Brachiopterygians Pulyplerus and Calamoichthys are the only 

 genera in this peculiar group of African fishes (Figure 2-5). 

 These genera have a distinct lobe at the base of the pectoral 

 fins, from which the name is derived. They differ also in that 

 the throat area, posterior to the opercular margin, is covered 

 by two large gular plates. 



The head is fairly large and broad, and the eyes lie far 

 forward. The anterior nasal opening is at the tip of a tube 

 extending forward above the fold of the upper lip; the pos- 

 terior opening is just anterior to the eye. On the head the 

 openings of the lateral-line canals are apparent. There is a 

 large slit-like spiracle at the anterior end of a fold extend- 

 ing back to the upper margin of the opercular flap. This fold 

 allows lateral movement of the operculum. The opercular 

 opening extends down onto the underside of the head where 

 a transverse membrane joins one side with the other; this 

 transverse membrane lies above the large gular plates of 

 either side. There is a fleshy lip on the lower jaw matching 

 that of the upper jaw. 



The body is elongate and slim; that of Calamoichthys is 

 eel-like. The dorsal fin is represented by a series of finlets, 

 about nine in number; each finlet is preceded by a spine with 

 a bifurcated tip. The most posterior finlet marks the ante- 

 rior end of the caudal fin, which extends around to the 

 underside of the caudal peduncle. The tail fin is rounded 

 and without lobes. There is a small anal fin almost touching 

 the anterior margin of the caudal fin. In front of the anal 

 fin is the V-shaped opening of the cloaca. There are two pairs 

 of lateral fins: the pectoral fins have extensive fleshy lobes; 

 the pelvic fins lack such lobes (Calamoichthys lacks pelvic 

 fins). 



The body is covered by thick rhomboid scales which allow 

 only limited flexion of the body. These scales are covered by 

 a thin layer of shiny enamel (ganoin). 



Choanate fishes 



This association of fishes is based on their usually having 

 both external and internal nasal openings, which amphib- 

 ians, reptiles, and mammals also have. 



The eoe/acanth Lafimeria The group name, coelacanth, is 

 derived from the hollow neural spines of the vertebral col- 

 umn. Lalimerm, which sprang into prominence in 1938 as a 

 living fossil, is known from several specimens collected in 

 African waters (Figure 2-6). The head is proportionally 

 large, resembling that of a typical fish. The mouth has 

 thick marginal folds. There is an anterior and a posterior 

 nasal opening; the anterior one is at the tip of a tube. There 

 are also three pairs of openings leading into a midline ros- 

 tral organ. The eye is large, and there is no spiracle. The 

 body is covered with large cycloid scales with an enameled 

 surface. There are two dorsal fins. The caudal fin is diphy- 

 cercal, with an upper and lower lobe as well as a slightly 

 separated terminal lobule. The anal fin has a fleshy lobe, 

 as do the two pairs of lateral fins and the posterior dorsal 

 fin. 



Latimena is a large species, four to five feet in length and 

 weighing 60 to 180 pounds. Since these fishes have been col- 

 lected during only a limited part of the year, their full life 

 history is not known. 



D/pnoans or /ung fishes This group gets its name. Dipnoi, 

 from its two breathing devices, gills and lungs. Protopterus is 

 the most easily obtained example of the lungfish (Figure 

 2-7). It is an elongated fish, round in cross section. The 

 mouth is small and in it the outermost nostril of either side 

 can be observed. Just inside the mouth margin hes the inner 

 narial opening. The fleshy lips extend back on the side of 

 the head, some distance from the mouth. The eye is rather 

 small. The opercular opening is limited to a slit just in front 

 of the pectoral fin, which almost appears to come out of the 

 opercular opening. 



The body is covered with large cycloid scales that are very 

 thin and covered by the skin. The scales extend forward 

 onto the head, and thus none of the cranial bones is exter- 

 nally evident. There is a dorsal fin, which is continuous with 

 the caudal fin. The caudal fin and its supporting fleshy lobe 

 taper to a posterior point, i.e. it is isocercal or protocercal. 

 The caudal fin is continuous with the anal fin. The cloaca 

 opens asymmetrically to the left of the anterior margin of 



spiracle 



nasal tube. 



finlet 



POLYPTERUS 



pectoral fin 



Figure 2-5. The brachiopterygians. 



26 • THE VERTEBRATES AND THEIR EXTERNAL ANATOMY 



