Columbian mammoth
In 1992 an attempt was made to extract a mitochondrial DNA sequence from the skeletal remains of "A.d.guildayi" to compare its relationship to other "Canis" species. The attempt was unsuccessful because these remains had been removed from the LaBrea pits and tar could not be removed from the bone material. In 2014 an attempt to extract DNA from a Columbian mammoth from the tar pits also failed, with the study concluding that organic compounds from the asphalt permeate the bones of all ancient samples from the LaBrea pits, hindering the extraction of DNA samples.