PHYLUM CHORDATA

Subphylum UROCHORDATA

Subphylum CEPHALOCHORDATA

lancelets [fig. 26.9]  45 species filter feeders no obvious head, no eyes more from Maureen Gramaglia's Webpage on Cephalochordata; Penn State  Branchiostoma: External features of a lancelet amphixous; drawing courtesy of BIODIDAC

SUBPHYLUM VERTEBRATA 

• Vertebrates in the Kingdom Animalia
• Introduction to the Vertebrates
• Characteristics of the Vertebrates [Fig. 27.2]
1. pronounced cephalization
2. endoskeleton of cartilage or bone
3. vertebrae (except for most primitive)
4. etc.

Superclass AGNATHA

• 80 species
• a paraphyletic group of jawless fishes
• includes the first vertebrates, the ostracoderms [Fig. 27.3], which have an external skeleton of bone
• living forms are elongate, scaleless, slimy parasites and scavengers that lack bone

Superclass GNATHOSTOMATA

• Characteristics [Fig. 27.7]
1. vertebrates with jaws that are modified gill supports
2. teeth - modified dermal scales
3. more efficient, paired pelvic and pectoral fins
4. three semicircular canals
5. more proficient predators than the jawless fish

CLASS CHONDRICHTHYES - 750 spp.

• Characteristics
  • internal skeleton of cartilage (cartilaginous fish)
  •  microscopic view of placoid scales from Univ. Wisconsin BioWeb - Zoo Lab 
  • etc.

Subclass ELASMOBRANCHII  --- sharks, rays, skates [fig. 27.8] Characteristics placoid scales modified to form teeth [Fig. 27.9, Box 27.2] 5-7 pairs of gill slits with separate external openings mainly carnivores and scavengers the largest sharks are filter feeders; the whale shark is the largest fish. Sharks and their relatives from SeaWorld	Prionace glauca, Blue Shark; photograph by : Joseph Dougherty,  Society for Environmental Education
Subclass Holocephali - ratfish (chimaeras) Characteristics naked skin operculum covers four gill openings

CLASS OSTEICHTHYES

• bony fishes--30,000 species [Fig. 27.12-27.13]
• Characteristics
  1. skeleton contains bone
  2. single external gill opening covered with operculum
  3. swim bladder or lung [Fig. 27.16]
  4. Bony Fishes from SeaWorld

Tetrapods

• invasion of the land required strong limbs, an interlocking backbone, a moveable head, etc.
• more from the UCMP

CLASS AMPHIBIA: 4,000 spp.

• Characteristics
1. Amphibians today include salamanders, toads and frogs
2. Amphibians usually shed eggs in water for external fertilization
3. aquatic larvae with external gills metamorphose to adults [Fig. 28.18]
4. Dermal respiration
5. Amphibians gave rise to the amniotes
6. Amphibian populations are undergoing dramatic declines.
7. more on Amphibia from the
   • UCMP
   • Tree of Life

Order Gymnophiona (Apoda) - Caecilians [Fig. 28.6] elongate bodies that lack limbs annular rings wormlike burrowers Ichthyophis bannanicus, photograph by Nikolai Orlov. Digital Library Project, University of California, Berkeley
Order Caudata (Urodela) - salamanders [Fig. 28.4-28.5] long tail, usually with two pairs of limbs much more from the Tree of Life Ambystoma texanum, Small-mouthed Salamander, photograph by John White. Digital Library Project, University of California, Berkeley
Order Anura (Salienta) - frogs [Fig. 28.1] and toads [Fig. 28.7] tailless, elongate hindlimbs, head and trunk fused [Fig. 28.8c] much more from the Tree of Life the Froggy Page Hyla cinerea, Green Treefrog, photograph by Joyce Gross. Digital Library Project, University of California, Berkeley

• adaptation for life on land
  1. amniotic egg - keeps embryo moist; requires internal fertilization
  2. adaptations of the skull and skeleton
• Amniote characteristics from the Tree of Life

CLASS REPTILIA

• turtles, alligators, lizards, snakes--7,000 species
• internal fertilization; oviparous & ovoviparaous
• impervious, dry scaly skin
• well developed lungs
• ectothermic; behavioral thermoregulation

Chelonia: turtles (225 species)

• shell of dorsal carapace and ventral plastron [Fig. 29.4, 29.5]
• more on turtles from the UCMP

Squamates

Lizards (3300 species) [Fig. 29.6-29.7] diapsids with lower temporal bar lost Sceloporos jarrovii --photograph © 2001by Dr. Allan H. Chaney,  used  with permission
Snakes (2300 species) kinetic skull:  middle and lower temporal bars lost vestigial pelvic girdle in booids Masticophis flagellum testaceus western coachwhip, red color phase, photograph © 2001by Dr. Allan H. Chaney,  used  with permission

Crocodilia: alligators and crocodiles (21 species)

American alligator; photograph taken at Aransas National Wildlife Refuge © 2001by Dr. Allan H. Chaney,  used  with permission

Class AVES

• 27 orders of birds (table 30.1)
• 9,100 species; hummingbird to Andean condor to ostrich
• flying dinosaurs; closest living relatives are crocodiles
• adaptations for flight
• Characteristics
  1. internal fertilization and oviparous
  2. Endotherms
  3. Feathers (modified reptilian scales) [Fig. 30.4]:
  4. Anatomical features related to flight [Fig. 30.5]
  5. Fusion of bones makes skeleton more rigid
  6. Horny bill that lacks teeth (toothed fossils)
  7. Four chambered heart
  8. Lungs with one-way air flow.
  9. Eat wide variety of food.
  10. complex social behavior.

Class MAMMALIA: 4,500 spp.

• Mammalia on the Animal Diversity Web University of Michigan
• UCMP Hall of Mammals
• Dr. Kaci Thompson's website for Mammalogy at the University of Maryland has chapter outlines outlines and photographs of representatives of the different groups of mammals.
• The Mammals of Texas - Online Edition
• Characteristics
1. hair - protection from heat loss
2. mammary glands [Fig. 31.8]
3. differentiated teeth
4. endotherms
5. 4 chambered heart; etc.

Monotremes [Fig. 31.4a,b]

1. egg layers
2. cloaca for excretory, digestive, and reproductive tracts
3. Platypus and two species of Echidnas from Australia and New Guinea
4. more from the UCMP

Marsupials (Subclass Metatheria):

• brief gestation period
• embryo continues development attached to a nipple, usually in a pouch
• prolonged lactation and parental care
• Marsupials include: opossum, kangaroo, koala [Fig. 31.4c], Tasmanian devil, wombat, etc.
• more from the UCMP

Placental Mammals (Subclass Eutheria):

• placentals
• complex placenta
• Young develop to an advanced stage prior to birth
• 19 of the 26 orders of mammals are placentals.
• Orders in this subclass have adapted to life on land, in water, and in the air
• More from the UCMP

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