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. Viviparie is also available in many snakes, lizards, salamanders (e.g. 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 warans 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 Mosasauriers close to the warans to the Squamata.
The mammals are composed of synapsid ancestors, who used to be Therapsida or “acid reptiles” were evolved. This term should also be understood as purely describing, because the reptiles do not exist for the above reasons. The early synapsids include the “Pelycosaurier” 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, e.g. 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 Trias, i.e. approximately at the same time with the dinosaurs. Traditionally, they are older than the birds that only occur in the middle-jura. 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 colonise 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), e.g. 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 “critic 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 much 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 chalk 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-vogel 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.
Die Evolution der Säugetiere ist ein graduell verlaufender Prozess, der mit der Trennung der Sauropsiden– und Synapsiden-Linie irgendwann im Oberkarbon vor mehr als 300 Millionen Jahren begann und bis heute andauert. Bereits in der mittleren Trias existierten Vertreter, die Säugetieren sehr ähnlich sahen. Die ersten „echten“ Säugetiere traten jedoch erst in der Oberen Trias oder im Unteren Jura auf.
Sinodelphys, der früheste bekannte Beutelsäuger, lebte vor 125 Millionen Jahren in der Unterkreide ungefähr zeitgleich mit Eomaia, dem ersten bekannten Höheren Säugetier. Nur zwei Millionen Jahre später erschien dann auch das erste Kloakentier Teinolophos. Nachdem die nichtvogelartigen Dinosaurier dem großen Massenaussterben an der Kreide-Tertiär-Grenze zum Opfer gefallen waren (die Vögel gelten gemeinhin als Nachfahren der Dinosaurier), konnten sich die Beutelsäuger und die Höheren Säuger im Verlauf des Tertiärs in viele neue Taxa aufspalten und neue ökologische Nischen einnehmen. Bis zum Ende des Tertiärs hatten sich dann sämtliche modernen Ordnungen herausgebildet.
https://de.wikipedia.org/wiki/Evolution_der_Säugetiere
Wahrscheinliche Ursachen von Massenaussterben
Die Ursachen von Massenaussterben sind ein vieldiskutiertes Thema in den verschiedenen Disziplinen der Geowissenschaften. Als eigentliche Auslöser, die ultimaten Ursachen, gelten mittlerweile vor allem der Vulkanismus magmatischer Großprovinzen und Einschläge kosmischer Kleinkörper. Von diesen auslösenden Ereignissen wird versucht, über mitunter komplexe Kausalketten hin zu unmittelbaren, proximaten Ursachen Erklärungen für Aussterbemuster zu finden. Dabei spielen als unmittelbare Faktoren, die massenhaft Arten ausgelöscht haben könnten, rasche Klimaveränderungen, Ozeanversauerung und marine Anoxie – neben anderen – eine wichtige Rolle.[7]
Von großer Bedeutung scheint zudem die Umweltsituation zu sein, in die das auslösende Ereignis tritt. So können die Vegetation über ihren Einfluss auf Verwitterungs- und Erosionsprozesse sowie überhaupt Organismen über ihren Stoffwechsel auf die Zusammensetzung von Meeren und Atmosphäre einwirken. Die Position und Anordnung von Landmassen wird ebenfalls als wichtige Randbedingung für die Wirksamkeit ultimater Aussterbeursachen genannt (ihre Änderung mitunter auch als eigentlicher Auslöser). Einer jüngst entwickelten Hypothese zufolge war die ausgeprägte Kontinentalität des 138 Millionen km² umfassenden Superkontinents Pangaea ein Hauptgrund, warum zu dieser Zeit die Biosphäre besonders verwundbar gegenüber dem Ausstoß vulkanischer Gase und Asche war – es fehlten negative Rückkopplungen, die das Erdsystem stabilisiert hätten. Nach der Auflösung Pangaeas hätten die höhere Verwitterungsrate auf den fragmentierten Kontinenten und eine höhere Produktivität Kohlenstoff bindender Organismen der Atmosphäre vermehrt Kohlenstoffdioxid entzogen und so den Folgen des Vulkanismus und damit letztlich einem Massenaussterben entgegengewirkt.[7][10]
https://de.wikipedia.org/wiki/Massenaussterben#Wahrscheinliche_Ursachen_von_Massenaussterben
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