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8/19/2013

Topic 4: The Origin of Topic 4: The Origin of Tetrapods

 Next two lectures will deal with:  What is the geological time scale and why is it important?

 Origin of Tetrapods, transition from  Where do herps fit in the to land. phylogeny?

 What are the evolutionary origins of  Origin of , transition to dry tetrapods? .  What changes were involved in the transition from water to land?

The geological time scale The geological time scale

 Organizes the history of the Eon MYA  accounts for 0-65 ~88% of Earth  Based on geological and biological/ criteria history 65-245  We will  Allows us to consider “______” concentrate on Phanerozoic 245-570  Time scale over which geological and ______phenomena occur st 570-2500 1 multicellular organisms  Organized into hierarchical ______, ______, Precambrian Archaen 2500-3800 1st unicellular organisms ______, and ______Age of oldest rocks 3800-4600

The Paleozoic Era The Mesozoic Era

Period MYA Events Period MYA Events - Mass at end of 1st ______Permian 245-286 Cretaceous 65-144 - 1st modern 1st , 286-320 specialize

st st 360-408 1 amphibians - 1 Urodela, Anura - 1st Rynchocephalia st 144-208 408-438 1 jawed - High diversity - 1st 1st jawless fishes & st 438-505 land -1 Angiosperms, , 1st 505-570 208-245 - 1st Testudines, ______

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The Cenozoic Era What are stem and crown groups?

Period MYA Comments  ______– smallest Modern Recent monophyletic group to contain the last common ancestor of all extant members Quanternary of humans 0.01-1.5 of a 1st hominines 1.5-5  ______– contains crown 5-24 group plus closely related extinct taxa. Last common ancestor is older than that Tertiary 24-37 for its extant members 37-58 -1st 58-65 - 1st pacental mammals

Where do herps fit into the What are stem and crown groups? vertebrate phylogeny?

 Crown groups:  Stem groups:  Phylogeny of jawed  Are monophyletic  Are also monophyletic vertebrates  Contain all extant taxa  Contain all extant &  What are outgroups of Tetrapoda (3)?  Can contain extinct taxa extinct taxa  (6)  Actinistia (7)  Dipnoi (8)

 ______(6) are ray-finned fishes  Extremely diverse (~25,000 spp.)  Highly derived  have extrinsic muscle

Benton Fig 9.11 Pough et al 2004, Fig 2-1

Where do herps fit into the vertebrate phylogeny? Sarcopterygian lineages

 ______(2)  ______ Lobe-finned fishes  ,  Contain Actinistia (7),  2 extant species Dipnoi (8), Tetrapoda  Symmetrical, 3-lobed (3) ______ “living fossil” Benton Fig 9.11  Fins/limbs are supported by bone and  ______contain ______ fishes muscle  3 extant genera  Teeth have enamel  Gondwanan distribution  What kind of characters  1 in S. America, 1 in are these? , 1 in

Pough et al 2004, Fig 2-1 Vertebrate Fig 8-35

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Where do herps fit into the Sarcopterygian lineages vertebrate phylogeny?

 Tetrapoda  This phylogeny includes  Includes all modern only extant taxa amphibians and amniotes, and their  Many species of early last common ancestor. tetrapods and  ______stegocephalians are ______extinct  Fully developed ______girdle  Pectoral girdle free  Therefore, must look at from the (not the both stem and crown case in non-tetrapods) Amphibia  Discrete shaft of ______

Pough et al 2004, Fig 2-1

Stem and Crown Amphibia

Most groups of Amphibians and all early tetrapods are ______

Benton 1997, Fig 4-21

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Early relationships are contentious How do these two hypotheses differ? How are they the same? Why might we prefer one over the other?

Stegocephali Tetrapoda Lepospondyls Temnospondyls Laurin & Reisz 1997 Traditional hypothesis No a priori assumptions, many more taxa included Inclusion of only some taxa, assumption of Temnospondyl-Lissamphibian association Pough et al. 2004 Fig 2-8

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What are the evolutionary origins of tetrapods? What are the evolutionary origins of tetrapods?

 Elpistostegidae ()  Outgroup to Stegocephalia but closer than Dipnoi  Laurin & Reisz 1997  Dorsoventrally ______, no dorsal , dorsal  Lepospondyls are:  ______water  ______ Tetrapod-like body but with fins  Sister to  Developed frontal bones a  Amniotes (including reptiles) are: synapomorphy with  Sister group to stegocephalia Lissamphibia+Lepospondyls

Stegocephali Tetrapoda

Lepospondyls Stegocephali Lepospondyls Temnospondyls Pough et al. 2004 Fig 2-8 Tetrapoda Temnospondyls Pough et al. 2004 Fig 2-3

What are the evolutionary origins of tetrapods? What are the evolutionary origins of tetrapods?

 Acanthostega &  Acanthostega & Ichthyostega  ______from Devonian  ______(360mya) of Greenland and  6-8 digits per  What does this mean for  Four limbs with digits, but also a ancestral number of digits? branchial apparatus with  ______

Stegocephali Lepospondyls Stegocephali Lepospondyls Tetrapoda Temnospondyls Pough et al. 2004 Fig 2-2 Tetrapoda Temnospondyls Vertebrate Life Fig 10-3

What are the evolutionary origins of tetrapods? What are the evolutionary origins of tetrapods?

 Temnospondyls  Amniota  Carboniferous  We will come back to these  Few centimeters to over 1m  Mammals, birds, &  Limbed, posture more upright , , crocidilians than Acanthostega/Ichthyostega  Some aquatic, others (below) terrestrial  Typically ______

 Next slide

Stegocephali Lepospondyls Stegocephali Lepospondyls Tetrapoda Temnospondyls Pough et al. 2004 Fig 2-7 Tetrapoda Temnospondyls

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What are the evolutionary origins of tetrapods? What are the evolutionary origins of tetrapods?

 Lepospondyls  Lissamphibia  Carboniferous &  Urodela, Anura, Gymnophiona  Diverse  Extant (finally)  – ______& small  Aisopoda – ______ – ______& -like

Stegocephali Lepospondyls Pough et al. 2004 Fig 2-4b,c; 4-14, 4-15 Tetrapoda Temnospondyls Photos: KP Bergmann, Pough et al. Fig 3-8

What changes were involved in the transition What changes were involved in the from water to land? transition from water to land?

 This transition involved aspects Obligate Aquatic of structure and function associated with:

What is involved in  ______this major  ______evolutionary  ______transition?  ______ ______ ______ ______Terrestrial  ______

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What changes were involved in the What changes were involved in the transition from water to land? transition from water to land?

 Body support  Ground reaction forces  Moving onto land means coping  Pectoral girdle became with ______from the head  In the water, the body is  Minimizes forces exerted on supported by the water, on skull and brain, increases head land by limbs Actinopterygii ______ Coping with ______ Small in water  Large on land

Ichthyostega Panderichthys

Benton 1997 pg 183; Benton Fig 4-2a; Pough et al 2004 Fig 2-2

What changes were involved in the What changes were involved in the transition from water to land? transition from water to land?

 Ground reaction forces  Locomotion  Limb girdles became more ______to the  A switch from ______vertebral column to and  Allows limbs to become support structures and transfer  is much forces to the axis harder on the ______ Fin-based swimming is replaced by pushing off a substrate with the limbs  Lateral undulation plays a role in both  ______less of an Protopterus issue on land (African )

Acanthostega

Benton 1997 Fig 3.22; Pough et al 2004 Fig 2-2a

What changes were involved in the What changes were involved in the transition from water to land? transition from water to land?

 Locomotion  Locomotion  Limbs change dramatically:  Vertebral morphology becomes more ______ More ______ Zygapophyses limit excessive intervertebral forces,  More ______especially ______ Switch from extrinsic to intrinsic limb musculature

Panderichthys & Acanthostega Acanthostega Vertebrate Life Fig 10-3 Kardong & Zalisko 2002: Fig 5.8c, 5.11b

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What changes were involved in the What changes were involved in the transition from water to land? transition from water to land?

  Body shape  Gills only to gills & to  Very ______in fishes lungs only  Streamline but dorsoventrally flattened in Panderichthys  Both gills and lungs are  Allows invasion of shallow ancestral because lungs water arose from ______

 Also dorsal eyes, no  Decrease in hydrodynamics in  Acanthostega still had gills terrestrial forms  Ventilation increasingly powered by ______of the ______

What changes were involved in the What changes were involved in the transition from water to land? transition from water to land?

 Excretion  Water balance  Trend from excreting  Fishes live in excess water to ______to ______

 Lissamphibia live in moist  Ammonia is most toxic but also environments, but more water- most water soluble ______

 Ammonia is voided quickly  Mucous glands limit evaporation through ______from an ’s body

 and Uric Acid are  Lissamphibia have various concentrated and excreted by behaviors and postures that limit ______water loss

What changes were involved in the What changes were involved in the transition from water to land? transition from water to land?

 Hearing  Feeding  Sound travels differently in air than in water  ______is prevalent in fishes, impossible on land  Other organisms are similar density to water  On land, and the play a more important role  In air there is a differential between densities  bone of the 1 st arch gives rise to the ______, an bone that connects to the ______ This allows for better conduction of vibrations to the inner ear

Kardong & Zalisko Fig 5.29d Pough et al 2004, Fig 11-19

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