User:Ly1729560145/Sauropsida

Structure difference with synapsids
The last common ancestor of synapsids and Sauropsida lived at around 320mya during Carboniferous, known as Reptiliomorpha.

Thermal and secretion
The early synapsids inherited the abundant gland on skin from their amphibian ancestors. The advantage part is that they can use those glands as sweat gland, which grant them with the ability to maintain constant body temperature. However, the coming Triassic period is an arid period. Even worse is that the way synapsids secret nitrogeneous waste is though urea, which is toxic, so they have to be dissolved in water for secretion. As a result, only a small amount of early synapsids survived, at the land between South Africa to the Antarctica for today’s geography. Different from the miserable situation of synapsids during Triassic period, Sauropsida are great at against arid environments (even today most vertebrates we can find in deserts are still synapsids like lizards or snacks). The ability to secret nitrogen waste product through uric acid do not require water and can be excreted with feces allows them to minimize the water required for activities.

Brain structure
Different from how synapsids have their cortex in 6 different layers of neurons which is called neocortex, the cerebrum of Sauropsida have completely different structures. Comparing an avian brain to that to a mammal, one hypothesis proposed by Karten（1969）, called nuclear-to-layered hypothesis, suggested that the cells, that form layers in synapsids' neocortex, gather individually by type and form several nuclei. For synapsids, when one new function is adapted in evolution it will be assigned to a separated area of cortex, so for each function synapsids will have to develop a separate area of cortex, and damage of that specific cortex may cause disability. However, for Sauropsida functions are disassembled and assigned to all nuclei. In this case, brain function is highly flexible for synapsids. Even with a small brain many synapsids can still have a relatively high intelligence compared to mammals, for example Corvidae. So, it is possible that dinosaurs, like T-rex which we know have tiny brain compared to their enormous body size, to be much more intelligent than what people imagined.

Another variation worth considering is the corresponding structure of cerebrum. In classic view, the neocortex of synapsids is homology with only the Archicortex of avian brain. However, in modern view appeared since 1960s, behavioral studies suggested that avian neostriatum and hyperstriatum can receive signals of vision, hearing and body sense, which means, they act just like neocortex.