What body structured indicate that mammals descended from reptiles?

Explanation:

Many of the most important and diagnostic mammalian characteristics serve to further intelligence and sensibility, promote endothermy, or to increase the efficiency of reproduction or the securing and processing of food.

Basic structural body plan is inherited from Therapsid mammal-like reptiles.

Survival through mammalian evolution was perhaps due to their ability to move and to think more quickly than their Archosaurian counterparts.

Morphological trends were toward structural simplification:

� skull and jaw bones lost or reduced in size

� limbs and limb girdles simplified, reduced, and less laterally splayed

Fossil record provides little evidence on when endothermy actually developed.

Diagnostic or Distinguishable Characteristics of Mammals:

Soft Tissues

Skin glands: Mammalian skin contains several kinds of glands not found in other vertebrates.

Mammary Glands: Provide nourishment for the young during their postnatal period of rapid growth.

answer; polycythemia is the correct answer;