2i 4 ELOPIFORM FISHES 



6. The Albulidae and Pterothrissidae are similar to one another in many advanced 

 features such as : the pattern of sensory canals ; the inferior mouth in which the 

 immobile premaxilla is the major functional component of the upper jaw ; the 

 development of a hyopalatine series characterized by a hyomandibular-metaptery- 

 goid foramen, a flattened symplectic, a well-developed ectopterygoid process and a 

 double articulation of the palatine with the neurocranium ; certain specializations 

 of the dentition borne by the gill arches ; and loss of the seventh hypural and third 

 uroneural in the caudal skeleton. The shared specializations indicate a common 

 ancestry for the two families which is to be found within the Osmeroididae. 



The Albulidae and the Pterothrissidae are divergently specialized in features 

 related to different diets. Both families may be traced back to Cenomanian times. 



7. The Notacanthiformes show certain similarities in snout morphology with 

 the albuloids indicating that the albuloids may stand ancestral to that order. The 

 Recent albuloids (the only albuloids sufficiently well known in details of snout 

 morphology) are too specialized to be considered ancestral, but the possibility of some 

 Cretaceous albuloid ancestry of notacanthiforms is suspected, the early pterothrissids 

 being the most likely candidates. 



8. Relationships of Elopiformes with basal groups of other cohorts are briefly 

 reviewed. It is suggested that there is no relationship within the Teleostei between 

 elopiforms and the Clupeomorpha or between the elopiforms and the Osteoglosso- 

 morpha. The possibility of a relationship between the elopiforms and any euteleo- 

 stean group is difficult to analyse because of the sparse information available on the 

 early evolution of the more primitive members of the Euteleostei. Attention is 

 drawn to a few minor features of caudal anatomy seen in both euteleosts and 

 elopiforms which may indicate the existence of a common teleostean ancestor. 



VI. ACKNOWLEDGEMENTS 



I wish to thank Dr H. W. Ball, Keeper of Palaeontology in the British Museum 

 (Natural History), for the opportunity of studying the collections which form the 

 basis of this work. I am grateful to Dr B. G. Gardiner of Queen Elizabeth College 

 (London University) for his supervision of the work ; to Professor G. Chapman in 

 whose Department the work was done ; to Drs C. Patterson and P. H. Greenwood 

 of the British Museum (Natural History) for fruitful discussion, and to the authorities 

 of Queen Elizabeth College for the provision of a Research Demonstratorship grant. 



VII. REFERENCES 



Agassiz, L. 1833-1844. Recherches sur les Poissons fossiles : 5 vols., 1420 pp., 396 pis., with 



supplement. Neuchatel. (For dates of publication see Woodward and Sherborn, 1890.) 

 1845. Rapport sur les poissons fossiles de l'argile de Londres. Rep. Br. Ass. Advmt Sci. 



York, 14 (1844) : 279-310. 

 Allis, E. P. 1903. The skull and the cranial and first spinal nerves in Scomber scomber. J. 



Morpk., Philadelphia, 18 : 45-328, 10 pis. 

 Applegate, S. P. 1970. The vertebrate fauna of the Selma Formation of Alabama. Fieldiana, 



Geol. Mem., Chicago, 3 : 383-433, 30 figs. 



