Question

this is a series of skulls and front leg fossils of organisms believed to be ancestors of the modern-day horse.
equus (modern horse)
pliohippus
merychippus
mesohippus
eohippus (dawn horse)
source: http://www.lq.poquoson.org

1. give two similarities between each of the skulls that might lead to the conclusion that these are all related species.

Explanation:

All the skulls share two key structural similarities:

1. They all have a elongated, jawed structure that houses teeth, adapted for a herbivorous diet.
2. They all have a distinct opening (orbital cavity) for the eye, positioned in a similar lateral location on the skull.

These shared features indicate a common evolutionary ancestor, supporting that the species are related.

Answer:

1. All skulls have a jaw with teeth suited for grazing/feeding.
2. All skulls have a similarly positioned orbital (eye) cavity.