【摘 要】
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Living birds are unique among vertebrates in the formation of a female-specific bone tissue called medullary bone (MB) that is strictly associated with reproduc
【机 构】
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Key Laboratory of Vertebrate Evolution and Human Origins,Institute of Vertebrate Paleontology and Pa
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Living birds are unique among vertebrates in the formation of a female-specific bone tissue called medullary bone (MB) that is strictly associated with reproductive activity.MB is a rapidly mobilized source of calcium and phosphorus for the production of eggshell.Among living taxa,its skeletal distribution can be highly extensive such that it even exists in the ribs of some species.Due to its ephemeral nature,MB is rarely fossilized and so little is understood with regard to the origin of MB and its skeletal distribution in early taxa.Here we describe a new Early Cretaceous enantioithine bird,Mirusavis parvus,gen.et.sp.nov.,indicating that skeleton-wide distribution of MB appeared early in avian evolution.We suggest that this represents the plesiomorphic condition for the Aves and that the distribution of MB observed among extant neoithines is a product of increased pneumatization in this lineage and natural selection for more efficient distribution of MB.
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