D. M. S. Watson— The Cheirotherium. 395 



III. — The CiiEmoTHERiuM. 



By D. M. S. Watson, M.Sc, Lecturer in Vertebrate Palaeontology in 

 University College, London. 



ALTHOUGH educated Europeans have never carried the art of 

 /V 'spooring', or tracking, to tlie perfection with which it is 

 employed by the Australian and African natives, it is possible for 

 us by applying a little common sense and certain experience of the 

 tracks of living beasts to the fossil footprints so commonly found in 

 terrestrial deposits laid down under arid conditions to find out many 

 features of the animals which made them. 



The tracks of Cheirotherium are commonly found in the Trias of 

 Britain and Germany. They occur in the Bunter and the lower part 

 of the Keuper, the faunas of which rocks are still very imperfectly 

 known in Europe. The most marked features of a Cheirotheroid 

 track are — 



1. That there are impressions of all four feet. 



2. That the fore-feet are very much smaller than the hind. 



3. That the hind-feet are always the more deeply impressed, 



4. That the track is extremely narrow, the feet of the two sides 

 being planted nearly on the same line. 



5. That the stride is long. 



1. Shows that the animal was four-footed. 



2. That the fore-legs were feeble in proportion to the hind. 



3. That the animal was very nearly balanced about its pelvis. 



There are two ways in which such a balance can be arrived at ; 

 either the beast stands bolt upiight like a meer-kat (Suricafa) or 

 a man, or it has a tail as long and massive as its body. The fact 

 that Cheirotherimn habitually touched the ground with its fore-feet 

 shows that it must have adopted the latter method and have had 

 a large massive tail. 



The fact that, the track is very narrow shows that Cheirotherium 

 was a very good walker ; any animal whicli has a wide track, like 

 a tortoise, has to swing from side to side whilst it is walking in order 

 to keep its centre of gravity over its track, and in doing so wastes 

 a large amount of muscular energy. Every animal which curries its 

 feet so close together that its ti-ack is nearly a single line must have 

 special arrangements to prevent it from kicking itself when running, 

 and is consequently likely to have well-ossified and ' finished' limb- 

 bones. An animal with a narrow track must, if it is to be efficient, 

 have a pelvis which is very narrow between the acetabula compared 

 with the length of its limb-hones; if it be otherwise, then, when the 

 animal is viewed from the front, the femur will not be in a vertical 

 plane, the animal being 'knock-kneed', a position wliich keeps the 

 abductors constantly in strain. Cheirotherium was thus a four-footed 

 animal with relatively small fore-legs and long heavy tail and narrow 

 pelvis. The very considerable stride, about a metre in the case of 

 the commonest British species, shows that it was at least as long in 

 the leg as a man. 



