WILLIAMS: CRABS OF THE GENUS CALLINECTES 



adapted to such an environment, but fossil evi- 

 dence for its existence in the Paleocene remains 

 indirect. 



There are constant structural differences be- 

 tween the early fossil series and modern Cal- 

 linectes. The palms of chelae of C. jamaicensis 

 Withers, 1924 (Eocene), C. alabamensis Rathbun, 

 1935 (01igocene),C. dedivis Rathbun, 1919a (low- 

 er Miocene), and C. reticulatus Rathbun, 1919a 

 (Oligocene-lower Miocene) are short and faceted 

 more like Callinectes than other living genera of 

 portunids, but they are relatively thinner than in 

 living members of the genus. The fingers in these 

 early forms have length-width proportions and 

 tooth arrangements that resemble modern C. 

 sapidus, but the tooth rows are relatively nar- 

 rower proximally on propodal fingers and less in- 

 clined toward development of a molariform crush- 

 ing surface. Of the four external facets on the 

 palm, the upper mesial one in the fossil series is 

 always inclined downward toward the inner sur- 

 face in major chelae whereas in modern Cal- 

 linectes species it is nearly horizontal in the major 

 chela and noticeably inclined downward only in 

 the minor one; moreover, the third or dorsolateral 

 facet is relatively wider in living Callinectes 

 species than in any of the early fossils. Compres- 

 sion and erosion may have altered relief but not 

 uniform angle of inclination of facets in the fos- 

 sils. Generally, fossils older than early-mid Mio- 

 cene attributed to Callinectes have less powerful 

 chelae than living species and these differences in 

 structure seem significant enough to warrant 

 generic separation of the two series when more 

 material comes to light. 



MODERN DISTRIBUTION 



Confined almost exclusively to shallow, often 

 brackish coastal waters as adults, the genus Cal- 

 linectes is represented by six species distributed 

 (Figures 24-27) around the Caribbean Sea and 

 southward to southern Brazil: C marginatus, or- 

 natus, danae, exasperatus, bocourti, and sapidus. 

 A seventh species, C maracaiboensis , is localized 

 in estuaries of Venezuela. One of these species, C 

 marginatus, bridges the Atlantic, ranging with C 

 gladiator and C. latimanus from Mauritania to 

 Angola in West Africa. It also reaches the Cape 

 Verde Islands. Only three species occur in the Gulf 

 of Mexico, exclusive of the southeastern part off 

 Florida: C rathbunae, an isolated relative of C. 

 bocourti in the western Gulf, C similis, an essen- 



tially Carolinian form ranging northward along 

 the coast, and C. sapidus, which ranges far 

 beyond, occasionally to the Maritime Provinces of 

 Canada. In the eastern Pacific, disregarding dis- 

 tant island occurrences, C. arcuatus is distributed 

 from extreme southern California to Peru, shar- 

 ing its range with C. bellicosus in the region of 

 Baja California and with C. toxotes from there 

 south. 



If one relies on structure of male first gonopods 

 alone for estimation of morphological similarity, 

 the following zoogeographical associations 

 emerge. The set of species with short first 

 gonopods (C marginatus, gladiator, ornatus, and 

 similis) has separate eastern and western Atlan- 

 tic components, and one member on both sides of 

 the tropical Atlantic. The second set with longer 

 first gonopods (C. arcuatus, bellicosus, danae, and 

 exasperatus) occurs in the tropical western Atlan- 

 tic and eastern Pacific. The third set with quite 

 long first gonopods (C toxotes, bocourti, rath- 

 bunae, maracaiboensis, latimanus, and sapidus) 

 has representatives in all regions. Distributions of 

 all species fit patterns accepted by Ekman 

 (1953:30, ff.) as representative of many along the 

 tropical-subtropical Atlantic and east Pacific 

 coasts, but one, C. sapidus, has a latitudinal range 

 that seems to exceed this pattern. In this species, 

 development of a northern and southern form may 

 be in progress. 



The amphi-Atlantic distribution of C. mar- 

 ginatus, records of C exasperatus, marginatus, 

 ornatus, and sapidus from Bermuda, C. arcuatus 

 from the Galapagos Islands, C. toxotes from Juan 

 Fernandez, as well as less removed northern mar- 

 ginal records for essentially southern species 

 along the North American continent (C. bocourti 

 in southern Florida and Mississippi; C. mar- 

 ginatus in North Carolina; C. similis in New Jer- 

 sey; C sapidus in Nova Scotia) all point to exten- 

 sions of range by larval transport in currents 

 (Verrill, 1908b; Garth, 1966). Investigators work- 

 ing with larval stages (reviewed in Williams, 

 1971) suggest that larvae and megalopae can 

 move considerable distances; zoeae have been 

 found off St. Johns River, Fla., at stations up to 

 160 km, and megalopae in the same area up to 128 

 km from shore. In Chesapeake Bay and Pamlico 

 Sound, N.C., megalopae have been found 170 and 

 100 km respectively from presumed points of 

 entry to the estuarine systems. Most of this off- 

 and-onshore movement of larval stages appears to 

 be a homeostatic developmental feature in the life 



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