Chapter 14 - Life of the Cenozoic

I.	Overview of Cenozoic:  "Age of Mammals"
	A.  More facts available about lift and evolution because of relative young age of 
	fossils
	B.  Biological evolution strongly linked to environmental and tectonic changes
	C.  Continental breakup stimulated biological diversity and radiations
	    1.  Separated land mosses
	    2.  Isolated marine basins
	D.  Groups that flourished
	    1.  Marine:  Bivalves, gastropods, crustaceans, echinoids, bony fishes, whales
	    2.  Terrestrial:  Mammals (rodents, bats, carnivores, elephants bison, camels,
     	    horses, rabbits)
	E.  Southern continents split from N. America and Eurasia (S. America, Australia, 
	Antarctica) were sites for evolution of distinctive isolated assemblages of 
	mammals:  Evidence of convergent evolution
	F.  Key Migration due to Land Bridges
	    1.  Isthmus of Panama:  Extinction of S. American Marsupials
	    2.  Boring Land Bridge:  Camels and horses reintroduced to N. America
	G.  Primate Evolution
	    1.  Late Tertiary:  Human ancestor primates
	    2.  Pleistocene:  Homo sapiens appeared

II.	Plant Evolution and link to Mammalian Evolution
	A.  Pre Cenozoic (Mid Cretaceous) "explosion" of plants
	    1.  Angiosperms appeared in Mid Cretaceous
	    2.  Rapidly spread and dominated floras
	B.  Cenozoic steady progress of plants
	    1.  Gradual evolution toward today’s flora
	    2.  Development of complex plant populations
	    3.  Miocene:  Grasses appeared ; grassy plains developed
	C.  Link to Mammalian Evolution
	    1.  Miocene grasslands led to proliferation of foraging and grazing mammals
		a.  changes in dentition:  High crown cheek teeth that continually grow
		b.  length of face increase to accommodate teeth
		c.  folding of enamel layers increased grinding surfaces
		d.  incisors aligned for nipping and chopping grass
		e.  four chambered stomach developed for grass digestion (unglates)
	    2.  Miocene open plains
		a.  Speedy flight (running) modifications:  Lengthening of limb and foot
		bones
		b.  redesign foot and limb to reduce rotation and allow fore aft motion
		c.  elevation of ankle for speed (toe running)
		d.  loss of useless side toes
		e.  protective hoofs developed

III.	Marine Phytoplankton
	A.  Most families lost in terminal Cretaceous extinction
	B.  Few species in each family survived into Cenozoic
	C.  Rapid diversification of few survivors
	D.  Peaks in Cenozoic Diversity of Phytoplankton
	    1.  Eocene
	    2.  Miocene
	E.  Decrease in diversity:  Oligocene
	F.  Main, most abundant groups
	    1.  Diatoms
	    2.  Dinoflagellates
	    3.  Coccolithophores
IV.	Invertebrates (No new groups appeared in Cenozoic)
	A.  Protozoans
	    1.  Foraminifers:  Prolific and diverse
		a.  benthic and planktic forms
		b.  remarkable large foraminifers:  Nummulitic "coin shaped" foraminifer
		tests (e.g. Gizeh Limestone, Egypt)
		c.  all types useful for extensive chronostratigraphic correlation of Gulf 
		Coast. U.S., California, Venezuela, East Indies, Near East
	B.  Corals:  Flourished in warm water areas
	    1.  Early Tertiary solitary corals:  Shallow water deposits of Gulf Coast U.S.
    	    and Europe
	    2.  Cenozoic fossil reefs (colonial scleractinian corals)
		a.  most extensive in Tethyan realm
		b.  ubiquitous in Pacific atolls
		c.  common in fringing reefs built during Pleistocene sea level rise
	C.  Mollusks
	    1.  Look like modern forms
	    2.  Bivalves (pelecypods) and Gastropods:  Dominant 2 classes
		a.  great adaptive range
		b.  pelecypods characterized by abundant:  Arcoids, mytiloids pectinoids, 
		cardioids, veneroids, and oysters
	    3.  Cephalopods:  Relatively sparse fossil record
		a.  nautilus (sole surviving nautiloid)
		b.  squid, octopi, cuttlefish (rarely preserved)
	D.  Echinoderms, Bryozoans, Crustaceans, and Brachiopods
	    1.  Echinoderms:  Free moving types particularly abundant
	    2.  Bryozoans:  especially common in Tertiary rocks
	    3.  Crustaceans:  Modern forms evolved (including fresh water)
	    4.  Brachiopods:  Decline in abundance and diversity
		a.  fewer than 60 genera today
		b.  main groups:  Terebratiulids and rhynehonellids
		c.  inarticulate form:  Lingula (living since Cambrian)

V.	Non Mammalian Vertebrates
	A.  Fish
	    1.  Boney fish (teleosts):  Fresh and Salt Water
		a.  achieved enormous range of adaptive radiation
		b.  forms included:  Perches, bass, snappers, sawhorses, sailfish, 
		barracudas, swordfish, flounders, etc.
		c.  sites of well preserved teleosts:  Green River Fm., Monte Bolca (Italy)
	    2.  Cartilaginous fish (sharks, etc.)
		a.  common in Tertiary as today
		b.  Carcharodon:  12m Tertiary shark
	B.  Amphibians
	    1.  Small body and smooth skin as today
	    2.  Abundant forms:  Frogs, toads, salamanders
	C.  Reptiles
	    1.  Rhynchocephalians (one surviving species):  Sphenadon, the tuatara "lizard"
    	    of New Zealand
	    2.  Turtles
		a.  shell adaptation:  Rib expansion to form carapace, basal body covering 
		(plastron), horny sheath about shell
		b.  toothless jaws (beaks) for slicing
	    3.  Crocodilians:  3 groups according to snout width
		a.  alligators (broad snout)
		b.  crocodiles (narrow)
		c.  gavials (very narrow)
	    4.  Sauamata:  Lizards and snakes
		a.  most varied of living reptiles
		b.  lizards gave rise to snakes
		c.  snake modifications:  skull flexibility for swallowing prey, multiplication 
		of ribs
		d.  Miocene:  Evolution of poisonous snakes (specialized teeth = fangs)
		e.  Poison type may be related to evolution of mammalian prey:  
		Neurotoxins versus hemotoxins
	D.  Birds
	    1.  Basic skeletal structure constant over Cenozoic
		a.  fusion of hand bones as wing support
		b.  sternum keel for muscle support of flight
		c.  fusion of pelvic girdle and vertebrae (rigidity in flight)
		d.  body cover with feathers
		e.  light porous bones
		f.  toothless horny beak
		g.  four chambered heart
		h.  constant body temperature (endothermy)
	    2.  Families of birds
		a.  song birds (robins)
		b.  upland birds (pheasants)
		c.  forest birds (owls)
		d.  oceanic birds (albatrosses)
		e.  wading birds (plovers)
		f.  flightless aquatic birds (penguins)
		g.  flightless land birds (ostriches)
	    3.  Best fossil lineage preserved:  Flightless land birds
		a.  Diatryma:  Extinct in Eocene, 3 m tall, New Zealand
		b.  Andalgalormis: Extinct South American predatory bird
		c.  Moas:  Exterminated by Maori people (New Zealand)
		d.  Dodos:  Exterminated by sailors in 1700 (Mauritius)
		e.  Extant (living) forms:  African ostrich, S. American rhea, Australian 
		cassowaries, emus

VI.	Non Placental Mammalian Vertebrates
	A.  Mammalian characteristics (Placental and Non Placental)
	    1.  Non fossilized:  Mammary glands, hair covering
	    2.  Fossilized:  Lower jaw of a single dentary bone; 3 bones of inner ear (not 
	    commonly preserved); 7 cervical vertebra (neck); expanded brain case; diverse 
	    teeth; separate oral and nasal passages (palate)
	    3.  Differences with reptiles and birds
		a.  reptile and bird jaws have several bones
		b.  two of 3 inner ear bones (incus and malleus) are modified from reptilian
 		jaw bones
	B.  Origin of Mammalian Traits
	    1.  Permo Triassic and Early Cenozoic cooling
		a.  favored warm blooded, fur bearing animals
		b.  promoted post natal care for survival
		c.  familial incubation to combat small body heat loss
		d.  incubation period and nurturing favored development of nursing as
		feeding mechanism for young
	    2.  Cenozoic rifting and continental separation
		a.  specific adaptations to varied conditions
		b.  opportunities for diversification in post dinosaur world
	C.  Earliest Mammals
	    1.  Evolutionary lineage
		a.  Late Paleozoic:  Mammal like reptiles (insect eaters)
		b.  Upper Triassic:  Morganucodonts
		c.  Eocene survivors:  Multituberculates (rodents); Decodonts (monotreme 
		ancestors); Euphantotheres (marsupial and placental ancestors)
	    2.  New Characteristics of Mammals
		a.  more efficient nervous system
		b.  better reproductive system
		c.  greater speed and agility
		d.  reliable body temperature control
		e.  larger brains, more intelligence
	    3.  New Classes of Mammals
		a.  18 in Paleocene
		b.  30 in Pliocene
	D.  Monotremes:  Egg Layers (most primitive)
	    1.  Range:  Early Cretaceous to present
	    2.  Characteristics:  Lay egg, mammary glands
	    3.  Surviving forms
		a.  platypus
		b.  spiny anteaters
	F.  Marsupials:  Nurture young in pouch (marsupium)
	    1.  Living forms:  Kangaroo, wallabies, wombats, phalanger, bandicots, koalas, 
	    opossums
	    2.  Greatest success in Australia and S. America
		a.  continents isolated during Tertiary
		b.  lack of competition from placentals
		c.  convergent evolution produced forms that mimic moles, dogs
 		sabertooth cats, bears, and hippos
	    3.  Fossil record
		a.  Pleistocene of Australia
		b.  Pliocene to present of S. America:  Evolution from opossum like
		ancestors; carnivorous (e.g. Thylacosmilus)
	    4.  Effect of Central American land bridge
		a.  established 3 million years ago
		b.  permitted interchange of southern marsupials and northern placentals
		c.  entering S. America:  camels, elephants, dear, bears, peccaries, horses, 
		tapirs, skunks, rabbits, cats and dogs
		d.  entering N. America:  monkeys, opossums, rats, shrews, sloths, 
		porcupines, and anteaters
		e.  for a time groups flourished together
		f.  eventually marsupials declined
		g.  all hoofed marsupials became extinct, also sloths and glyptodonts

VII.  Placental Mammalian Vertebrates
	A.  Insectivora (Cretaceous to present):  Ancestral order of placentals
	    1.  moles and shrews:  Modern members
	    2.  descendants of order:  Edentates, bats, primates, rodents, carnivores, 
	    herbivores marine forms
	B.  Edentates
	    1.  Extant (Paleocene to present) forms:  Armadillos, tree sloths, anteaters
	    2.  Extinct in Pleistocene
		a.  Glyptodon (spiked knob on tail)
		b.  megatherium (ground sloth)
		c.  Thallassanus (aquatic sloth)
	C.  Rodents
	    1.  Characteristics of group
		a.  most diverse mammalian group today
		b.  possess continuously growing incisors in both jaws
		c.  outer surface of incisor is hard enamel
		d.  sharpened teeth (chisel edge ) due to chewing
		e.  diastema is gap between incisors and cheek teeth
		f.  taxonomy based on disposition of muscles associated with jaw 
		movement
	    2.  ancestral group:  Protorogomorphs
		a.  ancestors of true squirrels and old world porcupines
		b.  Paramys:  Paleocene squirrel like form
		c.  Ceratogaulus:  Extinct horned rodent
		d.  Extant forms:  thick furred sewellels
	    3.  Ancestral beavers (castorimorphs)
		a.  Paleocastor:  Pleistocene form that made corkscrew burrows
		b.  Casteroides:  Pleistocene bear sized form
	    4.  Ancestral porcupine groups
		a.  Hystricomorphs:  Old world porcupines
		b.  Caviomorphs:  New world porcupines
	    5.  Hystricomorph diversification (Oligocene to Recent)
		a.  rats, mice, and dormice
		b.  pocket gophers, jerboas, and kangaroo rats
	    6.  Caviomorph diversification
		a.  capybaras and agontis
		b.  chinchillas and spiney rats
	     7.  Habitat invasion by rodents 
		a.  burrowing:  Marmot and chipmunk
		b.  aquatic:  Muskrat and beaver
		c.  desert:  Jerboas and kangaroo rats
		d.  arboreal:  Squirrels
	D.  Lagomorpha:  Gnawers and nibblers
	    1.  Includes:  Rabbits, hares, pikas
	    2.  Range:  Paleocene (Mongolia) to present
	E.  Bats:  true flying mammals
	    1.  Range:  Early Eocene (WY) to present
	    2.  Adaptations
		a.  elongate finger bones to support skin of wing
		b.  echo location
		c.  insect catching behavior
		d.  tooth adaptation (S. America) for wounding prey
	F.  Terrestrial Carnivores
	    1.  Range late cretaceous to recent
	    2.  Common ancestral form:  Cimolestes (a small weasel like animal with 
	    carnassial teeth)
	    3.  Cretaceous Paleocene division into two orders
		a.  Order Credonta:  Small brained animals with short limbs, clawed toes 
		and long tails
		b.  Order Carnivora:  Large brained animals with carnissial teeth near front 
		jaw
	    4.  Miocene Recent expansion:  Carnivora replace Credonta resulting in 
	    expansion of Carnivora
	    5.  Carnivore diversification:  Bears, raccoons, weasels, genets, hyenas, dogs, 
	   cats, civets, mongooses, and true hyenas
	    6.  Cat record
		a.  Pleistocene stabbing cat:  Smilodon
		b.  Pleistocene biting cats:  Leopard, puma
	    7.  Dog record:  Canis (dire wolf);  Pleistocene to Recent
	    8.  Carnivore Herbivore ecologic balance
		a.  competition as predator/prey for speed and agility
		b.  defensive adaptation by herbivores
		c.  carnivore effect:  cull out weak, sick, deformed, counteract degenerative 
		mutation, and overpopulation
	G.  Marine Carnivores
	    1.  Range:  Early Cenozoic to present
	    2.  tooth characteristics
		a.  sharp pointed teeth (seal)
		b.  tusks plus broad, flat shell crushing teeth (walrus)
	    3.  3 basic groups:  seals, sea lions, walruses
	H.  Cetaceans (whales and porpoises)
	    1.  Earliest whales (Eocene)
		a.  descended from terrestrial hoofed carnivores (mesonychids)
		b.  able to walk and swim
		c.  Pakicetus (Eocene):  few meters long, inhabited streams lakes and 
		estuaries
		d.  Ambulocetus (Eocene):  5 m long, hind webbed feet front flippers
		e.  Basilosaurus (late Eocene):  20 m long, front flippers, useless hind limbs
		f.  Eocene trend in evolution:  Increasing body length and dimuntion of 
		hind limbs
	   2.  Modern whales:  Descendants of Basilosaurus (2 lineage’s)
		a.  toothed whale lineage (Oligocene to present):  porpoises, sperm whales
		b.  Whale bone lineage (Miocene to present): blue whale, right whale, 
		toothless with ridges of hairy, hard skin from roof of mouth:  great size 
		attained by blue whales (30 m, 3 T)
	I.  Unglates:  Hoofed herbivores
	    1.  Groups whose ancestors were unglates
		a.  whales
		b.  sirenians (manatees and dugongs)
		c.  gyraxes (coneys and dassies)
		d.  proboscideans (mastodons and elephants)
		e.  desmostylids
		f.  arsinotheres
	    2.  Primitive, earliest unglates (Condylarths)
		a.  Range:  Late Paleocene Eocene
		b.  Phenocodus:  Primitive cheek teeth; shorter two outer toes; inner three 
		toes longer; plantigrade
		c.  Uintatherium:  6 horns; canine teeth in males plantigrade
	    3.  Perissodactyls:  Modern odd toed unglates
		a.  Range:  late Paleocene to present; Miocene peak
		b.  Site of origin:  N. America
		c.  Ancestral lineage:  Condylarths
		d.  Common modern forms:  horse; tapir; rhinoceroses
		e.  Extinct forms:  Chalicotheres; titanotheres; hyracodonts; amynodonts
		f.  Distinctive characteristics:  odd number of toes per foot: weight support 
		on middle toe; lateral toes smaller or missing as in modern horse); run on 
		toes (digigrade)
		g.  Oldest form:  Radinskya (Paleocene, China)
		h.  Mesohippus (Oligocene):  Intermediate form with large size but low 
		crowned teeth; less abrasive diet
		i.  Miocene trends in horse evolution:  Progressive size increase; leg length
 		increase; tooth crown height increase; brain size increase; straightening of 
		back; strengthening of middle toe, lateral toes reduced; pre molars changed 
		to molars; increased complexity of enamel tooth ridges
		j.  Miocene radiation due to spread of grassland prairie, but conservative 
		forms remained in forested areas
		k.  Merychippus:  Vanguard grassland horse; single middle toe support; 
		reduced side toes; head deeper; face longer; long cheek teeth
		l.  Hippariaon:  Three toed horse that migrated from N. America to Europe
		m.  Pliohippus:  one toed horse with lateral digits as splints
		n.  Hippidium:  Migrating ancestor of Merychippus that populated S. 
		America
		o.  Equus:  Non migrating ancestor of Merychippus that populated N.
		America
		p.  Equus occidentalis and Equus giganteus:  small and large horses, 
		respectively, that spread over N. America, Eurasia, and Africa
		q.  Holocene extinction of Equus in N. America:  Last horses died few 
		thousand years ago due to disease or overkilling by humans; horses 
		reintroduced by Spanish in 1500’s
		r.  Tapirs:  Primitive feet (4 toes front 3 in rear); low crowned teeth; forest 
		dwellers leaf eaters
		s.  Rhinoceroses:  primitive forms (Paraceratherium, 5 m tall) evolved into 
		3 groups; by end of Ice age all but 5 species of rhino were extinct
		t.  Brontotheres:  Pair of horns over snout; large body size
		u.  Chalicotheres:  3 claws on feet; horse like; fore legs longer than rear; 
		back slopes
	    3.  Artiodactyls:  Even toed Unglates
		a.  Range:  Early Eocene to Recent
		b.  Site of Origin:  Eurasia and Africa, except N. American camels
		c.  Ancestral lineage:  Condylarths
		d.  Modern forms:  pigs, deer, hippopotamuses, goats, cattle, camel, 
		antelope
		e.  Extinct forms:  Oredonts and entelodonts
		f.  Distinct characteristics;  Even number of toes on each foot (4 or 2); 
		weight carried on middle toes; molar and premolar are not alike; ankle and 
		leg bones form a double pulley system
		g.  success of group: most varied, abundant, numerous and superior of all 
		unglates
		h.  Older extinct forms:  Oredonts (short stocky grazers of N. American
		grassy plains)  and Entelodonts (hog like form with bony processes on skull 
		and jaws)
		i.  Eocene trends in evolutionary radiation produced three major groups: 
		Swine and hippopotamuses; tylopoda; ruminants
		j.  Swine and hippopotami:  most primitive group; four toes; weight on
		middle digits; swing includes pigs and peccaries; hippopotamuses are only 
		amphibians forms (descended from Miocene anthracotheres)
		k.  Tylopoda (camels and lamas):  Eocene small common ancestor; 
		Oligocene forms lost side toes and gained leg and neck length; Miocene 
		Oxydactylus (leaf browser like giraffe);  Pleistocene migration from N. 
		America (llamas to S. America and camels to Eurasia and Africa);  
		Holocene extinction in N. America (reason unknown)
		l.  Ruminants (from rumen the first of 4 stomach chambers);  Most varied 
		and abundant artiodactyls; 2 main groups – Tragulids and Pecorans
		m.  Tragulid Ruminants:  Early Oligocene Hypertragulus; Pliocene 
		Synthetoceras (3 horns); modern deer and giraffes
		n.  Pecoran Ruminants:  Deer lineage; Giraffe branch of deer lineage; 
		Borids; Proboscideans
		o.  Deer lineage Ruminants:  Oligocene common deer ancestor; Miocene 
		Blastomeryx (N. American small hornless deer); Pleistocene Megaloceros 
		(N. American large heavily antlered deer; modern deer)
		p.  Giraffe branch Ruminants:  Miocene Palaeotragus (ancestral giraffe);  
		Pliocene leg and neck elongation of giraffes; modern giraffes
		q.  Bovid Ruminants:  Miocene common ancestors of cattle, bison, sheep, 
		goats, Pleistocene evolution of 7 bison species in N. America
		r.  Proboscidean Ruminants:  Eocene ancestral forms Barytherium and 
		Moeritherium (tapir like, Egypt); Miocene Pliocene split into two lines – 
		Dinotheres (tusked) and Gomphotheres (trunked forms such as mastodons, 
		elephants, and mammoths)
		s.  Dinotheres (Miocene Pliocene):  Tusk on lower jaws; tusks curved 
		down and back; Dinotherium (Europe)
		t.  Gomphotheres:  Tusk on upper jaw; tusk curves upward and back;  
		Paleomastadon (Oligocene, north Africa; Gompotherium) Miocene 
		ancestral mammoth, Eurasia and N. America; Trilophodon (Pliocene "long 
		jaw" mammoth); Amebelodon (Pliocene, "shovel tusk" mammoth); 
		Mammut (Pleistocene, N. American mammoth); woolly mammoth extinct 
		in Holocene; Stegolophodon (Miocene, common ancestor of true elephants 
		and mastodons); Stegodon (Pliocene, tuskless); modern elephants 
		(Holocene)

VIII.	Pleistocene Extinction’s of Large Land Animals
	A.  Overview
	    1.  Maximum continental glaciation 11,000 yrs ago
	    2.  Northern Hemisphere supported maximum variety and diversity of large land 
	    animals 11,000 yrs ago
	    3.  Rapid decline of populations 8,000 yrs. ago
		a. many groups became extinct
		b.  many groups severely reduced
	B.  Causes of terminal Pleistocene extinction’s (8,000 yrs ago):  2 theories
	    1.  Human overkill
	    2.  Climatically controlled environmental changes
	    3.  Hunters selected best animals in herds
	    4.  Predatory animals suffered due to reduced prey
	    5.  Support for theory
		a.  Large terrestrial animals only
		b.  Marine genera not affected
		c.  Small animals not so affected
		d.  Extinction began in Africa where human populations were greater
	    6.  Criticism of Theory
		a.  Human populations too small, nomadic
		b.  Some non hunted species became extinct
		c.  Primitive hunters today do not endanger herds by overkill
	D.  Environmental change Theory
	    1.  Greatest variety and diversity during glacial intervals of Pleistocene
	    2.  Glacial intervals averaged 100,000 yr duration; interglacials averaged 10,000 
	    yr.
	    3.  Greater adaptation to cooler conditions versus relatively short warm intervals
	    4.  Curtailment of reproductive capacity in warmer climates due to 
	    surface/volume ratio of large female animals (increased blood flow to cooling 
	    surface versus uterus and embryo)
	    5.  Evolutionary selection for smaller animals thus explained; explains large 
	    animal loss