In which biological age were the first mollusks and trilobites produced

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<> trilobites are animals of the Cambrian period hundreds of millions of years ago. They belong to the phylum Arthropod and live in the ocean. The body of the trilobite is flattened and consists of a head, thorax and tail.

They are named after the three segments on their chest, each with a pair of legs. Trilobites use these legs to swim and crawl.

They have a pair of compound eyes on their heads and many tentacle cavities, which they can use to sense their surroundings and prey on prey. Trilobites come in all sizes and shapes and were very common in the oceans during the Cambrian period. They played an important role in the ecosystem at the time and were an important link in the food chain.

However, over time, trilobites gradually decrease and eventually become extinct, possibly due to decreased oxygen levels, environmental changes, etc. However, they left behind a rich fossil record that provides important clues to our understanding of the evolution of life in the Cambrian.

Trilobites are animals of the Cambrian period before the 100 million manuscript of the year. （）

a.Accurate and accurate.

b.Mistake. Correct Answer: a

Trilobites are animals of the Cambrian period dating back hundreds of millions of years, and this statement is correct.

Trilobites are extinct arthropods that lived from the Cambrian period 100 million years ago to the end of the Permian period about 100 million years ago. In the history of the earth, trilobites were one of the earliest compound eyes and have important paleoecological and geological significance, and the wild simple model is also an important fossil for biostratigraphic research, paleoenvironment and geological age.

In animal taxonomy, trilobites belong to the phylum Arthropods, the class Trilobites. They lived in the ancient oceans, mainly in the Cambrian period, and reached their peak in the late Cambrian period. After that, the trilobite went from its peak to decline, and continued to become extinct at the end of the Permian, and did not enter the Mesozoic Era.

Trilobites have flourished throughout the long geological history of the Paleozoic Era for more than 300 million years, and have produced numerous groups and huge numbers, and the trilobites can be divided into 10 orders: Globular Symphytes, Ledriki, Rods, Cheeks, Specular Eyes, Schizozodes, Ctenophores, Fusariums, Calenders and Dentodes. There are more than 1,500 genera and more than 10,000 species, of which about 500 genera are found in China.

Trilobite habits

Trilobites live in symbiosis with animals such as corals, sea lilies, brachiopods, cephalopods, etc. Most of them are adapted to shallow benthic crawling or semi-swimming life, and some swim or float in the open ocean. Different living habits determine the different body structures.

Benthic trilobites have flat bodies, some of which can burrow into sediment and live, and their heads are hard and the front edge is shaped like a flat shovel, which is easy to dig. Some have healed head carapaces, slow down the development of rib spines, and have a small tail with sharp thorns to advance through the mud and sand.

In addition, it is suitable for crawling on soft or silty seabeds, and its rib spines and tail spines are well developed, making it difficult for the body to fall into the mud. The camp floats the type of life, often with long slender spines on its body. They feed on the carcasses of protozoa, sponges, coelenterates, brachiopods, or on tiny organisms such as seaweed.

Foreword: Trilobita is an extinct class of arthropods.

They first appeared in the Cambrian period, peaked in the early Paleozoic, and then gradually decreased to extinction. The latest trilobite (Scallopidae) disappeared during the extinction of the biomass at the end of the Permian period 100 million years ago. Trilobites are very well-known fossil animals, probably second only to dinosaurs in their popularity.

The extinct trilobite hemiecantha subgenus, red moss, hemiecanthidae, 163 mm, from Morocco, grew in the middle Cambrian period.

The trilobite gets its name from its transverse division into a middle lobe and two symmetrical lateral lobes.

Elrathia (scientific name: Elrathia) is a genus of trilobites that live in the Cambrian ocean, living on the bottom of the continental shelf. The head of this type of trilobite is smaller than the chest.

The glabellum is small and pot-shaped, with small eyes and short triangular cheek spines growing in the center. The thorax is divided into 13 segments, with a narrow central axis and broad lateral plates, ending with a short, spiny distal. The tail is medium in size and twice as wide as it is long.

Summary. Trilobite geologic time period prokaryotes were not flourishing.

Trilobite geologic time period prokaryotes were not flourishing.

The Cambrian Earth has a large number of algae and complex structures, which are the best conditions for the development of invertebrates. Trilobites are the most abundant animals, and the species also account for 60% of the total animal species, in addition to brachiopods account for 30%, and 10% are round-skinned sponges, jellyfish cavities, worms, and molluscs.

Good. Is there anything else I can do to help you, if not, I would like to ask you to give a thumbs up.

Trilobites are hundreds of millions of years old, which can be said to be very old, and they are also very representative of some ancient creatures. The whole body is divided into three parts, which are the head, thorax, and tail. The back is very stiff and there is a dorsal groove that divides the carapace of the back into three equal and uniform parts.

1. Morphological structure of trilobites

Trilobites are mainly oval and oval, but trilobites vary greatly in size. The largest trilobite can reach a total length of 70 cm. The smallest trilobite can reach 6 mm in length, and the more common ones should be between 3 cm and 10 cm in length and 1 cm in width.

Under normal circumstances, more than 20cm is relatively large.

The main feature of trilobites is the dorsal shell structure, with a "head saddle" at the most ** position of the head, which is convex. The surface is smooth and devoid of any ornamentation, but there are some spots and many unequal grooves. There are a pair of eyes on both sides, and there will be some transverse grooves behind the eyes, called "saddle grooves".

There are tentacles on the ventral surface of the head, which are also the mobile organs of the clover, and at the same time the sensory organs of the clover. Behind the tentacles there is a lip flap that serves the same purpose as the mouth and is able to chew. There will be a lot of hair on the limbs, and the main function is to breathe.

The thoracic part has many segments, which are mainly used for the flexibility of the body when it is curled.

The main component of trilobites' eyes is calcium carbonate, but some trilobites use their eyes, while others only use their sense of smell for their senses. In fact, trilobites only regard their eyes as compound eyes, while some trilobites are basically blind and can't see anything. Because they often live in the deep sea, there is no light there, and there is no need to be hungry and use your eyes.

2. The living habits of trilobites

Trilobites live with some brachiopods and other me, crawling and swimming on the ocean floor. There are also trilobites that can swim in the deep sea while living a floating life. Lifestyle habits have a certain relationship with the body structure of trilobites.

Trilobites: The most fossilized class of arthropods.