Vertebrate paleontology

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  1. Basal amniote evolution
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    • amniota
    • synapsida
    • eureptilia
    • anapsida
    • diapsida
    • neodiapsida
  2. Amniotes
    • Can lay eggs out of water
    • ancestors of all subsequent tetrapods groups (Permian to present); Reptiles, birds and mammals
    • Traditionally used Class Reptilia=paraphyletic becasue it excludes birds and mammals which are descendants of these earlier forms
    • Early forms small and lizard-like
    • Ate small prey (insects and worms)

    appeared in mid Carboniferous, small bodied, small headed
  3. Amniote skullImage Upload
    • Divided into 5 regions
    • 1. Cheek -10 bones
    •     Premaxilla and maxilla bear teeth
    • 2. Skull table - three paired bones
    •     Parietal foramen
    • 3. Palate - four paired bones and one unpaired
    •     Early animals have palatal teeth-lost later
    • 4. Occiput - six paired bones and one unpaired
    •     Contain bones that support the innter ear semicircular canals
    • 5. Lower jaw - five paired bones
    • Extensive dermal roof bones
    • No temporal notch or eardrum
  4. Amniote postcranial skeleton
    • Lightly built
    • vertebrae= large pleurocentra with small intercentra between
    • modified C1 and C2 allow head to turn on neck
    • Atlas derived from six elemnts
    • Axis - fused plurocentrum and neural arch; small anterior intercentrum
    • dorsals
    • sacrals
    • caudals
  5. Atlas (C1)
    accommodates ball-and-socket of skull occipital condyles to allow rotational movements
  6. Axis (C2)
    • allows "no" movement
    • subsequent 2-4 cervicals similar but with smaller neural arches; short ribs
  7. Dorsals
    bear long ribs; form rib cage
  8. Vertebral regionalizationImage Upload
    • Fishes have trunk and caudal vertebrae
    • Other vertebrates, vertebrae differentiated into up to five types
  9. Pectoral girdle
    • large fused scapulocoracoid
    • -scabula and two coracoids
    • -screw shaped glenoid fossa for humearl head
    • -Cleithrum and clavicle reduced to thin bone strips anterior to scapulocoracoid
    • -interclavical long and "T" shaped
  10. Arm and hand
    • Short arm
    • Long and slender hand with the same wrist bones as in Eryops
    • Phalangeal formula=2,3,4,5,3
  11. Pelvis
    Narrow ilium and pubis and ischium beneath
  12. Hindlimb and foot
    • Longer than hand
    • More slender ankle bones
    • Tibiale, centrale and intermedium fused to form astragalus
    • Fibulare enlarges to become calcaneum
    • Foot phalangeal formula=2,3,4,5,3 (same number of digits for hand and foot
  13. Gastralia
    abdominal ribs protect belly region
  14. Early amniote characteristics
    • Light skulls and small sharp teeth for feeding on invertebrates (insects and millipedes)
    • Pterygoid muscles assist jaw adductors to increase closing strength
    • Stapes heavy and limited to hearing low frequency sounds
    • Early amniotes lack otic notch and therefore, no tympanum
    • Light animals fossilized in tree trunks!
  15. Traps or fissures
    • ex: small animals fell into holes left by rotted tree trunks and could not extricate themselves, so became well preserved
    • A sad event for each poor little critter, but good for paleontologists!
  16. Paleothyris
    earliest identified amniote
  17. Cleidoic egg
    • Image UploadSemipermeable shells
    • Contains sufficient fluid and food for embryonic development
    • Not laid in water; can be laid on dry land
    • No aquatic larval stage of life
    • Requires internal fertilization
    • complex egg type probably evolved only once
  18. Extraembryonic membranes of a Cleodic egg
    • Chorion surrounds embryo and yolk sac
    • Amnion surrounds embryo with water
    • Allantois - sac for respiration and waste storage
  19. four types of amniote skulls
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    • Anapsid - no fenestrae
    • Synapsid - one fenestrae
    • Diapsid - two fenestrae, one above the other
    • Euryapsid - one upper fenestra
  20. Dermatocranial Evolution
    changes to accommodate different numbers of fenestrae and positionsImage Upload
  21. Mesosaurs
    • small, Permian anapsids
    • fully aquatic, up to 1m long
    • slender teeth work as strainers for small prey
  22. Milleretids
    • small, active, insectivorous as are modern lizards
    • Permian anapsid
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    • Bolosaurids - 5-6 genera, lower Permian
    • First bipedal tetrapod
    • Herbivorous, with occluding (interlocking) teeth
  24. Bromacker
    • locality, found in 1930s in East Germany.
    • New tetrapod locality became known after fall of Berlin wall and East and West Germany reunited and their scientists gained  contact with the rest of the world.
    • Many complete, delicate speciments "Death assemblages"
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    • Parieosaurus-heavily built
    • A Procolophonid
    • Herbivores
    • sister groups of turtles
    • Heart shaped heads with multiple rows of peg-like teeth - ate inverts or tough plants - tooth replacement to outside jaws
  26. Image Upload
    • Areoscelids-early diapsids
    • Both aquatic and terrestrial forms
    • had suborbital fenestrae
    • sharp teeth
    • ate insects
  27. Image Upload
    • Late Permian diapsids
    • Coelurosauravus - glider as is living Draco
    • Protosaurus - earliest archosauromorph
    • Youngina - lizard-like insectivore and carnivore
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    • Coelurosauravus restoration
    • doing what comes naturally
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    • Ophiacodonts
    • 6-7 genera
    • Mid-Carbinferous-Early Permian
    • Archaeothyris-poorly known (top)
    • Ophiacodon-largest anmiote so far 1.5m in length, large headed carnivore, eating fish and other tetrapods
  30. Image Upload
    Ophiacodon eating lunch
  31. Image Upload
    • Eothrysis (top left)
    • Cotylorhynchus- Herbivore, very small skull, caseids-herbivorous pelycosaurs (sail backs) (top right)
    • Varanops- usually long tooth row (bottom)
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    • edaphosaurus- one of two groups of sail-backed reptiles
    • Herbivorous with beg-like teeth, deep jaw, head relatively small for body size, jaw movement anteroposterior (propralinal) and large battery of crusing palatal teeth
    • pelycosaurs
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    • Dimetrodon-large, carnivorous pleycosaur (sphenacodontid)
    • Upper Carboniferous and Lower Permian
    • (Texas and Europe)
    • Large-up to 3m long
    • "sail" richly vascularized-probably for thermoregulation
    • One of the best known spenacodontids
    • pelycosaur
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    • Early therapsids
    • Both herbivorous and carnivorous
    • Identify anatomical characters that correlate with feeding habits
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    • Moschops-a herbivorous dinocephalian
    • probably head-butted as do mountain sheep
    • Identify anatomical characters that account for ability to perform this kind of behavior
    • What does head butting reveal about overall life habits of the animal?
  36. Image Upload
    • Dicynodonts-
    • dominant herbivores of late Permian
    • could also be carnivorous
    • Medium sized
    • Died out mostly in Permian mass extinctions
    • Surviving lineages into Triassic became as long as 3m; ecologically similar to present browsing mammals
    • some dicynodonts lived in burrows, and could have died in floods
    • burrows indicate life habits to this level of precision
    • could chew
    • had a beak, and probably used like turtles for cropping plants
  37. Image Upload
    • Gorgonopsidians showing off (dicynodont)
    • dominant late Permian carnivores
  38. Cranial kinesis fnction in a lizardImage Upload
    • joints allow snout to lift or bend down
    • changes angle at which teeth engage prey to prevent it squirting out of mouth from teeth at wrong angle to grasp it
  39. Image UploadShift in jaw muscle attachements to skull
    • Anapsids (no temporal openings) -all muscles attach deep to dermatocranial elements-neurocranium to lower jaw
    • Therapsids with temporal openings-jaw muscles shift to edges of openings, form initial zygomatic arch
    • Jaw muscles move onto dermatocranial surface in therapsids and modern mammals
  40. Squamate cranial kinesis
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    • 3 kinds, named depending on where joint is and what parts move
  41. Turtles solved the muscle position and space problem
    • Posterior skull bones emarginated for muscle origin
    • Trend increases through time.
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    • Sphenodon-two temporal fenestrae
    • living diapsid
  43. Lizards
    diapsids with lower border of lower opening missing, increasing cranial kinesis
  44. Machine linkage
    • analysis of movement of parts of skull of lizard with a mesokinetic joint
    • changes angle of closure of teeth
    • allows for better grasp of prey by improving angle at which teeth hold prey
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  45. Image Upload
    • Chameleon uses the tongue to capture prey
    • supported by large hyoid apparatus (which branchial arch derivative?)
    • elongate lingual process at bottom
  46. Image Upload
    • snake skull biomechanics, water moccasin
    • moveable bones are in color
    • mechanical model of machine that allows kinesis in the anima
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    • Alligator skull with composite elements
    • Lacks kinesis-secondary loss
    • Kinetic-inertial feeding mechanism instead
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    bird skulls have kinesis also because they are light and bones bend, even though they rae fused in the adult
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    • cranial kinesis in a crow
    • nasifrontal hinge allows bill to flex upward
    • sliding crank mechanism model
    • range of movement and gape is increased by cranial kinesis-sliding of joint allows jaw to open farther
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    Rhynochokinesis- Additional flexibility allowed by tips of beak;they can open without entire beak opening
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    • Paleognathous palate of ostrich
    • Primitive pattern of palatal bone arrangement
    • Compare bone patterns to those of other birds and reptilian ancestors
  52. Image Upload
    • Radiation of therapsids
    • They continue synapsid line and have great body form diversity (and some are really cute!)
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    • Chondrocranium (blue) supports internal structures
    • Jointed by splanchnocranium (yellow)
    • These elements give rise to-
    • Epipterygoid
    • Articular
    • Quadrate
    • Hyomandibula
    • Hyoid apparatus
    • Dermatocranium encases most of chondrocranium
  54. Reptilia
    • amnoita-eggs which survive on land and nourish embryos with membranes
    • Two major lineages-
    • sauropsida
    • synapsida
    • Diverged by Carboniferous or earlier
  55. Sauropsida
    • birds, dinosaurs, modern reptiles and Mesozoic reptiles
    • two groups-
    • Parareptilia
    • Eureptilia
  56. Synapsids
    • Monophyletic
    • Therapsids, modern mammals and extinct forms
  57. Image Upload
    • Amniote skull types used to be used in classification, but no longer.  Now, functional types only.
    • Traditional means of dividing groups by skull opening pattern
    • No longer used phylogenetically
  58. Image Upload
    • Stem amniotes, diadectomorphs
    • Late Carboniferous
    • Related to Seymouriomorphs and amphibia
    • Perhaps belong with anthracosaurs and other late non-amniotes
    • also called Cotylosauria
    • what we believe all other amniotes came from
Card Set:
Vertebrate paleontology
2014-03-04 01:20:26

The evolution of early amniotes
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