CARNIVORA 185 



3. Except for the Mesonycliidae, the tracing back of the phyla of Creo- 

 donta points to derivation from arboreal ancestry. 



4. The geographical dispersal of the Carnivora appears to be from a 

 Holarctic center and the various families are presumably derived from 

 different dispersal points within that realm. 



5. Derivation of the Felidae from Dinictis, while the Machserodonts 

 are derived from Hoplophoneus. 



INVESTIGATIONS DESIRABLE 



1. Basal Eocene Creodonts — skulls and skeletons to decide their affin- 

 ities. 



2. Eocene ancestors for the Felidae. While derivable from the Mia- 

 cidas, this family is clearly not derivable from any known group of 

 Miacidae. 



3. What is the real significance of the resemblances between Mesony- 

 chidae and Artiodactyla ? Does it mean that the Mesonychidae are not 

 Creodonts, but a flesh-eating specialization from the pro-Artiodactyls ? 

 or does it mean that the Artiodactyls are derived from Creodont an- 

 cestry ? 



4. What are the real affinities of the Mustelid-Canid-Viverrid group 

 of European Oligocene Carnivora. Are they ancestral to all, or merely 

 analogous to one or two of these three modern families? The problem 

 can not be definitely settled on the dentition only. 



5. What are the real affinities of the Ursidae? The morphologic data 

 point to Mustelid derivation. The paleontologic data seem to indicate 

 a nearer affinity to the Canidae, but are not altogether convincing. They 

 are usually regarded as of old-world derivation through Ursavus and 

 Cephalogale. But it must be remembered that exactly as good evidence 

 might be adduced for deriving them from the American Cynarctus and 

 CynodesTfritis. 



6. What is the derivation of the Hyaenidae? Is Ictitherium an annec- 

 tant type indicating Viverrid affinities, or merely another case of con- 

 vergence in dentition? Have they anything to do with Aelurodon? 

 Here, again, the morphologic and paleontologic evidence are in apparent 

 conflict, the latter pointing to close Viverrid affinities, the former to 

 more remote Canid affinities. 



RODENTIA 

 MATERIAL 



The overwhelming predominance of rodents among modern mammals 

 is well known. They are by no means so common as fossils, and of those 



