Complex sentence: The insignia of this tribe, evidenced in their art and design, is the fiddlehead, in this case an immature frond of the Ostrich fern, "Mattueccia struthiopteris", that grows along the banks of the Penobscot River.
Split into simpler sentences: The insignia of this tribe, evidenced in their art and design, is the fiddlehead. This is the immature frond of the Ostrich fern, (Mattueccia struthiopteris) that grows along the banks of the Penobscot River.