Vertebrate Evolution: Mammals and Primates

Vertebrate Evolution

Mammalian Evolution

• Mammals evolved from synapsid reptiles around 320 million years ago
• Key characteristics:
  • Hair or fur
  • Mammary glands
  • Three middle ear bones
  • Live birth
• Early mammals:
  • Small, insectivorous, and nocturnal
  • Examples: Morganucodon and Hadrocodium
• Evolution of mammalian traits:
  • Development of warm-bloodedness (endothermy)
  • Increased brain size and complexity
  • Specialization of teeth and jaws

Primate Evolution

• Primates evolved from a common ancestor with other mammals around 65 million years ago
• Early primates:
  • Small, nocturnal, and insectivorous
  • Examples: Omomyiforms and Adapiforms
• Key primate characteristics:
  • Advanced cognitive abilities
  • Binocular vision
  • Dexterous hands and feet
  • Social behavior
• Evolution of primate groups:
  • Prosimians (lemurs, lorises)
  • New World monkeys (capuchin, tamarins)
  • Old World monkeys (macaques, baboons)
  • Apes (gorillas, chimpanzees, humans)

Amniote Evolution

• Amniotes evolved from a common ancestor with other tetrapods around 340 million years ago
• Key characteristics:
  • Eggs with an amnios, chorion, and allantois
  • Development of a waterproof skin
  • Ability to lay eggs on land
• Early amniotes:
  • Small, reptile-like animals
  • Examples: Hylonomus and Paleothyris
• Evolution of amniote groups:
  • Reptiles (snakes, lizards, turtles)
  • Mammals (monotremes, marsupials, placentals)

Fish-tetrapod Transition

• Transition from fish to tetrapods occurred around 360 million years ago
• Key characteristics:
  • Development of limbs
  • Changes in skull and brain structure
  • Shift from aquatic to terrestrial environment
• Early tetrapods:
  • Fish-like animals with limbs
  • Examples: Acanthostega and Ichthyostega
• Important transitional fossils:
  • Tiktaalik (fish-like with tetrapod features)
  • Panderichthys (tetrapod-like with fish features)

Origin of Tetrapods

• Tetrapods evolved from a group of lobe-finned fish
• Key characteristics:
  • Development of paired limbs
  • Changes in body shape and skeletal structure
  • Shift from aquatic to terrestrial environment
• Early tetrapod habitats:
  • Shallow, oxygen-poor waters
  • Brackish or freshwater environments
• Theories on tetrapod origin:
  • "Fish-out-of-water" hypothesis
  • "Environmental pressures" hypothesis

Vertebrate Evolution

• Mammals evolved from synapsid reptiles around 320 million years ago
• Key characteristics of mammals:
  • Hair or fur
  • Mammary glands
  • Three middle ear bones
  • Live birth
• Early mammals:
  • Small, insectivorous, and nocturnal
  • Examples: Morganucodon and Hadrocodium
• Evolution of mammalian traits:
  • Development of warm-bloodedness (endothermy)
  • Increased brain size and complexity
  • Specialization of teeth and jaws

Primate Evolution

• Primates evolved from a common ancestor with other mammals around 65 million years ago
• Early primates:
  • Small, nocturnal, and insectivorous
  • Examples: Omomyiforms and Adapiforms
• Key primate characteristics:
  • Advanced cognitive abilities
  • Binocular vision
  • Dexterous hands and feet
  • Social behavior
• Evolution of primate groups:
  • Prosimians (lemurs, lorises)
  • New World monkeys (capuchin, tamarins)
  • Old World monkeys (macaques, baboons)
  • Apes (gorillas, chimpanzees, humans)

Amniote Evolution

• Amniotes evolved from a common ancestor with other tetrapods around 340 million years ago
• Key characteristics:
  • Eggs with an amnios, chorion, and allantois
  • Development of a waterproof skin
  • Ability to lay eggs on land
• Early amniotes:
  • Small, reptile-like animals
  • Examples: Hylonomus and Paleothyris
• Evolution of amniote groups:
  • Reptiles (snakes, lizards, turtles)
  • Mammals (monotremes, marsupials, placentals)

Fish-tetrapod Transition

• Transition from fish to tetrapods occurred around 360 million years ago
• Key characteristics:
  • Development of limbs
  • Changes in skull and brain structure
  • Shift from aquatic to terrestrial environment
• Early tetrapods:
  • Fish-like animals with limbs
  • Examples: Acanthostega and Ichthyostega
• Important transitional fossils:
  • Tiktaalik (fish-like with tetrapod features)
  • Panderichthys (tetrapod-like with fish features)

Origin of Tetrapods

• Tetrapods evolved from a group of lobe-finned fish
• Key characteristics:
  • Development of paired limbs
  • Changes in body shape and skeletal structure
  • Shift from aquatic to terrestrial environment
• Early tetrapod habitats:
  • Shallow, oxygen-poor waters
  • Brackish or freshwater environments
• Theories on tetrapod origin:
  • "Fish-out-of-water" hypothesis
  • "Environmental pressures" hypothesis

Mammalian Evolution

• Mammals evolved from synapsid reptiles during the Paleozoic Era, around 300 million years ago
• Key characteristics of mammals include hair or fur, mammary glands, three middle ear bones, and live birth
• Early mammals, such as Morganucodon, were small, insectivorous, and had a primitive brain
• Mammals diversified during the Cretaceous Period, around 100 million years ago

Origin Of Tetrapods

• Tetrapods evolved from lobe-finned fish during the Devonian Period, around 360 million years ago
• Key transitional fossils include Tiktaalik, Acanthostega, and Ichthyostega, dating back to around 375-365 million years ago
• Tetrapods developed limbs from paired fins and lungs from swim bladders

Fish-tetrapod Transition

• The transition from fish to tetrapods involved changes in body shape and size, skeletal system, respiratory system, and sensory systems
• The transition likely occurred in shallow, oxygen-poor water environments

Primate Evolution

• Primates evolved from small, nocturnal, insectivorous mammals during the Paleocene Epoch, around 60 million years ago
• Key characteristics of primates include a large brain-to-body mass ratio, advanced grasping abilities, and binocular vision
• Early primates, such as Omomyiforms, were small and primarily arboreal
• Anthropoids, including monkeys and apes, emerged during the Oligocene Epoch, around 30 million years ago

Amniote Evolution

• Amniotes evolved from amphibians during the Carboniferous Period, around 320 million years ago
• Key characteristics of amniotes include egg-laying, water-conserving skin and kidneys, and development of lungs and air-breathing
• Early amniotes, such as Hylonomus, were small, reptile-like, and lived in terrestrial environments

Dinosaurs

• Dinosaurs evolved from archosaurs during the Middle Triassic, around 245 million years ago
• Key characteristics of dinosaurs include erect posture, herbivorous or carnivorous diets, scaly skin, and a bony skeleton
• Dinosaurs dominated terrestrial ecosystems during the Mesozoic Era, from around 250-65 million years ago
• A mass extinction event at the end of the Cretaceous Period, around 65 million years ago, led to the demise of non-avian dinosaurs