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Ceratopsians were herbivorous dinosaurs that dominated many of the terrestrial ecosystems in Asia and North America during the Cretaceous. The bizarre variety of skulls and lower jaw morphologies as well as the inferred ecological abundance of many species in this clade indicate that Ceratopsia was a successful group. Here we analyzed 126 lower jaws from 50 ceratopsian species, using two-dimensional geometric morphometrics and finite element analysis to investigate differences in shape and structural performance of this part of the feeding apparatus across Ceratopsia. Morphological differences in lower jaws across ceratopsian clades are said to originate from feeding adaptation.Our results show that the stress (physical loadings modeled in response to biting) in lower jaws was quite similar between “basal” and “derived” taxa, whereas major differences among clades occur for stress values associated with the coronoid process. The basal ceratopsians Hualianceratops and Yinlong had a highly stressed and primitive lower jaw, indicating that those animals may have fed on relatively soft foliage and fruits. A similar condition was found for basal neoceratopsians and protoceratopsids. Psittacosaurids possessed a well-integrated and compact lower jaw able to withstand high stress, at the cost of having a highly stressed coronoid process. Leptoceratopsids were characterized by the opposite condition. Taxa such as Leptoceratops, Prenoceratops, Zhuchengceratops and Cerasinops appear to have had a comparatively efficient feeding apparatus. Ceratopsidae represents the clade with the most efficient masticatory apparatus within Ceratopsia, even if the horizontal ramus of the lower jaw appears less able to withstand high levels of stress as compared with other ceratopsians. Additionally, we found the dentary and surangular–angular complex co-evolved to generate a masticatory apparatus able to withstand high stress, particularly in Protoceratopsidae and Triceratopsini. The major phenotypic evolutionary rate and morphological changes occurred during the mid- to Late Cretaceous, when intense climate change and angiosperm diversification could have affected the evolution of ecological diversity and feeding biomechanics in Ceratopsia. 相似文献
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刘静 《中国海洋湖沼学报》1997,15(3):224-226
ImOUocrON0verevoluti0narytirne,intetspeCiliccomPctitioncanresultincharactedisplacementSthatfadiitateresourcepartitioningamongspedesffeper,l985,Wilirarnanayake,l99O).Fisharenotablyopportunisticintheirfeding,toknowWhereandhowtheybowilloftenprovidemoreinsightintotheirerelogythansbolyknowingtheactUalcomPonentSoftheirdiet(Motta,l988,HUmPhrieS,l993).ArmrdinglymorphologicalcomParisonsamongcoxiccutwspchprovidemportantinfonnationnotonlytosySteInatistsfaedwithtaxonondcprobbo,butaIsot0erelogistS… 相似文献
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环境污染物二噁英中毒性最强的2，3，7，8-四氯二苯并对二噁英(2，3，7，8-tetrachlorodibenzo-p-dioxin，以下简称TCDD)经由芳烃基受体(aryl hydrocarbon receptor，Ahr)引起啮齿类口唇开裂，斑马鱼下颌短小等典型特征，本试验研究了TCDD引起的下颌短小与形态发育基因Sonic hedgehog(shh)的关系，用0-1．0μg／L的TCDD给受精后24h(24hpf)的斑马鱼胚染毒直至观察并进行形态学观察及原位杂交，结果观察到TCDD引起斑马鱼的下颌短小与其浓度相依存．同时观察到TCDD染毒群的Shh基因表达以及类似基因tiggy-winkle hedgehog(twhh)的低下．观察Shh缺失的斑马鱼变异体Syu，或给正常斑马鱼染毒，添加Shh阻断药Cycopamant Cyclopamine，可以同样观察到斑马鱼的下颌短小，本试验表明TCDD引起的下颌短小与shh和twhh表达是相关联的．同时也说明斑马鱼有可能作为二噁英类污染物的生物学毒性评价生物。 相似文献
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Abstract. Tube blennies ( Chaenopsidae ) have the largest relative mouth size compared with other blennioids. Their peculiar oral jaw apparatus may be interpreted as adaptation towards opportunistic feeding, making a wide spectrum of prey types and sizes accessible for these "hemisessile" fishes.
Three sympatric species of Gulf of California Acanthemblemaria show different, though overlapping habitat and microhabitat utilization, but are nearly identical in feeding. Accordingly, sizes and shapes of the oral jaw apparati are very similar in the species under consideration. Possible reasons for this apparent lack of ecomorphological divergence are discussed. 相似文献
Three sympatric species of Gulf of California Acanthemblemaria show different, though overlapping habitat and microhabitat utilization, but are nearly identical in feeding. Accordingly, sizes and shapes of the oral jaw apparati are very similar in the species under consideration. Possible reasons for this apparent lack of ecomorphological divergence are discussed. 相似文献
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沟槽式卡瓦与钻杆摩擦系数的试验研究 总被引：4，自引：0，他引：4
卡瓦与钻杆之间的摩擦系数是卡盘夹紧能力计算的一个重要参数。本文介绍了该摩擦系数 的一种研究方法,并通过试验研究,得出了沟槽式卡瓦摩擦系数的变化范围和取值依据,明确了影 响该系数的诸多因素。本试验研究成果可直接应用于卡盘的设计计算。 相似文献
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