What is the correct sequence of origin of mammals?

Options

A. Sauropsids `to` Pelycosaurs `to` Therapsids `to` Mammals
B. Synapsids `to` Pelycosaurs `to` Therapsids `to` Mammals
C. Sauropsids `to` Synapsids `to` Thecodonts `to` Mammals
D. Synapsids `to` Sauropsids `to` Therapsids `to` Mammals

Answer

To determine the correct sequence of the origin of mammals, we need to understand the evolutionary lineage leading to mammals. Here’s a step-by-step breakdown:

1. **Synapsids**: The earliest group in the lineage leading to mammals. Synapsids are a clade of amniotes that include mammals and their ancestors. They are characterized by having a single temporal fenestra (an opening in the skull behind the eyes).

2. **Pelycosaurs**: This group is part of the synapsids and represents some of the earliest forms of synapsids. They were dominant during the Carboniferous and Permian periods and are often considered the first mammal-like reptiles.

3. **Therapsids**: Evolving from pelycosaurs, therapsids are more advanced synapsids that display features more similar to mammals. They emerged in the late Permian period and are often referred to as "mammal-like reptiles."

4. **Mammals**: Finally, from therapsids, true mammals evolved. This transition marks the emergence of the first true mammals, which appeared in the late Triassic period.

Thus, the correct sequence of origin of mammals is:
- Synapsids → Pelycosaurs → Therapsids → Mammals