124 J. F. Fitzpatrick, Jr. 



much of the phylogeny of Procambarus that he expressed in his review 

 of the Blandingii Section (1962a). Two of his "Groups" in that paper 

 were elevated to subgenera in 1972, with the remaining species of the 

 Section being assigned to the subgenus Ortmannicus. It is important to 

 reemphasize in this paper that certain members of the subgenus Pen- 

 nides (formerly the Spiculifer Group of the Blandingii Section) possess 

 many of the "primitive" characters assigned to the "ancestral procam- 

 barid" (multiple cervical spines; short, broad areola; strongly acuminate 

 rostrum; "striped saddle" pattern of coloration; male first pleopod with 

 full complement of terminal elements, those elements relatively simply 

 constructed; etc.). One must likewise keep in mind that in the Cambari- 

 dae the male and female organs associated with sperm transfer are the 

 most — and sometimes only — reliable taxonomic characters; one can 

 develop good concepts of initial (i.e., early) plesiomorphies in other char- 

 acters/structures, but they are all subject to considerable convergence 

 or modification in response to environmental habits, making determina- 

 tion of synapomorphies nearly impossible. 



Considerable data are accumulating to indicate that the "upper 

 Tennessee" river had independent access to the Gulf of Mexico at least 

 as recently as the early Pliocene. This new interpretation does not refute 

 the phylogeny of the Cambaridae accepted by the more recent workers, 

 but it does require reexamination of temporal assignments for events. 

 Certain zoogeographic confusions are partially resolved. Alternate 

 explanations to those currently accepted are proposed to (1) account for 

 the distribution of the early-emerging Cambarellinae, (2) elucidate the 

 existence of "primitive forms" of the subgenera Pennides and Ortman- 

 nicus of Procambarus in their present geographic distribution, (3) sug- 

 gest the origin of the subgenus Scapulicambarus as being in lower 

 Georgia in pre-Miocene times, (4) propose that the spread of the genus 

 Fallicambarus east of the Mississippi River is post-Miocene, (5) place 

 the origin of the genus Faxonella in central Louisiana during the 

 Eocene, (6) identify the origin of the genus Hobbseus as eastcentral 

 Mississippi during the Eocene, and (7) suggest pre-Eocene origins for 

 the genera Orconectes and Cambarus, with their spread into the area of 

 the Mississippi Embayment occurring only relatively late in geologic 

 time. 



PHYLETIC AND ZOOGEOGRAPHIC OVERVIEW 



The genera Barbie amb arus , Cambarus, Disto cambarus, Fallicam- 

 barus, Faxonella, Hobbseus, Orconectes, and Troglocambarus have 

 been demonstrated to be derivatives of the ancestral procambarid 

 (Hobbs 1967, 1969, 1981). Hobbs, however, did not visualize a more or 

 less lineal descent with a simple cladistic dichotomy. Instead, he postu- 

 lated radiate evolution in which some Procambarus, principally eastern 

 species, arose at one level of the tree and diversified, and a second, 

 somewhat later in time, series of diversifications in one of the stem 



