Vertebrate paleontology

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  1. Basal amniote evolution
    • 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 skull
    • 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 regionalization
    • 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
    • Semipermeable 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
    • 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 positions
  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
    • Bolosaurids - 5-6 genera, lower Permian
    • First bipedal tetrapod
    • Herbivorous, with occluding (interlocking) teeth
  23. 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"
    • 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
    • Areoscelids-early diapsids
    • Both aquatic and terrestrial forms
    • had suborbital fenestrae
    • sharp teeth
    • ate insects
    • Late Permian diapsids
    • Coelurosauravus - glider as is living Draco
    • Protosaurus - earliest archosauromorph
    • Youngina - lizard-like insectivore and carnivore
    • Coelurosauravus restoration
    • doing what comes naturally
    • 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
  24. Ophiacodon eating lunch
    • Eothrysis (top left)
    • Cotylorhynchus- Herbivore, very small skull, caseids-herbivorous pelycosaurs (sail backs) (top right)
    • Varanops- usually long tooth row (bottom)
    • 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
    • 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
    • Early therapsids
    • Both herbivorous and carnivorous
    • Identify anatomical characters that correlate with feeding habits
    • 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?
    • 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
    • Gorgonopsidians showing off (dicynodont)
    • dominant late Permian carnivores
  25. Cranial kinesis fnction in a lizard
    • 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
  26. Shift 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
  27. Squamate cranial kinesis
    • 3 kinds, named depending on where joint is and what parts move
  28. Turtles solved the muscle position and space problem
    • Posterior skull bones emarginated for muscle origin
    • Trend increases through time.
    • Sphenodon-two temporal fenestrae
    • living diapsid
  29. Lizards
    diapsids with lower border of lower opening missing, increasing cranial kinesis
  30. 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
    • Chameleon uses the tongue to capture prey
    • supported by large hyoid apparatus (which branchial arch derivative?)
    • elongate lingual process at bottom
    • snake skull biomechanics, water moccasin
    • moveable bones are in color
    • mechanical model of machine that allows kinesis in the anima
    • Alligator skull with composite elements
    • Lacks kinesis-secondary loss
    • Kinetic-inertial feeding mechanism instead
  31. bird skulls have kinesis also because they are light and bones bend, even though they rae fused in the adult
    • 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
  32. Rhynochokinesis- Additional flexibility allowed by tips of beak;they can open without entire beak opening
    • Paleognathous palate of ostrich
    • Primitive pattern of palatal bone arrangement
    • Compare bone patterns to those of other birds and reptilian ancestors
    • Radiation of therapsids
    • They continue synapsid line and have great body form diversity (and some are really cute!)
    • 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
  33. Reptilia
    • amnoita-eggs which survive on land and nourish embryos with membranes
    • Two major lineages-
    • sauropsida
    • synapsida
    • Diverged by Carboniferous or earlier
  34. Sauropsida
    • birds, dinosaurs, modern reptiles and Mesozoic reptiles
    • two groups-
    • Parareptilia
    • Eureptilia
  35. Synapsids
    • Monophyletic
    • Therapsids, modern mammals and extinct forms
    • 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
    • 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

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Vertebrate paleontology
2014-03-04 01:20:26

The evolution of early amniotes
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