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Journal Article 
Giants and pygmies: Mammoths of Santa Rosa Island, California (USA) 
Agenbroad, LD 
Quaternary International
ISSN: 1040-6182
EISSN: 1873-4553 
Mammoth remains have been known from the northern Channel
Islands of California since 1856. Initially, it was considered that there were several species of
mammoths on the islands. It has now been determined that there are only two species: 1) Mammuthus
exilis, the island pygmy mammoth, and 2) Mammuthus columbi, the giant, continental (mainland)
mammoths which were the ancestral mammoths from which M. exilis was derived. Discovery and
recovery of the most complete skeleton of M. exilis, in 1994 prompted new research efforts and a
numerical chronology for the pygmy mammoths, ranging from 11,030 BP to greater than 200.000 a by
U/Th (Uranium/Thorium). Little attention had been paid to the chronology of the less abundant M.
columbi remains. Uranium/Thorium dates on two M. columbi teeth yielded dates of 28,000 2000 a,
and 64,500 + 7400/-6900 a. If the U/TH dates are valid, they indicate a long history of shared
island occupation, with M. exilis, or repeated migrations of M. columbi from the mainland to the
islands. No M. exilis remains have been discovered on the mainland. In 2009 additional efforts to
date the Columbian mammoth remains were initiated, to ascertain whether they were: 1)
contemporary with the pygmy mammoths; 2) represented remnants of the founding population; or 3)
represented late migration from the North American mainland. (C) 2011 Elsevier Ltd and INQUA. All
rights reserved. 
• Uranium
     Merged reference set
     Secondary Refinement