Question

Pygostyle is complex formed by the fusion of
A. Thoracic and lumbar vertebrae
B. Tail vertebrae
C. Skull bones
D. of the above

Answer 1

Hint: Pygostyle is a skeletal condition in which the final few caudal vertebrae are fused to form a single pygostyle complex or ossification. The pygostyle supports the tail feathers and musculature.

Complete Answer:
- The pygostyle is the main component of uropygium ( it is a structure which is commonly called as bishop’s nose, parson’s nose, pope’s nose or sultan’s nose.
- Pygostyle visible at the posterior end of birds.
- The pygostyle has a swollen appearance because it contains uropygial gland.
- Uropygial gland produces preen oil.

Evolution of pygostyle:
- Pygo Styles began to evolve in the early Cretaceaous period.
- The members of Confuciusornis are the earliest who have evolved this structure.
- This advantage of this structure is that this structure provides complete mobility to tail.

Types of pygostyle:
1. The first type of pygostyle is long or dagger blade like pygostyle. Their fossils do not show the traces of well developed rectrices. This type of pygostyle is found in the members of Confucius Ornithi Dae, Enantiornithes, etc.
2. The second type of pygostyle is plowshare shaped. These pygostyles have well developed rectrices. The central pair of retrices attached to pygostyle. This type of pygostyle is found in the members of Ornithurae, Confuciusornis, etc.
Therefore it is clear from the above discussion that the pygostyle is a complex formed by the fusion of tail vertebrae.

Hence, option B is the right option for this question.

Note: In modern birds there are retrices attached to pygostyle found. Pygostyle of bird Turkey is usually used as a food also.