74 



DISCUSSION 



Morphological adaptations to nectarivory 



Tlie Glossophaginae represent small to medium-sized phyllostomid bats with a reduced 

 dentition, distinctly prolonged rostrimi and an extremely protrusible tongue - all tliis 

 indicates adaptations to a diet on nectar and fruit. In ecological terms, these bats may be 

 regarded as nocturnal equivalents of hummingbirds; their evolution having been influenced 

 by several parallel selective forces. Tliere are numerous convergences, such as limits of 

 body weight, hovering ability, elongate tongue, prolongation of tlie rostral components of 

 the skull. 



Gross morphology of the head 

 Since body shape as a whole hardly varies within the Chiroptera - presumably due to strict 

 requirements on undiminished flight ability (conspicous differences merely refer to body 

 size, wing area profile, development of the uropatagiiun and tail length) - their head shape 

 and thus their skull morphology did develop a remarkable morphological variety within 

 the mannnals. 



As already explained in chapter 1, this considerable variety is, above ah, an expression of 

 successful utilization of various food sources with a variety of forms presumably unique 

 on the level of a manmialian order: starting from insectivory, the superfamily Phyllosto- 

 matoidea developed any conceivable specialized feeders compatible with flight behaviour: 

 camivory (Phyllostominae), sanguivory (Desmodontüiae), piscivory (Noctilionidae), frugi- 

 vory (Stenoderminae, CaroUimae, Phyllostominae) and nectarivory (Carolliinae, Phyllo- 

 stominae, Brachyphyllinae, PhyUonycterinae, Glossophaginae and Lonchophyllinae) . 

 Merely browsers and grazers do not exist as an equivalent specialization would have 

 certainly required a digestive system incompatible with flight. 



Accordingly, above ah, nectarivory is marked by morphological adaptations of the head: 



- Prolongation of the muzzle witli size diminution of the nose leaf. 



- Prolongation and specialization of the tongue (bristle-hke papillae, lateral or median 

 nectar groove, musculature of the tongue base) for optimal nectar intake. 



- Lower lip with median notch guiding the tongue (lower incisivi very small or missing, 

 the resulting gap allows nectar intake with the tongue with closed jaws). 



- Pimiae and tragus are also reduced in size, the ears are rounded, equally broad as long 

 and, compared to other PhyUostomids using echolocation, quite short. 



Skull morphology 



In osteological terms, this morphological variety of head shape is expressed in a bounty of 

 different skull shapes within the family of the leaf nosed bats (Phyllostomatidae). Espe- 

 cially the visceral skull is an important substrate for evolutionary changes in order to 

 optimize utilization of various food sources. In this respect, the highly specialized flower 

 bats take an extreme position. Besides the prolongation of the viscerocranium and 

 variation of the dentition (referring to form, number and arrangement of tlie individual 

 tooth types), the adaptations comprise the masticatory and pharynx musculature as well as 

 corresponding bony components of the jaws, their attaclmient at the braincase and at the 

 mandible. 



