CRANIAL MOVEMENT OF LIZARDS 



Following Bradley's work (19O3), on li 

 i si i ngu i shed: the occipital, maxillary, a 

 "1 vertebrates and is considered to be immo 

 id also the basi- and paraspheno i ds. The 

 f interest to us here primarily is the mov 

 le term "cranial kinesis". The relationsh 

 Lready been described by Bradley, Versluys 

 ; have confined ourselves only to their en 

 ie quadrate, squamosal and the supra-tempo 

 -ocesses ( "metak i net ic axis" of Frazzetta) 

 ith the bas i pterygo i dal processes, sometim 

 ;sides this, both segments are joined by t 

 Lements of the brain case. All these conn 

 ixillary segment relative to the occipital 

 <is with the anterior end upward and forwa 

 ;sides this, the maxillary segment during 

 insists of a series of related divisions - 



rd skulls, t 

 mand i bular. 

 ble. It is 



other segm 

 i 1 i ty of the 

 s between th 

 Hofer, Frazz 

 eration. Th 



1 bones with 

 the parietal 



of the ep i p 



cart i lag i no 



tions allow 



first, as a 



( protract i 



0- and retra 



pa i red: ( 1 ) 



hree fund 



The occ 



formed of 



ents are 



ax illar 



maxilla 



etta, Oel 



ese relat 



the late 



with the 



terygo i ds 



us and me 



a 1 im i ted 



whole, i 



) or dow 



ction cha 



quadrate 



ntal segment 

 tal segment 

 e occipitals 

 able relativ 

 egment, whic 

 and occ i p i ta 

 h (1956) and 

 ships includ 

 ends of the 

 pra-occ i p i ta 

 th the proof 

 anous orb i to 

 gree of move 

 urns around 

 rd and back 

 s conf igurat 

 nes, (2) ep 



s [uni 

 was re 



and o 

 e to t 

 hiss 

 1 sect 



Webb 

 e: th 



paroc 

 1, the 

 ic bon 

 -tempo 

 ment 

 the me 

 ard (r 



on s i 

 pteryg 



tsj were 

 i nf orced 

 t i c bones, 

 he occ i p i tal. 

 i gn i f ied by 

 ions have 

 [1951) and 

 e union of 

 c ip-i tal 



pterygo i ds 

 es. 

 ral 

 f the 

 tak i ne t ic 

 e tract i or, ) . 

 nee it 

 i ds, 



-- P. 



1400 -- 



(3) palatal divisions; — and unpaired: (i) parietal division, and (5) the snout [muzzle], which 

 always breaks down further into (5 a ) central and paired (5 D ) lateral parts. The composition of 

 all these divisions with the exception of the quadrate and ep i pterygo i d. differs as also differ 

 the peculiarities of kinesis in the various forms of lizards (see table). 



-- fi 



1 -- 



eral, in the skull of a typical lizard, the following movements take place (figs 

 action, the lower ends of the quadrate bones turn back and to the side |_posterio 

 The palatal segments, movably joined with the quadrates, are drawn to the back 

 ng along the bas i pterygoi dal processes and spreading the latter to the sides (dr 

 e sections from the center line) [abductionj. The ep ip terygo i d, attached Dy th 

 ollows |_surfacesj to the dorsal surface of the pterygoid, rotates its lower end 

 side, as does also the quadrate, but at a lesser angle than the latter. The sno 

 rotates its anterior end downward around the transverse axis, passing along the 

 etal suture |_"mesok i ne t ic axis" of FrazzettaJ. The angle between the central pa 

 nd the palatine section is somewhat increased; the angle between the frontals an 



• 1-5). 



parietals below is decreased. At this point, the lateral parts of the snout, together with the 

 palatine sections, are diverted and their lateral margins rotate upward around the longitudinal 

 axis passing approximately along the lines of juncture of the lateral and median parts of the 

 snout. The parietal section, as Frazzetta correctly noted, and contrary to the opinion of 

 Versluys, rotates 



-- p. 1401 -- 



around the metakinetic axis with its anterior end upwards. 3 Finally, the lateral parts of the 

 parietal section, participating in the movement of the entire section, also arch upwards, and, 

 in forms with covered supra t emporal fenestrae, rotate around the linear axis, passing along their 

 articulation with the central part of the section, lateral margins upward. 



In general, during retraction, the anterior end of the snout turns downward, the dorsal 

 contour of the skull becomes more convex, the palatine arches, the lateral sections of the snout 

 and the lower ends of the quadrate bones and the ep i pterygo i ds are shifted to the rear, drawn 

 aside and rotated around the linear axis with the lateral edges upward. During protraction, an 



-- f i 



3 



Jin alcoholic connective-tissue preparations of lizard skulls may be found both variants of parie- 

 tal division movements -- its rotation in the same direction as the snout, and the reverse, 

 depending on the direction of force applied. Naturally, as examination shows, force applied to the 

 lizard skull by the jaw muscles should be regarded as the latter variant of motion. 



