IIatcher: Fore Limh and Mani.^ mk HRoxrosArRus. ;J75 



I am also strongly inclined to the opinion that the late Professor 

 Marsh was right when in plate XXXV^III. of his Dinosaurs of North 

 America he figured the manusof Morosaurus with digits I., II. and III. 

 provided with claws and IV. and V. deficient in those elements, thus 

 indicating an entaxonic structure of the nianus in this genus of sauropod 

 dinosaurs. The Morosaurus manus first described and figured by 

 Osborn,' and later associated and figured with a humerus, radius, and 

 ulna by Osborn and Granger does not appear to me as entirely demon- 

 strating the propriety of the arrangement of the phalanges and meta- 

 carpals as shown in the figures and described in the text of those 

 authors. A reproduction of Osborn' s figure of this foot is given 

 in fig. 14, and I wish especially to call attention to metacarpals II. 

 and III. The curvature of the shafts of fhese bones as well as the 

 nature of their proximal interarticulation, if their slight contact can be 

 thus designated, is such as to indicate that they pertain to opposite feet. 

 Compare the closely interlocked metacarpals II. and III. shown in figs. 

 4 and 1 1 and in plate XX. with the same bones in fig. 14. The arrange- 

 ment which obtains in the former is well adapted to give the necessary 

 strength and rigidity at that point where it w-as most needed in the 

 manus of these ponderous beasts, while that of the latter is indicative 

 of weakness and instability at the precise point where stability was to 

 be expected. In short I believe the right foot of Morosaurus as 

 figured by Osborn and Osborn and Granger has the metacarpals and 

 phalanges wrongly placed and that in the figure given by Marsh the 

 arrangement of these elements was essentially correct, although that 

 author may have erred in allowing one or more too many phalanges 

 for digit IV. 



Summary. 



The chief points regarding the structure of the fore limb and foot 

 of Brontosaurus established in the preceding paragraphs rnay be sum- 

 marized as follows : 



1. The humerus, radius and ulna are shorter and lighter than the 

 corresponding bones of the hind limbs. 



2. The radius and ulna do not cross completely as in the mammalia. 



3. The carpus, like the tarsus, consists very likely of a single ele- 

 ment — the scapho-lunar. 



4. The metacari)als are longer than the metatarsals. 

 'See Bull. Am. Mus. Nat. Hist., Vol. XII., pp. 161-172. 



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