Question

In diapsid skull of reptiles, the two temporal fossae are separated by these bones to form the upper temporal bar
A) Postorbital and squamosal
B) Squamosal and jugal
C) Postorbital and jugal
D) Post-frontal and squamosal.

Answer 1

Hint: Diapsids are a group of amniote tetrapods that developed two holes in each side of their skulls.One of the characteristic features of reptiles during their evolution was the formation of effective jaws and skulls.

Complete answer:
Reptiles are tetrapod animals of class Reptilia. They are a group of air-breathing vertebrates having internal fertilization and comprise turtles, crocodiles, alligators, snakes, lizards, etc.Reptiles evolved from labyrinthodont amphibians in 60 my after the amphibians arose. The reptiles evolved with some characteristics like stronger and more effective jaw mechanisms, amniotic egg development, effective locomotion on land, and the development of scales. Apart from this, their key features include a well-ossified skeleton, ribs with sternum except in snakes, metanephric kidney, ectotherms, separate sexes, eggs covered with calcareous or leathery shells, etc.The upper part of the skull, in reptiles, is modified giving them a far more efficient and powerful jaw action and making the skull light. The reptiles are majorly classified based on their skull structure, in which there are temporal fossae or empty spaces in the temporal region. They are classified into five subclasses based on the temporal fossae, which provides space for enlargement of the jaw muscles: Anapsida; Euryapsida; Parapsida; Synapsids, and Diapsida.
The anapsid skull has a skull roof with no temporal fossae in it. The parapsida had one temporal fossa high up on the skull. The synapsid had one inferior temporal fossae on each side of the skull.
The diapsid skull has two temporal fossa, the supratemporal fossa (upper) and the infratemporal fossa (lower) which is separated by two bones i.e. postorbital and squamosal. This type was found in the extinct species called dinosaurs and persists in Rhynchocephalia and Crocodilia. Snakes and lizards have modified diapsid skulls. Diapsids are the most successful and diverse of all the reptiles.

Hence the correct answer is option ‘A’./b>

Note:The diapsids include dinosaurs and pterosaurs which dominated the earth during the Mesozoic era and also the most successful of modern reptiles like crocodiles, snakes, and lizards.