BIOL 3300 Vertebrate Zoology:
Ectotherms - Herpetology
http://www.amphibian.com.au/
Extant Tetrapod Phylogeny!
• You should
be able
to provide a
common name
for each group
and describe
a MAJOR
feature of
each clade.
Extant Tetrapod Phylogeny!
Explain what is meant by…
“… Reptilia and Mammalia are sister
lineages among extant amniotes.”
Include terms synapomorphy, plesiomorphy to
describe/answer.
Figure 1.14 Linnean taxonomy places organisms in categories based on overall similarity. Evolutionary taxonomy places organisms in clades based on relatedness
(homologies), which has a clear time component. A dendogram based on Linnean taxonomy (a) contains many polytomies because categories are discreet, (b) can
contain some "species" (A–F and G–K) that are "equal" in rank with similar hierarchical organization to the subfamily level and others (L in particular) that contain this
structure only in name, and (c) has no time component. Thus species L is in L subfamily. Dashed lines indicate where the taxonomic categories would occur for species
L. A dendogram of evolutionary relationships has no clear genus, subfamily, or family structure but presents a relatively accurate hypothesis of known relationships and
relative divergence times. Species are endpoints of divergences. Because of the implicit lack of a time element, individual taxonomic groups in the Linnean system often
do not have comparable evolutionary histories across taxa. For example, a family of scorpions might have a much deeper (older) evolutionary history than a family of
snakes.
Figure 1.15 In evolutionary taxonomy, names of evolutionary groups of organisms (clades) can be confusing. Node-based clades are defined as the most recent
common ancestor (the black circle) and all descendents. For example, Anura is the most recent common ancestor of Ascaphus and Leiopelmatidae. Stem-based clades
are defined as those species sharing a more recent common ancestor with a particular organism (the stem) than with another. Thus Salientia is all taxa (in this case
Ascaphus and Leiopelmatidae) more closely related to Anura than to Caudata. Apomorphy-based clades share a particular unique character (the bar in the graphic on
the right). Thus Anura would be the clade stemming from the first amphibian to have a urostyle (a skeletal feature unique to frogs).
Ways to determine phylogeny!
What characters could you use to
determine relatedness or phylogeny?
Morphometric
Meristic
Qualitative
Macroscopic
Microscopic
Molecular
Cladistical terminology!
Figure 1.16 An abbreviated cladogram of tetrapods illustrating monophyly, paraphyly, and polyphyly. The heavier lines and capitalized group names depict the
monophyletic groups of Amphibia and Reptilia recognized in the text. The boxes define earlier concepts of Amphibia (polyphyletic) and Reptilia (paraphyletic).
What are the tenets of
phylogenetic systematics?
3 criteria:
1)
2)
3)
Figure 1.8 A branching diagram of the evolution within the Tetrapoda, based on sister group relationships. The diagram has no time axis, and each name represents a
formal clade-group name. After Clack, 1998; Gauthier et al., 1988a,b, 1989; and Lombard and Sumida, 1992; a strikingly different pattern is suggested by Laurin and
Reisz, 1997.
Figure 1.12 A branching diagram of the evolution within the Archosauromorpha, based on sister-group relationships. The diagram has no time axis; numerous clades
and branching events are excluded; and each capitalized name represents a formal clade-group name. After Benton and Clark, 1988; Gauthier et al., 1989; Gower and
Wilkinson, 1996 .
Figure 1.13 A branching diagram of the evolution within the Lepidosauromorpha, based on sister-group relationships. The diagram has no time axis; numerous clades
and branching events are excluded; and each capitalized name represents a formal clade-group name. After Gauthier et al., 1989; Rieppel, 1994; Caldwell (1996) and
deBraga and Rieppel (1997) provide different interpretations of lepidosauromorph relationships.
Figure 1.4 Relationships, body forms, and limb structure of the seven key fossil vertebrates used to recover the evolution of supportive limbs in tetrapods. Glyptolepis is
the outgroup. Adapted from Ahlberg and Clack, 2006; Clack 2006; Daeschler et al., 2006; and Schubin et al., 2006.
Tetrapod Phylogeny!
• Acanthostega and Ichthyostega are more
closely related to …
Tiktaalik
haysvillelibrary.wordpress.com
Acanthostega
http://universe-review.ca/I10-72-Acanthostega.jpg
Extant Tetrapod Phylogeny!
• Where would they fit in the cladogram?
From H2O to Land!
• What adaptations were necessary?
–
–
–
–
• Many likely evolved while still primarily
aquatic… adaptations vs. exaptations
• If amphibians evolved from fish… then why do
we still have fish?
Figure 3.2 Geological occurrence of some early tetrapods, and extinct and living amphibians. Abbreviations for Cenozoic epochs: Paleo, Paleocene; Eo, Eocene; Oligo,
Oligocene; Mio, Miocene; Pli, Pliocene; Pleistocene is the narrow, unlabeled epoch on the far right side of the chart. The Dicamptodontidae is now included in
Ambystomatidae.
What feature(s) are “frog”; what is
missing?
Figure 3.5 Triadobatrachus massinoti, the earliest known frog, from the Triassic of Madagascar. Adapted as a partial reconstruction from Estes and Reig, 1973. Scale bar
= 1 cm.
Figure 3.8 Vieraella herbstii, an ancient frog from the Jurassic of Patagonia. Scale bar = 2 mm. Adapted from Estes and Reig, 1973.
Figure 3.9 Paleobatrachus grandiceps, a representative of the extinct Paleobatrachidae, from the Oligocene of eastern Europe. Scale bar = 10 mm.
Adapted from Estes and Reig, 1973.
What feature(s) are “salamander”; what
is missing?
Figure 3.7 Karuarus sharovi (about 15 cm TL), the earliest known salamander, from the Late Jurassic of Russia. Adapted as a partial reconstruction from Carroll, 1988.
Figure 3.10 Geological occurrence of some early anthracosaurs and amniotes, and extinct and living reptiles. Abbreviations for Cenozoic epochs: Paleo, Paleocene; Eo,
Eocene; Oligo, Oligocene; Mio, Miocene; Pli, Pliocene; Pleistocene is the narrow, unlabeled epoch at the top of the chart. Asterisk indicates insuffficient fossil material
to depict how long the taxon persisted.
Figure 3.11 Hylonomus lyelli, the earliest known reptile, from the Early Permian of Nova Scotia. Size, about 42 cm SVL. Adapted from Carroll and Baird, 1972.
Figure 3.14 Cretaceous sea showing several typical reptiles, including the turtle Protostega (left), the mosasaur Platecarpus (largest reptile), and a plesiosaur (top). The
extinct bony fish Xiphactinus (bottom right) and the aquatic bird Hesperornis (center right) are also shown. By Karen Carr, with permission of the Sam Noble Oklahoma
Museum of Natural History.
What are Reptilia features?
• What is a turtle?
An ancestral turtle from the Late Triassic of southwestern China
Chun Li, Xiao-Chun Wu, Olivier Rieppel, Li-Ting Wang & Li-Jun Zhao
Nature 456, 497-501(27 November 2008)
doi:10.1038/nature07533
Figure 3.20 Proganochelys quenstedti, the most ancient turtle, from the Lower Triassic of Germany; approximately 15 cm CL. From Gaffney, 1990; courtesy of the
American Museum of Natural History.
Figure 3.23 The newly described fossil snake Najash not only has bony elements of the sacrum and hindlimbs but was also terrestrial/subterranean. Combined with
other skeletal features, Najash appears to be sister to all known snakes, suggesting that snakes had a terrestrial origin rather than a marine one. Elements of the pelvis
and hindlimbs are shown for Najash, Pachyrhachis, and the Boinae for comparison. Adapted from Apesteguía and Zaher, 2006
Figure 3.22 The structure of the head of the fossil snake Pachyrhachis problematicus (upper) was reconstructed using X-ray computed tomography (lower image),
showing that the skull is indeed that of a basal macrostomatan snake, which means that limb loss occurred independently in different snake clades. Adapted from
Polcyn et al., 2006.
Define the following terms in a
sentence:
OTU
Clade
Sister taxa
Synapomorphy
Type specimen (holotype, paratype,
syntype)
• Phyly (mono, para, poly)
•
•
•
•
•
Why was the recently discovered fossil of
the tetrapodamorph fish Tiktaalik such an
important find?
Why was the amniotic egg such an
important innovation in the evolution of
tetrapods?
Explain the difference between
evolutionary taxonomy and Linnean
taxonomy.
Are amphibians more closely related to
fishes or mammals?
Describe in detail how the transition from
water to land occurred and what the major
morphological preadaptations
(exaptations) were that facilitated this
transition.
Describe the early evolution of caecilians,
salamanders, frogs, turtles, and snakes…
what key features tie fossils/extinct forms
to extant groups?