e621 2018 4_toes 5_fingers all_fours angry animal_genitalia anthro balls barefoot biceps bigmaster biped black_balls black_claws black_fur black_nipples black_nose black_pawpads black_tail brown_fur brown_tail canine claws collar color_swatch digital_media_(artwork) digitigrade dog drooling explicital eyebrow_piercing facial_piercing fangs floppy_ears fully_sheathed fur green_eyes grey_background lip_piercing lip_ring looking_at_viewer male mammal model_sheet multicolored_fur multicolored_tail musclegut muscular muscular_male nevarrio nipples nude open_mouth pawpads paws pecs piercing rottweiler saliva sheath short_tail simple_background small_tail solo standing teeth toe_claws toes two_tone_fur two_tone_tail were weredog
 

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This looks like this may actually be the next step of evolution for four-legged land animals

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