i know horseshoe crabs are living fossil's but are rosenbergi or other's a very old species ? i look at pics and im thinking if something that nasty must be a survivor ? im jsut curious
Macros are not living fossils. They developed from supposedly one marine ancestor about 10 million years ago. Considering the worldwide distribution of these shrimp I would not be surprised if several, closely related marine shrimp were the ancestors of macros.