SUBORDER E 



PYROTHERIA 245 



more especially Metamynodon, have a rather short skull with a broad 

 forehead, broad palate and narrow cranium, but lacking the usual character- 

 istic among notungulates of an inflated mastoid region. The humerus has 

 a deltoid crest extending far down the shaft, and a low, simple trochlea, 

 but no entepicondylar foramen. The ulna is well developed, the femur is 

 compressed antero-posteriorly and has a lamella-like third trochanter ; is 

 not much longer than the rather slender tibia, which is not fused with the 

 fibula. The calcaneum is short and stout. The flattened, broad astragalus 

 articulates closely with the fibula and cuboid, and is very similar to the 

 astragalus of amblypods. Manus and pes are pentadactyl. The metapodials 

 are short and stout. The terminal phalanges were apparently short, broad 

 hoofs. In the milk dentition |- D are still present. 



Astrapotherium Burm. [Mesembriotherinm Moreno ; Listriotherium, Xylotherium 

 Mercerat) (Fig. 330). \ premolars. Of this genus only, the skull and 

 extremities are known. Miocene of Patagonia. 



Astrapothericulus Ameghino. Miocene. 



Parastrapotherium Ameghino. f premolars. Liarthrus Ameghino. Lower 

 Miocene ; Pyrotherium beds. 



Astraponotus Ameghino. Supposed to have complete dentition. Oligocene. 



Proplanodus Ameghino. Eocene ; Notostylops beds. 



Suborder E. PYROTHERIA. i 



2.1 0.3.3. 



Skull short and anteriorly elongated. Dentition reduced. ^ ^ „ ■ Lower 



■^ ^ 1. 0.2.3. 



incisors long and stout, projecting forward. Cheek teeth each tvith two parallel 



transverse ridges. Bones of the extremities stout. Extremities presimiably pentadactyl. 



The Pyrotheria are restricted to the lower Tertiary of Patagonia, and 

 comprise the largest of all South American ungulates. They appear first 

 in the Notostylops beds, and become extinct after attaining their maximum 

 development in the Pyrotherium beds. 



The skull must have been short because the cheek teeth begin near the 

 tusk-like incisors. The orbits in the adult are situated above the fourth 

 premolar. The dentition lacks one upper incisor. P- is triangular and 

 consists of two outer and two small inner cusps, P^ has an anterior cusp 

 and a cross ridge. All of the remaining premolars are similar to the molars 

 and have two parallel cross ridges and a basal cingulum, which on the 

 upper molars is on the outer and anterior surface and on the lower on 

 the inner and posterior surface. The lower jaw exhibits a broad ascending 

 ramus and a weak slender coronoid process. 



The scapula has a well - developed coracoid process. The humerus 

 and femur are much longer respectively than the forearm and lower leg. 

 The humerus is antero - posteriorly compressed, without entepicondylar 

 foramen, but with a very prominent epicondylar crest on both sides, and 

 with well- developed exterior deltoid crest. According to Gaudry, this 

 specialisation points to digging habits and great mobility of the digits. 



^ Ameghino, Florentino, Mammiferes cretac«s de TArgentine. Boletin del Iiistit. Geogralico 

 Argentino, 1897. — Linea filogenetica de los Proboscideos. Anales del Miiseo Nacioiial, Buenos 

 Aires, 1902. — Oaudry, A., Fossiles de Patagonie. Annales de Paleont., Paris, 1909. 



