A skull of Early Pleistocene Paracamelus gigas(Artiodactyla,Mammalia)from Luotuo Hill in Dalian,Northeast China
Originated in North America in the Middle Eocene,camelids were a successful group with very large diversity.But the camels emigrated to the Old World from North America,probably during the middle stage of the Middle Miocene,and did not radiate much as those in North America,represented by only two genera Paracamelus and Camelus.The former was considered as giving rise to the latter,but the detailed relationship of the Old World camelines was controversial.The new camel material unearthed from Layer 4 in the Jinyuan Cave at Luotuo Hill in Dalian,Liaodong peninsula in Northeast China,was described and referred to as Paracamelus gigas.Its dentition length is slightly longer than that of Camelus knoblochi but evidently larger than that of C.ferus and C.dromedarius.Based on the fossil records and morphometric evidences,P.gigas originated from a form similar to P.alexejevi in the Late Pliocene in the Old World,instead of from Megatylopus gigas of North America and then migrated into Asia as previously thought.The morphometric similarities between the Early Pleistocene Dalian specimens and those of the Middle and Late Pleistocene C.knoblochi indicate that P.gigas probably gave rise to C.knoblochi as formerly postulated and likely in the late Early Pleistocene by reduction or simplifying of P3 and P4,disappearance of p3 and shortening of dentition length.P.gigas inhabited in the forest steppe environment of Liaodong peninsula from 1.1 to 1.52 Ma based on paleomagnetic dating and pollen evidence.
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