Source: Montbrook :: Florida Museum of Natural History
An overall description of the Montbrook site)

“Montbrook is the first late Hemphillian site found in north Florida. It is about 120 miles (200 km) north of the Palmetto Fauna, the state’s only other source of late Hemphillian fossils. But unlike that region, Montbrook is producing more complete specimens and contains the first significant terrestrial small vertebrate fauna of this age from Florida. The fossil fish in the Palmetto Fauna are predominately marine, while at Montbrook a much larger percentage of the fish lived in fresh water. Similarly, more of the bird fossils found at Montbrook are from taxa associated with freshwater or terrestrial habitats (Fig.4), while all of the common birds in the Palmetto Fauna live along the coast and fed in the ocean. Despite over a century of collecting, the Palmetto Fauna contains less than half a dozen snake vertebra and no small rodents. There have already been several lower jaws of small rodents and numerous snake vertebrae found at Montbrook despite the fact that only a relatively small percentage of its sediment has been screenwashed and picked for microvertebrates. So Montbrook is providing the first direct evidence of its age about vertebrate life in a coastal river and adjacent habitats in the Southeastern United States.”