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How does the location of ovaries differ between mammals and other vertebrates?

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Detailed cross-sectional illustration of a human ovary showing the stages of follicle development, ovulation, and corpus luteum formation, with labeled structures including primordial, primary, secondary, and mature follicles, a ruptured follicle releasing an ovum, and corpus luteum and albicans. An inset at the bottom shows the ovary's location in the female reproductive system. — ovary The steps of ovulation, beginning with a dormant primordial follicle that grows and matures and is eventually released from the ovary into the fallopian tube.

In vertebrates, the location of the ovaries varies significantly based on the animal's evolutionary group.1

Primitive Vertebrates: In hagfish, the ovaries are elongated and stretch nearly the entire length of the body cavity. Similarly, in most fishes (excluding very primitive forms), the ovaries are elongated and occupy a large portion of the body trunk.12
Other Tetrapods: In non-mammalian tetrapods—such as amphibians, reptiles, and birds—the ovaries are typically confined to the middle third or half of the body cavity, particularly outside of breeding seasons.1
Mammals: The ovaries of mammals undergo a moderate caudal (posterior) displacement during development, ultimately coming to rest in a position between the kidney and the pelvis.1

While most vertebrates possess paired ovaries, some species exhibit an unpaired condition, such as most birds (which typically lack a right ovary) and certain teleosts, sharks, and bats, where only one ovary develops.2