Question

The scales of Scoliodon are
A. ctenoid
B. cycloid
C. cosmoid
D. placoid

Answer 1

Hint: Here, in this question, we need to know about Scoliodon. We need to elaborate on the scales of Scoliodon. After that, we will find the correct answer.

Complete step-by-step answer:

Scoliodon is a genus of requiem sharks in the Carcharhinidae family. It was previously thought to consist of only one Indo-Pacific species, the spadenose shark, but recent taxonomic research has discovered another species, the Pacific spadenose shark.
1. Scoliodon has a long, spindly body that tapers at the ends, making it a very fast swimmer.
2. The trunk and tail are compressed laterally, while the head region is compressed dorsoventrally.
3. An exoskeleton of placoid scales covers the entire body.
4. The mouth is located on the ventral side and is surrounded by jaws on both sides.
5. It has two rows of homodont or polyphyodont teeth that correspond to the placoid scales that cover the body.
i. Male Scoliodon species reach maturity at 33 cm, while female Scoliodon species reach maturity at 36
cm.
ii. Scolion laticuadus has a minimum of 8 to a maximum of 19 embryos when conceiving and is mostly ovoviviparous when reproducing.
iii. The Scolion laticaudus is about 13.7 cm long at birth. Because of its low fecundity, the Scoliodon shark genus is vulnerable to targeted fishing and habitat degradation.

The scales of Scoliodon - A typical Scoliodon placoid scale has two parts:
1. A wide rhomboidal basal plate
2. A flat trident spine arising from its centre.
One median and two lateral spines form the backward-directed trident spine that protrudes from the skin.


So, option D is the correct answer.


Note: For this question candidate must aware of the correct scale of Scoliodon and about Scoliodon.