there weren't any jackal-headed gods in Sumeria. unless it was a minor god in some back alley. the Sumerians and Akkadians didn't have any physical representations of their gods.

for the OP,

1. the Sumerians had been there since 6500 BC. the Egyptians had been there since 5500 BC.

2. the Egyptians were completely different from the Sumerians in writing, language, religion, culture, and genetics. they were not at all related to the Sumerians and came from some other region. nobody knows where they came from actually.

3. there are two periods of Sumerian history. the first period, from 6500 BC to 2150 BC (4350 years!!!) the Sumerians were just Sumerians. they probably came from the north. they were not Semitic.

4. the Sumerians and Sumerian gods you are thinking about, came into existence when Semite tribes (not yet hebrew, arab, or anything) united under a leader named Sargon, invaded and conquered Sumeria, in 2150 BC. the Semites adapted to Sumerian culture and made their adaptations of Sumerian gods.

that is the "Sumeria" we are familiar with, sometimes referred to as Akkad or "Akkadian Sumeria". since they made their capital in Babylon it is more commonly referred to as Babylonia. but Akkadian Sumeria would be more correct.

so what we think of as Semitic gods are actually Sumerian. the Semites, previously in the wilderness, had whatever sort of animistic polytheist (quasi-pagan) religion, much as the Arabs had before the Muslim conquest, and they adapted the Sumerian gods much as Mohammed adapted christianity. you can see how an adaptation would be different, but in the end, just an adaptation.

there were other upheavals such as the Assyrian conquest, and the united Chaldean/Persian/Median invasion, but Sumeria more or less remained Sumeria. that second period of Sumeria (Akkad, Babylonia) lasted almost two thousand years, when Alexander the Great conquered them in 330 BC.