Protungulatum, Confirmed Cretaceous Occurrence of an Otherwise Paleocene Eutherian (Placental?) Mammal
Protungulatum, Confirmed Cretaceous Occurrence of an Otherwise Paleocene Eutherian (Placental?) Mammal
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DOI：
10.1007/s10914-011-9162-1
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发表时间：
2011-09-01
影响因子：
1.9
通讯作者：
Cifelli, Richard L.
中科院分区：
文献类型：
--
作者：
Archibald, J. David;Zhang, Yue;Cifelli, Richard L.
无论是前新生代冠真兽目哺乳动物（胎盘动物）还是古有蹄类动物（“髁状动物”）都不能根据化石记录确定。在此，我们报告了一个新的物种的古新世古有蹄类（“髁”）Protungulatum从毫无争议的晚白垩世年龄的岩石在美国蒙大拿州的基础上，孤立的最后一个上前磨牙，表明这些常见的早期第三纪哺乳动物的罕见代表出现在北美的灭绝前至少30万年的非鸟类恐龙。其他1200个哺乳动物标本来自该地区的特征晚白垩世类群。这一发现推翻了目前的假设，即古代有蹄类动物直到白垩纪/第三纪（K/T）边界之后才出现在北美，也表明其他关于北美晚白垩世古代有蹄类动物的报道可能是正确的。最近的研究，包括我们的，不能确定是否Protungulatum不属于冠枝胎盘。
Neither pre-Cenozoic crown eutherian mammals (placentals) nor archaic ungulates ("condylarths") are known with certainty based on the fossil record. Herein we report a new species of the Paleocene archaic ungulate ("condylarth") Protungulatum from undisputed Late Cretaceous aged rocks in Montana USA based on an isolated last upper premolar, indicating rare representatives of these common early Tertiary mammals appeared in North America a minimum of 300 k years before the extinction of non-avian dinosaurs. The other 1200 mammal specimens from the locality are characteristic Late Cretaceous taxa. This discovery overturns the current hypothesis that archaic ungulates did not appear in North America until after the Cretaceous/Tertiary (K/T) boundary and also suggests that other reports of North American Late Cretaceous archaic ungulates may be correct. Recent studies, including ours, cannot determine whether Protungulatum does or does not belong to the crown clade Placentalia.