606 PROCEEDINGS OF THE NATIONAL MUSEUM vol. us 



Rhizoprionodon (Rhizoprionodon) porosus Poey 



FiGUKES 7, 8 



Squalus porosus Poey, 1861, Memorias sobre la historia natural de Cuba, vol. 2, 

 p. 339, pi. 19, figs. 11, 12 (Cuba). 



Diagnosis. — Upper labial furrow well developed, 1.8-2.3 percent 

 of t.l. (1.3 and 1.5 in 2 out of 19 specimens); precaudal centra 

 markedly elongate in posterior monospondylous region (as in Plate 

 2a) ; precaudal vertebrae less in number than caudal vertebrae ; 

 anterior margin of pectoral fin usually longer than total length of 

 first dorsal fin (32 out of 35 specimens) ; snout in front of nostrils 

 3.7-4.5 percent of t.l. in specimens less than 575 mm. t.l.; 3.3-4.3 

 percent of t.l. in specimens over 575 mm. t.l.; total teeth in outer row 

 of upper jaw usually 25 (19 out of 22 specimens) ; total teeth in outer 

 row of lower jaw 24; total enlarged hyomandibular pores on both 

 sides of head more than 17; first dorsal origin usually slightly behind, 

 or over, level of appressed pectoral inner corner (ranging to slightly 

 in advance of inner corner) ; origin of second dorsal fin ranges from 

 above midpoint of anal base to over posterior fourth of anal base; 

 tip of appressed pectoral fin reaches beyond level of anterior third of 

 first dorsal base. Males maturing at a size between 575 and 644 mm. 



Description (see also table 13). — Precaudal vertebrae 66-75 (66 

 in only 2 out of 58 specimens; table 12); caudal vertebrae 69-85; 

 total vertebrae 136-159 (only 1 with less than 140); upper teeth 

 11-1-12 to 13-1-13 (usually 12-1-12); lower teeth 12-12; cusps of 

 some upper teeth in large specimens faintlj^ to moderately serrulate; 

 cusps of lower teeth adumbrating this condition; dentition of mature 

 males (one seen) and females similar; enlarged hyomandibular pores 

 9-19 on each side of head. 



Denticles imbricate, 3-ridged and 3-toothed in young; 3- to 5- 

 ridged and 3-toothed or irregularly margined in adults. 



Color of preserved specimens similar to that in R. terraenovae 

 (p. 601). Springer (1950) described the color of a fresh specimen (as 

 Scoliodon terraenovae) from deep water off the Bahamas. It was 

 characterized as having "unusually vivid markings of white spots and 

 white edges on the fins." 



A low interdorsal ridge present or absent. Both precaudal pits 

 present, the upper best developed. 



Growth changes: From the data at hand (table 13) growth changes 

 do not appear to be as marked as in the cognate R. terraenovae. Such 

 changes possibly are obscured because of the variability to be ex- 

 pected among insular populations and the great geographical range 

 represented. In contrast, the R. terraenovae figures were obtained, 

 with one exception, from GuK of Mexico specimens. Such dimen- 



