MANDIBULOHYOID CONNECTION IN CIRRHITOID FISHES 



93 



LIGAMENTOUS AND OTHER CONNECTIVE 

 TISSUE LINKAGES BETWEEN THE 

 MANDIBLE, THE PALATOQUADRATE, THE 

 HYOID ARCH, AND THE OPERULAR SERIES 

 IN THREE CIRRHITOID FAMILIES 



The family Cirrhitidae 



On the basis of their mandibulohyoid connections, two 

 distinct groups can be recognised within the cirrhitid species 

 examined. A third group, represented by Amblycirrhitus 

 bimacula (Jenkins), has no macroscopically detectable man- 

 dibulohyoid linkage (see below). 



Group I species (viz. Cyprinocirrhites polyactis [Bleeker], 

 Cirrhitichthys oxycephalus [Bleeker] and Cirrhitops fasciatus 

 [Bennett] have a stout, ligament-like connection between the 

 ceratohyal of each side and the coronoid process of the 

 corresponding dentary ramus (Fig. 1A). Group II species 

 (viz. Paracirrhites arcatus [Cuvier] and P. forsteri [Schneider] 

 also have a ligament-like band of tissue stemming from the 

 lateral aspect of each ceratohyal, but here it links each hyoid 

 arch with, predominantly, the corresponding quadrate, on 

 which it inserts immediately above that bone's process for 

 articulation with the anguloarticular. Part of this tissue, 

 however, is apparently continous with the tendinous insertion 

 of the Aw division of the adductor mandibulae muscle, (Fig. 

 1C). There is no macroscopically obvious and clearly defined 

 connective tissue linkage between the mandible and hyoid 

 arch in Amblycirrhitus bimacula (hereafter referred to as 

 Group III). 



In all three groups the adductor mandibulae Aw division 

 originates on the quadrate through a posterior extension of 

 the muscle's tendinous central aponeurosis, and thus is of the 

 basic perciform type as defined by Gosline (1986). The 

 extension is well-demarcated and moderately deep, and lies 

 across the quadrate-anguloarticular joint. Amblycirrhitus 

 bimacula (the single Group III species examined) is excep- 

 tional in this respect because the tendon lies very slightly 

 above the jaw articulation. Members of all three groups have 

 the fascia covering the Aw muscle extending posteriorly onto 

 the lower half of the quadrate, part of the preoperculum, and 

 the upper margin of the interoperculum as well. 



Within the three species of Group I there are differences in 

 the association between the mandibulohyoid connection and 

 the tendon of the adductor mandibulae A x muscle inserting 

 on the maxilla. Cyprinocirrhites polyactis is unique in having 

 what appears to be a short branch of the mandibulohyoid 

 connection arising near the latter's attachment to the coro- 

 noid process of the dentary and then joining the maxillary 

 tendon of the adductor mandibulae A Y muscle (Fig. 1A). In 

 Cirrhitichthys oxycephalus and Cirrhitops fasciatus , the maxil- 

 ! lary tendon partially fuses with the mandibulohyoid connec- 

 i tion at the point where the two cross over each other (the 

 latter lying medial to the maxillary tendon). From the point 

 i of fusion a short section (interpreted as a continuation of the 

 , maxillary tendon) runs into the tendinous central aponeurosis 

 of the adductor mandibulae Aw muscle (Fig. IB). 



There are also intergroup differences in other ligamentous 



land tendinous linkages (Fig. 1). Species of Groups I and III 



have a small upper, anterior division of the adductor man- 



[dibulae muscle A! inserting onto the maxilla only via the 



ligamentum primordium. Group II species, in contrast, have 



that division of the muscle inserting on the maxilla through 

 both the ligamentum primordium and the maxillary ligament 

 of adductor mandibulae Aj muscle. In all three groups the 

 major (ie lower) division of the muscle is attached to the 

 ligamentum primordium and the maxillary ligament, the 

 latter inserting on the ventral aspect of the maxilla, and the 

 former on the bone's dorsolateral aspect. 



Other intergroup differences involve the epihyal- 

 interopercular and the interhyal-interopercular ligaments 

 (For comparison of these and other ligaments with the 

 situation in other cirrhitoid families, see pp. 94 and pp. 97-98 

 and Figs 2-4). Group II species have the latter ligament 

 partly associated with the epihyal as well as the interhyal, as 

 does the single Group III species dissected; in Group I taxa, 

 however, the ligament is confined to the interhyal. The 

 epihyal-interopercular ligament shows more marked inter- 

 group differences, especially when species of Group I are 

 compared with those of the other two groups, a difference 

 possibly associated with the manner in which the epihyal 

 contacts the interoperculum. In Group II taxa, the lateral 

 face of the epihyal head articulates with a well-defined, 

 prominently raised and posteriorly directed facet situated a 

 little below the dorsal margin of the interoperculum and 

 slightly behind the bone's midpoint. The epihyal- 

 interopercular ligament in these fishes is short and stout, 

 originates on the lateral face of the epihyal near its dorsal tip, 

 and runs forward at approximately 45 to the sagital plane. It 

 inserts on the upper and anterior faces of the prominence 

 supporting the facet on the interoperculum against which the 

 epihyal articulates. A similar epihyal-interopercular ligament 

 occurs in the single Group III species examined, viz. Ambly- 

 cirrhitus bimacula. However, in this species, unlike those of 

 Group II, the interopercular facet is located on a relatively 

 lower base. 



The epihyal-interopercular ligament is most distinctive in 

 Group II. In species of this group (unlike the other groups) 

 the epihyal articulates directly with the medial face of the 

 interoperculum and not with a facet carried on a distinct and 

 elevated base (albeit only slightly so in the single Group III 

 species examined). The ligament itself is a prominent feature 

 originating (as in other groups) on the dorsal tip of the 

 epihyal's lateral face, from which it runs anteriorly onto the 

 dorsal margin of the interoperculum at a point near the 

 bone's anterior tip, where it is narrowly separated from the 

 attachment point of the mandibulo-interopercular ligament 

 (cf. Acantholatris monodactylus Fig. 3 & p. 94). 



A short interhyal-metapterygoid ligament is present in all 

 three groups. 



No interhyal-preopercular ligament is present in any exam- 

 ined species of the three groups (cf. the other cirrhitoids 

 described below). 



A stout mandibulo-interopercular ligament (Fig. 1C; lig. 3) 

 is present in taxa of the three groups. It is confined to the 

 lateral face of both elements in all species except Cyprinocir- 

 rhites polyactis and Cirrhitichthys oxycephalus (both members 

 of Group I). In these two species it divides anteriorly to insert 

 on both the lateral and the medial aspects of the anguloarticu- 

 lar bone. 



Also common to species of the three groups is a short and 

 deep, ventrally located ligament connecting the anguloarticu- 

 lar and dentary. 



