Editing Central nervous system (section)

====Chordata====
The CNS of [[chordate]]s differs from that of other animals in being placed [[dorsal nerve cord|dorsally]] in the body, above the gut and [[notochord]]/[[Vertebral column|spine]].<ref name=Romer>Romer, A.S. (1949): ''The Vertebrate Body.'' W.B. Saunders, Philadelphia. (2nd ed. 1955; 3rd ed. 1962; 4th ed. 1970)</ref> The basic pattern of the CNS is highly conserved throughout the different species of [[vertebrate]]s and during evolution. The major trend that can be observed is towards a progressive telencephalisation: the [[telencephalon]] of reptiles is only an appendix to the large [[olfactory bulb]], while in mammals it makes up most of the volume of the CNS. In the human brain, the telencephalon covers most of the [[diencephalon]] and the entire [[mesencephalon]]. Indeed, the [[allometry|allometric]] study of brain size among different species shows a striking continuity from rats to whales, and allows us to complete the knowledge about the evolution of the CNS obtained through [[cranial endocast]]s.

=====Mammals=====
[[Mammal]]s – which appear in the fossil record after the first fishes, amphibians, and reptiles – are the only vertebrates to possess the evolutionarily recent, outermost part of the [[cerebral cortex]] (main part of the telencephalon excluding olfactory bulb) known as the [[neocortex]].<ref name=MarkFBear>{{cite book
| last = Bear
| first = Mark F.
|author2=Barry W. Connors|author3=Michael A. Paradiso
| title = Neuroscience: Exploring the Brain: Third Edition
| publisher = Lippincott Williams & Wilkins
| year = 2007
| location = Philadelphia, PA, US
| pages = 196–199
| url = https://books.google.com/books?id=75NgwLzueikC&q=neuroscience+exploring+the+brain
| isbn = 978-0-7817-6003-4}}</ref> This part of the brain is, in mammals, involved in higher thinking and further processing of all senses in the [[sensory cortex|sensory cortices]] (processing for smell was previously only done by its bulb while those for non-smell senses were only done by the [[tectum]]).<ref>Feinberg, T. E., & Mallatt, J. (2013). The evolutionary and genetic origins of consciousness in the Cambrian Period over 500 million years ago. Frontiers in psychology, 4, 667. https://doi.org/10.3389/fpsyg.2013.00667</ref> The neocortex of [[monotremes]] (the duck-billed [[platypus]] and several species of [[echidna|spiny anteater]]s) and of [[marsupials]] (such as [[kangaroo]]s, [[koala]]s, [[opossum]]s, [[wombat]]s, and [[Tasmanian devil]]s) lack the convolutions – [[gyri]] and [[sulcus (neuroanatomy)|sulci]] – found in the neocortex of most [[placental mammals]] ([[eutherians]]).<ref name=KentCarr>{{cite book
| last = Kent
| first = George C.
|author2=Robert K. Carr
| title = Comparative Anatomy of the Vertebrates: Ninth Edition
| publisher = McGraw-Hill Higher Education
| year = 2001
| location = New York, NY, US
| page = 409
| isbn = 0-07-303869-5}}</ref>
Within placental mammals, the size and complexity of the neocortex increased over time. The area of the neocortex of mice is only about 1/100 that of monkeys, and that of monkeys is only about 1/10 that of humans.<ref name=MarkFBear/> In addition, rats lack convolutions in their neocortex (possibly also because rats are small mammals), whereas cats have a moderate degree of convolutions, and humans have quite extensive convolutions.<ref name=MarkFBear/> Extreme convolution of the neocortex is found in [[dolphin]]s, possibly related to their complex [[Animal echolocation|echolocation]].