The "Cylindracanthus group" is currently in tax- 

 onomic chaos. Casier (1966) divided the group into 

 two parts; he placed one group in the family 

 Blochiidae of the Order Heteromi (=Notacanthi- 

 formes) and the other group in the family Xiphiidae 

 of the Order Scombromorphi ( = ?Scombroidei). 

 No explanation was given as to why there was a re- 

 lationship to the Order Notacanthiformes. Carter 

 (1927) showed that a Cylindracanthus rostrum was 

 similar histologically to a bill fragment of Blochius 

 and he also showed that it was similar to a spine of 

 the living trunkfish, Ostracion. Does this mean 

 that the Cylindracanthus structures are bills or 

 spines? What other structures would have a similar 

 histology? The microscopic interpretation is very 

 equivocal. Carter (1927) stated that the Cylindracan- 

 thus rostrum was composed of dentine. Tor Orvig 

 (pers. comm.) interpreted Cylindracanthus bills 

 to be composed of acellular bone. Rainier Zangerl 

 (pers. comm.) interpreted a photomicrograph (Fig. 

 14) of a ground thin section of a Glyptorhynchus 

 rostrum as dentine whereas, Melvin Moss (pers. 

 comm.) has suggested that the same structure is 

 composed of acellular bone. 



The rostra of the "Cylindracanthus group" are 

 characterized by two or more rows of "alveoli" 

 (Fig. 15) on one surface, the supposed ventral sur- 

 face. The "alveoli" are thought to have contained 

 denticles, but no tooth-like structures have ever 

 been present. I personally think that most, if not all, 



i i i I i i i i j i i i i j i i i i j i i i i i i i i i | i i i i I i i i 



Figure 15. — Rostrum of Glyptorhynchus sp. from the 

 Miocene of California. A. Lateral view. B. Ventral view 

 showing two alveolar grooves. 



of the "Cylindracanthus group" rostra will prove to 

 be fin spines. These structures are too numerous and 

 common in the fossil record for each to represent an 

 individual fish. 



Much of our lack of knowledge of fossil billfish 

 stems from the paucity of comparative anatomical 

 studies. Once this foundation is built there are many 

 intriguing problems to solve in the fossil record. It is 

 my hope that this paper has served as a stimulus for 

 others to enter an uncrowded research field. 



LITERATURE CITED 



AGASSIZ, L. 



1838. Recherches sur les Poissons fossiles. Neuchatel. 

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 BARDACK, D. 



1965. Anatomy and evolution of chirocentrid fishes. Univ. 

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BERG, L.S. 



1940. Classification of fishes both recent and fossil. (In Rus- 

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CARTER, J. 



1927. The rostrum of the fossil swordfish, Cylindracanthus 

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CASIER, E. 



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DANIL'CHENKO, P.G. 



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 In press. Xiphiorhynchus kimblalocki, a new species of fos- 

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1968. The suborders of perciform fishes. Proc. U.S. Natl. 



Mus. 124(3647): 1-78. 

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1966. Phyletic studies of Teleostean fishes, with a provi- 

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1937. The comparative osteology of the swordfish (Xiphias) 

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