This black fossil is somewhat of a puzzle. It was found in the Jeffersonville Limestone of Clark County, Indiana, USA. This layer would be Middle Devonian (approximately 390 million years ago). It is mixed in the remains of crinoid stems. Length is about 2.5 cm and it branches several times with maybe 18 offshoots.
Is it some sort of graptolite or plant remains washed in from another area?