FOSSIL AND RECENT 193 



Thus it is improbable that clupeiforms were derived from known elopiforms or 

 vice versa. However, this does not rule out the possibility that these two orders 

 shared a common ancestor above the pholidophorid level, within the teleosts. The 

 ancestry of clupeiforms is obscure. Prior to the Albian no teleost is known to possess 

 any of the primary clupeiform cranial characters (for these, see Patterson 1970a). 

 Despite this, both the Clupavidae and the Leptolepididae have been considered 

 ancestral to the clupeiforms (Arambourg 1950, 1954). 



Recently, Patterson (1970b) has indicated that the Clupavidae is a heterogeneous 

 assemblage containing many poorly known forms. Those species which may be 

 referred to the Clupavidae with any degree of certainty show a fusion of the first 

 ural centrum with the first preural centrum (Patterson, op. cit.), a feature only found 

 among euteleosteans. 



This leaves the leptolepids as candidates for clupeiform ancestors. A suggested 

 leptolepid-clupeiform relationship is based upon gross similarities of jaw, trunk and 

 fin shape (Arambourg 1950, 1954). At present there is no firm evidence that the 

 leptolepids are involved in the ancestry of the clupeiform fishes, yet there is no reason 

 to reject such a suggestion. 



The leptolepids could not have been ancestral to the elopiforms, since the latter 

 are more primitive in showing a dermethmoid which is separate from the mesethmoid. 

 In leptolepids the dermethmoid is fused with the mesethmoid. On the other hand, 

 elopiforms are more specialized than leptolepids in possessing a supraorbital-infraor- 

 bital sensory canal connection and in lacking a basipterygoid process. There is no 

 known teleost primitive enough to be considered ancestral to both the elopiforms and 

 the leptolepids or to the elopiforms and the clupeiforms. 



In short, it is very unlikely that the elopiforms and the leptolepids are related 

 above the pholidophorid level and it is even more unlikely that the elopiforms and 

 the clupeiforms are related within the Teleostei. 



Members of the Elopiformes have at one time or another been considered related 

 to members of the Osteoglossomorpha (following the work of Patterson 1967c, the 

 plethodonts are included in this assemblage : the ichthyodectids are also considered 

 related to osteoglossomorphs, Greenwood et al. 1966 ; Patterson 1967c). It is 

 unlikely that such a relationship exists within the Teleostei. 



Garstang (1931) suggested a relationship between the Elopoidei and the Hyo- 

 dontoidei + Mormyroidei on the basis that at least some members of all three groups 

 show the development of an otophysic connection and a similarity in the opposition 

 of parasphenoid and basihyal teeth. However, the type of otophysic connection is 

 very different in the two groups and was probably developed independently. The 

 similarity in buccal occlusion may be explained as the retention of a primitive 

 feature, such as is found in pholidophorids, and is therefore of little use in indicating 

 relationship. 



Woodward (1901) related the Osteoglossidae and Plethodontidae to the Albulidae, 

 mainly on the basis of the powerful buccal dentition seen in these families. In view 

 of the great dissimilarities in the pattern of the roofing bones, infraorbital bones, 

 vertebral column and caudal skeleton, the albulids appear far removed from these 

 osteoglossomorph fishes (see also p. 207). 



13 



