Dorsal surface of skull of frog

i) Skull is triangular, dorso-ventrally flattened and broad.

ii) Skull is dicondylic i.e two occipital condyles.

iii) Occipital region is highly reduced.

iv) On dorsal surface, premaxillae, maxillae, quadratojugal, squamosals, septomaxillaries, nasals, fronto-parietals, protics, exoccipital and occipital condyles can be seen.

Dorsal surface of skull of Varanus

i) Skull is compact and more or less elongated having the narrow anterior end.

ii) It is mono condylic i.e single condyle is borne by the basioccipital which articulates with the atlas vertebra.

iii) It is triploblastic, i.e the inner orbital septum is present between the two orbits.

Dorsal surface of skull of Fowl

i) The skull is light in weight due to pneumatic bones.

ii) It is monocondylic, i.e single occipital condyle is present above the basioccipital.

iii) The bones of the skull of adult birds are fused so intimately that it is difficult to make out their sutures.

Dorsal surface of skull of Rabbit.

i) Skull is dicondylic i.e two occipital condyles.

ii) It is completely ossified with more or less sutures.

iii) Triploblastic i.e inter-orbital septum is present.