36 
Carter R. Gilbert 
the peninsula to rise somewhat by epeirogenic adjustment. This same 
mechanism, recurring throughout the rest of the Cenozoic, may partly 
account for the pronounced elevational differences of successive shore- 
lines (Opdyke et al. 1984). As indicated earlier, the Pliocene “Wicomico 
Shoreline” (Cody Scarp) may have occupied a position closer to present 
mean sea level than the current (30 m) elevation of this land feature 
would seem to suggest. 
Peninsular Florida is believed to have maintained a more-or-less 
continuous connection to the adjacent mainland during the next 12 to 
14 million years (i.e., into the early mid-Miocene), at which time a 
gradual rise in sea level resulted in partial, or possibly complete, isola- 
tion of the peninsula (Vail et al. 1977, Vail and Hardenbol 1979) (Fig. 
5). In the late Miocene, ca. 10 million B.P., another sharp drop in sea 
level occurred (ca. 200 m below present mean sea level), which again 
caused peninsular Florida to be joined to the mainland. This connection 
was broken in the latest Miocene, ca. 5 million B.P., when another pro- 
nounced rise in sea level isolated the peninsula. This was the same 
marked eustatic cycle that produced the desiccation and subsequent 
refilling of the Mediterranean Sea by the Atlantic Ocean, an event Hsu 
(1972, 1978) believed to have occurred bewteen 5 and 5.5 million B.P. High 
sea levels persisted throughout the Pliocene, 5 to 2 million B.P., but 
dropped as a result of Pleistocene glaciation, when the Florida penin- 
sula was restored. 
Endemic fishes of the Florida peninsula fall into two basic groups: 
(a) well-defined insular populations (either subspecies or races) of wide- 
ranging eastern North American species; and (b) endemic peninsular 
species, mostly in the family Cyprinodontidae, that have no obviously 
close relatives elsewhere in eastern United States. The first group is 
represented by distinct subspecies of Notropis emiliae , Micropterus sal- 
moides, Lepomis macrochirus and possibly Lepomis marginatus, and by 
a racially distinct population of Ictalurus natalis. Subsequent study will 
probably reveal other examples. The second group is represented by 
Fundulus seminolis and Jordanella floridae (Gilbert 1980f, Gilbert and 
Burgess 1980e), and probably also by Fundulus cingulatus , Leptoluca- 
nia ommata, Lucania goodei and Heterandria formosa (Gilbert and 
Burgess 1980d,f,g; Martin 1980). The last four species are found 
throughout all or much of peninsular Florida ( L . ommata ranges about 
halfway down the peninsula), but also range narrowly outside this area. 
Fundulus cingulatus may be related to certain other freshwater species 
in North America (Chen 1971), the genus Lucania apparently is most 
closely related to certain Cuban and Jamaican genera (Hubbs and 
Miller 1965), and the relationships of F. seminolis are uncertain. The 
