VERGLEICHENDE UNTERSUCHUNGEN AN JYNGINEN UND PICINEN 



171 



SUMMARY 



The order of rank in birds and mammals is a problem-complex which has 

 been studied at the Zoological Institute in Basel for décades. One of the methods 

 of expressing the level of évolution (élévation) is to mesure the relative size of the 

 brain or of brain parts. Thèse indices, expecially those of the forebrain, are signifi- 

 cantly différent in the order of Picidae. Indices of forebrain-hemispheres: Wryneck, 

 Jynx torquilla L. 4,6; Great Spotted Woodpecker, Dendrocopos major L. 12,4; 

 Black Woodpecker, Dryocopus martius L. 19,4. 



The fact that the forebrain of the Black Woodpecker is 4 times heavier than 

 that of the Wryneck, though the two bird types belong to the same order, is 

 intriguing. The aim of this study then was to get an answer to the question whether 

 the quantitative variability has a parallel in the qualitative or structural one. 



External shape : The sculpturation of the Woodpecker forebrain is very 

 intensive on the dorsal as well as the ventral side. The Fissura ventralis and the 

 Vallecula are deep. 



The hémisphères of the Wryneck, on the contrary, are flat and elongated as 

 in other low cerebralised birds. The wulst is narrow. The big Bulbus olfactorius 

 in rostral position indicates a primitive condition, common in Woodpeckers and 

 Wrynecks. 



Internai structure : On the other hand histology shows that no basic différences 

 in the architecture can be stated; but différences in proportion of différent areas 

 clearly show up in parasagittal sections. In Woodpeckers the Neostriatum and 

 Hyperstriatum ventrale reach far more in rostral direction than they do in the 

 Wryneck (basale Frontbildung). 



Basale Frontbildung is an exception in Coraciomorph only realised in one 

 other order: the Psittaciform. 



There is no basic différence in the structure between Wryneck and Wood- 

 pecker forebrains, but Woodpeckers always show signs of higher évolution. A 

 Nucleus basalis which is well developed is evaluated as a primitive condition. In 

 the Wryneck the Nucleus basalis is better developed than in the Woodpecker. 

 Both Woodpecker and Wryneck have a small Palaeostriatum and Neostriatum. 

 The Lamina hyperstriatica, especially in Woodpecker, shows a strong curved 

 course. Neither Wrynecks nor Woodpeckers investigated have a true cortex; 

 cortex is a strongly limited cell-layer. A cell-layer not strongly limited against 

 the surrounding tissue should be called Corticoid-layer. 



The surface of the forebrain hémisphère in Woodpeckers and Wrynecks are 

 almost completely surrounded by a border of Corticoid. This border of Corticoid 

 is well developed in Woodpeckers while in Wrynecks it is hardly visible. The 

 area praepyriformes is missing in Woodpeckers while in the Wryneck it is clearly 



