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This is the third chapter in the history of the development of Mammals in the Mesozoic Era. As we mentioned earlier, under the pressure of dinosaurs, mammals have entered the golden age of the Mesozoic Era through the transformation of mammals and the exploration of proto-animals in multiple routes.
During this period, the Earth's climate and geology began to be in a relatively stable stage. This quiet and stable environment also provides a wonderful stage for biological evolution, the earth has entered the golden age of life development, and various life species have competed to bloom their own brilliant and brilliant light, leaving a strong mark in this great era. Mammals also ushered in an important inflection point in their own development during this period, and the most prosperous mammals in this period were the trilobites.
Mammals in the early Cretaceous period, at the height of the dinosaur age
< h1 class="pgc-h-decimal" data-index="01" > anatomical features of trilodonts</h1>
Tricuspids, as the name suggests, are three larger tips on the molars, arranged in a row. However, the teeth of groups such as Morgan and thief (mammals) also have similar characteristics, which can be judged to be a primitive feature of mammals.
Although all are "trichral", trilodonts differ from more primitive taxa in that their teeth are flattered in the left and right directions, with a certain cutting function, a mosaic structure formed between the molars, and a well-developed temporal fossa behind the lower jaw, which is used to attach more muscles to improve bite force. Because of the healing of the ossicles, there are no longer as many small bones between the lower jaw and the middle ear area as their ancestors, and the hearing has also improved significantly. As a result, trilobites are a more progressive group.
Modern mammals, including us humans, also have three larger tips on the molars, but instead of lining up, they are distributed in a triangular shape — one cusp on the inside and two cuses on the outside of the upper molars, and one cusp on the outside of the lower molars and two cuses on the medial side. When the teeth bite together, the tips of the upper and lower molars are just in the "concave" between each other's tips. This "triangular sharp tooth" bite is more efficient and progressive. It can be seen that compared with modern mammals, the structure of the trilobit is still relatively primitive.
The location of the triangular toothed beast is more advanced than the existing single-hole class, but it is more primitive than the post-beast and the true beast
<h1 class="pgc-h-decimal" data-index="02" > early taxa: insectivores</h1>
The earliest named member of the Tricorn family is the Triconodon. Like other Mesozoic beasts, the trinosaurus looks like a bulk rat, and has inherited the tradition of mammals who slam their ears on technologies, and the middle ear area has become particularly wide.
The structural characteristics of the teeth of the trilobite are that the height of the three main tips of the molars is basically equal and conical; the large tip on the front side of the molar has a groove or a shallow groove in front of the tip, which can be locked with the last small tip of the front molar to form a mosaic structure. Overall, the teeth of the trilobit are well suited for crushing bugs.
The teeth of the tricorn, the "triangular teeth" are clearly visible
The genus Meiconodon, which is also part of the family Tricornidae, differs greatly from its molars. The molar dentition of this taxon shows a tendency to degenerate, with the molars being shorter and thicker. The remaining undeveloped molars are unusually large, tapering from front to back, with the tip slightly reclined and relatively wide spaced. The most peculiar point is that the tip of the coal-horned beast is asymmetrical from top to bottom, and its tip is rounded towards the cheek side and angular towards the side of the tongue.
Judging by these strange molars, the authors are more inclined to be omnivorous, with complex teeth that can help them handle different foods, including insects, seeds, leaves, and even carrion.
Coal-tipped toothed beast jaw and teeth
The three large pointed teeth on the molars are important features of trilobits, but there is also an outlier in this taxon: Fruitafossor (some believe to belong to a more primitive position than trilobites, which this article adopts is the view that it belongs to the trilobit).
Unlike other tricorns, the teeth of the Friuta are hollow, tubular, and devoid of a enamel layer. And such a strange structure can still be seen in today's aardvark. At the same time, the thick limbs have large and sharp claws for digging the ground. Perhaps the Fruta digging beast, like today's aardvarks and anteaters, will dig out the ants in the ground with developed hands and send them into their mouths to enjoy.
The Furuta Digger
Yanocondon and Jeholodens are both typical tricorns, both belonging to the family Ofelope. Unlike other trilobits, their molars have a noticeable tendency to enlarge and are well involved in chewing. It can be seen that although these two taxa are small, they have an efficient mechanism for handling insects.
Hot river beast skeleton and teeth
The Hot River Beast evolved progressive real-beast-like shoulder straps, with movable shoulder blades and collarbones, retractable joints, and the ability to rotate flexibly, indicating that the forelimbs of the Hot River Beast could not only walk upright, but even complete more complex movements, which is characteristic of mammals. However, the hind limbs of the Hot River Beast still look very primitive, and the legs can only be stretched outwards, and it can only crawl forward like a reptile.
The hearing of the birds's sharp tooth has developed to a relatively advanced stage of transition: at this time, the three auditory ossicles have been fully formed, and the excess bones have either disappeared or healed with other ossicles. However, its middle ear area is still connected to the lower jaw through cartilage, which is a primitive feature; the middle ear and lower jaw of modern true animals have been completely separated, the hearing is further enhanced, and the connection between the middle ear and the lower jaw is only faintly visible at the embryonic stage.
Skeleton of the swallow-toothed beast
In the Liaoconodon of the Family of Thermopods, the canine teeth, lower incisors and molars have a tendency to continue to increase, and the main tips of the molars have also begun to grow longer and thicker, which is a signal of evolution toward predators. Judging by its longer body and paddle-like limbs, this should be a semi-aquatic mammal.
Skeleton of the Liao-horned beast
<h1 class="pgc-h-decimal" data-index="03" > progress into the group: towards predation</h1>
Trilobits feed mainly on insects, but slightly larger species have acquired carnivorous characteristics and have begun to develop in the direction of scavengers and even predators, which is the first time mammals have marched in the direction of active predators.
Gobi condonon, named after the fossils unearthed in the Gobi, but the period in which it lived was a period completely unrelated to desolation, and the fossils of this taxon were unearthed in Xinjiang, China, Inner Mongolia and Liaoning, Mongolia, Siberia in Russia and even montana in the United States, with an extremely wide distribution range, and was the most successful mammal of that era.
Skeleton of the Gobi sharp toothed beast
The lower incisors of gobi cenotes not only increase sharply and have a tendency to tilt forward, but the lower canine teeth begin to shrink, while the canine teeth, incisors, and premolars all have a tendency to conicalize and become sharp, and some species have also found developed sagittal ridges and zygomatic arches (which are the sites where the chewing muscles are attached). All the evidence suggests that it was a fierce predator, perhaps hunting other beasts, lizards, or even small dinosaurs, or using its petite body to sneak up on the table of a flesh dinosaur that was eating and rub a meal? It's really exciting to run after pretending, and this sentence is not too much to apply to the Gobi cone-toothed beast.
Gobi sharp toothed beast
Next I'm going to introduce the big star of the trinacle: Repenomamidae. Because when this species was discovered, it shocked the entire paleontological world: at that time, people thought that the mammals under the rule of the dinosaurs were a bunch of pitifully small things, and only dared to lie out at night and come out to catch bugs under the protection of night.
However, the fossils of the strong reptiles that were found to be 70-80 centimeters long, not only that, but the remains of a psittaciosaur were also found in the stomach. At this time, arrogant human scientists discovered an unprecedented fact: in Liaoning 130 million years ago, a mammal ate a dinosaur. This upended the perception of many people, and people learned that there was already a small predator in the mammals of the dinosaur period.
Strong reptiles feeding on dinosaurs/Zhao Chuang
Reptiles, as the name suggests, are beasts with reptile characteristics. Its limbs are on both sides of the body, and it cannot walk upright, but can only do crawling movements. Reptiles have a short, wide snout and large temporal fossa filled with occlusal muscles, somewhat similar to today's jaguars with powerful bites.
The canine teeth, incisors and anterior molars of the lower jaw have the characteristic of forward tilt, while the tips of the canine teeth, incisors and anterior molars of the upper jaw are curved backwards; the canine teeth are relatively small and similar to the incisors, while the canine teeth, incisors, and anterior molars are all conical. The molars begin to widen and the large tip in the middle expands sharply, while the small tip on both sides begins to show a clear downward trend.
These tooth features indicate that reptiles hunt differently than conventional mammals. Conventional mammalian predators will use canine teeth to kill prey when hunting, through the front teeth to tear, split teeth cutting, molars chew and then swallow the prey, teeth have a very clear division of labor, and the teeth of reptiles are more similar to homomorphic teeth, hunting will be sharp teeth embedded in the body of the prey, using strong bite force to tear down a piece of meat after swallowing, this way is more like dinosaurs, crocodiles and other reptiles, can be described as a veritable reptile.
Strong reptile
Then a larger giant reptile was discovered, a mammal that was 1 meter long and weighed 12-15 kilograms at that time, even the size of a coyote today. The incisors of the giant reptile have become thicker, the upper canine teeth have become bi-toothed roots, thus becoming stronger, and the tips on both sides of the main tip of the lower molars have become larger, just enough to form an occlusal bite with the upper molars, and the distance between the teeth is also becoming smaller.
In addition , giant reptiles have stronger jaws , more developed sagittal ridges , and zygomatic arches. Everything shows that the giant reptile is not an ordinary amplification of a strong reptile, but a more well-equipped hunter. Although the reptile made an attempt in the direction of the predator and challenged the dinosaurs, in that era of unshakable dinosaur hegemony, the reptile could only bully the small dinosaurs and even their cubs, and was only a baby in front of the real overlords such as the feather king dragon and the Chinese tyrannosaurus.
The skulls and teeth of giant reptiles
<h1 class="pgc-h-decimal" data-index="04" > marched to the sky</h1>
As mammals diversified, one mammal in the trilodon family once again learned the skill of gliding, volaticotherium.
Prior to this, the Aho's tree thief beast, the wishbonoid ancestral wing beast (named after the healing between the collarbone and the collarbone, forming a Y-shaped shape, very similar to the wishbones of birds), and the double bowl gliding tooth beast (named after its teeth have an abrasive function very similar to a mortar) have all learned gliding skills.
Ancient Xiang Beast/Zhao Chuang
Similar to these predecessors, the beast's puffed tail and slender limbs have a huge wing membrane covered with hairs used to keep warm. However, unlike the vegetarian predecessors who mainly fed on the young leaves, shoots, cones and seeds of pine cypress, ferns, cycads, and ginkgo biloba, the canine teeth of the xiang beast are long and pointed, the incisors are small and conical, and the three sharp tips of the molars are tilted backwards, which is a highly insecticidal feature.
Some scientists believe that the xiang beast belongs to the trinity based on the three tooth tips, while some scientists think that the xiang beast is a triangular evolution, but it should be in a more advanced classification position, which is not discussed.
Flying beasts
It is not difficult to imagine what the lively sky was like at that time: a huge pterosaur overlooking the sentient beings on the ground in the blue sky; arboreal pterosaurs flying in the forest chasing insects; newly rising birds flapping their immature wings on the stones and groping for a still unfamiliar way of flying; a flying beast on a branch leaping in the air against the wind, and behind it was a small black and shiny little thief dragon waving four wings in pursuit. As everyone knows, hiding in the dense leaves, a Chinese bird dragon is secretly watching all this, and looking for the right time to be ready to take off at any time...
At this point, mammals have diversified in the Mesozoic, but behind this flourishing development, we can also see the cruel and ruthless competition and hard-working survival, and the earth has entered a stable period of development, which is both an opportunity and a challenge - in order to obtain a good environment for development, but also to face the competition of opponents who also have good development opportunities.
The life of a flying beast
In the face of challenges from all sides, some mammals choose to take the side of the sword, open up new paths of survival, and stagger the competition with opponents; some unlock new skills and escape in the face of predators; some face difficulties and fight to the end, choosing a hard-hitting way to turn themselves from prey into hunters; some optimize the structure in order to have more capital to participate in competition.
Nowadays, we can experience the passion of competition through pieces of solidified fossils, feel the grandeur of evolution, appreciate the colorful colors of life, and understand the thrill of survival. The little life on the fossils is unfortunate because their lives can only be frozen in that moment; the little life on the fossils is lucky because their struggling posture is enough to move the offspring who caress their remains.
Perhaps we should say "thank you" to those ancestors who, in those difficult years, faced many difficulties and obstacles, still did not give up hope, and stubbornly struggled to survive in every inch of land.
Life goes on and on and on.