There are a few humanoid figures in the north of Norway with spread arms and legs like the one above. A typical interpretation of this type of figure is that of a pregnant woman about to give birth, perhaps seen from above when lying on the ground. But there are several aspects of the figure that does not fit with human anatomy.
There is a narrowing of the hips just below the belly in the figure that is similar to the hips in frogs, while in a human the hips would be widest just below the belly. Frogs have irregularly shaped fingers and toes, in varying numbers depending on the species, and this also fits with the figure.
The outspread arms remind me of wings, but the parts close to the body are too thin for wings and they seem to end in hands at the ends. So I rendered this version of the figure as a mix between bird and human. The legs also look like spindly bird legs, while the thighs in frogs and humans would typically be larger than in the figure.
This last rendering of the figure as a pregnant human is probably the most likely interpretation, but the arms and legs look very strange. The bird rendering also looks strange within the figure, but I think the one of the frog works quite well. Perhaps the figure is representing a mix of frog and human and this was used to symbolize something. Frogs have a lot of offspring and their life cycle is very evident from eggs, to tadpoles, to froglets to adult frogs. This could fit with the interpretation of the symbol as a humanoid about the give birth, and maybe it was a fertility symbol to represent hope for many and healthy children. The frogs also live both on land and in water, and this life in two “worlds” is another reason why frogs may have been used as a symbol. Such as the two worlds of the frogs representing the realms of life and death. Interpreting it as a mix of frog, human and bird would also add the realm of the sky.
This is just pure speculation based on how I’ve noticed a few rock art figures that reminds me of frogs. I also used this symbol in a workshop with first-year archeology students, and many of them also thought the symbol looked like a frog or a bird. I will do some more research to see if I can find examples of frogs or birds used as a symbol in prehistoric Norway.