Question

What is the affinities of sphenodon?

Answer 1

Affinities with amphibia
1) Aortic arches arise from a short common stalk which is comparable to conus arteriosus of the amphibians.

2) Presence of ductus arteriosus and ductus caroticus

Affinities with Dinosaurs
1) Dentition is thecodont in dinosaurs

2) Absence of clavicle and interclavicle

3) Absence of Parietal foramen

Chelonian affinities
1) Fixed quadrate bone

2) Ribs of caudal region fused with the vertebrae

3) Pecten not present in the eye

Affinities with Crocodilia
1) Diapsid condition of the skull

2) Fixed quadrate

3) Presence of Pro-atlas

Affinities with Lacertilia
1) The body plan is similar

2) Pro-atlas present

3) Amplucoelous vertebrae in certain geckos