From lizards to mammals – how did #dinosaurs come about?
As far as I know, in the age of the dinosaurs, there were mainly just these: giant lizards, some bird-like creatures, some fish, and some insects. All egg-laying animals, all very closely related to lizards or their ancestors. Then, at some point, mammals appeared (for whatever reason, nature thought, "let's create children in our bodies, lol")
Do you know how the world lost this huge number of lizards? And I'm not talking about the mass extinction, I mean why the mammals had it so much easier, even though they were outnumbered.
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First of all, it's not unusual that mammals are living. Vivipary is also available in many snakes, lizards, salamanders (eg our native alpine slamander, fire slamander native living larvae) and even in sharks.
Secondly, there are "the lizards", as you imagine, not at all. The rural vertebrates are divided into two groups: Lissamphibia (the amphibians still alive today) and amniota .
The amniota can be divided into two groups: Synapsida and Sauropsida. The mammals (Mammalia) have developed from synapsid ancestors and are today the only still living representatives of the Synapsida .
The second group soropsida , include all other land vertebrates:
The crimes or reptiles ("Reptilia") as a relationship group are therefore not available! This term should therefore be avoided.
The actual lizards as part of the squamata are also not a natural relationship group, because the monitor lizards are related to the snakes closer than the other lizards. They form a natural relationship group only as squamata together with the snakes. The squamata are neither ancestors of mammals nor dinosaurs. However, the extinct mosasaurs close to the monitor lizards to the Squamata.
The mammals are composed of synapsid ancestors, which used to be Therapsida or "acid reptiles" were evolved. This term should also be understood as purely descriptive, because the reptiles do not exist for the above reasons. The early synapsids include the "Pelycosaur" as dimetrodone . However, these do not represent direct ancestors of mammals, but rather a side branch from which there are no descendants today.
The mammals from the cynodontia (In fact, they themselves are part of the Cynodontia). The evolution of the mammals did not take place abruptly, but gradual and mosaic-like. The different mammalian characteristics have gradually developed within the synapsida.
Original cynodontia such as cynognathus went up like mammals and didn't wear their limbs sideways spread like "reptias" do it. Most probably owned cynognathus already a coat and was warm-blooded. Possibly, the genus already had skin glands, in particular dairy glands. Other features were, on the other hand, classic "reptia" features, eg the primary jaw joint and the presence of only one ear bone (columella). The real mammals finally developed a secondary jaw joint, initially in addition to the primary jaw joint, such as transition forms such as morganucodon , The primary jaw joint was later displaced into the middle ear and transformed into two additional ear bones, hammer and anvil. From the Columella became the stirrup. The first real mammals probably occurred in the late Triassic, ie approximately at the same time with the dinosaurs. Traditionally, they are older than the birds that only occur in the middle-Jurassic. In the Jura, the mammals had already entered the three major groups: monotremata (early mammals), bag animals (Marsupialia) and placental animals (Placentalia).
An essential reason for the success of mammals, just like the birds, is that they are warm-blooded. They were also able to colonize regions that usually remain denied cold-blooded animals. Although the "crime animals" occur in around 11 400 species worldwide (they are much more successful than the mammals with only 5000 to 6000 species), eg only about 15 species in Germany, but there are 105 mammals. Through their warm-bloodedness, mammals can also be active at night when it is cooler. Classic "critical animals" are not permanently night-active only in tropical regions with night temperatures below 20 °C.
The most successful agriturismo group is the group of birds with nearly 12,000 known species (probably there are many species more, namely 18,000 to 22,000 species). So we are still in the age of dinosaurs and not in the age of mammals.
Why, with the exception of birds, all dinosaurs died at the end of the Chalc period, just like many other groups, while other taxa survived, is not quite clear. It is certain that at the end of the Cretaceous period it has hit large species, so species that were larger than a sheep. But why all the smaller non-avian dinosaurs stared out is uncertain, because they were also warm-blooded like birds and mammals, and on the other hand some cold-blooded animals survived the mass extinction.
I don’t think it’s more detailed, thank you very much
Thank you for the star.
The evolution of mammals is a gradual process that began with the split of the sauropsid and synapsid lines sometime in the Late Carboniferous more than 300 million years ago and continues to this day. Representatives that closely resembled mammals already existed in the Middle Triassic . However, the first "true" mammals did not appear until the Upper Triassic or the Early Jurassic .
Sinodelphys , the earliest known marsupial , lived 125 million years ago in the Early Cretaceous at about the same time as Eomaia , the first known higher mammal . Only two million years later, the first monotremes appeared. Teinolophos . After the non-avian dinosaurs fell victim to the great mass extinction at the Cretaceous-Tertiary boundary ( birds are generally considered the descendants of the dinosaurs), marsupials and higher mammals were able to diverge into many new taxa and occupy new ecological niches during the Tertiary . By the end of the Tertiary, all modern orders had emerged.
https://de.wikipedia.org/wiki/Evolution_der_Säugetiere
Probable causes of mass extinctions
The causes of mass extinctions are a much-discussed topic in various disciplines of geoscience. The actual triggers, the ultimate causes, are now primarily considered to be the volcanism of large magmatic provinces and the impacts of small cosmic bodies. From these triggering events, attempts are made to find explanations for extinction patterns through sometimes complex causal chains to immediate, proximate causes. Rapid climate change, ocean acidification, and marine anoxia—among others—play an important role as immediate factors that could have wiped out species on a massive scale. [7]
The environmental situation in which the triggering event occurs also appears to be of great importance. Vegetation, for example, can influence the composition of the oceans and atmosphere through its influence on weathering and erosion processes, and organisms in general can influence the composition of the oceans and atmosphere through their metabolism. The position and arrangement of land masses is also cited as an important boundary condition for the effectiveness of ultimate extinction causes (their change is sometimes also the actual trigger). According to a recently developed hypothesis, the pronounced continentality of the 138 million km² supercontinent Pangaea was a major reason why the biosphere was particularly vulnerable to the emission of volcanic gases and ash at that time – there were no negative feedback loops that would have stabilized the Earth system. After the breakup of Pangaea, the higher rate of weathering on the fragmented continents and the higher productivity of carbon-binding organisms would have removed more carbon dioxide from the atmosphere, thus counteracting the consequences of volcanism and ultimately a mass extinction. [7] [10]
https://de.wikipedia.org/wiki/Massenausdenken#Wahrscheinliche_Ursachen_von_Massenausdenken
Young animals are far better protected in the abdomen than an egg in the nest.
In addition, the maternal animal does not have to dwell in place to protect the nest, weather conditions can also have a pregnant mammal less than that an egg in the nest is beaten/brushed or flooded by a falling tree or striking lightning or flooding.
I have a sleep deficit! My sentence is anything but German, but have no bock to repair xD