172 



THE OS PREY. 



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All Illustrated Magazine of Popular Ornithology. 



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Vol. IV, 



JULY AND AUGUST, 1000. Nos. ii and 12. 



Comments. 



THE AFFINITIES OF HESPEKOKNIS. 

 It is not often that we feel called upon to 

 quarrel with any of the statements contained in 

 the series of Contributions to the Osteologj^ of 

 Birds by Mr. W. P. Pycraft of the British Mu- 

 seum, but we do take exception to the statement 

 in his paper on the Pj'gopodes that Hesperornis 

 belon.gs to that sub-order. In the first place 

 the long- separate vomers and the freedom 

 from one another of the bones composing- the 

 palatine portion of the skull are, not Ratite^ 

 but generalized characters shared with the 

 Ostriches and a few other "left over" birds 

 among- existing- forms and these are quite suffi- 

 cient to exclude Hesperornis from tlie society of 

 the g-rebes and loons. In the second place the 

 shoulder girdle of Hesperornis is so unique and 

 reptilian, with its free clavicles, united with one 

 another by their larger ends, and articulating 

 with the coracoids in a manner different from that 

 found in any other known bird, that this charac- 

 ter in itself is sufficient to keep their possessor 

 out of the Pygopodes. Usually the clavicle 



is one of the earliest bones to disappear in a de- 

 g-enerate shoulder g-irdle; Rhea has none, and 

 Rhea has a g-ood sized wing-, but in Hesperornis 

 the clavicle is complete and functional although 

 nothing- is left of the wing- save the humerus. 

 It has always seemed to us that too little atten- 

 tion has been given this feature of the big 

 toothed bird. 



Passing- bj' the lack of union between ilium 

 and ischium, (a generalized character,) it re- 

 mains to be said that the pelvic girdle of Hespe- 

 rornis exhibits a g-reater degree of specializa- 

 tion than that of anj' other bird. The great 

 length of the pelvis, its great compression and 

 the depth of the ilia are all modifications to 

 adapt the bird for swimming. So, also, is the 

 great development of the outer toe and the peg 

 and socket articulations of its larger phalanges. 

 All birds that swim with their feet alone, and 

 are at all proficient in the art, such as the 

 Grebes, L,oons and Cormorants, have the outer 

 toe well developed, a mechanical feature which 

 lessens the tendency' of the foot to turn the bird 

 at each stroke. This feature is carried to the 

 extreme in Hesperornis and, coupled with the 

 narrowness of the pelvis, brings the center of 

 effort of each foot stroke more nearly under the 

 center of the bodj^ than in any other bird. In 

 bipeds which run well, such as man and the 

 Ostrich, it is the inner toe that carries the 

 weight, and is most developed; hence the suppo- 

 sition that Hesperornis lost its wing-s on land 

 and then took to water is quite untenable. The 

 wings of Hesperornis were too large to be used 

 under water, and hence they became atrophied 

 through disuse. At least this seems to be a 

 good working- hypothesis and is supported by 

 the fact that the flightless Cormorant of the 

 Galapagos has very small wing-s while the pelvic 

 g-irdle is uutre robust than in any other Cormo- 

 rant, the nearest approach being- Pallas' Cormo- 

 rant which is said to have been flightless, 

 although the degeneration of the wings is but 

 .slight. 



The position of Hesperornis seems lo us anal- 

 ogous to that of Zeuglodon; the one is a hig-hh- 

 specialized aquatic bird, and the other a highlj' 

 modified aquatic mammal. The one is a branch 

 of the stem from which the grebes may have 

 been derived, the other a branch of the stem 

 from which the cetaceans may have descended. 

 But the one is not a grebe nor the other a 

 cetacean, and neither has left any known suc- 

 cessors. 



F. A. L. 



