Answer: They compare the number of mutations to determine how long ago species separated and evolved.
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Answer;
This is because most likely some time a ago there use to be Ammonites living there and as they died there, they got fossilized.
Explanation;
-Fossils of a marine animal called Ammonite are found in large numbers in the Kali Gandaki river in Nepal. Ammonites were sea animals having shells - either straight or coiled. When the Tethys sea disappeared, they were caught in the shale layers of clay and transformed into fossils. This is one of the proofs that the Himalayas were indeed once under water.
<span>The awnser is adaptive radiation</span>
The two main clades branch from the most recent ancestor is called <span>Cnidaria and Bilateria. Please have in mind that Cnidaria is a phylum containing 10.000 species of animals. Now on the other hand, Bilateria is a major group of animals. After looing at the figure 33.2 we can conclude that these two are part of the ancestor of the eumetazoans which is a clade comprising all major animals. </span>