Question

An animal having both exoskeleton and endoskeleton is
(a) Freshwater Mussel
(b) Frog
(c) Tortoise
(d) Jellyfish

Answer 1

Hint The shell of this animal has remained almost unaltered by two hundred million years of evolution. This shell is basically an extension of the rib cage, which unlike most vertebrates is housed on the “outside” rather than inside the body making the exoskeleton.

Complete answer:
The characteristic feature of any tortoise is the shell. For a tortoise, it is the primary defense mechanism against predators.
This shell is made up of two halves:
-Plastron is the underneath shell
-Carapace is the top shell
 Both the parts are fused together at the sides by a “bridge”. This shell is basically the exoskeleton of a tortoise.
The skeleton of a tortoise comprises of two parts
-The exoskeleton which includes carapace and plastron
- The endoskeleton includes internal bones. The endoskeleton also consists of two main groups; the appendicular skeleton (limb bones and girdles) and the axial skeleton (ribs, vertebrae, and skull).
In addition to this, the whole shell of the tortoise is made up of numerous small bones which are covered by separate plates of keratin on top called scutes.
Very old tortoise often have extremely worn scutes that give their
 shells a completely smooth appearance.

Additional information:
The scutes of the carapace are divided into five parts:
-The Nuchal: Scute that is directly above the head
-The Supracaudal: Scute that is directly above the tail
-The Vertebral: Single line of scutes that continue centrally from the head to the tail
-The Costals: runs parallel to and is present at either side of, the Vertebral
-The Marginals: Above Costals and attach to the bridge
The scutes of the plastron are divided into six parts:
-The Gular
-The Humeral
-The Pectoral
-The Abdominal
-The Femoral
-The Anal

So, the correct answer is ‘Tortoise’.

Notes: The Marginal scutes have a large impact on the overall shape of a tortoise’s shell. In some species like Testudo Marginata, the Marginal scutes are extremely flared.