ENVIRONMENT, PAST AND PRESENT 65 



like a lizard's, with feathers springing in pairs op- 

 posite each other at intervals down its full extent. 

 The wings have three fingers (with free meta-carpals) 

 each with a well developed claw. The skull, with a 

 full complement of teeth, is reptilian rather than 

 avian. The wing feathers were well-developed, 

 however, and there seems little reason to question 

 their ability to fly in the true sense. They were 

 virtually feathered reptiles. 



Between these and the next known fossils there is 

 a long gap. The lower Cretaceous (some forty mil- 

 lion years back) produced what might be termed the 

 first pseudo-modern bird in Ichthyornis, a gull-like 

 species. Judged by its wing construction and the 

 presence of a well developed keel on the breast bone 

 for the attachment of large flight muscles, it was 

 already an expert on the wing. But it still retained 

 teeth although those of the premaxillae (approxi- 

 mately the anterior half of the upper mandible) were 

 already lost. The skull is now much more bird-like 

 with a convincing bill. One of its most interesting 

 contemporaries was the large flightless diver 

 (Hesperornis), reminiscent in many respects of 

 modern loons (excepting its flightless condition) 

 but still retaining various reptilian structures in- 

 cluding teeth (absent, as in Ichthyornis, on the pre- 

 maxillae). 



