Figure ii.~Acanthopleurus serratus: 



lateral view of entire specimen, syntype, 



ca. 95 mm SL, Oligocene of Canton Glarus, 



Switzerland (Agassiz 1842:pl. 75). 



triacanthodids and establish it as an intermediate 

 between the two famiHes, as discussed more fully in the 

 preceding section on the relationships of the Triacan- 

 thodidae. 



The fossil species of Triacanthinae are represented 

 mainly by several dozen specimens of the Oligocene 

 Acanthopleurus. These specimens are little more than 

 impressions, although in some cases rather complete, left 

 in the black schist of Canton Glarus, Switzerland, and 18 

 of them have recently been reexamined for this work. 

 The general appearance of all the specimens is decidedly 

 like that of Recent triacanthids. The specimens of 

 Acanthopleurus examined fall naturally into two 

 groups: 1) moderately elongate, like most of the Recent 

 species; and 2) decidedly elongate, much more so than 

 any of the Recent species. The moderately elongate 

 specimens differ from all the Recent species by having a 



slightly deeper (5-8% SL vs. 2-4% SL) caudal peduncle, 

 i.e., less constricted just in front of the caudal fin base. 

 Only one specific name is available in Acanthopleurus, 

 this being serratus Agassiz (1842 illustration, 1844b 

 description), based on decidedly elongate specimens. 



The deeper bodied Acanthopleurus is described here as 

 collettei in honor of Bruce B. CoUette, National Marine 

 Fisheries Service, National Systematics Laboratory, who 

 is a valued colleague, diving companion, editor of this 

 monograph, and a responsible agent for having it 

 published. It is diagnosed on the basis of the depth of its 

 body and caudal peduncle, as specified above and in the 

 measurements given below and in Figure 46. The seven 

 type specimens of collettei are designated in the list of 

 fossil specimens examined for this work. 



Proportional measurements as percent of standard 

 length for A. collettei are as follows, with the number of 

 specimens on which data were recorded for the character 

 preceding in parenthesis the range, which is followed by 

 the average value in parenthesis when ap- 

 propriate: greatest depth (7) 24.0-31.4 (27.7)% SL; 

 least caudal peduncle depth (6) 5.5-8.3 (6.7)% SL; length 

 of pelvic spine (6) 20.0-30.8 (25.5)% SL; length of first 

 dorsal spine (6) 20.3-35.2 (27.1)% SL; length of second 

 dorsal spine (6) 6.1-10.3 (8.2)% SL; length of third dorsal 

 spine (5) 2.6-3.9 (3.7)% SL; length of fourth dorsal spine 



Figure iH.— Acanthopleurus serratus (above), lateral 

 views of entire specimens, left, 153 mm SL, and, 

 right, 127 mm SL. to contrast with the deeper bodied 

 A. collettei (below), left, ca. 120 mm SL, paratype, an( 

 right, 96.2 mm SL, paratype: all specimens from 

 the Oligocene of Canton Glarus, Switzerland. 



