, 1951;You and Dodson, 2003;Makovicky and Norell, 2006;Xu et al., 2006). ...
... Both Auroraceratops and Archaeoceratops possess a process of the ectopterygoid bracing the jugal. No ectopterygoids have been reported from Xuanhuaceratops (Zhao et al., 2006), Prenoceratops (Chinnery, 2004), Montanoceratops (Brown and Schlaikjer, 1942;Chinnery andWeishampel, 1998), or Yinlong (Xu et al., 2006). The pterygoid-palatine foramina are much larger and more ovate in an adult specimen of Liaoceratops (Xu et al., 2002) and in Yamaceratops (Makovicky and Norell, 2006) than in Auroraceratops. ...
... Xuanhuaceratops has a much more extensive dentary symphysis, in contrast to the relatively small symphysis seen in some specimens of Auroraceratops (GSGM-FV-00505) (Zhao et al., 2006). ...
The basal neoceratopsian dinosaur Auroraceratops rugosus was described based on a single skull from the Gongpoquan Basin in northwestern Gansu Province, China. The genus is now known from over 80 specimens, including many from the neighboring Yujingzi Basin. Auroraceratops is one of the best-known basal neoceratopsians. Auroraceratops can be diagnosed by the following autapomorphies: inflated premaxillary teeth; a fungiform expansion of the lacrimal; large tuber caudodorsally on the dentary near the contact with the surangular; and tubercle on the lateral face of the dentary at about the middle of the mandible. Auroraceratops also has a combination of plesiomorphic and derived characters. It possesses characters plesiomorphic to Neoceratopsia, such as broad nasals (seen in basal ceratopsians, such as Yinlong), the absence of a lateral ridge on the surangular, a relatively high number of premaxillary teeth (three), and rugosity on the dentary, jugal, surangular, and sometimes the postorbital, which is in detail similar to that seen in chaoyangsaurids. At the same time, Auroraceratops possesses derived characters not seen in Liaoceratops, the earliest diverging member of Neoceratopsia. These features include an epijugal and a surangular wall lateral to the mandibular glenoid fossa. The cranial anatomy of the early horned dinosaur Auroraceratops rugosus is described.
Citation for this article: Morschhauser, E. M., D. Li, H. You, and P. Dodson. 2019. Cranial anatomy of the basal neoceratopsian Auroraceratops rugosus (Ornithischia: Ceratopsia) from the Yujingzi Basin, Gansu Province, China; pp. 36–68 in Hailu You, Peter Dodson, and Eric Morschhauser (eds.), Auroraceratops rugosus (Ornithischia, Ceratopsia) from the Early Cretaceous of northwestern Gansu Province, China. Society of Vertebrate Paleontology Memoir 18. Journal of Vertebrate Paleontology 38(Supplement). DOI: 10.1080/02724634.2017.1399136.
... It is very small in Psittacosaurus mongoliensis (e.g., AMNH 6535, 6534, NHMW 1998z0064/0001; (Chinnery & Weishampel, 1998; Fig. 4N). The glenoid expands more laterally in small subadult Protoceratops andrewsi (ZPAL MgD-II/3; MgD-II/35; Fig. 4B) and a lateral extension of the glenoid is similar to that in Xuanhuaceratops (Zhao et al., 2006;Fig. 4J Fig. 4M), the glenoid is more laterally expanded than in AMNH 6418, but less than in AMNH 6471. ...
... The caudoventral projection occurs in non-ceratopsid neoceratopsians. The caudal notch is shallow in Psittacosaurus mongoliensis (NHMW 1998z0064/0001), Xuanhuaceratops (Zhao et al., 2006), Graciliceratops (ZPAL MgD-I/156), and young Montanoceratops (Chinnery & Weishampel, 1998). By contrast, in Leptoceratops (AMNH 5205), Auroraceratops (Morschhauser, 2012) and Protoceratops (e.g., AMNH 6471), the caudal notch is deep and narrow (Fig. 4). ...
Protoceratops andrewsi is a well-known ceratopsian dinosaur from the Djadokhta Formation (Upper Cretaceous, Mongolia). Since the 1920s, numerous skeletons of different ontogenetic stages from hatchlings to adults, including fully articulated specimens, have been discovered, but the postcranial anatomy of Protoceratops has not been studied in detail. A new, mostly articulated subadult individual provides an excellent opportunity for us to comprehensively describe the anatomy of the limb skeleton, to compare to other ceratopsian dinosaurs, and to study the ontogenetic and intraspecific variation in this species. New data provided by the specimen shed light on the lifestyle of P. andrewsi. The young subadult individuals present an array of morphological characters intermediate between the bipedal Psittacosaurus and fully quadrupedal adult P. andrewsi. We compare these observations with a broad range of non-ceratopsid Neoceratopsia (of various locomotor adaptations) and Psittacosauridae (obligate bipeds), which gives us insight into the evolution of the skeletal characters informative for the postural change in ceratopsian dinosaurs.
... Few non-track fossils have been reported from the Tuchengzi Formation but include a small number of conchostracans (Wang et al., 2013), plants (Zheng et al., 2001), spores and pollen (Pu et al., 1982). Vertebrate skeletal fossils are scarce, and the currently described dinosaur material consists of one brachiosaurid sauropod (Dong, 2001) and two basal ceratopsians: Chaoyangsaurus youngi (Zhao et al., 1999) and Xuanhuaceratops (Zhao et al., 2006). ...
In northern China, mainly within Western Liaoning, Northern Hebei and Beijing, vertebrate skeletons from the Tuchengzi Formation (Upper Jurassic to Lower Cretaceous) are scarce. However, a large number of new dinosaur track discoveries have made in past 10 years. So far, a total of 19 dinosaur track sites have been found in the Tuchengzi Formation, collectively containing 2,637 individual tracks and representing at least 2,091 trackmakers. This track record has become an important sample for understanding the Tuchengzi dinosaur fauna. The abundant Tuchengzi track record includes six non-avian theropod ichnogenera (Asianopodus, Eubrontes, Grallator, Menglongipus, Therangospodus, and Velociraptorichnus), three bird ichnogenera (Aquatilavipes, Pullornipes, and Koreanaornis), two sauropod ichnogenera (Brontopodus and cf. Parabrontopodus isp.), and a possible ornithopod ichnogenus (cf. Dinehichnu). This assemblage is saurischian-dominated, which is consistent with most Jurassic and Cretaceous track sites in China. The presence of deinonychosaurian tracks is consistent with the rich skeletal record from the Yanliao Biota or Jehol Biota, and the bird tracks are consistent with the record of shorebirds in Jehol Biota. The existence of ornithopod tracks is doubtful and needs further discoveries to be confirmed.
... Together with the contemporary tracksites from Liaoning Province, in Northeast China, these sites reveal the relatively diverse Tuchengzi dinosaur ichnofauna (Yabe et al., 1940;Shikama, 1942;Young, 1960;Zhang et al., 2004;Matsukawa et al., 2006;Fujita et al., 2007), which is saurischian-dominated and includes tridactyl and didactyl non-avian theropods, birds, sauropods, and possible small ornithopods. The faunal composition indicated by the track record differs substantially from the local skeleton records, which only consist of the basal ceratopsians Chaoyangsaurus youngi and Xuanhuaceratops niei (Zhao et al., 1999(Zhao et al., , 2006) and a brachiosaurid sauropod (Dong, 2001). The degree of correspondence between body fossils and tracks (Lockley, 1991;Lockley et al., 1994) makes the Tuchengzi dinosaur ichnofauna a Type 2b deposit, where the fossil track record dominates, and bone evidence is inconsistent with the track fauna. ...
Previously known theropod dinosaur footprints preserved as natural casts in the Tuchengzi Formation, on a rock wall beside the railway in Nanshuangmiao Village, Shangbancheng Town, Chengde City, were originally assigned to ichnogenus Anchisauripus and tentatively attributed to oviraptosaurs. The assemblage was restudied in more detail by examining the entire assemblage of 55 tracks associated with two horizons. The size range of the 27 measured tracks suggests a more diverse grallatorid–eubrontid assemblage and potentially greater diversity of theropod trackmakers. The label Anchisauripus, which has fallen into disuse in some recent literature, implies trackmakers of medium shape and size in the grallatorid–eubrontid morphological spectrum. However, given the presence of other theropod ichnotaxa in the Jurassic to Early Cretaceous strata of the Tuchengzi Formation and time equivalent units we suggest that explicit reference to the Grallator-Anchisauripus-Eubrontes (GAE) plexus, or simply the term Grallator-Eubrontes plexus be confined to Lower Jurassic assemblages as originally defined and intended. Further study centered on the 16 known Tuchengzi assemblages and older theropod ichnfaunas is necessary to confirm or refute the degree to which grallatorid–eubrontid assemblages from these different epochs are similar or convergent. Even if the tracks are morphologically very similar inferences regarding trackmaker identity are problematic because the same theropodan trackmaker species, genera or even families were not present in both epochs.
... The preserved part forms a smooth anteriorly descending surface with the prefrontal. As in other basal ceratopsians, there is no sign of a nasal horn 4,7,22 . ...
Ceratopsia is a diverse dinosaur clade from the Middle Jurassic to Late Cretaceous with early diversification in East Asia. However, the phylogeny of basal ceratopsians remains unclear. Here we report a new basal neoceratopsian dinosaur Beg tse based on a partial skull from Baruunbayan, Ömnögovi aimag, Mongolia. Beg is diagnosed by a unique combination of primitive and derived characters including a primitively deep premaxilla with four premaxillary teeth, a trapezoidal antorbital fossa with a poorly delineated anterior margin, very short dentary with an expanded and shallow groove on lateral surface, the derived presence of a robust jugal having a foramen on its anteromedial surface, and five equally spaced tubercles on the lateral ridge of the surangular. This is to our knowledge the earliest known occurrence of basal neoceratopsian in Mongolia, where this group was previously only known from Late Cretaceous strata. Phylogenetic analysis indicates that it is sister to all other neoceratopsian dinosaurs.
... Most analyses of basal ceratopsian phylogeny were conducted as part of the naming of new taxa (e.g., Makovicky and Norell, 2006) and had a primary goal of placing these in phylogenetic context. The rapid pace of new discoveries, particularly out of Asia (Xu et al., 2002You et al., 2005;Zhao et al., 2006;Lee et al., 2011;Han et al., 2015Han et al., , 2017He et al., 2015;Zheng et al., 2015), has resulted in numerous studies of phylogeny, but many analyses lack complete overlap in taxonomic scope. In some instances, the focus on the taxon of interest has caused a very limited sampling of basal Neoceratopsia (Zhao et al., 1999;Xu et al., 2006;Han et al., 2015), because the primary goal of many of these shorter works was not a broad taxonomic review. ...
Basal neoceratopsians are a relatively diverse group of small- to medium-sized herbivorous dinosaurs from the Early to Late Cretaceous of Asia and North America. Although known for over a century, this group has only relatively recently received intense independent study, tied to the rapid increase in known diversity since 1997. Auroraceratops rugosus is one of these recently discovered species and is one of the best-known basal neoceratopsians, being represented by over 80 specimens, and is also the most completely represented neoceratopsian from the Early Cretaceous. A phylogenetic analysis focusing on non-ceratopsid ceratopsians examines the phylogenetic context of Auroraceratops. The analysis is based on a new matrix of 41 taxa and 257 characters. The results recover an Auroraceratops-Aquilops-ZPAL MgD-I/156 clade within basal Neoceratopsia that is sister to a clade composed of Asiaceratops, Yamaceratops, Mosaiceratops, and the larger clades Leptoceratopsidae and Coronosauria. This phylogeny recovers a monophyletic Coronosauria, Leptoceratopsidae, and Protoceratopsidae. Helioceratops is recovered as sister to the rest of Leptoceratopsidae, Ischioceratops is recovered nested within Leptoceratopsidae, and the enigmatic genus Mosaiceratops is recovered as a basal neoceratopsian, sister to Yamaceratops. Yinlong, and Hualianceratops are recovered in an expanded Chaoyangsauridae, and the genus Psittacosaurus is recovered as the earliest diverging lineage in Ceratopsia. Ajkaceratops, the only European ceratopsian, is robustly recovered as sister to the rest of Ceratopsoidea.
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
Citation for this article: Morschhauser, E. M., H. You, D. Li, and P. Dodson. 2019. Phylogenetic history of Auroraceratops rugosus (Ceratopsia: Ornithischia) from the Lower Cretaceous of Gansu Province, China; pp. 117–147 in Hailu You, Peter Dodson, and Eric Morschhauser (eds.), Auroraceratops rugosus (Ornithischia, Ceratopsia) from the Early Cretaceous of northwestern Gansu Province, China. Society of Vertebrate Paleontology Memoir 18. Journal of Vertebrate Paleontology 38(Supplement). DOI: 10.1080/02724634.2017.1509866.
Investigating the influences of geological parent materials on the behavior, affinity, and bioavailability of major elements in cassava-growing soils in Thailand is lacking. This study aimed to analyze the total major elemental composition of cassava-growing soils and to investigate the relationship between elements and soil properties for grouping elements according to their affinity of major elements in 37 cassava-growing soils derived from different geological parent materials in Nakhon Ratchasima province. The study was conducted by analysis of physicochemical properties, elemental composition, and principal component analysis (PCA) to correlate multivariable soil data influencing elemental behaviors. The results showed that most cassava-growing soils were coarse-textured soils with dominant high sand content, very acidic to moderately alkaline pH, and low soil fertility. The results of PCA analysis grouping by rock formation and soil series could be classified elements into 3 principal components (PC) including PC1 deals with base-associated elements, i.e., Ca, Mg, K, Na, and P, which was closely related to silt content (Silt), cation exchange capacity (CEC), calcium carbonate equivalent (CCE), soil pH (pH), and base saturation (BS). Chatturat series (Ct) developed from Maha Sarakham (KTms) and Quaternary alluvium (Qa) formations were the major soils found in this group. The soils were clayey textured, having high pH, CEC, CCE, and bases. PC2 dealed with metal elements and oxides, i.e., Al, Fe, Mn, and N, which were closely related to clay content (Clay), extractable acidity (EA), and organic matter (OM). Chok Chai (Ci) and Surin (Su) series developed from Khok Kruat formation (Kkk) and Quaternary Basalts (Qbs) were the major soils found in this group and accumulated high metal and sesquioxide content. PC3 associated with silicon (Si) and sand content (Sand). Korat series developed from Phu Phan (Kpp), Sao Khua (Ksk) and Qa formations were the major soil found in this group. They had a coarse texture with high sand content. The results indicated that soil parent materials strongly influenced the geochemical behavior and affinity associated with soil properties which could affect the bioavailability of elements and be major constraints for cassava production in Nakhon Ratchasima province.
The Jurassic-Cretaceous Tuchengzi Formation has yielded at least 16 known theropod-dominated tracksites from northeast China, and in this paper, a new locality, the Lishi site in Hebei Province, is documented. A tuff layer positioned stratigraphically 90 m below the trackway layer yielded a UPb date of 142.2 ± 0.9 Ma, placing the site in the Berriasian stage. The site includes sauropod tracks, assigned to Brontopodus, and large theropod tracks, informally assigned to Therangospodus and Megalosauripus as well as a well-preserved morphotype here named as Asianopodus wangi ichnosp. Nov. The Tuchengzi Formation theropod track assemblages have implications for theropod ontogeny, paleocommunity structure, palaeobiology and preferred habitats of different size groups, based on comparison with data from the skeletal record. The size-frequency distribution indicates that small theropod tracks (Footprint length, FL < 25 cm) represent the dominant trackmakers with estimated body masses of <100 kg, whereas intermediate sized trackmakers (FL 25.0 – ~38.0 cm) are comparatively scarce and there are no tracks suggestive of megatheropods with body masses of >1000 kg. The latter phenomenon is in contrast to recently published analyses from Cretaceous theropod skeletal data that recognize a gap between small and very large megatheropod individuals.
Slabs with tetrapod tracks from the Madigou Village quarry in the Tuchengzi Formation have famously been used as building stones at the imperial summer resort locality, also referred to in the ichnological literature as the “Chengde Summer Palace.” The Jurassic-Cretaceous boundary Tuchengzi Formation has elsewhere in the region yielded differently composed ichnofaunas with non-avian and avian theropod and sauropod tracks. The Madigou assemblage is remarkable because it shows the co-occurrence of abundant and diverse non-avian and avian theropod tracks. The non-avian theropod tracks are mostly Grallator- and Eubrontes-like with a few that registered faint hallux traces. A small number of didactyl deinonychosaurian tracks were recognized which we here label as Velociraptorichnus isp. The avian theropod tracks can tentatively be referred to Aquatilavipes and Koreanaornis, with wide digit divarications. Growing geochronological and biostratigraphic evidence suggests that these are among the oldest known bird tracks, similar in age to Pullornipes, also from the Tuchengzi Formation in northeastern China and dating close to the Tithonian-Berriasian boundary. Theropod tracks are dominating, even if an isolated possible sauropod track and some questionable tridactyl imprints that could either represent theropods or ornithopods, may indicate the presence of further dinosaur groups. The Tuchengzi ichnofauna is important because of the stratigraphic age close to the famous Jehol Biota.
In traditional Linnaean taxonomy, classifications are constructed and maintained principally as dichotomous hierarchies. In phylogenetic taxonomy, such hierarchies are restricted to monophyletic groups defined explicitly on the basis of common ancestry. A definitional configuration termed a node-stem triplet is described that stabilizes the relationship between a given taxon and its subordinate taxa. I outline a rationale within phylogenetic taxonomy for construction of a stable taxonomic framework, as demonstrated by application to the higher-level taxonomy of Dinosauria.
Closure of neurocentral sutures in the crocodylian vertebral column follows a distinct caudal to cranial sequence during ontogeny. The sutures in most caudal vertebrae are fully closed at hatching, but closure of remaining sutures occurs later in ontogeny. Closure of cervical sutures is a consistent indicator of morphological maturity in Alligator mississippiensis, Alligator sinensis, Osteolaemus tetraspis, and Crocodylus acutus; the final transformation is the closure of the axial neurocentral suture, which occurs after the closure of the axis-odontoid suture. Because these transformations occur near the end of ontogeny in all three taxa, regardless of maximum size, closure of these sutures is a size-independent criterion of maturity; however, it is not certain if suture closure indicates the stoppage of growth. These transformations are readily identifiable in fossils, permitting the objective characterization of maturity in fossil crocodylians and possibly at least some of their closer extinct relatives.
We report new 40Ar÷39Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found
interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun
tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et
al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered
by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion 40Ar÷39Ar dating of biotite, argues for a Jurassic age for the Yixian Formation. The third tuff is a previously undated tuff from
the upper part of the underlying Tuchengzi Formation. Single crystal total fusion 40Ar÷39Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca÷K ratios, excellent reproducibility and gave a mean
age of 125.0±0.18 (1SD)±0.04 (SE) Ma. Single sanidine crystal total fusion 40Ar÷39Ar analyses of the Hengdaozi tuff gave a mean age of 125.0±0.19 (1SD)±0.04 (SE) Ma, which is indistinguishable from the Sihetun
tuff. The Tuchengzi Formation tuff gave a mean age of 139.4±0.19 (1SD)±0.05 (SE) Ma. Detailed laser incremental-heating analyses
of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components.
We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating
of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of
the Tuchengzi Formation can be referred to the Early Cretaceous.
Approximately half of existing dinosaur species belonging to the Order Ornithischia, or the 'bird-hipped' dinosaurs, which include such familiar forms as the stegosaurs, ankylosaurs, hadrosaurs, and ceratopsids. Although ornithischians are generally conceded to have descended from a common ancestor, little is known about the pattern of descent. Comparison of more recently discovered ornithischian fossils from China and Mongolia to better-known North American forms has shed light on the pattern of evolutionary diversification among ornithischians, a pattern that began approximately 200 My ago and ended abruptly nearly 140 My later at the end of the Cretaceous.-from Author
A new ceratopsian specimen, Chaoyangsaurus youngi gen. et sp. nov., was collected from the Tuchengzi Formation (Middle or Late Jurassic) of Liaoning, China. Distinctive characteristics of the new species include quad-ratojugal overlapping posterior side of quadrate shaft; lack of a broad lateral surface of the quadrate shaft; convex posterior margin of the ventral portion of the quadrate; a ridge between the planar lateral and ventral surface of the angular. The discovery of Chaoyangsaurus youngi extends the record of ceratopsian from back in time from the Early Cretaceous into the Middle or Late Jurassic. Some characters of C. youngi may suggest a close relationship between Ceratopsia and Heterodontosauridae.
Psittacosaur materials were collected from seven localities in the course of Dinosaur Project fieldwork in Inner Mongolia. Two new species of Psittacosaurus are recognized, bringing the number of well-defined species to six. One, based on a nearly complete skeleton, resembles Psittacosaurus mongoliensis, but is a smaller animal with a relatively larger head and longer tail. The other species possesses jugal horns, but exhibits a different combination of characters than Psittacosaurus sinensis and Psittacosaurus xinjiangensis. A larger matrix of taxa and characters than is presently available will be necessary to resolve adequately phylogenetic relationships within the genus. Psittacosaurs were small dinosaurs, the skeletons of which are preserved in unusual completeness in proximity to aeolian environments of deposition. Their small brain size relative to that of modern mammals of similar body size implies a relatively restricted behavioral repertoire.