Contents 



Introduction-. An Historical Sketch i 



1. Chordates. Protociwrdates, s 

 and their Relationship 



THE PHYLUM CHORDATA 5 



THE PROTOCHORDATES 5 



Cephalochordata 5 

 Urochordata (Tunicafa): Embryological development 9 



Hemichordata: Enteropneusts, Pterobranchs 12 



General observations 16 



2. The Vertebrates and their 



External Anatomy i8 



A SURVEY OF THE MATERIALS 18 



LIVING REPRESENTATIVE VERTEBRATES 18 



Cyclostomes 1 8 



Chondrlchthyes: Elasmobranchs (selachians and 23 



rays), Holocephalans 



Aclinopterygians: Chondrosteans, Holosteans and 24 

 teleosts, Brachiopterygians 



Choanate fishes: The coelacanth Latimeria, 26 

 Dipnoans or lung fishes 



Amphibians 27 



Reptiles 28 



Birds 28 



Mammals: Monotremes, Marsupials, Placentals 29 



FOSSIL VERTEBRATES 30 



3. Osteology and the Mammalian 34 

 Head Skeleton 



OSTEOLOGY AND HUMAN ANATOMY 34 



MAMMALIAN HEAD SKELETON 35 



Introductory concepts 35 



Head skeleton of placental mammals: Human head 35 

 skeleton. Head skeleton of other placentals, Joints 

 of the head skeleton. General observations 



Head skeleton of the marsupial 43 



Head skeleton of the monotreme: Ornithorhynchus, 44 

 the Platypus, Tachyglossus, the Echidna 



DEVELOPMENT OF THE HEAD SKELETON 49 



Chondrocranium: Placental mammals, Marsupial, 49 

 Monotreme 



Development of the bony head skeleton: Placental. 57 

 Marsupial, Monotreme, General observations 



4. The Head Skeleton of Other 6i 

 Jetrapods and the Choanate Fishes 



OTHER TETRAPODS 61 



Reptiles: Lizard, Sphenodon, the Tuatara, Turtle, 61 

 Alligator 



Bird 75 



Origin of birds and mammals 76 



Living amphibians: Salamander or urodele. Frog or 78 

 anuran. General observations on living amphibians 



Fossil amphibians: Early amphibians, 85 

 Seymouriamorphs and origin of reptiles 



Earliest reptiles 88 



General observations on the letrapods 91 



CHOANATE FISHES 92 



Crossopterygians: Osteolepiform, Porolepiform 92 

 crossopterygian, Coelacanth or actinistian 

 crossopterygian 



Dipnoan: Embryological development 99 



General observations on the choanate fishes 104 



ORIGIN OF THE AMPHIBIAN OR TETRAPOD 104 



5. Tfie Head Skeleton of Other Fishes los 



GNATHOSTOME FISHES 105 



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