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PNEUMATIZATION OF THE SKULL IN THE PARULIDAE

Abstract Pneumatization of the skull roof and cerebellum region of the occipital bone was studied in 193 skulls of 18 genera and 56 species in the family Parulidae (wood warblers). The grundtypus type of pneumatization, which closes the windows anteriorly in immatures of migratory species, was present in fall migration and was completed on the wintering grounds during December and January. The only genera to show what I call the geospizid type of skull pneumatization were Basileuterus and Phaeothlypis, supporting their treatment as congeners. The geospizid type of skull pneumatization is typical of all species in the Galapagos Finches (Geospizidae). In this type the skull roof closes posteriorly in the parietal bone; large members of the family exhibited midline pneumatization, and smaller members the peripheral type. Genera Setophaga, Myioborus, and Basileuterus retained cerebellar windows for an extended period after skull roof pneumatization had been completed. Basileuterus is set apart from other parulids by four trenchant characters and is considered primitive.