160 LÖNNBERG, SOME REMAIXS OP -NEOMYLODON LISTAI. 



]e, welche an verschiedenen Stellen vereinzelt auftritt und 

 später zu einem einheitlichen Panzer verschmilzt» Römer 1. c. 

 p. 531). It is thus as if the ossification was caused by the 

 need of strengthening the primary horny shields. If the onto- 

 genesis should be regarded as a true record of phylogenesis 

 the horny shields of the Dasypodidce must also be phylo- 

 genetically older than the bony scutes. It could, however, 

 be assumed that the ancestors of both the Dasypodidce and 

 *Mylodontidce have had some indifferent ossification in the cutis 

 or in the subcutanean layers, but that these did not become 

 fully developed before at a comparatively late ontogenetical 

 period. If then the ancestors of Dasypodidrr for some reason 

 or other got well developed horny scales and shields, it is 

 easy to think that these secondarily came into connection 

 with the ossiiications which were already present. In con- 

 nection with the horny shields the, in reality primary, ossi- 

 fications were now transformed and got a more superficial 

 Situation to become more active as a support for the horny 

 shields. In such a way it could also be explained that the, 

 in reality older, ossifications became ontogenetically later 

 developed, because their new function was to strengthen and 

 to be an addition to the horny shields. Simultaneously the 

 mode of ossification of each scute from several different points 

 at the same time is explained when each scute might be con- 

 sidered to be a union of several primary ossicles. 



But there may be still another theory. If the ancestors 

 of all South American Edentata have had scales and hair 

 and later developed ossifications in the cutis we can think of 

 two diverging ways of evolution. In one of these we find 

 the ancestors of Dasypodidce and Glyptodontidce. These ani- 

 ni als got their scales better and better developed and united 

 into horny shields which, as has been mentioned above, be- 

 came connected with the ossifications in the cutis and deve- 

 loped into an armour which made the growth of hair more 

 and more unnecessary and impossible. The other brauch 

 again reduced the scales and kept the ossifications as Mylo- 

 dontidce or got even those reduced because they had no use 

 for theni as Megatherium, Bradypodid.ee, Myrmecophagidte etc. 

 If this is true the prior ontogenetical development of the 

 horny shields in the youngs of Dasypus is congruent with 

 the phylogenesis. 



