Identification request discovered in Missouri

[Maneralization]

discovered this in SW MO in a heavily timbered area buried roughly 10” deep. It measures 9 1/2” in length. If someone has some thoughts of what it could be I would love to hear your ideas. 

[ScottBlooded]

Looked at this and was totally prepared to say “you found a rock” and move on but wait, what’s that! Enhance! 
 

Shell imprint! My first thought is always brachiopod but nail, hammer, etc. I see a lot of brachiopods, and I don’t know the geologic age of the rocks you would have pulled this from. But shell, for sure, which almost certainly means (at least most) of the rest of the marks and indentations are shells too, just in cross section. Maybe someone more knowledgeable/who knows the area better will weigh in. 

[Rockwood]

I gather from the tags that this may not have been the expected answer. The external shape of this piece does not suggest that it is fossil as a whole.

[Mark Kmiecik]

Google "bird skull" and look at the images. This is not a bird skull. It appears that many of the pits and pockets on this rock are indeed fossils. However they are molluscs and bits of shell and other marine organisms. Most are difficult to ID as such because of the amount of weathering on the rock's surface. Cracking the rock open may reveal some specimens that are better-preserved.