The Life Cycle of the Dinosaurs: From Destruction to Catastrophe

From birth to growth to death, the fossil record preserves interesting clues about the life cycles of dinosaurs.

reproduction

The sex of dinosaurs is a hotly debated topic, with wonderful images conjuring up in people's minds. But unfortunately, figuring out how they did it remains speculation. The passion for dinosaurs cannot be preserved in stone.

male or female?

Determining the sex of dinosaur bones is difficult. Various suggestions have been made based on differences between fossils of the same species. However, the evidence is not clear-cut and there is much debate among scientists.

It is often thought that hadrosaurs such as Parasaurolophus showed consistent size differences in their crests, and that those with more prominent crests were likely males. The fact that physical differences between the sexes exist in many living animals suggests that this may be a possibility. Unfortunately, fossil evidence is difficult to interpret.

life begins

A dinosaur's life began as a hard-shell egg. They vary in shape and size depending on the species, but the internal structure of their shells are more similar to modern bird eggs than to any living reptile. Most sauropods laid their eggs in mud nests or holes dug in the sand, but some appeared to lay their eggs in simple lines. Large nesting colonies were also found, suggesting that some species reproduced socially - like many birds today.

Where were eggs found?

Dinosaur eggs have been found at more than 200 sites around the world, with significant locations in the United States, China, France, Argentina and India. Eggs have not yet been discovered in Australia.

egg size

The goose is an extinct bird that lays the largest eggs of any known animal. Its eggs are close to the maximum size of a chicken egg. Larger eggs require thicker shells so they don't collapse. However, if the eggshell is too thick, the hatchlings cannot escape, and if the egg is too large, the embryo suffocates because there is not enough oxygen and carbon dioxide to pass through the membrane.

Whose eggs?

The vast majority of dinosaur eggs found are empty eggshell fossils. If you want to know what dinosaurs laid them, then that's not much use. However, we can distinguish a wide range of egg species based on size, shape, and shell characteristics. Shell characteristics found on fossils can be used to identify eggs. The thickness and surface texture of an egg can be quite clear, but the crystal structure and pore pattern can only be seen under a microscope. If more evidence is later found, these groups can be assigned to a family or species. Sometimes tasks get easier. Some eggs contain embryonic remains that can identify a specific species. Some extremely rare fossils even preserve adults that died in their nests.

Some examples of identified egg fossils include:

• Hadrosaurus eggs from China

• Saltosaurus was a large sauropod titanosaur and one of the few species whose eggs have been unequivocally identified from preserved embryos.

• Gobiornis was a primitive bird (and therefore a dinosaur) that lived alongside other Cretaceous dinosaurs. Fossils of embryos have been discovered in Mongolia, allowing eggs to be identified.

• An adult oviraptor discovered in Mongolia in 1995. It appears to have died while incubating or protecting the eggs.

Nature or nurture?

Did dinosaurs adopt the "lay off" strategy of many modern reptiles, or did they raise their offspring like most birds? Dinosaurs seemed to care for their eggs and hatchlings in different ways, just like living animals. Some species may leave their young to fend for themselves, while others use their bodies to incubate or protect their eggs. Many birds build nests in the habitat, and some even lay eggs together with the hatchlings - typical bird behavior.

Mayasaurus, whose name means "good lizard mother," is one of the dinosaurs for which there are the most complete records of eggs, embryos, nests, and young. There is evidence that they use communal nesting sites and care for their hatchlings. The cubs also grow very quickly, reaching about three meters in length after one year.

growing up

Did dinosaurs grow quickly, like most warm-blooded mammals and birds, or slowly, like cold-blooded reptiles?
Many dinosaurs, especially large theropods, hadrosaurs, and sauropods, may have grown very rapidly early in life, but by the time they reached adulthood The growth rate then slows down. However, they appear to have had a unique growth pattern, faster than living reptiles but slower than most living mammals or birds.

evidence of growth

• Some dinosaurs had internal skeletal structures, such as blood vessels, that are characteristic of fast-growing living animals.

• Cross-sections of bones can reveal growth rings. These layers of bone form during periods of interruption or slowing in growth—usually due to cold seasons. Some scientists believe the rings may reflect annual stages of growth, and counting the rings can provide an approximate age of an individual.

• Comparing the same skeleton from individuals of different sizes of the same species can help create an approximate growth sequence. This is combined with approximate age determined by other methods to create a growth curve of age versus size. For example, according to fossil evidence, hadrosaurus larvae could grow to more than three meters in a year.

estimated weight

There are two ways to estimate the weight of a dinosaur. One method uses the cross-sections of load-bearing bones, usually limb bones, to calculate how much weight they can support. Another measures the volume of liquid displaced when a precisely scaled dinosaur model is placed in water. Both methods are fraught with uncertainty, which explains why any given dinosaur ranged in weight.

min and max

the smallest:

• Epidexipteryx hui (China): 25 cm long (or 44.5 cm including long tail feathers) and 0.16 kg

• Parvicursor remotus (Mongolia): 39 cm long, 0.16 kg

• Anchiornis huxleyi (China): 40 cm long, 0.25 kg

Largest: Titanosauridae sauropod dinosaur

• Argentinosaurus huinculensis  (Argentina): 35-40 m long, 80 tons in weight

• Puertasaurus reuili (Argentina): 35-40 m long, 80 tons

• Maraapunisaurus fragillimus (USA): 35 m long, 70 tons

• Paralititan stromeri (Egypt): 32 m long, 65-80 tons

Tallest: Brachiosaurus sauropod dinosaur

• Sauroposeidon proteles (USA): 17-18 m or higher

• Giraffatitan brancai (Tanzania): height 12 m

• Brachiosaurus high-chest (USA): height 12 m

The largest carnivore:

• Mapusaurus rosaea (Argentina): 14 m long, 7-8 tons

• Carolinian Giganotosaurus (Argentina): 13–14 m long, 7 tons

• Spinosaurus aegypti (Egypt): 15 m long, 5-7 tons

• Tyrannosaurus rex (USA): 12–13 m long, 7 tons

Dead like a dinosaur!

How long did dinosaurs live? In living animals, lifespan depends primarily on body size and metabolism. For example, reptiles with slow metabolisms tend to live longer than warm-blooded birds and mammals of the same size. There is evidence that many dinosaurs had metabolisms more like those of birds, but their relative longevity may have been shorter than that of larger reptiles. Sauropods probably lived 50-100 years, large theropods were shorter, and smaller dinosaurs probably lived about 10 or 20 years.

animal tags： Dinosaur