As one of the longest-existing creatures on Earth, what kind of vicissitudes has the trilobite experienced?
Trilobites are an extinct class of arthropods that lived in the marine environment of the Paleozoic era, and their fossil record began in the Cambrian period 540 million years ago and ended at the end of the Permian 251 million years ago.
Trilobites have a flattened oval shape with three distinct bulges on the back, hence the name "trilobites", which usually have compound eyes and antennae, and sometimes antennas and feet for finding food and avoiding predation.
Trilobites were widely distributed in the marine environment at that time, including different types of habitats such as coral reefs, Devonian continental shelves, and sediments.
They are an important link in the marine food chain and are regarded as one of the indicator species of biodiversity and ecosystem evolution, and are of great significance for paleontological and geological research because of the well-preserved and abundant number of trilobite fossils.
However, between the end of the Permian and the early Triassic, trilobites suddenly experienced mass extinctions, with about 90% of species disappearing.
This event has had a profound impact on the earth's ecosystem and has become one of the important topics in the study of trilobites.
The trunk of the trilobite is located in the central part of the body and consists of a series of thoracic segments, usually 6-21, with a pair of lateral limbs on each thoracic segment, and multiple segments on each pair of lateral limbs, the first of which is the shoulder segment.
The head is located at the anterior end of the trunk, including the eyes, antennae, mouthparts, etc., and the tail is located at the posterior end of the trunk and is usually composed of multiple segments, the last of which is called the plate.
The digestive system of the trilobite includes organs such as the mouth, esophagus, intestines, etc., usually in the head or central part of the trilobite, and its nervous system is composed of ganglia and nerve cords, located in the trunk part of the trilobite.
The circulatory system, including the heart, blood vessels and other organs, is located in the trunk part of the trilobite, and its reproductive glands and reproductive tubes and other organs are located in the trunk or tail part of the trilobite.
According to the morphological characteristics of trilobite organs, their development and evolution laws can be revealed, and the mouthparts of trilobites are diverse and differ between different species, which indicates that they have adapted to different ecological environments in the process of evolution.
At the same time, the morphology and number of gills of trilobites are also different, which reflects their differences in ecological habits and environmental adaptation.
In addition, the nervous and circulatory systems of trilobites have changed during evolution, and in early species, ganglia and nerve cords were simpler, and over time they became more complex and developed.
The ecological habits of trilobites are also one of the important factors in their evolution and adaptation to the environment, and trilobites can swim freely in the water or inhabit the bottom.
The swimming style, swimming speed, swimming depth and swimming time are also different between different species, they mainly feed on plankton and organic sediment, and the feeding mode, feeding habits and feeding selectivity between different species are also different.
Trilobites reproduce both sexually and asexually, and the reproductive patterns and breeding habits vary between different species.
Some trilobites evolved to develop complex eye structures that allowed them to better catch food in the water, find mates, and avoid predators.
In addition, some trilobites have evolved to develop special survival strategies, such as species living in deep-sea environments gradually becoming flatter, which allows them to swim more flexibly in the water.
In the course of biological evolution, mutations and genetic drift are inevitable, and in some cases, these mutations may lead to a decline in the species fitness of trilobites, thus accelerating their extinction.
The extinction of trilobites has had a profound impact on the Earth's ecosystem, and as an important link in the marine food chain, their demise has a great impact on the survival and evolution of other biological groups.
There are still many unsolved mysteries about the causes and mechanisms of trilobite extinction, and further research is needed to explore the reasons behind it.
