While both monocots and dicots evolved from a common ancestor, dicots are thought to be more closely related to the ancestral flowering plant.

Here's why:

* Fossil evidence: Fossil records suggest that dicots appeared earlier than monocots.

* Phylogenetic analysis: Molecular studies and genetic comparisons consistently place dicots as a basal group within flowering plants, with monocots branching off later.

* Structural features: Dicots possess a wider range of structural features, including a more complex vascular system and a greater diversity in flower structures, suggesting a more primitive state.

Evolutionary Timeline:

* Early Angiosperms: The earliest flowering plants were likely neither monocots nor dicots, but a common ancestor that evolved into both groups.

* Dicots: Dicots diverged from the common ancestor earlier than monocots, evolving around 140 million years ago.

* Monocots: Monocots diverged from the common ancestor later, around 130 million years ago.

Conclusion:

Based on fossil evidence, phylogenetic analysis, and structural features, dicots are considered to have evolved before monocots. This means they are a more ancient and diverse group within flowering plants.