XipDias 



Istiophorus 



Figure 4. — Caudal skeletons of billfish. (From Gregory 

 and Conrad. 1937.) 



Tr 



The Blochiidae contains two distinct fossil forms, 

 Blochius longirostris and what I call the "Cylin- 

 dracanthus group". Complete skeletons of Blochius 

 (Fig. 6) have been found in the Lower Eocene de- 

 posits of Monte Bolca, Italy. The skeletons are 

 about 1 m long and exhibit many billfish characters 

 such as: a round and elongate rostrum, a low ver- 

 tebral number, elongate vertebrae, and a deeply 

 forked caudal fin. To the best of my knowledge no 

 one has critically studied Blochius since Woodward 

 (1901) published his catalogue of fossil fishes. 



Figure 5. — Two successive caudal vertebrae from a black 

 marlin (Makaira indica) showing the transverse flanges 

 (Tr) that project from each centrum. 



Figure 6. — A. Reconstruction of Paleorhynchus 

 glarisianus. B. Reconstruction of Blochius longirostris. 

 (From Gregory and Conrad. 1937: after Woodward. 1901.) 



The "Cylindracanthus group" (Aglyptorhynchus, 

 Congorhynchus, Cylindracanthus , Glyptorhyn- 

 chus, Hemirhabdorhynchus , etc.) are all known by 

 small, cylindrical, elongate structures (Fig. 7) that 

 are thought to be rostral fragments of aBlochius-like 

 fish (Carter, 1927). A few vertebrae have been 

 attributed to the "Cylindracanthus group" because 

 they were found associated with the rostra (Leriche, 

 1910), but the evidence that they belong to the 

 "Cylindracanthus group" is simply circumstantial. 



In order to tidy up the billfish classification, I have 

 chosen (Fierstine and Applegate, in press) to put the 

 "Cylindracanthus group" and Blochius into the 

 Xiphioidei Incertae Sedis. Although the establish- 

 ment of a category with uncertain affinities avoids 

 the responsibility of making a precise taxonomic 

 decision, it emphasizes our lack of knowledge of its 

 members. 



The Istiophoridae contains the living genera Is- 

 tiophorus, Makaira, and Tetrapturus, and the fossil 

 genera Brachyrhynchus, and possibly Acestrus. 

 Acestrus (Fig. 8) is only known from the Early 

 Eocene and the remains consist of the posterior part 

 of skulls. Casier (1966) felt that these crania be- 

 longed to a billfish, but he also noted the similarity to 

 the extinct scombrid, Scombrinus. The cranial 

 fragments of Acestrus are quite small, only 50-60 mm 



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