pelvic fin origin distance, the western Atlantic and 

 Mediterranean populations have a longer distance 

 (286-304, X 296 and 280-302, x 288 respectively) than 

 does the Gulf of Guinea population (267-284, x 275). 

 Of the three widespread species of Sarda, there 

 is at least as much justification for recognition of 

 subspecies in S. sarda as in S. chiliensis. However, 

 there appears to be no available name for the 

 western Atlantic population, the Azores 

 specimens appear intermediate in some 

 characters, and the differences are not great 

 enough to warrant recognition of this population 

 as a distinct subspecies at this time. Additional 

 study is needed on this problem. 



Gymnosarda Gill 



Gymnosarda Gill 1862:125 (type-species Thynnus 

 unicolor Ruppell 1838 by original designation). 



Comparative Diagnosis. -The monotypic genus 

 Gymnosarda differs from other bonitos in having 

 a well-developed swim bladder, in lacking any in- 

 termuscular bones on the back of the skull, and in 

 having more olfactory lamellae (48-56 vs. 21-39 in 

 the other Sardini). It is the only bonito with 19 

 precaudal and 19 caudal vertebrae. Gymnosarda 

 has a differently shaped head than do other boni- 

 tos (Tables 1, 22); the interorbital distance is much 

 wider, the eyes are larger, the postorbital distance 

 is shorter, and the distance between the origins of 

 the pectoral and pelvic fins is much larger. The 

 opercular bones are more elongate in Gymnosarda 

 than in other bonitos. 



Gymnosarda and Sarda share characters that 

 distinguish them from Orcynopsis and Cybiosar- 

 da: the bony caudal peduncle keels are well 

 developed, but each keel is divided into anterior 

 and posterior portions on each vertebrae; the 

 spleen is large and prominent in ventral view ver- 

 sus small and not visible in ventral view; the right 

 and left lobes of the liver are both much longer 

 than the middle lobe versus only the right lobe 

 being greatly elongate. 



The two genera also differ in several characters. 

 Gymnosarda has a pair of glossohyal tooth plates 

 which are absent in Sarda. Gymnosarda has a 

 naked body; Sarda is covered with tiny scales 

 behind the anterior corselet. Gymnosarda lacks 

 the horizontal stripes characteristic of Sarda. The 

 intestine makes a loop before reaching the anus in 

 Gymnosarda; the intestine runs straight from the 

 stomach to the anus in Sarda. In ventral view, the 



Table 22,-Morphometric characters of Pacific Gymnosarda 

 unicolor. First set of numbers are measurements expressed as 

 thousandths of fork length, second set as thousandths of head 

 length. 



spleen is visible on the right side in Gymnosarda; 

 it is centrally located in the posterior half of the 

 body cavity in Sarda. 



Remarks. -There has been a question as to the 

 valid name for the species in this monotypic 

 genus-unicolor Ruppell or nuda Giinther. The 

 problem arose when Giinther placed both Scomber 

 unicolor Geoff roy St. Hilaire 1817 and Thynnus 

 (Pelamis) unicolor Ruppell 1838 in the genus 

 Pelamys Cuvier 1831. This action made P. unicolor 

 Ruppell a junior secondary homonym of P. 

 unicolor Geoff roy St. Hilaire so Giinther replaced 

 the former name with P. nuda Giinther. Gill (1862) 

 eliminated the homonomy by describing new 

 genera for both unicolor Geoff roy St. Hilaire (Or- 

 cynopsis) and unicolor Rtippell (Gymnosarda). We 

 recognize unicolor Riippell as the valid name for 

 the type-species of Gymnosarda. Review of the 

 following synonymy shows equal usage of the 



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