Siren lacertina, Eel-like Amphibian (like a Salamander in appearance) found in Northern Florida, USA. Pleistocene age. The Greater Siren is found usually as isolated vertebrae fossils, and some other smaller limbs. Most of these fossils are found in rivers and by sieving. So you can expect to only find a few nice ones here and there.
The box size is 6.0cm x 4.0cm.