The diagrams below show the development of the horse over a period of 40 million years.  Summarise the information by selecting and reporting the main features, and make comparisons where relevant.

The diagram provides a detailed overview of the evolutionary process of the horse, highlighting the significant increase in body

size

and the structural evolution of its

foot

bones.

Overall

, the development of horses has undergone four distinct stages over a span of 40

million

years

, beginning with Eohippus and culminating in the modern horse.

Additionally

, the bone

structure

of their feet has become simpler,

while

their bodies have grown larger over time. As shown in the diagram, the earliest horses, scientifically known as Eohippus, first appeared 40

million

years

ago. These species were characterized by their small body

size

and complex

foot

bone

structure

, which featured four slender digits. Over the following 10

million

years

, the presence of Mesohippus was recorded, displaying a larger body

size

and a

foot

structure

with only three digits, the middle one being the largest. Approximately 15

million

years

ago,

while

the

foot

bone

structure

of Merychippus remained identical to that of Mesohippus, its

overall

size

increased significantly.

Finally

, the modern horse, the largest among its predecessors, evolved a completely different

foot

structure

. All toes fused into a single hoof, enhancing its upright posture and stability.