Tiktaalik roseae

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Tiktaalik roseae
Edward B. Daeschler, Neil H. Shubin and Farish A.
Jenkins, Jr (6 April 2006). A Devonian
tetrapod-like fish and the evolution of the
tetrapod body plan. Nature 440 757763.
DOI10.1038/nature04639.
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III. Amphibian evolution - Lissamphibia
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A. Synapomorphies of Lissamphibia

• Hearing apparatus Stapes is directed
  dorsolaterally from the fenestra ovalis
  operculum present (caecilians?)
• Articular surface of the atlas is convex
• Exocipital bones have a suture articulation to
  the dermal roofing bones
• Hand has 4 digits and foot has 5 digits

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B. Extinct tetrapods and their relationship to
Lissamphibia???

• Late Carboniferous explosion of tetrapod
  diversity
• Lepospondyls Temnospondyls (gt200 genera), all
  taxa are highly derived when they first appear in
  the fossil record (no intermediates)
• Lissamphibians in whole, or part could be most
  closely related to either of these groups

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• 1). Lepospondyls Mississippian to lower
  Permian, 60 genera
• lack an otic notch
• they lack labyrinthine infolding in the teeth
• the centrum of lepospondyls is large and
  cylindrical
• usually have a single central element (at least
  in the presacral series),
• There are 4 major groups of lepospondyls
  Aïstopoda, Nectridea, Microsauria, and
  Lysorophidae.

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• 2. Temnospondyls Mississippian to lower
  Jurassic
• Bipartite vertebral centrum
• labyrinthodont teeth (sharp, pointed teeth with a
  complex folding of the wall of the pulp cavity)

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Triadobatrachus 245mya
Virealla, 190 mya
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Hypothesis 1
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Hypothesis 2
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C. Within Amphibia, what is the correct phylogeny?
or

• Uncertainty derives from the long time gap
  between the potential Temnospondyl ancestors in
  the upper Carboniferous and the occurrence of all
  3 extant groups in the early to middle Jurassic.

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D. Extant amphibians

• pair of sensory papillae
• two sound transmission channels in the inner ear
  (stapes-basilar papilla channel
  opercular-amphibian papilla)
• specialized visual cells
• presence of 2 types of skin glands
• fat bodies that develop from the germinal ridge
  of the embryo and retain an association w/the
  gonads in adults

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IV. Evolution of reptiles
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A. Reptiles life on land
specific events occurring during the
Carboniferous period (354-290 mya) ability to
live on land totally
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B. Necessary steps leading up to the amniotic egg
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New Extra-embryonic Membranes amnion innermost
membrane encloses embryo in amniotic fluid
supports body in fluid for normal development
allantois storage sac for nitrogenous wastes
off of cloaca protects embryos from toxic
buildup parts of it may fuse with chorion
chorion outermost membrane encloses all others
embryo chorioallantois membrane - merger forms
a vascularized gas exchange membrane attached to
egg shell or to a placenta
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C. Some synapomorphies of amniota

1. embryonic membranes (amnion, chorion, allantois,
   yolk sac)
2. Scaled skin cutaneious respiration
3. Complete Rib Cage signals the use of a thoracic
   respiratory pump for ventilation of the lungs
   (nolonger buccal pump)
4. Change in vertebral structure more robust
   supporting arch
5. Pleurocentrum becomes main component, neural
   archers broaden

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Anthracosauria
Ancestor to the amniotes, primarily
aquatic Possess features present in amniotes but
not in later amphibians, highly aquatic.
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Probably sister taxa to Amniotes Amphibia
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Synapormorphies of extant Reptilia
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Anapsids Testudines (Chelonia)
Sauropterygia sister taxa to turtles??? Molecula
r evidence supports this hypothesis
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Diapsids

• Lepidosauromorpha
• Rynocephalia
• Squamata
• Archosauromorpha
• Archosauria

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