August. 1929 



EVOLUTION 



Page Five 



Written words could be kept strai,i;ht, kejit tor future 

 generations. Knowledge began to accumulate. Each 

 generation started where the last one left off. Printing 

 helped too. Knowledge could be spread, all over the 

 world, to scholar and layman. With knowledge popu- 

 larized, nearl}- evervone was thinking. Bright minds 



got their starts, emerged to discover and invent, to help 

 lift mankind higher. So the rate of progress increased. 

 More thinking men and women on the job. More tested 

 knowledge to work with. The result — man making his 

 world lietter, making life happier. It sounds strange, 

 l:ut he talked himself into it. 



When Birds Had Teeth 



Bv FREDERIC A. LUCAS 



C EPARATED b}- millions of years from that 

 earliest of all known birds, the toothed Archaeop- 

 teryx of the Jurassic period (described last month), 

 the next birds that we know come from the chalk beds 

 of western Kansas. Time enough had passed for mem- 

 bers of one group to have quite lost their wings, yet 

 they still retained teeth, the most bird-like of them be- 

 ing quite unlike any modern bird in this respeci. The 

 first specimens were obtained by Professor Marsh in 

 his expeditions of 1870 and 1871, but not until a few- 

 years later, after the material had been cleaned and 

 was being studied, was it ascertained that these birds 

 were armed with teeth. The smaller of these birds was 

 not unlike a small gull and was, saving its teeth, so 

 thoroughly a bird that it may be passed by without 

 further notice. The larger, however, was remarkable 



Draw inii lj>- (ileeson 

 The Toothed Diver. Hesperornis Regalis 



in many ways. Hesperornis was a great diver, in some 

 ways the greatest of the divers, slender and graceful 

 in general build, looking somewhat like an overgrown, 

 absolutely wingless loon. 



The penguins, as everyone knows, swim with their 

 front limbs — we can't call them wings — which, though 

 containing all the hones of a wing, have become trans- 

 formed into powerful paddles. Hesperornis, on the 

 other hand, swam altogether with its legs — swam so 

 well with them, indeed, that through natural selection 

 the disused wings dwindled away and vanished, save 

 one bone. Hesperornis was large, upwards of five feet 

 long, and if its ancestors were equally bulky, their 

 wings were c|uite too big for swimming under water as 

 do the short-winged Auks which fly under water quite 

 as they fly over it. Hence the big wings were closelv 

 fiildud upon the body to off'er tlr* least possible resi-t- 



ance, and it was advantageous that th>jy and their 

 muscles dwindled, while the bones and muscles of the 

 legs increased by constant use. By the time the wings 

 were small enough to be used in so dense a medium as 

 water, the muscles had become too feeble to move 

 them, and so degeneration proceeded until but one bone 

 remained, a mere vestige. The penguins retain their 

 great breast muscles, as did the Great Auk, since it 

 takes even more strength to move a small wing in 

 water than a large wing in the thinner air. 



As a swimming bird, one that swims with its legs 

 and not with its wings, Hesperornis has probably never 

 been equalled, for the size and appearance of the bones 

 indicate great power, while the bones of the foot were 

 so joined to those of the leg as to turn edgewise as the 

 foot was brought forward, thus offering less resistance 

 to the water. It is remarkable that these leg bones are 

 hollow, because as a rule the bones of aquatic animals 

 are more or less solid, their weight being supported 

 by the water; liut those of the great diver were almost 

 as light as if it had dwelt on dry land. That it did not 

 dwell there is conclusively shown by its feet. 



The most extraordinary thing about Hesperornis is 

 the position of the legs relative to the body, and this is 

 something that was not even suspected until the skele- 

 ton was mounted in a swimming attitude. As anyone 

 knows who has watched a duck swim, the usual place 

 for the feet and legs is beneath and in line with the 

 body. But in our great extinct diver, the joints of the 

 leg bones are such that this was impossible, and the 

 feet and lower legs must have stood out nearly at right 

 angles to the body, like a pair of oars. This is such 

 a peculiar attitude for a bird's legs that, although ap- 

 parently indicated by the shape of the bones, it was at 

 first thought to be due to the crushing and consequent 

 distortion to which the bones had been subjected, and 

 an endeavor was made to place them in the ordinary 

 position, even at the expense of a dislocation of the 

 joints. But when the mounting of the skeleton had 

 advanced further, it became evident that Hesperornis 

 was no ordinary bird and could not swim in the usual 

 manner, since this would have brought his knee-caps 

 uncomfortably up into his body. And so, at the cost of 

 much time and trouble, the mountings were so changed 

 that the legs stood out at the sides of the body, as 

 shown in the picture, a position verified later by the 

 discovery of the specimen now in the American Mu- 

 seum of Natural History, in which the limbs lay in 

 jii^t the position given them by the artist. Mr. Glceson. 



