52 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 124 



Relationships of the Blennioidei 



In the first part of this section, the Blennioidei have been delimited. 



Within the group, there is a whole series of what might be called 

 central tendencies that will distinguish the group from its ancestral 

 percoid type. Thus, in the Blennioidei, the body musculature (except 

 Prolatilus) does not extend forward over the top of the head, and 

 supraoccipital and frontal-parietal crests for its attachment are 

 lacking. The supratemporal commissure usually is complete, extending 

 across the supraoccipital. There are always more than 25 vertebrae. 

 Predorsal bones usually are absent. The anal fin rarely has pungent 

 spines, though there may be one of two unsegmented rays anteriorly; 

 the anterior interhemals are not enlarged and do not abut against 

 the first hemal arch. The pelvic fins either have fewer than five soft 

 rays or the inner rays are the longer. Pectoral and caudal fins usually 

 are rounded. In the caudal (except Parapercidae), there are fewer 

 than 15 branched rays. The gas bladder usually is absent in the adult. 



Most or all of the above characters are associated with the basal 

 mode of life of the Blennioidei noted previously; however, some 

 members show secondary modifications. These cause some of the 

 principal difficulties in distinguishing the lineages within the suborder 

 (fig. 12) and, for that matter, in defining the Blennioidei. Thus, cer- 

 tain members of the Blennioidei of various ancestries have developed 

 secondarily a more or less pelagic existence, e.g., the petroscirtines 

 among tropical blennies and Zaprora among zoarceoids. When this 

 happens, the tail may be more or less lunate, as in Runula, instead of 

 having the rounded form typical of the Blennioidei. Furthermore, the 

 pelvic rays of the petroscirtines tend to become filiform and weak 

 (completely lacking in Plagiotremus) rather than sturdy, as in other 

 tropical blennies. 



Some forms of the Notothenioidae and Blennioidae and all of the 

 Trachinoidae apparently bury themselves at least up to the eyes in 

 sand. This obviously creates several problems in breathing and 

 probably is associated with the wide gill openings of the notothenioid 

 family Trichonotidae and the superfamily Trachinoidae (see previous 

 section), as contrasted with the usual ventral restriction of the gill 

 slits in the Blennioidei. 



Certain members of the notothenioid family Trichonotidae have 

 become sand divers. Here, as elsew 7 here when this habit occurs — 

 e.g., in the Ammodytidae and Kraemeriidae — certain morphological 

 features seem to develop. Thus, unlike the rest of the notothenioids, 

 the pelvics of sand-diving trichonotids are close together and may 

 be reduced or disappear completely, as in, e.g., Apocreedia. 



Among eel-shaped forms, there is the usual tendency for the pelvics 

 to dwindle away and disappear first, followed by the pectorals. These 



