Not a reptile-
I would tend to agree with Paul.
Perhaps the text intended the heads to be obscured. The left creature certainly is more mammalian and the tail on the right still looks like a cat (mountain lion).
Then bend in the tail seems to mask functionality drawn in by the artist and implicates some kind of muscular bulk able to apply some torque. Rattlesnakes move tailes left to right but this is at the terminus not up the vertebrae. Lizard tails that are funtional tend to move left and right but not up and down as this pic presents.
I think it is supposed to be two mammals interacting instead.
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