Several million years ago, strange and unexplored animals inhabited our land. If you believe the theory of evolution, then all living organisms descended from each other. One species turned into another and so on. Today, all animals on the planet are the result of improvement. For example, ichthyosaurs, stegocephals and trilobites. The latter are the ancestors of modern isopods. And the ancestors of trilobites are spriggins, organisms living in the Proterozoic era. The size of the creatures reached up to 3 cm.
Who are trilobites?
Trilobites are the first class of arthropods that lived on the planet in the deep bowels of the ocean. Their population disappeared 200 million years ago. But scientists and archaeologists still find trilobite fossils.
The heyday of the “kingdom” of trilobites falls on the Paleozoic era. At the end of the era, the number of these amazing creatures exceeded the number of all multicellular animals that lived at that time. If the Mesozoic era was the era of dinosaurs, then the Paleozoic era was trilobites. This is a scientific assumption.
Description of appearance
The structural features of the trilobite body are based on hypotheses and research scientists. Findings of the remains help restore the picture of the appearance of arthropods.
Shell
The body of the prehistoric creature was flattened. In addition, it was completely covered with a solid shell consisting of several parts. The size of these creatures ranged from 5 mm to 81 cm. Spikes or horns could be on the hard surface of the trilobites.
There were other subspecies that could curl up and hide their body in shell. The pharynx of this animal was located on the peritoneum. The thick “armor” for these arthropods also serves to attach the internal organs. In small trilobites, the coating was impregnated with chitin, and in large individuals, calcium carbonate. This is essential for excellent durability.
Internal organs and body reflexes
The head was round. It contained all the most important organs for life: the brain, heart and stomach. In this regard, the head was also covered in a hard shell. In addition, the limbs of trilobites are functions of the motor, chewing and respiratory systems. Undoubtedly, they are no less significant reflexes in the body of prehistoric creatures.
But the most notable among extinct trilobites were the sense organs. True, in some individuals they were absent. Prehistoric animals lived in muddy water or at the very bottom of the ocean. In other subspecies, the sensory organs were located on strong legs. When they buried themselves in the sand, their eyes remained on the surface.
But, what is especially surprising is the facet structure of the eyes. Trilobites instead of the usual lens had calcite lenses of mineral origin. The arthropod angle of view was 360 degrees.
The sense of touch of these creatures was a small antennae located on the head. Trilobites lived mainly on the seabed. But there were such specimens that lived in algae and in the water column.
Trilobite evolution
For the first time, these extinct animals appeared in the Cambrian period. But already in the Carboniferous era, their population began to decline gradually. When the end of the Paleozoic period came, the extinction of trilobites became inevitable.
In the process of their development, they acquired the tail and the head section. It was not divided into separate sections, but had a continuous shell. The tail section has also changed: it has significantly increased in size. This was very helpful, because when cephalopods appeared, they began to eat arthropods.
Nutrition and reproduction of trilobites
There was more than one species of these amazing organisms. Some ate algae and silt, others at plankton. But there were predatory individuals on the planet. Despite the absence of jaws, they crushed their prey with tentacles. The evidence for this hypothesis was the finding of food in the stomachs of trilobites. These were the remains of brachiopods, sponges and worm-shaped creatures. It was suggested that carnivorous trilobites attacked their victims, who lived in the ground. Extinct organisms could also feed on ammonites. Fossils found testified to this.
Examining the remains, scientists came to the conclusion that extinct animals were heterosexual. Confirmation of this was the found output bag. The female laid eggs. After a while, a larva hatched from there (1 mm) and slowly moved along the bottom.
At first, she had a solid body. Then it gradually increased mass and was divided into 6 segments. Trilobites, like all arthropods, periodically molted. Due to this, the larva rapidly increased in size by attaching another segment. Having reached the peak of its growth, the body does not stop shedding.
Trilobites in the modern world and their mining
The only animals that are remotely similar to trilobites are horseshoe crabs. They also appeared in the Ordovician era. Five species of these creatures live in the oceans to this day. Horseshoe crabs are similar to trilobites in several ways : lifestyle, mode of movement, dorsal carapace and faceted eyes. Both species are the antics of one ancestor, but the horseshoe crabs still belong to another class of arthropods.
Surprisingly, the remains of trilobites are still found. And not in the depths of the seas or oceans, but in the usual habitable places of Russia. Most of all they met in the Leningrad region and in eastern Siberia (Yakutia). In Yakutia, trilobites are diverse and huge. But all of their hard coatings are either crushed or segmented. In the Leningrad Region, the opposite is true: the number of extinct creatures is much smaller, but the fossilized remains are striking in their safety. In these places, trilobites with a solid shell and dark brown color are found. This is due to incompletely decomposed organic substances.
Due to the aesthetic appearance, prehistoric animals in the Leningrad Region are considered the main exhibits for sale abroad. Foreign collectors have a great interest in these amazing creatures. This is pleasing, but regular excavation work leads to the destruction of nearby surroundings. As a result, the flora and fauna of those places suffer. And sometimes the trilobite structure suffers from the barbaric attitude of the pickers. They could easily collect arthropods from other parts of animals.
From all over the country they write that they allegedly find living trilobites. However, these are just shields that are crustaceans. Simply put, crustaceans that do not crawl but swim. The size of these creatures reaches up to 8 mm wide. Indeed, they are very much like trilobites. But here the fault is the convergence (animals in the process of evolution acquire a similar image).