Topic 13

1
Topic 13 Origins of Order Cetacea

• Cetaceans are Mammals
• A. Phylogeny of extant lineages

1998
2
Topic 13 Origins of Cetacea

• Cetaceans are Mammals
• B. Shared mammalian characteristics
• -warm-blooded
• -breathe air via lungs
• -live young
• -mammary glands

Baby cetaceans swim on side, nurse from nipples
concealed in abdominal mammary slits
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Topic 13 Origins of Cetacea

• Cetaceans are Mammals
• B. Shared mammalian characteristics
• -warm-blooded
• -breathe air via lungs
• -live young
• -mammary glands
• -hair (snout, chin, behind blow hole)

4
Topic 13 Origins of Cetacea
They are not fish e.g., tail (fluke) and
mobility of cetaceans
Fluke of a humpback whale
Tail fin of a yellow-taill snapper
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Topic 13 Origins of Cetacea
They are not fish e.g., blowhole
sperm whale surfacing
sperm whale starts to exhale just below surface
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Topic 13 Origins of Order Cetacea
II. The order Cetacea
Toothed whales
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Topic 13 Origins of Order Cetacea
II. The order Cetacea
Baleen whales
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Topic 13 Origins of Order Cetacea
Baleen whales
Baleen in two parallel rows of plates from
upper jaw modified epidermis keratin (stiff,
elastic) plus hydroxyapatite (bony mineral) w/
trace Ca, Mn, Cu, B, Fe.
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea Terrestria
l gtgt semi-terrestrial origin among the ungulates
1998
10
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea A.
Terrestrial gtgt semi-terrestrial origin among the
ungulates

• Necessary evidence
• Phylogenetic evidence
• Terrestrial gtgt aquatic
• Front limbs gtgt flippers
• Hind legs gtgt no legs
• Nostril migration

1998
11
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

1. Phylogenetic evidence
2. Terrestrial gtgt semi-aquatic gtgt aquatic

1998
12
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt semi-aquatic gtgt aquatic (Marine)
• cetaceans b. sirenians c. pinnipeds d. otters

1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt semi-aquatic gtgt aquatic
• sirenians
• Evolved from protoungulates, related to
  elephants, aardvarks, etc.
• ca. 40 Ma
• Dugongs shallow coastal waters of Indo-Pacific
• Manatees shallow costal waters rivers of
  Caribbean, Amazon, West Africa
• Hind legs lost, but foreflippers have remained
  pliable for maneuvering
• Habitat shallow coastal waters, freshwater
  rivers

1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt semi-aquatic gtgt aquatic
• Pinnipeds (fin-feet or wing-feet)
• Evolved from bear-like, carnivore ancestors ca.
  30 Ma
• Seals, sea lions, and walruses

Bull elephant seals, CA, USA
1998
15
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt semi-aquatic gtgt aquatic
• Pinnipeds (fin-feet or wing-feet)
• Evolved from bear-like, carnivore ancestors ca.
  30 Ma
• Seals, sea lions, and walruses

Bull elephant seals, CA, USA
1998
16
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt semi-aquatic gtgt aquatic
• Pinnipeds (fin-feet or wing-feet)
• Evolved from bear-like, carnivore ancestors ca.
  30 Ma
• Seals, sea lions, and walruses

Bull elephant seals, CA, USA
1998
17
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt semi-aquatic gtgt aquatic
• Pinnipeds (fin-feet or wing-feet)
• Evolved from bear-like, carnivore ancestors ca.
  30 Ma
• Seals, sea lions, and walruses

1998
CA sea lion
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt semi-aquatic gtgt aquatic
• Pinnipeds (fin-feet or wing-feet)
• Evolved from bear-like, carnivore ancestors ca.
  30 Ma
• Seals, sea lions, and walruses

Pacific Walrus
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt semi-aquatic gtgt aquatic
• Otters (13 spp.)
• Related to badgers, weasels, polecats evolved
  ca. 5-7 Ma
• Least streamlined of marine mammals.
• Hind feet gtgt flippers, front limbs are those of
  terrestrial carnivore

Pacific sea otter
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt semi-aquatic gtgt aquatic
• Otters (13 spp.)
• Related to badgers, weasels, polecats evolved
  ca. 5-7 Ma
• Least streamlined of marine mammals.
• Hind feet gtgt flippers, front limbs are those of
  terrestrial carnivore

Northern river otter
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

1. Phylogenetic evidence
2. Terrestrial gtgt aquatic

1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea
1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea
Fossils
1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt aquatic
• Front limbs gtgt flippers
• Hind legs gtgt no legs

1998
Modern cetaceans vesitigial pelvis hind limbs
occasional atavisms
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt aquatic
• Front limbs gtgt flippers
• Hind legs gtgt no legs

basilosaurids dorudontids
1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• 4. Hind legs gtgt no legs basilosaurids and
  dorudontids (ca. 40-30 Ma)

Basilosaurus had 2 tiny legs, probably used as
claspers when mating.
1998
27
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• 4. Hind legs gtgt no legs basilosaurids and
  dorudontids (ca. 40-30 Ma)

Durodon, had 2 tiny legs, probably used as
claspers when mating.
1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• 4. Hind legs gtgt no legs basilosaurids and
  dorudontids (ca. 40-30 Ma)

1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• Phylogenetic evidence
• Terrestrial gtgt aquatic
• Front limbs gtgt flippers
• Hind legs gtgt no legs

protocetids
1998
30
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• 4. Hind legs gtgt no legs protocetids (ca.
  45-35 Ma)

e.g., Rodhocetus fore and hind limbs could
support body on land Therefore, likely to have
been amphibious. Unclear at present if they had
flukes.
1998
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Doubled-pulleyed Astragalus of Rodhocetus and
Artiocetus (pronghorn in middle)
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(No Transcript)
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• 4. Hind legs gtgt no legs ambulocetids
  remingtonocetid (ca. 50-40 Ma)

ambulocetids remingtonocetids
1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• 4. Hind legs gtgt no legs ambulocetids
  remingtonocetid (ca. 50-40 Ma)

1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• 4. Hind legs gtgt no legs ambulocetids
  remingtonocetid (ca. 50-40 Ma)

1998
36
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• 4. Hind legs gtgt no legs ambulocetids
  remingtonocetid (ca. 50-40 Ma)

1998
37
Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

1. Phylogenetic evidence
2. Terrestrial gtgt aquatic
3. Front limbs gtgt flippers
4. Hind legs gtgt no legs
5. Nostril migration

Nasal drift in cetaceans
1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

• 5. Nostril migration

Nasal drift in cetaceans
ambulocetids remingtonocetids
1998
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Topic 13 Origins of Order Cetacea
III. Evolutionary origins of Cetacea

1. Phylogenetic evidence
2. Terrestrial gtgt aquatic
3. Front limbs gtgt flippers
4. Hind legs gtgt no legs
5. Nostril migration

1998