140 NEW YORK STATE MUSEUM 



Genus TITANICHTHYS Newberry 



Plates of head and trunk resembling- those of Dinichthys, but relatively 

 thinner, and more laterally expanded. Pineal plate elliptical, broader than 

 long, in contact with the centrals, and pierced by one or two foramina, the 

 latter sometimes capped by a small bony operculum. Lower dental pJates 

 long and slender, without denticulations, grooved in the anterior portion of 

 the oral margin as if for a horny sheath, and somewhat turned upwards at 

 the symphysis. Outer (free) portion of clavicular developed as a stout arm, 

 rounded or semicylindrical in cross-section. 



The remarkable fishes comprised by this genus represent the ultimate 

 stage of specialization attained by Dinichthyids. Unable to maintain an 

 existence except under peculiarly favorable conditions — their gigantic size, 

 unwieldy organization and w^eak dentition presupposing an estuarine habitat 

 and abundant food supply — they survived for a relatively short period, and 

 within a limited area. Their remains are confined, so far as known, to the 

 Upper Devonic of Ohio. Forerunners of the genus, however, make their 

 appearance as early as the Ulsterian, and fragmentary plates very suggestive 

 of Titanichthys occur in the Hamilton limestone of Milwaukee, Wis. 



The arrangement of cranial plates conforms closely to the pattern of 

 typical Coccosteans. The bone substance, however, is much thinner, the 

 sutures more intimately fused, and all of the plates are relatively broader. 

 The long axis of the pineal, too, is transverse instead of longitudinal, as in 

 Dinichthys and Coccosteus. The enormous width and fiatness of the 

 cranial and abdominal armor plainly indicate a depressed, raylike form of 

 body, probably correlated with bottom-feeding and generally sluggish 

 habits. Certainly the degenerate character of the dentition does not 

 permit us to look upon these creatures as very formidable competitors of 

 Dinichthys and the much more agile Cladoselache. 



Interesting features are displayed by the abdominal armor. The mode 

 of articulation between the head shield and antero-dorsolateral plates is less 

 complicated than in Dinichthys, the condyle and socket of the latter form 

 being replaced by an elongated flange and groove, which probably admitted 



