Question

Thecodont teeth are present in
a. Sphenodon
b. Crocodiles
c. Mammals
d. Scoliodon

A. c only
B. b & c only
C. a, b and c only
D. a, b,c,d

Answer 1

Thecodont dentition is a morphological arrangement in which the tooth is completely embedded within a deep socket of bone, as seen in crocodilians, dinosaurs and mammals, and opposite to the Acrodont and Pleurodont dentition seen in Squamate reptiles. The name thecodont meaning in Greek is "socket-tooth”.

Complete answer:
Thecodont is a type of tooth present in the animals where the base of the teeth is firmly attached to in the socket of the jawbone. This is the strongest attachment of teeth and is found in mammals. Sphenodon has a dentary form of teeth. Crocodiles also are thecodonts. And scoliodon has two rows of homodont and polyphyodont. Hence only mammals have thecodont teeth arrangement.

Hence, the correct answer is option (B).

Additional information:
Thecodontia (meaning "socket-teeth"), now considered an obsolete taxonomic categorization grouping, was formerly accustomed to describe various "order" of early archosaurian reptiles that were first seen in the latest Permian period and flourished until the end of the Triassic period. This cluster or group includes the ancestors of dinosaurs, pterosaurs, and crocodiles. Mostly fish, amphibians, and reptiles have their teeth either resting on the surface of the jaw bone called as acrodont dentition or more broadly attached to the jaw on its rim and an inner wall which is known as pleurodont dentition
Primitive appearances of the heterodont tooth condition were found to be in fossil forms of early mammals. The triconodont cheek teeth appeared in some numbers of the earliest prototherian mammals. Later prototherians had the tri tuberculate tooth form, with the cusps or points offset from one another and interlocking with the cusps of the opposing jaw. Humans and most other mammals are diphyodont, which means that they grow two sets of teeth in their lifetime:-baby teeth and permanent teeth. As we age the temporary teeth (baby teeth, milk teeth) are lost and replaced with permanent teeth. Mammals have a dental formula of $2102$/$2102$including two incisors, two molars, one canine and zero premolars in each quadrant.

Note: The dentition of modern mammals can be represented by dental formulas. The dental formula of a mammal lists the number of each of the tooth variety that is, incisors, canines, premolars, and molars, from one side of the upper jaw, above a similar list from the lower jaw.