cetaceans. cetacean evolution n the cetacea probably originated in the palaeocene, and had an eocene...

CetaceansCetaceans

Cetacean EvolutionCetacean Evolution

The Cetacea probably originated in The Cetacea probably originated in the Palaeocene, and had an the Palaeocene, and had an Eocene differentiation.Eocene differentiation.

We have 2 questions:We have 2 questions:– 1) From which mammalian group did 1) From which mammalian group did

the Cetacea evolve?the Cetacea evolve?– 2) Do the 2 modern suborders share a 2) Do the 2 modern suborders share a

common ancestor?common ancestor?

Cetaceans: EvolutionCetaceans: Evolution

The earliest cetacean fossils date to the The earliest cetacean fossils date to the Eocene of Pakistan and belong to the Eocene of Pakistan and belong to the suborder: Archaeoceti.suborder: Archaeoceti.

Other early fossils are from the middle Other early fossils are from the middle Eocene of Egypt and southern Nigeria.Eocene of Egypt and southern Nigeria.

These fossils are members of the These fossils are members of the suborder Archaeoceti (sometimes suborder Archaeoceti (sometimes referred to as Zeuglodont).referred to as Zeuglodont).

This suborder includes This suborder includes Pakicetus Pakicetus and and AmbulocetusAmbulocetus, species , species associated with shallow seas.associated with shallow seas.

The ancestral group, as we noted The ancestral group, as we noted in our discussion of ungulates and in our discussion of ungulates and subungulates, is probably the subungulates, is probably the Condylarthran family Condylarthran family Mesonychidae.Mesonychidae.


Recall that the Condylarthrans also Recall that the Condylarthrans also gave rise to the subungulates and gave rise to the subungulates and ungulates, particularly the ungulates, particularly the Perissodactyla. Condylarthran Perissodactyla. Condylarthran Mesonychids were carnivorous - Mesonychids were carnivorous - scavenging ungulates.scavenging ungulates.


By the mid to late Eocene, most By the mid to late Eocene, most Archaeocetes were so specialized Archaeocetes were so specialized that they were probably not ancestral that they were probably not ancestral to the Odontocetes and Mystecetes.to the Odontocetes and Mystecetes.

Archaeocete skulls are characteristic Archaeocete skulls are characteristic of early Eocene Creodonts (of early Eocene Creodonts (ancestral ancestral group for the Carnivora - wait, what is group for the Carnivora - wait, what is going on?going on?).).


Archaeocete skull characteristics:Archaeocete skull characteristics:– Slightly modified tribosphenic teeth.Slightly modified tribosphenic teeth.– Presence of turbinal bonesPresence of turbinal bones– Incisors, canines, premolars, and Incisors, canines, premolars, and

molars are primitive: 3/3, 1/1, 4/4, 3/3.molars are primitive: 3/3, 1/1, 4/4, 3/3.– Posterior extension of palate via Posterior extension of palate via

pterygoid and palatines.pterygoid and palatines.– Sagital crest on parietals.Sagital crest on parietals.


– External nares lie halfway to orbit, External nares lie halfway to orbit, inline with first premolars.inline with first premolars.

– Rostrum is narrowed posteriorly.Rostrum is narrowed posteriorly.– Nasals are much narrower than Nasals are much narrower than

Creodonts.Creodonts.

Now, what is the connection with Now, what is the connection with the Creodonts?the Creodonts?


In the Cretaceous and Paleocene, In the Cretaceous and Paleocene, there was considerable differentiation there was considerable differentiation in important mammalian groups, in important mammalian groups, probably derived from the probably derived from the insectivores.insectivores.

These groups were probably closely These groups were probably closely related to the Ungulata.related to the Ungulata.

Suborder Arctocyonia was probably Suborder Arctocyonia was probably ancestral to the Ungulates.ancestral to the Ungulates.


A related order, the Mesonychia, was A related order, the Mesonychia, was probably ancestral to the Cetacea (NOTE: probably ancestral to the Cetacea (NOTE: taxonomy has changed - now the order taxonomy has changed - now the order containing the Arctocyonia and containing the Arctocyonia and Mesonychia is the Condylarthra, Mesonychia is the Condylarthra, containing the family Mesonychidae.containing the family Mesonychidae.

As early as 1969, VanValen (Evol. 23: 118-As early as 1969, VanValen (Evol. 23: 118-130) did serological studies demonstrating 130) did serological studies demonstrating a close affinity between Artiodactyla and a close affinity between Artiodactyla and Cetacea.Cetacea.


Zeuglodonts (and perhaps all other Zeuglodonts (and perhaps all other Cetacea) probably diverged from the Cetacea) probably diverged from the Mesonychidae at the end of the Mesonychidae at the end of the Cretaceous, taking to the sea in the early Cretaceous, taking to the sea in the early Paleocene.Paleocene.– Skulls of Zeuglodonts and Mesonychidae are Skulls of Zeuglodonts and Mesonychidae are

very similar in cranial and dental characters.very similar in cranial and dental characters.– Mesonychids were differentiated and Mesonychids were differentiated and

widespread in the late Cretaceous.widespread in the late Cretaceous.


Basilosaurus Basilosaurus had functional hind had functional hind limb elements. Other species were limb elements. Other species were clearly transitional between clearly transitional between terrestrial and aquatic. By the terrestrial and aquatic. By the mid-Miocene, the Archaeoceti were mid-Miocene, the Archaeoceti were fully aquatic.fully aquatic.

2 Zeuglodonts: 2 Zeuglodonts: BasilosaurusBasilosaurus and and Zeuglodon Zeuglodon osiris.osiris. Note the remnants of the pelvic Note the remnants of the pelvic

girdle and hind-limb elements in girdle and hind-limb elements in ZeuglodonZeuglodon, elongation in , elongation in BasilosaurusBasilosaurus, ,

dentition, and elongation of both skulls. dentition, and elongation of both skulls.


Conclusion:Conclusion:– Archeoceti (Zeuglodonts) probably Archeoceti (Zeuglodonts) probably

diverged from Mesonychids at the diverged from Mesonychids at the end of the cretaceous. Mesonychids end of the cretaceous. Mesonychids were closely related to the were closely related to the Arctocyonia, which probably gave rise Arctocyonia, which probably gave rise to the Ungulates. Mesonychids to the Ungulates. Mesonychids actually gave rise to the actually gave rise to the Perissodactyla.Perissodactyla.

Colonization of the SeaColonization of the Sea

Early Zeuglodont fossils are Early Zeuglodont fossils are associated with relatively restricted associated with relatively restricted western arm of the Tethyan Sea western arm of the Tethyan Sea (approximately Mediterranean - (approximately Mediterranean - Persian Gulf) in the Paleocene, and Persian Gulf) in the Paleocene, and dispersed through the warm shallow dispersed through the warm shallow coastal waters of the greatly re-coastal waters of the greatly re-enlarged Tethys during the Eocene.enlarged Tethys during the Eocene.


Tethys sea was shallow warm water basin Tethys sea was shallow warm water basin throughout the Mesozoic.throughout the Mesozoic.

During the Paleocene, western arm of During the Paleocene, western arm of Tethys became constricted and semi-Tethys became constricted and semi-enclosed.enclosed.

Condylarthrans probably utilized Condylarthrans probably utilized riverbanks and shores of the Tethys, riverbanks and shores of the Tethys, feeding on aquatic invertebrates and fish.feeding on aquatic invertebrates and fish.

CompartCompartmentalizementalize

d d stomach: stomach: evodence evodence

for for ungulate ungulate origins?origins?


Natural selection may have favored Natural selection may have favored those individuals which avoided intense those individuals which avoided intense inter- and intra-specific competition by inter- and intra-specific competition by foraging in deeper mud and waters.foraging in deeper mud and waters.

Those individuals which had forms of Those individuals which had forms of variation which enabled them to exploit variation which enabled them to exploit food resources in deeper waters food resources in deeper waters probably had greater reproductive probably had greater reproductive success.success.


Perissodactyls graze, and are limited by Perissodactyls graze, and are limited by availability of food - or so we imagine.availability of food - or so we imagine.

Diversity of Perissodactyls was much Diversity of Perissodactyls was much greater in the Eocene than it is now.greater in the Eocene than it is now.

Warm shallow seas are extremely Warm shallow seas are extremely productive for both plant and animals.productive for both plant and animals.

Foraging in shallow water makes sense Foraging in shallow water makes sense if other resources are limiting.if other resources are limiting.


If you forage in the water, what If you forage in the water, what kinds of morphological attributes kinds of morphological attributes might be favorable?might be favorable?– Longer and narrower rostrum for use Longer and narrower rostrum for use

in catching fish.in catching fish.– Webbed appendages.Webbed appendages.– Migration of nares to top of the skull.Migration of nares to top of the skull.

Major Major morphological morphological developments developments

in the transition in the transition from terrestrial from terrestrial to fully aquatic to fully aquatic

marine marine mammal.mammal.


Could a small rodent or insectivore Could a small rodent or insectivore have done this?have done this?


Why are there no transitional forms Why are there no transitional forms to bare out this hypothesis?to bare out this hypothesis?– Evolutionary event took place over a Evolutionary event took place over a

very restricted area.very restricted area.– Event was probably very rapid (in Event was probably very rapid (in

geological time scale).geological time scale).– Fragmentation of skeletons after death.Fragmentation of skeletons after death.– Perhaps limited sediment deposition.Perhaps limited sediment deposition.


The transition to aquatic feeders is The transition to aquatic feeders is not difficult to imagine. It has been not difficult to imagine. It has been done before:done before:– IchthyosaursIchthyosaurs– PlesiosaursPlesiosaurs– Other reptile groups.Other reptile groups.

Aquatic reptilian groups went extinct Aquatic reptilian groups went extinct by the end of the Cretaceous.by the end of the Cretaceous.


Last Archaeocetes are from the Last Archaeocetes are from the middle Miocene of France.middle Miocene of France.

Early Odontocetes and Mysticetes Early Odontocetes and Mysticetes were present in the middle were present in the middle Oligocene, and completely Oligocene, and completely replaced the Archaeocetes by the replaced the Archaeocetes by the middle Miocene.middle Miocene.

Note: most Note: most modern modern

families of families of cetaceans are cetaceans are present by the present by the

Miocene.Miocene.


Characteristics of the suborders with Characteristics of the suborders with living representatives:living representatives:– Resistance to lactic acid accumulation.Resistance to lactic acid accumulation.– Tolerance of oxygen debt in muscle Tolerance of oxygen debt in muscle

tissue.tissue.– High titre of muscle myoglobin for rapid High titre of muscle myoglobin for rapid

transfer of oxygen to the cells.transfer of oxygen to the cells.– Hypodermal blubber layer for energy Hypodermal blubber layer for energy

storage, thermoregulation (?)storage, thermoregulation (?)


– Oil storage in bones for energy.Oil storage in bones for energy.– Development of flukes for locomotion.Development of flukes for locomotion.– Development of dorsal fin for stability Development of dorsal fin for stability

and thermoregulation in smaller forms.and thermoregulation in smaller forms.– External nares located on top of skull External nares located on top of skull

with means of sealing out water.with means of sealing out water.– Modification of tracheal system and Modification of tracheal system and

lungs to withstand high pressure.lungs to withstand high pressure.

Gray WhaleGray Whale

Baleanoptera: Blue WhaleBaleanoptera: Blue Whale

Cetacean EvolutionCetacean Evolution- Loss of pelvic appendages & - Loss of pelvic appendages &

girdlesgirdles


- Loss of mobility of the neck.- Loss of mobility of the neck.


– Modification of the eyes to tolerate Modification of the eyes to tolerate salt water and extreme pressure.salt water and extreme pressure.

– Modification of sound conducting Modification of sound conducting routes and sound production routes.routes and sound production routes.

– Modification of dentition to reflect a Modification of dentition to reflect a filterfeeding or piscivorous diet.filterfeeding or piscivorous diet.

Genital grooves in a) male and Genital grooves in a) male and b) female. Forelimbs of c) pilot b) female. Forelimbs of c) pilot

whale, d) right whale, and e) whale, d) right whale, and e) human.human.


Unresolved is the question of how the 2 Unresolved is the question of how the 2 extant cetacean suborders are related extant cetacean suborders are related to one another, or how either suborder to one another, or how either suborder is related to the Archaeoceti.is related to the Archaeoceti.

Are they polyphyletic? Probably not.Are they polyphyletic? Probably not. Odontocetes and Mysticetes are clearly Odontocetes and Mysticetes are clearly

differentiated by the Oligocene.differentiated by the Oligocene.

Spinner DolphinSpinner Dolphin

Delphinidae: Delphinidae: LagenorhynchusLagenorhynchus

Evolutionary Patterns Evolutionary Patterns Within the OdontocetiWithin the Odontoceti

How do odontocetes differ from the How do odontocetes differ from the Zeuglodonts?Zeuglodonts?– Odontocete lachrymal bones abut Odontocete lachrymal bones abut

onto the ventral area of the onto the ventral area of the maxillaries, not on to their lateral maxillaries, not on to their lateral surfaces.surfaces.

– The maxillaries have migrated The maxillaries have migrated posteriad to lie over the supraorbital posteriad to lie over the supraorbital region of the frontal bones.region of the frontal bones.

Evolutionary Patterns Evolutionary Patterns Within the OdontocetiWithin the Odontoceti

– Significant telescoping of skull with Significant telescoping of skull with accomodation for melon, nasal accomodation for melon, nasal diverticula, and spermaceti organ diverticula, and spermaceti organ associated with sound production and associated with sound production and sound reception.sound reception.

– Odontocetes have homodont Odontocetes have homodont dentition.dentition.

HorseHorse

BasilosauruBasilosauruss

DelphinusDelphinus

BalaenopteBalaenopterara

Tursiops Tursiops truncatustruncatus

Homodont dentition of an odontocete.Homodont dentition of an odontocete.

Evolutionary Patterns Evolutionary Patterns Within the MysticetiWithin the Mysticeti

Mysticete skulls have great forward Mysticete skulls have great forward extension of the upper margin of the extension of the upper margin of the occipital shield. This results from occipital shield. This results from forces operating on anterior portion of forces operating on anterior portion of the animals:the animals:– forward motion against water resistance.forward motion against water resistance.– Strain on cranial and mandibular system Strain on cranial and mandibular system

each time animal opens its mouth.each time animal opens its mouth.

Evolutionary Patterns Evolutionary Patterns Within the MysticetiWithin the Mysticeti

Mysticetes have teeth, embryonically. Mysticetes have teeth, embryonically. (the first recognizable mysticete (the first recognizable mysticete (Aetiocetidae: (Aetiocetidae: AetiocetusAetiocetus) from the ) from the Oligocene does not have baleen, but Oligocene does not have baleen, but teeth instead.)teeth instead.)

Baleen is of secondary dermal origin.Baleen is of secondary dermal origin. Long nasal bones are partially enveloped Long nasal bones are partially enveloped

by the premaxillaries and maxillaries.by the premaxillaries and maxillaries.

a) Minke, b) Sei, c) Bryde’s, d) pygmy right, a) Minke, b) Sei, c) Bryde’s, d) pygmy right, e) gray, f) humpback, g) fin, h) blue, i) e) gray, f) humpback, g) fin, h) blue, i)

right, j) bowhead.right, j) bowhead.

Baleanoptera: Minke Baleanoptera: Minke WhaleWhale

Gray WhaleGray Whale

HumpbackHumpback

Baleanoptera: Fin WhaleBaleanoptera: Fin Whale

Baleanoptera: Blue WhaleBaleanoptera: Blue Whale

Are the Cetacea Are the Cetacea monophyletic or monophyletic or

polyphyletic?polyphyletic?

Many published works favor a Many published works favor a polyphyletic origin for the polyphyletic origin for the Odontocetes, Mysticetes, and Odontocetes, Mysticetes, and Archaeocetes.Archaeocetes.

What is the liklihood of 3 separate What is the liklihood of 3 separate lines invading the aquatic environment lines invading the aquatic environment at roughly the same geological time?at roughly the same geological time?

Is this parsimonoius?Is this parsimonoius?

Polyphyly: Anatomical Polyphyly: Anatomical considerations.considerations.

Similarities (result of supposed Similarities (result of supposed convergence in an aquatic convergence in an aquatic environment)environment)– loss of true vocal cords.loss of true vocal cords.– Loss of pelageLoss of pelage– lung shape and oblique position of lung shape and oblique position of

diaphragm.diaphragm.– Streamlined body shape.Streamlined body shape.– Dorsal migration of external nares.Dorsal migration of external nares.


Differences (result of diphyletic Differences (result of diphyletic origin, supposedly)origin, supposedly)– biochemical differences in the biochemical differences in the

blubber.blubber.– Lower jaw is symphysial in Lower jaw is symphysial in

Odontocetes, but not in Mysticetes.Odontocetes, but not in Mysticetes.– Skull is symmetrical in Mysticetes but Skull is symmetrical in Mysticetes but

not in Odontocetes.not in Odontocetes.

Risso’s Risso’s dolphin dolphin

and and northern northern

right right whale.whale.


– Ethmoturbinals are present in Ethmoturbinals are present in Mysticetes but not in Odontocetes.Mysticetes but not in Odontocetes.

– Females are the larger sex in Females are the larger sex in Mysticetes while for the most part, Mysticetes while for the most part, males are larger in the Odontocetes.males are larger in the Odontocetes.

Note: if you look long enough, you can find an Note: if you look long enough, you can find an impressive list of skeletal characters which are impressive list of skeletal characters which are similar, and for which the Archaeocetes are similar, and for which the Archaeocetes are intermediate between Odontocetes and intermediate between Odontocetes and Mysticetes.Mysticetes.

Echolocation in odontocetesEcholocation in odontocetes

Karyotypic considerations: Major Karyotypic considerations: Major argument in favor of a monophyletic argument in favor of a monophyletic

origin.origin.

Both suborders share the same Both suborders share the same characteristic distribution of C-characteristic distribution of C-heterochromatin in the heterochromatin in the chromosomes. (However, several chromosomes. (However, several divergent and probably secondary divergent and probably secondary karyotypes were found in the karyotypes were found in the odontocetes)odontocetes)

Both have the same diploid number Both have the same diploid number of 22 chromosomes.of 22 chromosomes.

Physiological attributes of the Physiological attributes of the Cetacea: metabolic rates and Cetacea: metabolic rates and

energy budgets.energy budgets.

Some primary factors which have Some primary factors which have governed the evolution of modern governed the evolution of modern Cetaceans.Cetaceans.– Food sources are discontinuously Food sources are discontinuously

distributed in the world oceans.distributed in the world oceans.– Within areas of food availability, the Within areas of food availability, the

food is frequently available only food is frequently available only seasonally.seasonally.

Physiological attributes of the Physiological attributes of the Cetacea: metabolic rates and Cetacea: metabolic rates and

energy budgets.energy budgets.

– Even when food is present and Even when food is present and abundant, it is discontinuously abundant, it is discontinuously distributed from the viewpoint of an distributed from the viewpoint of an individual whale.individual whale.

– Presuming that an animal can locate Presuming that an animal can locate and stay with optimal feeding and stay with optimal feeding conditions, these conditions are conditions, these conditions are probably not optimal for reproductive probably not optimal for reproductive requirements.requirements.

Diving Adaptations in Diving Adaptations in MammalsMammals

Occurs in the Pinnipedia, Sirenia, and Occurs in the Pinnipedia, Sirenia, and Cetacea.Cetacea.

Maximum duratin of dive in minutes Maximum duratin of dive in minutes for varioius mammals:for varioius mammals:– man=2.5min.man=2.5min. Dog = 4.5minDog = 4.5min– Beaver = 15min.Beaver = 15min. Seal = 15minSeal = 15min– Muskrat = 12min.Muskrat = 12min. Gray seal = Gray seal =

20min20min– White rat = 3.1min.White rat = 3.1min. Elephant seal = Elephant seal =

Diving AdaptationsDiving Adaptations

Maximum duratin of dive in minutes for varioius Maximum duratin of dive in minutes for varioius mammals:mammals:– man=2.5min.man=2.5min. Weddells seal = 43min.Weddells seal = 43min.– Beaver = 15min.Beaver = 15min. Sperm whale = 75min.Sperm whale = 75min.– Muskrat = 12min.Muskrat = 12min. Bottle nosed whale = 120min Bottle nosed whale = 120min

atat– White rat = 3.1min.White rat = 3.1min. A depth of 2.5mi.A depth of 2.5mi.– Dog = 4.5min.Dog = 4.5min.– Seal = 15min.Seal = 15min.– Gray seal = 20min.Gray seal = 20min.– Elephant seal = 30min.Elephant seal = 30min.– Manatee = 16min.Manatee = 16min.


Problems:Problems:– Brain and heart must have oxygen at Brain and heart must have oxygen at

all times.all times.– You can’t take the air with you, you You can’t take the air with you, you

must hold your breath.must hold your breath. Apnia = holding breathApnia = holding breath Asphixia = going without oxygenAsphixia = going without oxygen Eupea = normal breathing.Eupea = normal breathing.


Problems cont:Problems cont:– Must avoid the bends. The bends are Must avoid the bends. The bends are

caused by nitrogen in the blood. The caused by nitrogen in the blood. The greatest portion of the atmosphere is greatest portion of the atmosphere is composed of Ncomposed of N22. Under pressure, . Under pressure, nitrogen is forced through the lun and nitrogen is forced through the lun and into the blood. When you come up too into the blood. When you come up too fast, the nitrogen expands in muscle fast, the nitrogen expands in muscle tissue etc and causes great pain.tissue etc and causes great pain.


– You must watch out for COYou must watch out for CO22 levels. levels. When COWhen CO22 level is high enough, the level is high enough, the vagus nerve causes you to breathe.vagus nerve causes you to breathe.

Solutions as determined by Solutions as determined by Sholander for Harbor SealsSholander for Harbor Seals– Harbor seals display bradycardia Harbor seals display bradycardia

(reduce heart rate).(reduce heart rate).


– They have a rete mirabile system They have a rete mirabile system surrounding the spinal cord and surrounding the spinal cord and vertebral column. During dives, blood vertebral column. During dives, blood is shunted away from the periphery of is shunted away from the periphery of the body and into the rete mirabile the body and into the rete mirabile surrounding the spinal cord. Thus all surrounding the spinal cord. Thus all the Othe O22 now surrounds the spinal cord, now surrounds the spinal cord, the heart, and the brain.the heart, and the brain.


Some solutions for whales:Some solutions for whales:– BradycardiaBradycardia– MyoglobinMyoglobin

– Can tolerate a high OCan tolerate a high O2 2 debt.debt.

– Vasoconstrict and put blood into the rete Vasoconstrict and put blood into the rete mirabile surrounding the vertebral column.mirabile surrounding the vertebral column.

– Exhale before diving. The typical whale has a Exhale before diving. The typical whale has a lung volume of 100,000 liters. After having lung volume of 100,000 liters. After having exhaled, there is a residual 10,000 liters of gas exhaled, there is a residual 10,000 liters of gas in the trachea.in the trachea.


– The trachea are reinforced with The trachea are reinforced with cartilaginous/bone rings which prevent cartilaginous/bone rings which prevent the trachea from collapsing at great the trachea from collapsing at great depths. However, the lungs collapse.depths. However, the lungs collapse.

– In sperm whales, there is no sternum In sperm whales, there is no sternum and the ribs can pivot on their and the ribs can pivot on their articulation with the vertebra, thus all articulation with the vertebra, thus all the air can be exhaled from the lungs the air can be exhaled from the lungs and the lungs can collapse.and the lungs can collapse.


– Whales have a very high COWhales have a very high CO2 2

tolerance.tolerance.

– Whales have a relatively low OWhales have a relatively low O2 2

demand.demand.

GlobicephelaGlobicephela

Mysticetes: BalaenidaeMysticetes: Balaenidae

2 genera and 3 species.2 genera and 3 species.– Bowhead whaleBowhead whale– Northern right whaleNorthern right whale– Southern right whaleSouthern right whale

Lack throat grooves and dorsal fin.Lack throat grooves and dorsal fin. Callosities on head.Callosities on head. Feed by skimming or gulping just Feed by skimming or gulping just

below surface.below surface.

Mysticetes: BalaenidaeMysticetes: Balaenidae

Easy to whale because they are Easy to whale because they are slow, they float a long time, and slow, they float a long time, and they contain a lot of blubber.they contain a lot of blubber.

Overexploited, and populations Overexploited, and populations have not recovered.have not recovered.

Mysticetes: Mysticetes: BalaenopteridaeBalaenopteridae

2 genera and 5 species of rorquals.2 genera and 5 species of rorquals.– Fin whaleFin whale– Sei whaleSei whale– Blue whaleBlue whale– Bryde’s whaleBryde’s whale– Minke whaleMinke whale– Humpback whaleHumpback whale

They all have throat grooves for bucal They all have throat grooves for bucal expansion during feeding.expansion during feeding.

Mysticetes: Mysticetes: BalaenopteridaeBalaenopteridae

Humpbacks occur closer to shore. Humpbacks occur closer to shore. They have numerous bumps on They have numerous bumps on head, each containing a sensory hair.head, each containing a sensory hair.

Humpbacks use ‘bubblenetting’ while Humpbacks use ‘bubblenetting’ while others use gulping or skimming.others use gulping or skimming.

Humpbacks have complex Humpbacks have complex vocalizations, with regional dialects. vocalizations, with regional dialects. Songs throughout the season.Songs throughout the season.

Baleanoptera: Minke Baleanoptera: Minke WhaleWhale

BaleanopteraBaleanoptera

Baleanoptera: Fin WhaleBaleanoptera: Fin Whale

HumpbackHumpback

Mysticetes: EschrichtiidaeMysticetes: Eschrichtiidae

Monotypic, only Monotypic, only Eschrichtius robustusEschrichtius robustus.. Crenulations on back, few throat grooves.Crenulations on back, few throat grooves. Feed in arctic in summer, then migrate Feed in arctic in summer, then migrate

18000km to Baja or Sea of Japan, where 18000km to Baja or Sea of Japan, where they calve.they calve.

Why migrate? Males do not necessarily Why migrate? Males do not necessarily migrate. Do not feed on southward migrate. Do not feed on southward migration.migration.

Mysticetes: NeobalaenidaeMysticetes: Neobalaenidae

Monotypic: pygmy right whale.Monotypic: pygmy right whale. Only in temperate, southern Only in temperate, southern

hemisphere waters.hemisphere waters. Unlike other right whales, it has 2 Unlike other right whales, it has 2

shallow throat grooves.shallow throat grooves. These are small, only about 6m in These are small, only about 6m in

length. length.

a&d) Balaenidae, b&e) Eschrichtiidae, a&d) Balaenidae, b&e) Eschrichtiidae, c&f) Balaenopteridae.c&f) Balaenopteridae.

Odontocete Odontocete vs. vs.

MysticeteMysticete

Odontocetes: DelphinidaeOdontocetes: Delphinidae

17 genera and 32 species.17 genera and 32 species. Size ranges from 1.7m to Killer Size ranges from 1.7m to Killer

whale at 9m.whale at 9m. Spinner dolphins are species most Spinner dolphins are species most

often caught in tuna nets.often caught in tuna nets.

Tooth number in Risso’s Tooth number in Risso’s dolphin and spinner dolphin.dolphin and spinner dolphin.

Spotted DolphinSpotted Dolphin

DelphinidaeDelphinidae

Spinner DolphinSpinner Dolphin

Tursiops truncatusTursiops truncatus

Odontocetes: Odontocetes: MonodontidaeMonodontidae

2 genera and 2 species: narwhal and beluga.2 genera and 2 species: narwhal and beluga. Lack dorsal fin.Lack dorsal fin. Circumarctic distribution.Circumarctic distribution. Both have robust bodies and heads.Both have robust bodies and heads. Narwhals have 2 incisors: right incisor does Narwhals have 2 incisors: right incisor does

not erupt in males, left incisor erupts w/ not erupt in males, left incisor erupts w/ counterclockwise spiral. Neither incisor counterclockwise spiral. Neither incisor erupts in females.erupts in females.

Beluga, Beluga, LaganorhynchusLaganorhynchus, , and and GlobicephalaGlobicephala..

Odontocetes: PhocoenidaeOdontocetes: Phocoenidae

4 genera and 6 species of 4 genera and 6 species of porpoises: they differ from porpoises: they differ from dolphins in that dolphins generally dolphins in that dolphins generally have a beak while porpoises do have a beak while porpoises do not.not.

Porpoise teeth are blunt crowned, Porpoise teeth are blunt crowned, while dolphin teeth are sharp and while dolphin teeth are sharp and conical.conical.

Homodont dentition of an odontocete.Homodont dentition of an odontocete.

Odontocetes: PhyseteridaeOdontocetes: Physeteridae

2 genera and 3 species of Sperm 2 genera and 3 species of Sperm whales.whales.

Head consitutes 1/3 of total length.Head consitutes 1/3 of total length. Possess a spermaceti organ to Possess a spermaceti organ to

regulate bouyancy.regulate bouyancy. Dive to 3.2km for 2 hrs.Dive to 3.2km for 2 hrs.

Spermaceti organ in the Sperm Whale: May Spermaceti organ in the Sperm Whale: May function to modify bouyancy, or as a lens to focus function to modify bouyancy, or as a lens to focus

outgoing soundwaves.outgoing soundwaves.

Sperm WhaleSperm Whale

Odontocetes: PlatanistidaeOdontocetes: Platanistidae

4 genera and 5 species of river 4 genera and 5 species of river dolphin, 2-3m in length.dolphin, 2-3m in length.

Found in Amazon, Yangtze, La Plata Found in Amazon, Yangtze, La Plata river, and the Ganges and Indus river river, and the Ganges and Indus river dolphins of India, Pakistan, and dolphins of India, Pakistan, and Bangladesh.Bangladesh.

Eyes lack lenses, and are functionally Eyes lack lenses, and are functionally blind - find prey via echolocation.blind - find prey via echolocation.

Odontocetes: ZiphiidaeOdontocetes: Ziphiidae

6 general and 19 species of 6 general and 19 species of beaked whales - slender, 4 to 13m.beaked whales - slender, 4 to 13m.

Reverse sexual size dimorphism - Reverse sexual size dimorphism - like baleens.like baleens.

Very reduced number of teeth, and Very reduced number of teeth, and usually found only in males.usually found only in males.

ZiphiidaeZiphiidae

More on whales:More on whales:

Check out the web site for the Los Check out the web site for the Los Angeles County Museum of Natural Angeles County Museum of Natural History.History.

cetaceans. cetacean evolution n the cetacea probably originated in the palaeocene, and had an eocene...

Documents

evolution n basilosaurus

evolution n recall

n suborder arctocyonia

n archaeocete skulls

eocene differentiation

late eocene

early fossils

suborder archaeoceti