My original tumblr post was here. This image was originally posted on Tumblr by Vintage Geek Culture with an attribution to Ed Emshwiller. It looks to me like a pulp cover but I have been unable to find on the Internet any examples of it used as such.
Venture Science Fiction, January 1957, Vol. 1. #1, the first issue, illustrating, I believe, Poul Anderson’s “Virgin Planet.”
http://www.philsp.com/data/images/v/venture_science_fiction_195701_v1_n1.jpg
The art on the cover is the reverse of this; I can’t say what orientation the original would have had.
You’re better at this than I, I think.
Just a sign of my misspent youth.
The planet won’t be virgin for long.