Why Dinosaurs Grew So Large and Coloring their Vibrant Hearts

Theories on Why Dinosaurs Grew So Large

Dinosaurs captured our imaginations from the time their bones were first discovered. These prehistoric beasts reached incredible sizes, prompting the question: why did they grow so big? Several theories aim to explain the massive growth of dinosaurs and other creatures during the Mesozoic era.

Higher Oxygen Levels

Some scientists hypothesize that greater oxygen levels enabled dinosaurs to grow to gigantic sizes. During the Mesozoic era, oxygen concentrations reached 35%, significantly higher than the 21% today. More oxygen may have accelerated growth rates and enabled their large bodies to function.

Warmer Climate

The global climate during the time of the dinosaurs was much warmer, lacking polar ice caps. This warmer climate meant the dinosaurs didn't need to expend energy regulating their body temperature and had abundant vegetation to feed their rapid growth.

Evolutionary Arms Race

As predators evolved to take down large prey, plant-eating dinosaurs had to keep growing larger to defend themselves. This evolutionary arms race toward greater size ensured the survival of gigantic sauropods, hadrosaurs, and more. Their massive size was a key evolutionary adaptation.

The Heart of a Dinosaur

We tend to envision dinosaurs only in terms of their bones and appearance. But these were living, breathing animals, with organs like hearts that pumped blood throughout their bodies. Learning about a dinosaur's heart gives insight into how they thrived.

Size of Dinosaur Hearts

Fossil evidence shows some dinosaur hearts were enormous. An Apatosaurus likely had a 15-foot long heart! Like other organs, a dinosaur's heart had to be sizable enough to supply their huge bodies with blood and oxygen. Whales today have relatively largest hearts to meet the demands of their size.

Structure Similar to Reptiles

Modern birds and reptiles both evolved from dinosaurs. Comparing their hearts gives clues to dinosaurs' cardiovascular function. In birds and reptiles, the heart structure has two atria to collect blood plus a main pumping ventricle. Dinosaurs likely shared this efficient system.

High Blood Pressure Needed

The towering heights reached by many sauropod dinosaurs required incredible blood pressure to pump blood all the way to their brains. Scientists estimate their central blood pressure exceeded 300 mm Hg, over 5 times that of large mammals today! This enabled sufficient oxygenation at extreme sizes.

Colorful Dinosaur Hearts

While actual dinosaur heart tissue is rarely preserved as fossils, we can still imagine how vibrantly-colored and detailed a dinosaur heart may have been. Vivid colors and patterns are useful in many modern animal organs for identification and attraction. Coloring a dinosaur heart page allows creativity in envisioning these lost aspects of dinosaurs.

Bright Red Color

A healthy heart pumped plenty of iron-rich blood through a dinosaur's circulation. Oxygenated blood carries hemoglobin proteins with iron molecules. Just like in many mammals and birds today, dinosaurs likely had bright crimson hearts, essential for distributing oxygen throughout the body.

Detailed Exterior Structures

The hearts of large animals often have grooves, vessels, pores and bumps covering the exterior surface. These structures supply blood vessels while also anchoring the organ. When coloring a dinosaur heart page, creativity is welcome in detailing ridges, arteries and specific sections like chambers and valves.

Vibrant Interior Color

While somewhat speculative, it's enjoyable to imagine the muscle tissue lining a dinosaur heart vividly colored by oxygenated blood flow. Coloring the inside of the heart with pinks, reds, oranges and yellows captures the energy and vibrancy of this crucial organ. What colors would be swirling within chambers and vessels?

FAQs

Why were dinosaur hearts so large?

Dinosaur hearts needed to be very large in proportion to their huge overall size, in order to generate the required blood pressure and circulation to supply oxygen to their bodies and brains. Scientists estimate dinosaur hearts were enormous - up to 15 feet long in a large Apatosaurus.

How do we know what dinosaur hearts looked like?

While no actual dinosaur heart tissue has survived as fossils, we can extrapolate from the heart anatomy in their modern dinosaur descendants - birds and reptiles. Both have a similar structure with two collecting atria and a main pumping ventricle. Heart shape likely varied among dinosaur species.

Could dinosaurs really have blood pressure over 300 mm Hg?

Yes, the towering heights of many giant sauropods would have required exceptional blood pressure to pump blood upwards against gravity to reach their brains. This blood pressure vastly exceeds what's typical for large mammals today.

What colors would dinosaur heart muscle tissue have been?

The actual colors are speculative, but since iron-rich oxygenated blood likely made dinosaur hearts a bright red color externally, we can imagine vibrant reds, oranges and pinks coloring the muscle lining the heart chambers and vessels. This reflects the energy and vitality of the dinosaur cardiovascular system.