Comparative Anatomy Vertebrate Phylogeny: Amphibians, Reptiles, and Birds

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Comparative AnatomyVertebrate Phylogeny
Amphibians, Reptiles, and Birds
Kardong Chapter 3 Part 5
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Amphibian Characteristics

• 1st vertebrates to possess cervical vertebrae
• Lost scales
• Some primitive frogs have dermal scales
• Anamniotic eggs
• 3 chambered heart
• Metamorphosis
• 10 pairs of cranial nerves
• 2 occipital condyles

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Modern Amphibians

• Order Caudata
• Order Anura
• Order Gymnophiona (Apoda)

Figure 5.1.
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Reptiles (the Parareptilia and Eureptilia)

• Mesozoic Era - Age of Reptiles
• Carboniferous - Divided into Pennsylvanian
  (upper)
• and Mississippian (lower)
• Extinction took place at end of Paleozoic Era
  with placoderms

Figure 5.2. Carboniferous Period.
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Figure 5.3. Cotylosuars, stem reptiles.

• Labyrinthodont amphibians led to stem reptiles-
  cotylosaurs (p. 109)
• Which gave rise to all reptiles and mammals

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Figure 5.4. Phylogenetic grouping of amniotes
(book figure 3.30.).
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Phylogeny of Amniote Groups
Figure 5.5.
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Reptilian Characteristics

• True claws
• Amniotic eggs
• No metamorphosis
• 12 pairs of cranial nerves
• Single occipital condyle

Figure 5.6. Nile monitor.
Figure 5.7. Reptile egg.
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Reptilian Classification

• Parareptilia - anapsida (today applies to skull
  type)
• Order Testudines (Chelodina)
• Ex turtles
• Diapsida (within the Eureptilia)
• Majority of reptiles
• Order Squamata
• Ex lizards and snakes
• Suborders Serpentes and Sauria
• Order Sphenodontida
• Ex tuatara (Sphenodon)
• Order Crocodylia

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Reptilian Oral Cavity

• Tooth type
• Acrodont
• Tooth on surface of jaw
• Ex fish and Sphenodon (tuatara)
• Pleurodont
• Tooth attached on medial surface of jaw
• Ex lizards and snakes
• Thecodont
• Teeth embedded in jaw bone
• Ex crocodile

Figure 5.8. Jaw cross section.
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Skull Type
Figure 5.9. Skull types.

• Amniotes possess different skull types
• Anapsid- lack temporal fossa
• Diapsid- two temporal fossa
• One dorsal and one ventral
• Synapsid- single, lower temporal fossa
• Gave rise to mammal-like reptiles

Figure 5.10. Sarcopterygian skull.
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Reptilian Radiation
Figure 5.11. Phylogenetic tree of reptiles.
Figure 5.12. Relationships among higher
vertebrates.
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Pliosaur (a type of plesiosaur). Mayborn
Museum, Baylor University
Sea Serpents
Nothosaurus (Berlin Natural History Museum)
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Dinosaur Groups

• Morphological character of pelvis separate
  groups
• Saurischians
• Triradiate pelvis
• Lizard-like
• Ornithischians
• Tetraradiate pelvis
• Bird-like

Figure 5.13. Pelvic of two dinosaur groups (book
figure 3.35).
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Figure 5.14. Size of selected dinosaurs.
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Dinosaur Groups (cont.)

• Saurischians
• Gave rise to dominant
• reptiles
• Birds evolved
• Parallel convergence

Figure 5.15. Reptilian cladogram.
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Aves - Birds

• Archeopteryx- discovered in 1861 ancestral
  bird
• Feathers and teeth present
• Read Discovery of the First Bird p. 119.

Figure 5.16. Archeopteryx fossil.
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Birds (cont.)

• Keeled sternum in birds that fly.
• (carinates)
• Flightless birds (ratites)

Figure 5.17. (a) Archaeopteryx (b) pigeon.
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Relative Diversity of Terrestrial Vertebrates
Fig. 5.18.
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Characteristics of Birds

• Feathers present
• Homeothermic
• Single occipital condyle
• Scales on legs and feet

Figure 5.19.
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Flier and Flightless Birds

• Archeopteryx- glider
• Reduced sternum

Figure 5.20. (a) Archaeopteryx (b) pigeon.
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Avian Classification

• Modern birds - Subclass Neornithes
• Ancient birds - Subclass Archaeornithes
• Passeriformes - largest order of birds
• Birds arose in mid-Jurassic Period