It seems to us that the advantage of the kinetic skull in comparison to the akinetic is not 

 any kind of capture, but in holding the still living, moving prey. The kinetic and akinetic 

 <s can be identically effective in catching prey. But it is easier for kinetic jaws to hold it. 

 can note that akinetic straight jaws during the holding of prey will push forward on the object 

 ught (Fig. 8-l); and the resultant forces applied by them to the object held will also be 

 rected forward. In the akinetic skull this load lies in holding prey by the teeth. This may 

 avoided by the convex form of jaw, but then the jaws would always be "bent down" to some prey of 

 ited size and could not hold smaller prey. Kinesis provides the predominantly bent jaws with 

 re effective jaw pressure on any item seized, and eliminates their |_ t he jawsj deficiencies (Fig. 

 2). Akinetic jaws may be analogized to claws; the kinetic, to fingers; since fingers are more 

 itable than claws for holding objects, so kinetic jaws are more suitable than the akinetic for 

 e same purpose. The complexity of the movements of cranial kinesis is a result of the complexity 

 the cranial structure. 



In grasping prey, the kinetic skull has other advantages over the akinetic (analogous to the 

 advantages of fingers over claws): the kinetic upper jaw can transfer the prey along the lower 

 jaw, crushing its resistance and killing it. During squirming of the prey, the kinetic jaws holdinc 

 it can relax slightly, without releasing the victim, and finally exhausting it in the struggle 

 (the "spinning? principle"). The amort i zat ional hypothesis also does not contradict this role of 

 kinesis. All these functions of kinesis can exist together, as kinesis has a complex significance, 

 serving as the best means of holding prey. 



--p. 1408-- 



From this point of view, the relative weakness of the protractor muscles is understandable; 

 their fundamental role is to return the maxillary unit of the skull from the operative retractive 

 position to the normal position necessary for compact closing of the oral cleft. Also, protraction 

 is accomplished somewhat farther along than the "normal" central position of the maxillary segment 



and always accompanies the opening of the mouth and the closing of the jaws. There 

 of the hypothesis of Boltt and Ewer (156*) which says that protraction serves for free 

 teeth, stuck in the victim during the grasping of the prey and for momentum in swallow 



s the truth 

 ng the upper 

 no it. 



We ought 

 of vertebrate 

 t i on. The lo 

 prey--for the 

 among the Cot 

 giving a diff 

 forms which r 

 harmful (as i 

 for example P 

 of the adapti 

 adapta t i on is 

 This situat io 

 espec i all y 

 f eedi ng on 

 specific form 

 small (but no 

 predator's ja 

 When prey i s 

 is not so ess 

 Typical cases 

 others ( I orda 

 with long jaw 

 (Versluys, 19 

 be pointed ou 

 preserved; an 

 only to the m 



to g i ve here 

 s of loss of era 

 ss of k ines is 



, k i nes is is 

 ylosaur i a 

 erent explana 

 equire maximu 

 n some forms 

 lacodont i a, a 

 ve values of 



ore importa 

 n occurs info 

 portant, appa 

 ry small or 1 

 s of predatio 

 t very small) 

 ws, such as i 



cons i derably 

 ent ial, si nee 



of th is kind 

 nski i, 1963). 

 s due to the 

 12). The los 

 t that in the 



example of t 

 ore pr i m i t i ve 



an exp 

 nial ki 



is to 



useles 

 ny Chel 

 t ion, h 

 m press 

 of vege 

 lso not 

 k ines i s 

 nt for 

 rms for 

 rentl 

 arge pr 

 n, and 



relat i 

 nsects, 



smalle 



for se 



are 

 Kines 

 lesser 

 s of k i 



presen 

 h i s wou 



forms 



lanat i on 

 nes i s 

 be expec 

 'all s 

 on ia and 

 owever, 

 ure on t 

 tarians, 

 ed by Ve 



would b 

 a given 



h ich t 

 el im inat 

 ey. Kin 

 espec ial 

 ve to it 



by 1 i za 

 r than t 



zing it 

 Crocodil 

 is in th 

 f irmness 

 nes is in 

 ce of 

 Id be th 

 of k i nes 



of t 

 h ich 

 ted i 

 pec i a 



ma ny 

 for t 

 he f o 



but 

 rsluy 

 e adv 

 form, 

 he de 

 ing k 

 es i s 

 ly fo 

 s own 

 rds, 

 he pr 

 , long 

 ia, P 

 e for 



of t 



Pter 



sok i n 



Ion 



he hist 

 occurre 

 n (1) 

 1 i zed 



Ornith 

 he loss 

 od bein 

 espec ia 



s)j (3) 



antageo 

 exclud 

 velopme 

 ines is; 

 is adva 

 r the g 



s i ze; 

 and sma 

 edator, 

 , relat 

 hytosau 



of 

 he link 

 osaur ia 

 es i s an 

 g-beake 

 eta- an 



ory of the v 

 d independen 

 n imals wh ich 

 egetarian f 

 i sch ia; even 



of k ines is 

 g chewed — k 

 1 ly in mollu 



in some sit 

 us, but when 

 ing the poss 

 nt of the 



it also occ 

 ntageous ( i n 

 eneral ized p 

 prey of that 

 11 vertebrat 



the advanta 

 i vely thin, 

 r ia, Ichthyo 

 tak i nes i s ca 

 age of the 1 



is probably 

 d prok i nes i s 

 ian icht 

 ph ik ines 



ery 

 tly 



do 

 rms 



Ver 

 i n v 

 nes i 

 sk e 

 uat i 



som 

 ibil 

 cond 



ITS 



its 

 reda 



s i: 

 es b 

 ge 

 p i nc 

 saur 

 nnot 

 ong 



ass 



ki 



hyop 



numerou 

 i n var io 

 not need 



iadect 

 sluys re 

 egetaria 

 s i n th 

 aters an 

 ons i n 

 e other 

 i ty of r 

 ary pala 

 in the c 



unspec i 

 tors tha 

 e may be 

 the la 

 f k ines i 

 her-1 ike 

 ia, Me so 



be mai 

 jaws to 

 oc ia ted 

 nes i s i 

 hages. 



cases in the 

 us 1 i nes of e 



to hold squ i 



dae and Pare 

 marked about 

 n forms); (2) 

 s case would 

 d other such 

 hich the pres 

 kind of co 

 eta in ing k ine 

 te has proven 

 ase of specia 

 alized forms) 

 t feed mainly 



seized in th 

 rger [_predato 

 s for seizing 



jaws are adv 

 sauria, dolph 

 ta ined i n the 

 the brain cas 

 with this. I 



that case ca 

 The above per 



h i story 

 volu- 

 rming 

 iasaurs 

 this, 



those 

 even be 

 forms, 

 erva t ion 

 ting 

 sis. 



to be 

 lized 



1 n 



on prey 



■•]• 



it 



ant ageous. 

 ins and 

 spec ies 

 e 



t should 

 n be 

 tains 



It a predator specializes in feeding on coarser prey, subequal to itself or larger, the load 

 on the cranium during the capture, killing and chewing [of food] is so great that kinesis is dis- 

 advantageous, through lessening fhe solidity of the skull. Kinesis may be advantageous in absence 

 of food mastication by the jaws but it becomes disadvantageous for more or less prolonged chewing 

 of the food requiring, as said above, rather firm pressure on the object processed. The loss of 

 kinetism in the Therapsida line is associated with this fact. Snakes occupy a special position. 

 In snakes, a more highly specialized form of kinesis developed with an extreme degree of movability 

 of elements of the maxillary segment in relation to each other, which aids in swallowing large prey 

 whole. As a consequence, snakes in many cases kill 



