Collette and Gillis: Osteological differences between two species of Grammatorcynus 



27 



Figure 15 



Left anguiars and retroarticulars in lateral view, 

 (a) Scomberomorus semifasciatus. Port Moresby, 

 New Guinea, 510mm FL, 3.5 x ; (b) Acanthocybium 

 solandri, Miami, FL, 1403mm FL, Ix; (c) Gram- 

 matorcyniis bilineattis, Papua New Guinea, 382 mm 

 FL, 4.5 x; (d) G. bicarinatus, Western Australia. 

 765mm FL, 2x. 



is much narrower than the dorsal arm. 

 The length of the dentary from its 

 anterior margin to the tip of the ven- 

 tral arm is 97-109% of the length of 

 the dorsal arm. The ventral arm is 

 longer in G. bilineatus (104-109% of 

 dorsal arm length, Fig. 14c) than in 

 G. bicarinatus (97-98%, Fig. 14d). 

 The ventral arm is longer in Gramma- 

 torcynus than it is in Scomberomorus 

 (86-97%) and Acanthocybium (91- 

 96%). Species of Grammatorcynus and 

 Scomberomorus have a notch on the 

 anteroventral margin of the dentary 

 that is absent in Acanthocybium. Acan- 

 thocybium has a prominent notch on 

 the anterior margin of the dentary 

 that is indistinct or absent in Gram- 

 matorcynus and Scomberomorus. 



Angular (Fig. 15) The triang- 

 ular anterior end of the angular (fre- 

 quently called articular) fits into the 

 dentary anteriorly. The posterior end 

 of the angular bears three large pro- 

 cesses: the dorsal process, directed 

 forward and upward; the ventral pro- 

 cess, directed forward; and the pos- 

 terior process, directed backward and 

 upward. The posterior process is 

 hooked and carries a transverse artic- 

 ular facet for the quadrate. The length 

 from the tip of the posterior process 

 to the tip of the dorsal process is 

 40-47% of the total length of the bone. 

 The length from the tip of the poster- 

 ior process to the tip of the ventral pro- 

 cess is slightly longer, 44-52% of bone 

 length. The depth of the angular, mea- 

 sured from the tip of the dorsal pro- 

 cess to the tip of the ventral process, 

 is 36-48% of the total length, with the depth of G. 

 bicarinatus being greater (44-48%, Fig. 15d) than that 

 of G. bilineatus (36-41%, Fig. 15c). The ventral pro- 

 cess is approximately as long or longer than the dor- 

 sal process in Grammatorcynus. In G. bilineatus, the 



ANGULAR 



ventral process is 84-105% of the length of the dorsal 

 process, and in G. bicarinatus the ventral process is 

 longer than the dorsal process (153-200%). Only Acan- 

 thocybium (99-148%, Fig. 15b), S. commerson (99- 

 162%), and S. queenslandicus (115-136%) also have a 



