Did Southern Pacific ever have any Mallet steam locos?
Yes SP purchased a dozen modern 2-8-8-4 mallets in 1939 . They were coal burners as delivered numbered 3800 -3811 assigned to service between El Paso and Tucumcari, N.M. Those that remained in 1950 were converted to oil burners and assigned to Sparks, Nv to Klamath Falls Orgeon. It is believed only two survived past their fifteenth anniversary.
The earliest cab-forwards were all true Mallets (compounds). They were later rebuilt to simple articulateds and all of the newer cab-forwards plus the AC-9’s were built as simple articulateds.