When it comes to paleontology, everyone's first impression must be dinosaurs, and then you may think of saber-toothed tigers and mammoths, and paleontologists may also think of Dunn's fish, giant hornstones, and sea scorpions. Most of them are large animals, yes, the shape of the large animal that has its own aura to attract people's attention, and there is a small type of ancient animal, I believe most people will know its name, that is, trilobites.
Trilobite | in the Museum of Natural Sciences in Houston Daderot / Wikimedia Commons
Although the popularity of trilobites is high, I am afraid that most people do not understand it, what do they look like? What does it eat? Where does it live? Even many people think that the trilobite is "a" animal. I have a good friend, Brother Onigu Tsurugi, who calls the trilobite "the most familiar strange ancient creature". Today I will tell you the story of the trilobite.
<h1 class="pgc-h-arrow-right" data-track="20" > an ancient and thriving family</h1>
Trilobites, though small, are extremely large in their family: Trilobites have lived on Earth for nearly 300 million years, and for more than half of those three hundred million years, they have been an important part of Earth's ecosystem, like the insects of our time.
The body of the trilobite can be divided into three parts, both horizontally and vertically: from top to bottom is the head with a whole carapace, which is divided into many knots of the thorax and the tail at the end of the body. In the center of the body of the trilobite, there is a bulge called the axis, and the exoskeleton and appendage extend to the sides of the axis, forming two left and right rib lobes, which is the origin of the name trilobite. At that time, there were still a variety of trilobites, perhaps they were distant relatives of trilobites, but only trilobites could flourish.
Cambrian fossils in the Burgess Shale | Wikimedia Commons
The Cambrian period was a very prosperous era for the trilobite family, and it may be difficult for the average person to have an intuitive understanding, but in some strata, the species and number of trilobites exceed more than half of the total local biomass! If we could travel to that era on a time machine, when diving in the sea, we must be surrounded by trilobites.
The first family of trilobites to flourish was the Order Redlichiida, which can be said to have laid the basic body structure of the trilobites, with the head concentrating the sensory organ compound eyes of the trilobites, and the antennae evolved from the first pair of appendages. In that era, the eye was a fairly advanced perceptual organ, and without vision, most of the game of attack and defense between predators and prey would become "blind cats killing rats". The Lyderiki is covered with a hard carapace to give itself the most comprehensive protection, and the chest is divided into several segments, allowing the trilobite to move flexibly under the premise of maintaining strength.
Olenellus chiefensis in the late Cambrian | Dwergenpaartje / Wikimedia Commons
Most people have the impression that the image of the trilobite is a hard fossil, and the lower part of the living trilobite body is a lot of soft appendages, which not only allow the trilobite to crawl on the seabed, but also paddle the water to make the trilobite move forward quickly, and even some trilobites may evolve a backstroke posture. It is these advanced equipment that allows the trilobite family to spread throughout the ocean. Some trilobites are quite large, with a Paradoxides davidis described by British naturalists in 1863 as reaching a length of 37 cm.
<h1 class="pgc-h-arrow-right" data-track="20" > wearing armor</h1>
The flourishing Lederliki worm gradually died out in the middle and late Cambrian period, but the descendants inherited its mantle and continued the glory of the trilobite family. The order Ptychopariida, Asaphida, and Corynexochida took over the banner from the Order Ledriki and became the mainstay of the trilobite family. Their exoskeletons became thicker and thicker, and the spikes on their bodies began to increase gradually.
The trilobite family also had a "non-mainstream" – Agnostida (also translated as the order " , and I have reason to suspect that you're cursing... ）。 Many trilobites will roll up their bodies when they encounter danger, so that they can protect the soft parts of their bodies with a hard shell, and the ball connector will play this skill to the fullest, their head and tail armor evolve into a hemispherical shape, through the chest folding can achieve perfect alignment, see here Many students will exclaim: "Isn't this imitating a clam?" ”。
The armor of the ball picker has no "trilobite appearance" anymore| James St. John / Flickr
By the Ordovicians, the trilobites also became more numerous, with the order Harpetida, Proetida, Phacopida, Odontopleurida, and Lichida. In the mid-to-late Ordovician period, in order to fight against a new generation of large predators such as hornstones and plate-footed horseshoe crabs (hòu), trilobites used all their strength to add new skills to themselves.
The mirror-eyed trilobite curled up | Tylwyth Eldar / Flickr
The largest species in the family was born: the Isotelus rex, a 70-centimeter-long guy in solid armor, like an armored vehicle crawling on the shallow seabed, that could withstand the attacks of the plate-footed crab and any small and medium-sized hornstones, while the Kavala kowalewskii took a different path, with long eye stalks that allowed them to observe their surroundings even if their bodies were buried in the sand at the bottom of the sea.
<h1 class="pgc-h-arrow-right" data-track="20" > decline of the trilobite family</h1>
After the mass extinction at the end of the Ordovician, the Silurian trilobite family began to decline, and the number of species was only half that of the Ordovician, but the trilobites of this era had a very strange and even exaggerated appearance: the body was covered with various elongated and curly spines, and some species were covered with lumps and warts.
In the Devonian period, our protagonist, the Walliserops trifurcatus, finally appeared, found in morocco's Little Atlas Mountains. The spiked guy's head had a trident-like forehead horn that protruded forward. In the Natural Science Museum in Houston, USA, there are many exquisite trilobite fossils, including the excellent preservation of trilobites.
The first thing I saw this guy think of was a strange Cambrian animal, the Obavin sea scorpion with a long mouthpiece. However, this strange appendage is not a mouthpiece, it seems to be an extension of the head armor, what is this thing used for?
The same problem plagues paleontologists, some people think it's a tool for disguise, but what can this thing hold? Some people think that this is a weapon of self-defense, but the animals that can be toppled by it should also be quite wasteful. Some people think that this is a secondary sexual characteristic, and I think this is a bit reliable, but how can you find a female trilobite? Perhaps for us, this is destined to be a mystery, creating a space for endless reverie.
Ceratarges spinosus of the Devonian rift worm order, the appearance is very "sword-rattling" | James St. John / Wikimedia Commons
Mass extinctions at the end of the Devonian period, in terms of species, may have wiped out more than 70% of species in the oceans. The vast majority of the members of the trilobite family did not survive this catastrophe, leaving only the aphid head, however, it was the most inconspicuous taxa of the trilobites that actually survived the entire Carboniferous and Permian for this family, surviving for 110 million years, until the earth-shattering Permian mass extinction occurred, according to the known species, the earth at this time lost 96% of the marine life species, and the history of the trilobite family ended.
If the ecosystem is a pyramid, standing at the top of the tower are undoubtedly the dazzling giant predators: Tyrannosaurus rex, odd shrimp, Dunn's fish, fangjiaoshi, Leviathan whale, dragon, saber-toothed tiger, etc., but I think the really great should be those at the bottom of the tower, obscure small animals, it is they who use their weak bodies to form the cornerstone of the pyramid, support the entire pyramid, without them, where can the golden top of the tower be placed?
This article is from the species calendar, welcome to forward
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