Fig. 2.

Schematic phylogenetic relationship between regenerating animals. Simplified representation of the phylogenetic relationship between selected species capable of spinal cord regeneration (either within development or through their life span) following injury. Zebrafish, salamanders, and nemertea can regenerate their spinal cords throughout life following injury (red), frogs can do so at the tadpole stage (orange). Some higher-order animals are capable of this in the days following birth (green) including the opossum (until P17) and mouse (until P2). A number of other species (black) with common ancestors to these species are not known to regenerate their spinal cords following injury at any stage of development