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    Wyświetlanie 1-5 z 5
    Tytuł:
    Juvenile-only clusters and behaviour of the Early Cretaceous dinosaur Psittacosaurus
    Autorzy:
    Zhao, Q.
    Benton, M.J.
    Xu, X.
    Sander, P.M.
    Powiązania:
    https://bibliotekanauki.pl/articles/21989.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Opis:
    It has hitherto been hard to prove that any association of juvenile dinosaurs represents original behaviour rather than sedimentary accumulation, and it has been hard also to determine the ages of such juveniles. A previously described specimen, which consists of an “adult” Psittacosaurus with 34 fully articulated juveniles, turns out to be a composite: the “adult” skull probably has been added, and in any case it is below breeding age. Other juvenile-only clusters have been reported, but the best examples that likely reflect behaviour rather than sedimentary accumulation are specimens from the Early Cretaceous Lujiatun beds in NE China, which were entombed beneath pyroclastic flow deposits. A remarkable juvenile-only cluster of Psittacosaurus shows clear evidence of different ages (five 2-year olds and one 3-year old) based on bone histological analysis. These juveniles may have associated together as a close-knit, mixed-age herd either for protection, to enhance their foraging, or as putative helpers at the parental nest.
    Źródło:
    Acta Palaeontologica Polonica; 2014, 59, 4
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ontogenetic stages of ceratopsian dinosaur Psittacosaurus in bone histology
    Autorzy:
    Zhao, Q.
    Benton, M.J.
    Hayashi, S.
    Xu, X.
    Powiązania:
    https://bibliotekanauki.pl/articles/20498.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Opis:
    The early ceratopsians Psittacosaurus and Protoceratops have provided important information on dinosaurian development because of abundant specimens of adults, subadults, juveniles, and even hatchlings. Here we present new data and methods for identifying key growth stages from bone histology. Previous studies on Psittacosaurus lujiatunensis from the Early Cretaceous Jehol Biota of China did not present in-depth analysis of growth patterns. Based on a histological study of 43 thin sections from 17 individuals of this species, we recognize four histological ontogenetic stages, i.e., hatchling, juvenile, sub-adult, and adult, but no fully-grown stage. We estimate life history and longevity from diaphyseal growth line counts and other features of histology. We show that P. lujiatunensis grew fast in early stages (hatchling, juvenile, and subadult), according to the density of vascular canals and the different type of bone tissue; the deposition of parallel fibred bone tissue in the outer cortex of the subadult stage indicates that growth rate was slowing down. We introduce a new graphical method to estimate the occurrence and volumes of vascular canals from thin sections more accurately than current two-dimensional approaches.
    Źródło:
    Acta Palaeontologica Polonica; 2019, 64, 2
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A reassessment of the purported ankylosaurian dinosaur Bienosaurus lufengensis from the Lower Lufeng Formation of Yunnan, China
    Autorzy:
    Raven, T.J.
    Barrett, P.M.
    Xu, X.
    Maidment, S.C.R.
    Powiązania:
    https://bibliotekanauki.pl/articles/21669.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Opis:
    The earliest definitive ornithischian dinosaurs are from the Early Jurassic and are rare components of early dinosaur faunas. The Lower Lufeng Formation (Hettangian–Sinemurian) of Yunnan Province, China, has yielded a diverse Early Jurassic terrestrial vertebrate fauna. This includes several incomplete specimens have been referred to Ornithischia, including the type specimen of the thyreophoran “Tatisaurus” and other generically indeterminate material. The highly fragmentary Lufeng ornithischian Bienosaurus lufengensis was described briefly in 2001 and identified as an ankylosaurian dinosaur. Recent studies have cast doubt on this hypothesis, however, and given that the referral of Bienosaurus to Ankylosauria would result in an extensive ghost-lineage extending between it and the first definitive eurypodans (ankylosaurs + stegosaurs) in the Middle Jurassic, the holotype specimen is re-examined and re-described. We identify Bienosaurus as a probable thyreophoran dinosaur, although the fragmentary nature of the material and the absence of autapomorphies means that the specimen should be regarded as a nomen dubium.
    Źródło:
    Acta Palaeontologica Polonica; 2019, 64, 2
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Reconstruction of oviraptorid clutches illuminates their unique nesting biology
    Autorzy:
    Yang, T.-R.
    Wiemann, J.
    Xu, L.
    Cheng, Y.-N.
    Wu, X.-C.
    Sander, P.M.
    Powiązania:
    https://bibliotekanauki.pl/articles/19933.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Opis:
    Oviraptorosaurs, a group of non-avian theropod dinosaurs from the Cretaceous of Asia and North America, left behind the most abundant and informative fossil evidence of dinosaur reproductive biology. Previous studies had suggested that oviraptorosaur reproductive biology represents an intermediate stage and exhibited unique modern avian traits. For instance, the adult-associated clutches were predominantly considered as evidence for brooding/thermoregulatory contact incubation (TCI) behaviors, whereas the hypotheses of laying or protection were neglected. Despite numerous oviraptorid egg clutches uncovered from China and Mongolia, their nest architecture and clutch arrangement were rarely investigated in detail. Here we present a comprehensive reconstruction of an oviraptorid clutch based on five new oviraptorid clutches from Jiangxi Province, China. A detailed examination of the new clutches reveals a partially-open oviraptorid nest that contains 3–4 rings of paired eggs (more than 15 pairs total) whose blunt end points toward the center devoid of eggs at an angle of 35–40°. Our detailed three-dimensional reconstruction indicates that the oviraptorid clutch has a unique architecture unknown from extant bird clutches, implying an apomorphic nesting mode. Such a unique nest architecture further contradicts the TCI hypothesis in oviraptorids, hindering sufficient heat transfer to the inner (lower) ring(s) of eggs. Moreover, the size of the new oviraptorid clutches (>30 eggs) is significantly larger than that of the adult-associated clutches (<22 eggs), raising the alternative hypothesis that the adult-associated clutches were uncompleted. This clue thus supports the hypothesis that the clutch-associated oviraptorid adults possibly represent females after an oviposition before a catastrophic sandstorm/flooding burial.
    Źródło:
    Acta Palaeontologica Polonica; 2019, 64, 3
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Osteology of the Late Cretaceous alvarezsauroid Linhenykus monodactylus from China and comments on alvarezsauroid biogeography
    Autorzy:
    Xu, X.
    Upchurch, P.
    Ma, Q.
    Pittman, M.
    Choiniere, J.
    Sullivan, C.
    Hone, D.W.E.
    Tan, Q.
    Tan, L.
    Xiao, D.
    Han, F.
    Powiązania:
    https://bibliotekanauki.pl/articles/20629.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    osteology
    Cretaceous
    Late Cretaceous
    alvarezsauroid
    Linhenykus monodactylus
    China
    biogeography
    Dinosauria
    Theropoda
    Parvicursorinae
    Treefitte
    dispersal
    vicariance
    sympatry
    Wulansuhai Formation
    Inner Mongolia
    Opis:
    The alvarezsauroid theropod Linhenykus monodactylus from the Upper Cretaceous of Inner Mongolia, China is the first knownmonodactyl non−avian dinosaur, providing important information on the complex patterns of manual evolution seen in alvarezsauroids. Herewe provide a detailed description of the osteology of this taxon. Linhenykus shows a number of fea− tures that are transitional between parvicursorine and non−parvicursorine alvarezsauroids, but detailed comparisons also re− veal that some characters had a more complex distribution. We also use event−based tree−fitting to perform a quantitative analysis of alvarezsauroid biogeography incorporating several recently discovered taxa. The results suggest that there is no statistical support for previous biogeographic hypotheses that favour pure vicariance or pure dispersal scenarios as explana− tions for the distributions of alvarezsauroids across SouthAmerica, NorthAmerica andAsia. Instead, statistically significant biogeographic reconstructions suggest a dominant role for sympatric (or “within area”) events, combined with a mix of vicariance, dispersal and regional extinction. At present the alvarezsauroid data set is too small to completely resolve the biogeographic history of this group: future studies will need to create larger data sets that encompass additional clades.
    Źródło:
    Acta Palaeontologica Polonica; 2013, 58, 1
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-5 z 5

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