Paleocene

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(Mammals)
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Many new types of [[mammal]]s appear in a dramatic evolutionary radiation, filling the ecological roles vacated by the [[dinosaur]]s.  But compared to the majestic [[Cretaceous]] megafauna, these animals were puny.  No Paleocene mammal exceeded the size of a small modern bear, and most were a lot smaller. They were all short-legged and plantigrade (walking on the soles of their feet), and they had five toes on each foot, a primitive feature. Most or all have fourty-four low crowned teeth, another primitive feature. Almost all of them had slim heads with narrow muzzles and small brain cavities.  In terms of brain to body weight ratios they were well below late Cenozoic mammals.
Many new types of [[mammal]]s appear in a dramatic evolutionary radiation, filling the ecological roles vacated by the [[dinosaur]]s.  But compared to the majestic [[Cretaceous]] megafauna, these animals were puny.  No Paleocene mammal exceeded the size of a small modern bear, and most were a lot smaller. They were all short-legged and plantigrade (walking on the soles of their feet), and they had five toes on each foot, a primitive feature. Most or all have fourty-four low crowned teeth, another primitive feature. Almost all of them had slim heads with narrow muzzles and small brain cavities.  In terms of brain to body weight ratios they were well below late Cenozoic mammals.
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The predominant mammals of the period were members of groups that are now extinct. These included the flesh-eating [[Mesonychia]], such as ''Dissacus'' (=''Hyaenodictis'') known from the Middle Paleocene to Middle [[Eocene]] of Europe, East Asia, and North America (family Mesonychidae), which were actually (believe it or not) ancestral to the whales; and [[Creodonta]]; and the mostly herbivorous [[Condylartha]] (e.g. ''Periptychus'' - early Paleocene of North America, family Periptychidae)), which first appeared in the guise of the latest Cretaceous ''Protungulatum'', and were light-bodied animals; and the [[pantodont]]s such as ''Pantolambda'' (middle Paleocene of North America - family Pantolambdidae) and [[Dinocerata]], which were as yet still small to medium-sized, but heavy-bodied animals, all with small brains. Other Paleocene groups included Cretaceous survivors such as the [[multituberculates]], the [[marsupial]]s, and several groups of the insectivores and insectivore-like mammals, and the [[Plesiadapiformes]], a group of squirrel-like animals more or less transitional between insectivores and primates.  Other Paleocene mammals included two unrelated groups of large clumsy herbivores, the [[Tillodont]]s and the [[Tainodont]]s, the latter group including ''Psittacotherium'' (Middle Paleocene of North America, family Stylinodontidae).  Also living at this time, but still insignificant, were the first representatives of the [[rodent]]s and the Miacidae, the ancestors of modern [[Carnivora]].
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The predominant mammals of the period were members of groups that are now extinct. These included the flesh-eating [[Mesonychia]], such as ''Dissacus'' (=''Hyaenodictis'') known from the Middle Paleocene to Middle [[Eocene]] of Europe, East Asia, and North America (family Mesonychidae), which were actually (believe it or not) ancestral to the whales; and [[Creodonta]]; and the mostly herbivorous [[Condylartha]] (e.g. ''Periptychus'' - early Paleocene of North America, family Periptychidae)), which first appeared in the guise of the latest Cretaceous ''Protungulatum'', and were light-bodied animals; and the [[pantodont]]s such as ''Pantolambda'' (middle Paleocene of North America - family Pantolambdidae) and [[Dinocerata]], which were as yet still small to medium-sized, but heavy-bodied animals, all with small brains. Other Paleocene groups included Cretaceous survivors such as the [[multituberculates]], the [[marsupial]]s, and several groups of the insectivores and insectivore-like mammals, and the [[Plesiadapiformes]], a group of squirrel-like animals more or less transitional between insectivores and primates.  Other Paleocene mammals included two unrelated groups of large clumsy herbivores, the [[Tillodont]]s and the [[Tainodont]]s, the latter group including ''Psittacotherium'' (Middle Paleocene of North America, family Stylinodontidae).  Also living at this time, but still insignificant, were the first representatives of the [[rodent]]s and the Miacidae, the ancestors of modern [[Carnivora]]. As well as the [[Lagomorpha|Lagomorphs]] and [[Proboscidea|Proboscids]].
By the start of the [[Tertiary]] the present continental land masses were largely separate, and so independent evolutionary radiations of mammals took place in these relatively isolated areas). This allowed the well-known marsupial fauna of Australia to develop. Until the end of the Tertiary, South America was similarly isolated from the north and likewise developed a unique fauna. Until the middle Tertiary the faunas of Africa were also clearly distinct from those of Eurasia.
By the start of the [[Tertiary]] the present continental land masses were largely separate, and so independent evolutionary radiations of mammals took place in these relatively isolated areas). This allowed the well-known marsupial fauna of Australia to develop. Until the end of the Tertiary, South America was similarly isolated from the north and likewise developed a unique fauna. Until the middle Tertiary the faunas of Africa were also clearly distinct from those of Eurasia.

Revision as of 20:52, 23 November 2013

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