ANATOMY OF BIRDS
Bird Wings
Bird Bone Structure
Bird Feathers
Bird Pectoral Muscles
Bird Sternums
Bird Leg Bones
Bird Perching Bones
Bird Pelvic Bones
Bird Vertibrae
Bird Scull Structure
Woodpecker sculls
Bird Beaks
ANATOMY OF BIRDS
GEOGRAPHICAL DISTRIBUTION
MIGRATIONS OF BIRDS
CLASSIFICATION OF BIRDS
LIZARD-TAILED BIRD
AMERICAN TOOTHED-BIRDS
THE OSTRICHES
THE RHEAS
EMEUS AND CASSOWARIES
THE TINAMOUS
THE KIWIS
THE PENGUINS
LOONS AND GREBES
ALBATROSSES & PETRELS
STORK-LIKE BIRDS
GOOSE-LIKE BIRDS
FALCON-LIKE BIRDS
FOWL-LIKE BIRDS
CRANE-LIKE BIRDS
PLOVER-LIKE BIRDS
CUCKOO-LIKE BIRDS
THE ROLLER-LIKE BIRDS
SPARROW-LIKE BIRDS
Birds and Birding's Guide to:
Watching THE ANATOMY OF BIRDS
Bird Scull Structure
There are two existing types of skull structure by which birds are divided into two great groups, the Palaeognathae or Dromaeognathae, including the Ostriches and their allies, and the Neognathae, Euornithes, or Eurhipiduras, which comprise the vast majority of birds. These types are sharply marked, indicating that at the very outset of their career, birds split into these groups, if indeed they may not have originated from two distinct types of reptiles. Unfortunately, as previously noted, these modifications can be described only in technical language and can probably be best understood from a study of the accompanying figures.
In the dromaeognathous type of skull (Figs. 14, 15), so called because it is typically found in Ostriches, the vomer is broad and unites in front with the maxillopalatines, while behind it receives the posterior extremities of the palatines and the anterior ends of the pterygoids, which are thus shut out from joining the sphenoid; the sphenoid bears on its sides long basipterygoid processes which give it something of a cruciform shape. In birds with this type of skull the quadrate, the bone to which the lower jaw is joined, is rather short and clumsy and its articular head is single or but faintly divided into two portions; the quadrate is also locked into place by the surrounding bones. In all these particulars the dromaognathine skull more nearly resembles that of a reptile than does that of the majority of birds, a point that may be best appreciated by comparing the figures.
In the euornithic type of skull (Fig. 16) the palatines articulate with the pterygoids and both touch the sphenoid at their point of junction, and the back of the vomer embraces the sphenoid between and above the ends of the palatines. The quadrate has two heads and is loosely joined to the cranium. This arrangement prevails in the majority of birds, and is termed the euornithic type of skull because it is characteristic of the Euornithes; it is also called neognathic because it is believed to be more recent or newer than the Ostrich style and further removed from the reptilian skull.
Basipterygoid processes may be present, but usually in the form of low facets which articulate with projections on the pterygoids and often serve as braces to the beak when this is slightly movable, as in Ducks and Parrots.
The neognathous style of skull is subject to several important modifications which characterize great natural groups of birds. These are the schizognathous, desmognathous, and aegithognathous types,1 which may be briefly characterized as follows: When the vomer is pointed in front and entirely free from the maxillopalatines, and these are free from each other, the skull is termed schizognathous; when the maxillopalatines are expanded and fused with each other, the vomer being small or absent, the skull is desmognathous; when the vomer is expanded in front and free from the maxillopalatines, and these are slender at their point of origin and disjoined, the skull is said to be aegithognathous.
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