Question

A helically coiled ammonite Turrilites is differentiated from externally resembling Gastropoda Turritella by

• A. apical angle
• B. number of whorls
• C. direction of coiling
• D. chambered shell

Hint:

In paleontology, the shell structure is often a key feature for differentiating between species, with chambered shells being common in ammonites like Turrilites.

Answer 1

The Correct Option is D

Step 1: Understanding the question.
Turrilites is an ammonite with a helical coiling, and Turritella is a gastropod. The key differentiating factor between these two forms lies in their shell structure and not just the coiling direction.
Step 2: Analyzing the options.
(A) apical angle: This is not the defining characteristic that differentiates the ammonite Turrilites from the gastropod Turritella.
(B) number of whorls: Both ammonites and gastropods may have multiple whorls, but the number of whorls is not the key feature that sets Turrilites apart from Turritella.
(C) direction of coiling: While coiling direction is a difference between the two, it is not as significant as the difference in their shell structure.
(D) chambered shell: Correct — The primary difference lies in the chambered nature of the ammonite's shell. Turrilites has a chambered shell, which is not characteristic of Turritella. This structural difference is the key way to differentiate them.
Step 3: Conclusion.
The correct answer is (D) chambered shell, as the chambered structure of the shell is the key differentiating feature between Turrilites and Turritella.