PYROTHERIUM 163 



Pyrotheriidae Ameghino 



All the forms assigned to this family are supposed to be 

 closely related to Pyrotherium and to have much the same 

 structure. Ameghino has proposed the following genera, 

 Pyrotherium, Para pyrotherium, Richardowenia, Archaeolo- 

 phus, Propyrotherium. 



Para pyrotherium is based on a small molar and a tush 

 which Ameghino first described as Pyrotherium planum, 

 later elevating the species to a genus, designated as Para- 

 pyrotherium, differentiated by the transverse crests being 

 low and the valley at either end being blocked by an 

 intertubercular ridge. Gaudry considered that this genus 

 represented either the milk teeth of P. romeri, or a variation 

 of that species. I can not see the basis of a new genus in 

 the material. 



The genus Richardoii'eni is based on half of a molar, 

 which has the transverse crest interrupted in the middle. 

 Too little is known of this form to base a valid genus or 

 even to associate it with Pyrotherium. 



Archaeolophus is founded on a small tush and part of 

 an upper molar, also inadequate material for a genus. 

 It is probably Pyrotherium. 



Propyrotherium is a smaller form from the Astra ponotus 

 beds, apparently a good genus; the type species being 

 P. saxeum, of considerable smaller size than any of the 

 Deseado species. The distinctive features of the genus 

 can not be given until more material is known. 



Carlozitteli is based on a small form from the Casamayor 

 with narrow molars. An incisiform tush is associated with 

 the molar, which, if correctly associated, would indicate 

 a wide deviation from Pyrotherium, and would probably 

 be an ancestral form. A second species is reported from 

 the lower Deseado beds, but I am a little skeptical as to 

 the horizon. 



