VERTEBRATE PALEONTOLOGY MATTHEW 279 



Another interesting phase of recent progress in this group is the 

 probable difference in faunas widely apart geographically and in 

 different climatic zones. The splendid specimens secured by Charles 

 Ii. Sternberg in the last two seasons in the San Juan basin of New 

 Mexico appear to represent a fauna clearly distinct from any of the 

 three great northern faunas. Their true correlation has yet to be 

 determined by a more exact study of the fauna and stratigraphy, 

 but Mr. Sternberg's latest work, performed under heavy handicaps 

 opens up an important new field for dinosaur collecting and is the 

 last of a long series of important finds made by him during the 

 last 50 years. A fine skull and much of the skeleton of a gigantic 

 Ceratopsian has been secured by the American Museum; other im- 

 portant specimens are still in his hands and in the Upsala Museum 

 in Sweden. 



THE DINOSAURS NOT A NATURAL ORDER 



The dinosaurs are now generally recognized as not a natural order 

 of reptiles, but a composite group, including two distinct and rather 

 distantly related orders. 18 Dinosaurs correspond in a way to pachy- 

 derms among mammals, once considered a natural order, but now 

 recognized as an assemblage of animals superficially alike, owing 

 to parallel adaptation, but not really related. It is in this sense 

 that the term " dinosaurs " should henceforth be used and not as a 

 natural order of reptiles. The two orders are the Saurischia, in- 

 cluding Marsh's two groups of Sauropoda and Theropoda, and the 

 Ornithischia, or Orthopoda, the Predentata of Marsh. The first 

 group includes the gigantic amphibious dinosaurs, the great carnivor- 

 ous dinosaurs, and their slender, swift-running allies, and the more 

 primitive Triassic dinosaurs. Orthopoda include the iguanodonts 

 and duck-billed dinosaurs, the horned dinosaurs, and the armored 

 dinosaurs. All these are distinguished by a horny beak or bill and 

 a more birdlike arrangement of the pelvic bones, and have a cer- 

 tain degree of affinity to primitive birds, whereas the Saurischian 

 order has a corresponding relation to primitive crocodiles. The fine 

 memoirs by von Huene on various Triassic reptilia, 19 by Gilmore 20 

 on the carnivorous and armored dinosaurs, by Osborn on Camara- 



18 F. Von Huene (1909): Skizze zu einer Systematik und Stammesgeschichte der 

 Oinosaurior, Centralbi. f. Min. Geol. u. Pal., J'j?., 1909, s. 12-22 ; 1914. Natiirliehe Sys- 

 tem der Saurischia, idem, 1914, s. 154-158; 1914, Ueber die Zweistummigkeit der Dino- 

 saurler u. s. w., Neues Jabrb., B. B. xxxvii, s. 577-589. 



w Von Huene (1912-1916) : Series of memoirs and shorter articles chiefly in Palaeos- 

 tographica ; 1910-1914, Geol. u. Pal. Abhandl. ; 1920-1922, Acta Zoologica ; 1909-1922, 

 NenesJahrbuch and Centralbi. f. Min. Geol. u. Pal., etc. 



20 See p. 277, footnote 13. 



