Modern Mammals

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  • Modern Mammals
    • Facts
      • Decreasing diversity towards the latitudes
      • 95 million fold difference in mass
      • 3000m below to 5000m above sea level
      • 5,500 species
      • Mammalian Origin- early tetrapods
        • Don't know what parental care was like- whether they milk-fed their young
        • Therapsids
          • Advanced Synapsids
          • Legs positioned more vertically beneath bodies
          • Fenestrae were larger than pelycosaurs
          • Teeth and jaws more complex
        • Cretaceous period was an extinction even for mammals
          • 5 groups went extinct, leaving 3
    • Diagnostics
      • Hair
        • even hair follicles
      • Mammary glands
        • Feeds offspring milk
      • Sweat glands
      • Sebaceous glands
      • Four-chambered heart
      • Diaphragm
      • 3 ear bones
      • Epiglottis
        • lap in the throat that keeps food from entering the windpipe and the lungs.
      • 2 testes, 2 ovaries, internal fertilisation
    • Classification
      • Monotremes
        • Reptile-like
          • Meroblastic (contain food for developing embryo)
          • Oviparous
          • Single anogenital opening
        • Mammal-like
          • 3 ear bones
          • Nourish offspring with milk
          • 1 jaw bone
          • Hair
        • Other features
          • Toothless
          • Male platypus have venom
          • Skeletal features and posture resemble early mammals and even reptiles
          • Platypus have an intermediate gait between reptiles and mammals
      • Marsupials
        • 5 species: 4 echidnas, 1 platypus
        • Split penis
        • Marsupium (pouch)- not always present
        • Major split in interrelationships between American and Australasian marsupials
        • No flying marsupials
      • Eutherian mammals
        • 4 major clades
          • Afrotheria
            • Almost uniquely African species
            • Some have left Africa, but majority still there- possibly because it was the origin of eutherian mammals
            • Males have non-scrotal testes
            • features of placenta
            • Many have mobile proboscis
            • Osteological characteristics of the ankle and patterns of dental eruption
            • Afrosoricidae have a cloaca; golden moles have fossorial with no external ears; manatees are adapted for aquatic lifestyle
          • Xenathra
            • Was more diverse in the past
            • South American group, most of the species are still only found in South America
            • Related to Afrotheria
            • Pilosa (sloths and anteaters)
            • Cingulata (armadillos)
            • Insectivores and herbivores
            • Many are toothless
            • Lumbar vertebrate with xenarthrous articulations
            • Tympanic bone annular Septomaxilla in skull
            • Pangolins
              • •Superficially similar (no teeth, same diet) •Actually diverged from Carnivores •Unique keratinized scales

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