Question

The most advanced character of crocodile and Gavialis is
(a) Shelled egg
(b) Pleurodont dentition
(c) 4 chambered heart
(d) Powerful jaw and large body

Answer 1

Hint: All the reptile's blood in the left ventricle contains both oxygenated and deoxygenated blood whereas crocodiles and Gavialis contain only oxygenated blood.

Complete answer:
Crocodiles and Gavialis belong to the class reptilia of the Animalia kingdom. They evolved from labyrinthodont amphibians in the Carboniferous period. All the reptiles contain cleidoic eggs and dentation is acrodont, homodont, and polyphyodont except in crocodiles contain thecodont dentition seen in mammals. They have incompletely developed four-chambered hearts but in crocodiles, they have completely developed a four-chambered heart like in mammals. This is one of the most advanced characters seen in crocodiles and Gavialis.

Additional Information: - Reptiles are considered as the first true terrestrial, creeping, or burrowing amniotic tetrapods.
- The body is covered with rough and dry skin with horny epidermal scales, shields, and claws.
- Monocondylic skull with many temporal fossae. Each half of the lower jaw is made up of six bones and they have procoelous vertebrae. To facilitate independent movement of the head from the body they contain an atlas and axis.
- Respiratory type is pulmonary respiration with the help of ribs and intercostal muscles. In turtles exchange of gases takes place through the vascular cloacal wall.
- Incomplete four-chambered heart is present except in crocodiles, the heart is completely developed four-chambered heart is present.
- Sinus venosus is present but conus arteriosus is absent.
- Excretion is via kidneys that are mesonephric. Vas deferens in males is developed from the Wolffian duct of an embryo
So, the correct answer is ‘4 chambered heart’.

Note: -In chelone (marine green turtle) dentition is edentate.
-The Wolffian duct is also called the mesonephric duct.
-All the reptiles contain 12 pairs of cranial nerves whereas in snakes only 10 pairs of cranial nerves are present.
-The common name of Gavialis gangeticus is Indian gavial or gharial.