The mutual climatic range technique is (usually) not the area of sympatry technique when reconstructing paleoenvironments based on faunal remains

• Paleozoological area of sympatry (AOS) technique to reveal paleoenvironment developed in 1950s and 1960s, and named in 1966
• Paleozoological mutual climatic range (MCR) technique to reveal paleoenvironment was developed and named in the 1980s
• AOS plots individual geographic ranges of taxa whereas MCR plots individual climatic ranges of taxa
• A new paleozoological technique developed in 2009 was given the name MCR yet is similar to the AOS technique
• The new MCR technique should perhaps be renamed the UTM-MCR to distinguish it from the original MCR technique

Names applied to particular analytical techniques must be explicit and distinctive. The potential that two distinct techniques of paleoenvironmental reconstruction that use ancient faunal remains, each with a particular name, might be confused in the future has recently become a reality. The name “mutual climatic range” (MCR), coined and developed in the 1980s and concerning the modern climatic (not geographic) co-occurrence of species represented in a prehistoric collection of remains, has been applied multiple times to a different technique first published in 2009. The new MCR technique is very similar to a distinct one developed in the 1950s and 1960s that focuses on the location of the geographic co-occurrence of species in an assemblage relative to the location of the deposit producing the remains. The older method has been known as the “area of sympatry” (AOS) technique since 1966. Histories of the AOS and original MCR techniques suggest they were developed independently. The new MCR technique seems to have been developed without knowledge of the two earlier ones. To avoid future confusion of one technique with the other, it is suggested that the new one be renamed the UTM-MCR technique because rather than use isopleths of climatic variables, as the AOS technique does, it considers climatic variables within 10 × 10 km UTM squares.