Warm-Bloodedness

A warm-blooded animal generates its own body heat internally from large amounts of food it eats. It can be active whenever it wants, for long periods of time.

Living reptiles are "ectotherms."
Living birds and mammals are "endotherms."

A cold-blooded animal can't make its own heat, so it must absorb heat from the sun or its surroundings. It doesn't require aas much food as a warm-blooded animal, but it can be active only for as long as it stays warm. Such variable body temperature is called poikilothermy. They have low rates of metabolism and more or less sluggish levels of activity. (Main body remperatires remaining constant during day and night is homeothery.)

Were Dinosaurs Warm-Blooded?

The evidence is mixed. Like birds or mammals, dinosaurs had rapid rates of growth, and their bones show evidence of secondary reworking (Haversian canal systems). They could not sprawl like most living reptiles, and their obligate erect postures iplies continual expence of metabolic energy. Their footprint and long limbs that they were capable of high speeds. They look like organisms built for high levels of activity. [T-Rex]

Many small meat-eating dinosaurs were probably warm-blooded. Yet, most big dinosaurs could have been cold-blooded animals whose sheer bulk help them stay warm all the time.

Here's how it works:

Leatherbacks are the largest living turtles. Some leatherbacks reach 2.4 m (8 ft) in length and weigh 867 kg (1907 lb). The leatherback (Dermochelys coriacea) occurs in the Atlantic, Pacific, and Indian oceans, and sometimes in the Mediterranean Sea. Instead of horny scales on its shells, the leatherback has a leathery skin embedded with small bones. Its limbs are strong and paddle-shaped. Leatherbacks feed mostly on jellyfish but also eat seaweed, sea urchins, squids, and mollusks.
They spend most of their time in warm tropical waters, where it has no problem keeping warm. Yet, the leatherback manages to stay warm even when it visits the cold northern waters of the Atlantic. The turtle is so big that heat stores deep inside its body and takes a long time to reach the surface and radiate out into the water.
An insulating layer of blubber just beneath its skin helps prevent further heat loss. If a one-tonne turtle can stay warm in cold surroundings, surely a dinosaur 10 times its weight with a much greater heat storage capacity could easily do the same.

Possible no singal thermal regulation mechanism can describe all dinosaurs; mammals such as bats, cats, elephants, and whales control their body temperature in different ways, and the thermal regulation mechanisms of dinosaurs were probably equally varied.

Blood Filters

In most reptiles, the two kidneys are in the upper rear body. They filter the blood flowing through them and collect the fluid wastes, or urine.