综荐骨
是鸟类特有的结构,由后几枚胸椎、腰椎、荐椎和前几枚尾椎愈合而成,且与宽大的骨盘相愈合,使鸟类在地面步行时获得支持体重的坚实支架。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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