[Does so]

Sort of a sea-going "calprop". (Sorry, Google isn't helpful with an image for "calprop").

That yellow pine must be something else!

I thought yellow pine was a southern tree, but all the ones I've seen were pressure-treated, so...

[Cheburashka]

Caltrop

[Riley]

Try ‘caltrop’.

http://images.google.com/images?hl=en&q=caltrop&btnG=Search+Images&gbv=2

That was pretty much my first thought, as well.

[Fraxinus]

Yellow pine could be any of a number of 2-3 needled pines. In this case it is probably pitch or loblolly pine, both of which grow in south Jersey and Delaware. It also could be Virginia pine which in the uncommon case it is usable for timber is sold as southern yellow pine.

Probably was preserved by anoxic mud and water so polluted that almost all decay organisms cannot live.