Section 4 Professor Donald McFarlane

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1 A A R 3/31/2011 Craniates Vertebrates Gnathostomes Lobe fins Tetrapods Amniotes Reptilia Section 4 Professor Donald McFarlane Myxini (hagfish) Petro omyzontida (lampreys) (cartilaginous fishes) Chondrichthyes Actinoptery ygii (ray-finned fishes) Actinistia (coelacanths) Dipnoi (lungfishes) Amphibia (amphibians) Reptilia (turtles, lizards, sn nakes, crocodiles, birds) Mammalia (mammals) Milk, hair Amniotic egg Legs Lungs Lecture 16 Craniates 2: Reptiles, Birds and Mammals. Cranium Ancestral chordate Lobed fins Bony skeleton Jaws, internal skeleton Vertebral column KEY Critical innovations 2 Craniates 2 defining characteristics compared to invertebrate chordates 1. Cranium - protective bony or cartilaginous housing for brain 2. Neural crest - embryonic cells that will disperse throughout the embryo contributing to the development of the skeleton, jaws, and teeth Also, at least 2 Hox clusters 3 Vertebrates All chordate and craniate characteristics plus 1. Vertebral column - notochord is replaced by a bony or cartilaginous column of interlocking vertebrae 2. Endoskeleton of cartilage or bone most also have two pairs of appendages 3. Internal organs - liver, kidneys, endocrine glands, and a heart with at least two chambers Liver unique to vertebrates Heart, kidneys, and endocrine system are more complex than analogous structures in other taxa 4 1

2 Amniotes Critical innovation was the development of a shelled egg that sheltered the embryo from desiccating conditions on land Amniotic egg broke tie to water Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia Ancestral chordate 5 4 extraembryonic membranes 1. Amnion protects embryo in amniotic cavity 2. Yolk sac yolk 3. Allantois disposal of wastes 4. Chorion with allantois for gas exchange Amnion Embryo Amniotic cavity Allantois Shell Yolk sac Yolk Albumin Chorion 6 Other key innovations Desiccation resistant skin Thoracic breathing negative pressure sucks air in Water-conserving kidneys concentrate waste prior to elimination Internal fertilization Traditional classification has 3 living amniotes reptiles, birds and mammals Birds are now considered part of reptilian lineage 7 Class Testudines Turtles, tortoises and terrapins Virtually unchanged for 200 million years Hard protective shell In most, vertebrae and ribs fused to shell Lack teeth but have sharp beak 8 2

3 Class Lepidosauria Lizards and snakes Kinetic skull with extremely mobile joints Lizards have moveable eyelids and external ears while snakes do not Class Crocodilia Crocodiles and alligators Essentially unchanged for 200 million years 4 chambered heart Teeth in sockets Care for young 9 10 Dinosaurs Class Ornithischia bird-hipped dinosaurs Class Saurischia lizard-hipped dinosaurs Legs of dinosaurs were positioned directly under the body

4 Archaeopteryx lithographica Related to therapods, group of saurischian dinosaurs Caudipteryx zoui Confuciusornis sanctus Completely feathered, lacking bony tail and toothed jaw Top set of hips on the left is the saurischian form, the bottom set on the left is the ornithischian form Class Aves 4 features unique to birds (for flight) 1. Feathers modified scales keep birds warm and enable flight 2. Air sacs very efficient i breathing 3. Reduction of organs single ovary, no urinary bladder 4. Lightweight skeleton thin, hollow, honeycombed Sternum to anchor flight muscles, no teeth 15 Exhalation Inhalation 16 4

5 17 18 Birds also have Warm body temperature Double circulation with 4 chambered heart Acute A t vision i Most carnivores Eggs brooded Complex courtship 28 orders, 166 families, 9600 species Mammals Evolved from amniote ancestors earlier than birds Appeared about 225 mya After dinosaur extinction mammals flourished Range of sizes and body forms unmatched Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia Ancestral chordate

6 Distinguishing characters Mammary glands secrete milk All mammals have (more or less) hair Only vertebrates with specialized teeth Enlarged skull Brain enlarged in large skull Single lower jaw bone 3 inner ear bones External ears Some but not all mammals Digest plants using symbiotic bacteria Horns and antlers Horns bony outgrowth of skull Antlers entirely of bone Subclass Prototheria Order Monotremata Platypus and echidna lay eggs, lack placenta, poorly developed nipples Subclass Theria Clade Metatheria - marsupials 7 orders Once widespread, now confined mostly to Australia Opossum found in North America Very undeveloped young must make it to marsupium to finish development Subclass Theria Clade Eutheria Placental mammals Long-lived complex placenta Prolonged gestation

7 Primates Strepsirrhini Haplorrhini Anthropoidea Hominoidea Primarily tree-dwelling species Evolved about 85 mya Defining characteristics Grasping hands with opposable thumbs Large brain Some digits have flat nails (not claws) Binocular vision Complex social behavior and well-developed parental care 25 Bush babies, lemurs, pottos Tarsiers Monkeys Gibbons Family Hylobat tidae Orangutans Subfamily Pong ginae Family Gorillas Tribe Gor rillini Hominidae Chimpanzees Tribe Pa anini Subfamily Homininae Humans Tribe Hom minini 26 7