1912] Miller: Pacific Coast Avian Palaeontology 



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coast region today is the turtle-dove (Zanaidura macroura), a 

 bird of wide distribution over the Austral region and even to 

 the tropics. Its habits and its abundance are such that one can 

 scarcely concede as possible that it could have been present 

 during the deposition of the Pleistocene beds of Rancho La Brea 

 and yet not be preserved as a fossil. 



Palamedea and Cariama have in their present home in South 

 America a distribution and habits not unlike those of the stork, 

 Euxenura. Both groups are, however, absent from the fossil 

 collections. The peculiarly isolated positions which these birds 

 occupy in the scheme of classification, as well as the measure of 

 uncertainty as to their proper location systematically, makes any 

 light that palaeontology might throw upon the subject especially 

 desirable. Most careful search was made therefore to see if any 

 part of the skeleton of these birds had been preserved, but 

 nothing was found that resembled either species in the smallest 

 degree. 



The parrot order, abundant a few degrees to the southward, 

 is unrepresented in the deposits. This may be due to the fact 

 that the only forest fauna which we have preserved to us (cavern 

 deposits) is of Upper Sonoran and lower Transition zones, and 

 thus local conditions may have been unfavorable for these birds. 

 On the other hand, as suggested in the case of Ortalis, they may 

 have been driven southward before the deposition of any of 

 the beds thus far explored. 



All trace of true struthious birds is lacking in the collec- 

 tions also. The northward diffusion of such forms as the eden- 

 tates and Hyclroclioerus among the mammals, the presence since 

 early Pleistocene time of rheas in South America, the occurrence 

 of tridactyl struthionids in the Pliocene of northern India, and 

 of Struthiolithiis in the superficial deposits of northern China, 

 increase the probability that some day the discovery of true 

 struthious birds in North America will be announced. The most 

 potent factors that would bring about such distribution are 

 first, the possible northward diffusion of rheids along with eden- 

 tate mammals and, second, the passage of Struthiolithus or its 

 relatives along the line of proboscidean invasion from Asia by 

 way of the land bridge to Alaska. 



