MECHANICS OF LOCOMOTION 



Measurements, in millimeters, and ratios of limbs of Oligocene titanotheres 



739 



Gramportal rectigrades. — The graviportal rectigrades 

 are heavy-bodied, long-limbed, short-footed (brachy- 

 podal) quadrupeds, typified by the elephants. The 

 type has been called by Gaudry "rectigrade." We 

 do not yet know the stages of graviportal progression 

 in the evolution of the Proboscidea. Our knowledge 



of these stages must be gained by a comparison of the 

 ancestral series, which is still incomplete. The 

 measurements given below show the relatively short 

 tibia and radius and the very short metatarsus and 

 metacarpus, which are paralleled by those of the 

 graviportal Amblypoda and Pyrotheria. 



Measurements, in millimeters, and ratios of limbs of graviportal rectigrades 



Tibio- 

 femoral 

 ratio 



IVIeta- 

 tarso- 

 femoral 

 ratio 



Radio- 



bumeral 



ratio 



American mastodon (Mastodon americanus) 



Indian elephant (Elephas indicus) 



African elephant (Loxodonta africanus) 



Uintatherium mirable (Eocene) 



Pyrotherium sp. (Eocene) 



° 1, 020 



1,020 



1,050 



695 



622 



705 

 618 

 755 

 360 

 351 



117 



138 



144 



70 



540 



462 



670 

 685 

 870 

 380 

 238 



165 

 183 

 205 

 106 



18 

 33 

 30 

 19 



SUMMARY OF CTTRSORIAI AND GRAVIPORTAL PROPOR- 

 TIONS OF SEGMENTS OF IIMBS OF UNGULATES 



FEATURES CONSIDERED 



The foregoing principles of evolution of the ungulate 

 limbs are again illustrated in the widely varying types 

 of locomotion comprised within the nine typical 

 families of the great order Perissodactyla. These 

 families range from the extreme cursorial to the ex- 

 treme graviportal adaptation. A still more remarka- 

 ble fact is that within several single families both 

 extremes of adaptation are developed. The habits 

 and habitats of these families and subfamilies are 

 treated in Chapters I (Preliminary), II (Adaptive 

 radiation), X (Origin and evolution), and VIII 

 (Musculature of titanotheres and other Perissodac- 

 tyla) of this monograph. 



We may now examine the perissodactyls in respect 

 to the length, proportions, and other adaptive features 

 of the scapula, humerus, radius, ulna, ilium, femur, 

 tibia, and fibula. 



The student who desires to acquaint himself with 

 the muscles which control the shifting rugose areas of 

 origin and insertion should consult Chapter VIII. 



The foregoing summaries and comparisons of limb 

 ratios in the ungulates generally help to a compre- 

 hension of the adaptations of the arches and limbs of 

 101959— 29— VOL 1—4 



the titanotheres and other Perissodactyla, because 

 these animals naturally parallel members of other 

 groups of ungulates. 



The arch and limb elements of the Perissodactyla 

 are displayed in the following synoptic figures: 



Figures 671-673. Condylarthra and Perissodactyla. 



Figure 674. Artiodactyla and Perissodactyla. 



Figures 675, 676. Lophiodontidae (Helaletinae) (subcursorial) . 



Figure 676. Tapiridae (mediportal) . 



Figure 678. Palaeotheriidae (cursorial to mediportal) . 



Figure 679. Hyracodontidae (subcursorial). 



Figure 679. Amynodontidae (mediportal to graviportal) . 



Figures 679-682. Rhinocerotidae (subcursorial to graviportal). 



Figures 683, 684. Equidae (cursorial). 



Figures 685, 686. Brontotheriidae (mediportal to graviportal) . 



A comparative survey of these figures bone by bone 

 or segment by segment demonstrates afresh that in 

 each family respective adaptations to mediportal, to 

 graviportal, or to cursorial locomotion results in con- 

 vergent, parallel, or homoplastic forms, proportions, 

 ratios, and indices. 



Under this masterful influence of teleogeny, or 

 analogous adaptation, which masks, dominates, or 

 completely conceals the syngenetic or ancestral char- 

 acters, there still remain two causes of distinction or 

 separation between members of different phyla: 



