We tend to refer to all reptiles of the Mesozoic Era as dinosaurs, which is not true, in fact, we say "dinosaurs", which is equivalent to saying "primates". The relationship between ichthyosaurs, dinosaurs, and pterosaurs is like the relationship between cetaceans, primates, and bats. These three types of ancient animals are in the same period, and all have dragon names, but they are very different, and they can only be said to belong to reptiles.
Paleontologists prefer to distinguish between similar species by differences in skull structure —after all, skulls are the strongest and most likely to be preserved as fossils. Reptiles, birds, and mammals all have a structure called temporal temporal (pronounced Nieru) hole on the skull, and the strong masseter muscle passes through the hole, giving the animal bite force. The difference in the number, structure and location of temporal temporal holes is one of the bases for species classification.
The picture above shows the shape of the skull of the saber-toothed tiger. A pair of large temporal holes can be seen in the overhead viewing angle on the right.
According to the characteristics of temporal foramen , reptiles can be divided into four suborders:
1. Non-porous - Turtles and tortoises belong to this category. Their masseter muscles grow directly against the skull, and there is only one set, so the opening and closing of the mouth is generally not too large.
2. Lower hole class - including Panlonga, Theropoda. Theropods in the order Theropoda are the ancestors of mammals. The skull of such creatures has a temporal foramen on each side, and the masseter muscle passes through the hole, and is divided into upper and lower groups bounded by the hole. We also count in this category, you can touch your upper and lower masseter muscles, just behind the underside and the temples.
3. Concoction - members include ichthyosaurs and plesiosaurs. Their temporal foramen are also a pair, but grow near the top of the head. The purpose of such a long length should be not to destroy the perfect streamlined body type.
4. Diplodocus - Dinosaurs, pterosaurs and reptiles other than today's turtles and tortoises all belong to this category. They have two pairs of temporal foramen, both of which are strong muscles, so T. rex can have up to 20 tons of bite force.
In addition, the ancestors of birds, troodonts, also belong to the dipotass, so birds are direct descendants of dinosaurs.
Ichthyosaurs have only a pair of temporal foramen that grow almost to the top of their heads, and belong to the sea reptiles of the concoction class, which is not the same as dinosaurs in classification. They appeared earlier than dinosaurs and became extinct earlier (both about 15 million years earlier). And because the body is highly specialized into a fish shape, they cannot return to the shore to lay eggs, so they can only reproduce in the way of egg birth, directly laying small ichthyosaurs. This is a huge difference from the dinosaurs that laid their eggs.
And then there's the pterosaur. Like dinosaurs, they had two pairs of temporal foramen in their skulls, but significant differences in other parts of their bodies excluded pterosaurs from the dinosaur family. For example, the structure of the forelimbs of pterosaurs is completely different from that of dinosaurs, its fifth finger degenerates, and its fourth finger is lengthened into a flying finger, while dinosaurs are five-fingered.
In addition, scientists have also found that pterosaurs have some special bones, such as wing bones. The wrist of the pterosaur developed a characteristic wing bone that extended forward to the shoulder and supported the wing membrane, a structure that was also peculiar to the pterosaurs.
Another point is that by preserving perfect fossils, paleontologists found that pterosaurs were covered with warm hairs, and that the fossils were covered with a large number of blood vessel marks in the wing membrane. This confirms that pterosaurs are thermostatic animals, and whether dinosaurs are thermostatic animals is still highly controversial.
Well, now that you know that, it's enough to pack up on the wine table.