Mooncalf

         "...A rescue mission was immediately undertaken, with Cavor and Bedford following the Selenites’ tracks directly to a tunnel entrance. Discovering that the Moon’s interior held not only a breathable atmosphere, but an immense biome full of different animal and fungoid species, they discarded their space helmets. The largest animals they found were the “Mooncalves”, 80-foot-long, caterpillar-like omnivores that generally quietly browsed on the plants in the interior – until one individual grew aggressive and attacked them. The giant would have torn Bedford apart, but they found themselves saved by a small group of Selenites that electrocuted the brute with a “strange, gun-like apparatus that spat massive bolts of lightning all over the horror’s body”. The Selenites immediately swarmed all over the corpse, and sliced it apart with unerring precision for food, none of them noticing Bedford hiding in a nearby cavern… "

Reality check: this is one of the Mooncalves from the 1964 film "First Men in the Moon". I do not own the rights, etc etc...