BATHYPELAGIC SQUID BATHYTEUTHIS 75 



the buccal lappets by the Bathyteuthidae would be an example of the 

 retention of this primitive character in a deep-sea form only, with 

 no trace of the character in other groups. 



Naef (1923) believed the buccal suckers to be a primitive character 

 possessed by Protodecapus, a prototype. He placed the Metateuthoidea 

 at the base line leading to Metateuthoidea Oegopsida and Metateu- 

 thoidea Myopsida; the Myopsida and Oegopsida separate as equal 

 entities. At the base of the bush of recent Oegopsida, Naef split oflf 

 the Bathyteuthidae (including Ctenopteryx) and placed it closest to 

 the Myopsida. Then, at the same point he derived the Cranchiidae, 

 Chiroteuthidae, Brachioteuthidae, and Joubiniteuthidae in one line 

 at the top of the order, the Ommastrephidae and Thysanoteuthidae on 

 another, and finally all the rest of the oegopsids in the middle between 

 the Chiroteuthidae and Bathyteuthidae. Since the forerunner of recent 

 oegopsid families was supposed to have had buccal suckers and since 

 the Bathyteuthidae has buccal suckers, the character had to be lost 

 just prior to the appearance of all the other groups of Oegopsida. 



Naef's scheme, while possible, is not the only explanation that can 

 be offered. Several possibilities exist: (1) Buccal suckers could be 

 present if the Bathyteuthidae arose from the base of the myopsid stem 

 soon after the myopsids and oegopsids separated. (2) The Bathyteu- 

 thidae could have split off very early from the oegopsid main line, and 

 the Myopsida could have arisen from the base of the Bathyteuthidae. 

 Both of these situations could explain the presence of buccal suckers 

 either as a primitive character retained from the Protodecapus meta- 

 teuthoid stem and lost to the remaining Oegopsida, or as a new charac- 

 ter that appeared after the separation of the remaining Oegopsida. (3) 

 Another possibility allows the buccal suckers to be an independently 

 derived, convergent character. This situation would not require a closer 

 relationship of the Myopsida and Bathyteuthidae than can be rec- 

 onciled on tlie basis of existing information. The first two suggestions 

 would imply an immediate and rapid divergence of the groups in 

 structure and habitat: the Myopsida to a neritic and sublittoral 

 (epibenthic) existence and the Bathyteuthidae to a bathypelagic 

 existence. Naef's suggestion allows for the separation of the suborders 

 prior to the loss of buccal suckers to all oegopsids except Bathyteu- 

 thidae. The idea of convergence of the buccal suckers is compatible 

 with the very specialized nature of both of these groups. 



Number of Arm Suckers 



Bathyteuthis from different geographical areas show differences in 

 the numbers of suckers on the arms. Figure 16 shows the numbers of 

 suckers on each of the arms against mantle length for specimens of B. 

 abyssicola from Antarctic, Atlantic, and eastern Pacific waters and of 



321-534 O— 69 6 



