croc crocodile grass green reptile resting smiling skin texture armor armored armorment armour armoured armourment Australian-freshwater-crocodile backstraps basking bony ridges crocodilian crocodylus-johnsoni crocodylus-johnstoni danger dangerous dorsal-surface exotic fauna freshie hide hornback Johnston's-crocodile large leather leathery lethargic omnivorous opportunistic opportunistic-predator osteoderms patterns powerful predator reflection reptilian ridges rough rugged scales scutes tail territorial textured textures