The Alligator and Its Allies

CHAPTER IX

THE DEVELOPMENT OF THE ALLIGATOR 226

BIBLIOGRAPHY 343

INDEX 349

ILLUSTRATIONS

PAGE

ALLIGATOR MISSISSIPPIENSIS. (In color.) Frontispiece

FIGURE

A. SKULL OF BELODON 5

1. MAP SHOWING THE PRESENT DISTRIBUTION OF CROCODILIA 6

2. HEADS OF AMERICAN ALLIGATOR AND CROCODILE Facing 7

3. ALLIGATOR JOE IN THE EVERGLADES Facing 10

4. ALLIGATOR HUNTER IN THE OKEFINOKEE Facing 10

5. NEST OF C. POROSUS Facing 21

6. JACKSON SLOUGH Facing 21

7. A TYPICAL ALLIGATOR HOLE Facing 23

8. ALLIGATOR NEST, MADE CHIEFLY OF GRASS Facing 25

9. ALLIGATOR NEST, MADE CHIEFLY OF FLAGS Facing 27

10. TWO SPECIES OF CAIMAN: BROAD-NOSED CAIMAN, SPECTACLED CAIMAN Facing 35

11. TWO AFRICAN CROCODILES: NILE CROCODILE, WEST AFRICAN CROCODILE Facing 39

12. SALT WATER CROCODILE Facing 41

13. SKULL OF GAVIAL, VENTRAL VIEW Facing 43

14. SKULL OF GAVIAL, LATERAL VIEW Facing 43

15. ALLIGATOR SKINS Facing 46

16. ENTIRE SKELETON OF CROCODILE 50

17. FIRST FOUR CERVICAL VERTEBRÆ OF CROCODILE 52

18. THORACIC AND SACRAL VERTEBRÆ OF CROCODILE 55

19. DORSAL VIEW OF SKULL OF ALLIGATOR Facing 60

20. VENTRAL VIEW OF SKULL OF ALLIGATOR Facing 63

20A. LONGITUDINAL SECTION OF TOOTH OF CROCODILE Facing 66

21. LATERAL VIEW OF SKULL OF ALLIGATOR 69

22. POSTERIOR VIEW OF SKULL OF ALLIGATOR Facing 70

23. SAGITTAL SECTION OF THE SKULL OF ALLIGATOR 71

24. DORSAL VIEW OF LOWER JAW OF ALLIGATOR Facing 74

25. THE HYOID APPARATUS 77

26. THE STERNUM AND THE ASSOCIATED MEMBRANE BONES 79

27. THE PECTORAL GIRDLE AND ANTERIOR LIMB 82

28. THE PELVIS AND SACRUM 85

29. THE POSTERIOR LIMB 87

I. PLATE I. THE SHOULDER MUSCLES Following 130

II. PLATE II. THE MUSCLES OF THE ANTERIOR REGION Following 130

III. PLATE III. THE MUSCLES OF THE POSTERIOR REGION Following 130

IV. PLATE IV. THE MUSCLES OF THE POSTERIOR REGION Following 130

V. PLATE V. THE MUSCLES OF THE POSTERIOR REGION Following 130

30. THE BRAIN OF THE ALLIGATOR Facing 132

31. THE BRACHIAL PLEXUS OF C. ACUTUS 140

32. THE CRURAL PLEXUS OF A. MISSISSIPPIENSIS 142

33. INTERIOR OF THE MOUTH OF THE ALLIGATOR Facing 151

34. THE DIGESTIVE SYSTEM OF THE ALLIGATOR 152

35. OUTLINE OF THE DIGESTIVE TRACT OF THE ALLIGATOR 158

36. COVERING OF THE ANTERIOR REGION OF THE TONGUE 160

37. COVERING OF THE POSTERIOR REGION OF THE TONGUE 161

38. GLAND FROM THE POSTERIOR REGION OF THE TONGUE 162

39. GLAND FROM THE POSTERIOR REGION OF THE TONGUE 164

40. COVERING OF THE ROOF OF THE MOUTH 166

41. TRANSSECTION OF THE ANTERIOR REGION OF THE ŒSOPHAGUS 169

42. TRANSSECTION OF THE POSTERIOR REGION OF THE ŒSOPHAGUS 170

43. EPITHELIUM OF ANTERIOR REGION OF ŒSOPHAGUS 172

44. EPITHELIUM OF ANTERIOR REGION OF ŒSOPHAGUS 173

45. TRANSSECTION OF WALL OF PYLORIC STOMACH 176

46. GLANDS OF FUNDUS OF STOMACH 177

47. TRANSSECTION OF WALL OF ANTERIOR REGION OF SMALL INTESTINE 181

48. TRANSSECTION OF WALL OF MIDDLE REGION OF SMALL INTESTINE 182

49. TRANSSECTION OF WALL OF POSTERIOR REGION OF SMALL INTESTINE 183

50. MUCOSA OF THE ANTERIOR REGION OF SMALL INTESTINE 184

51. TRANSSECTION OF THE WALL OF THE MIDDLE REGION OF THE SMALL INTESTINE 185

52. TRANSSECTION OF THE WALL OF THE ANTERIOR REGION OF THE RECTUM 186

53. EPITHELIUM OF THE ANTERIOR REGION OF THE RECTUM 187

54. FEMALE UROGENITAL SYSTEM OF ALLIGATOR 193

55. MALE UROGENITAL SYSTEM OF ALLIGATOR Facing 195

56. MALE ORGAN OF ALLIGATOR Facing 195

57. RESPIRATORY ORGANS OF ALLIGATOR 198

58. HEART OF ALLIGATOR Facing 202

59. VEINS OF THE POSTERIOR REGION OF ALLIGATOR 204

60. VEINS OF THE ANTERIOR REGION OF THE ALLIGATOR 209

61. ARTERIES OF THE POSTERIOR REGION OF THE ALLIGATOR 213

62. ARTERIES OF THE ANTERIOR REGION OF THE ALLIGATOR 215

VI.-XXVIII. PLATES VI TO XXVIII. A SERIES OF FIGURES TO ILLUSTRATE THE DEVELOPMENT OF THE AMERICAN ALLIGATOR Following 342

THE ALLIGATOR AND ITS ALLIES

CHAPTER I. The Biology of the Crocodilia

THE BIOLOGY OF THE CROCODILIA

CLASSIFICATION

As in most groups of animals, there is considerable difference of opinion as to the proper classification of the Crocodilia.

One of the older textbooks (Claus and Sedgwick) divides the order Crocodilia into three sub-orders: the Teleosauria, Steneosauria, and Procœlia, the last only being represented by living forms. The Procœlia or Crocodilia proper are divided into three families,--the Crocodilidæ, the Alligatoridæ (including the caiman as well as the alligator), and the Gavialidæ.

This division into families seems to be based mainly on the shape of the head, or, at any rate, it throws those forms together that have heads of the same outline.

It is this outline of the head that Ditmars (Reptiles of the World) uses in classifying the Crocodilia, which, he says, are all included in the single family--Crocodilidæ. The following list, taken from his Reptiles of the World (pp. 68-69), will give a clear idea of the number, distribution, and maximum size of the members of the order Crocodilia. More will be said of some of the members of this list later.

---------------------------------------------+----------------+------- | Habitat | Max. | | Size ---------------------------------------------+----------------+------- A. Snout extremely long and slender, | | extending from the head like the handle of a | | frying pan | | Gavialis gangeticus, Indian Gavial |Northern India |30 ft. Tomistoma schlegeli, Malayan Gavial |Borneo and | |Sumatra |15 ft. | | B. Snout very sharp and slender; of | | triangular outline | | Crocodilus cataphractus, Sharp-nosed | | Crocodile |W. Africa |12 ft. Crocodilus johnstoni, Australian Crocodile |Australia |6-8 ft. Crocodilus intermedius, Orinoco Crocodile |Venezuela |12 ft. | | C. Snout moderately sharp; outline distinctly| | triangular | | Crocodilus americanus, American Crocodile |Fla.; Mexico; | |Central and S. | |America |14 ft. Crocodilus siamensis, Siamese Crocodile |Siam; Java |7 ft. Crocodilus niloticus, Nile Crocodile |Africa generally|16 ft. Crocodilus porosus, Salt-water Crocodile |India and | |Malasia |20 ft. | | D. Snout more oval; bluntly triangular | | Crocodilus robustus, Madagascar Crocodile |Madagascar |30 ft. Crocodilus rhombiferus, Cuban Crocodile |Cuba only |7 ft. Crocodilus moreletti, Guatemala Crocodile |Guatemala; | |Honduras |7 ft. | | E. Snout short and broad; conformation | | barely suggesting a triangular outline | | Crocodilus palustris, Swamp Crocodile |India and | |Malasia |12 ft. Osteolæmus tetrapis, Broad-nosed Crocodile |W. Africa |6 ft. | | D′. Outline of head similar to that of | |

Section D | |

Caiman trigonotus, Rough-backed Caiman |Upper Amazon |6 ft. Caiman sclerops, Spectacled Caiman |Central and S. | |America |7-8 ft. Caiman palpebrosus, Banded Caiman |Tropical South | |America |7-8 ft. | | F. Snout very broad; bluntly rounded at tip | | Caiman latirostris, Round-nosed Caiman |Tropical South | |America |7-8 ft. Caiman niger, Black Caiman |Tropical South | |America |20 ft. Alligator mississippiensis, American | | Alligator |Southeastern | |United States |16 ft. Alligator sinensis, Chinese Alligator |China |6 ft. ---------------------------------------------+----------------+-------

These species are exceptions in their genus. The snout is blunt like that of the genus Alligator.

Alleged to grow to this size by competent observers.

Gadow in the Cambridge Natural History (p. 450) agrees with Boulanger in believing that the recent Crocodilia cannot be separated into different families, yet he describes seven families of Crocodilia, two of which, the Gavialidæ and Crocodilidæ, include the living members of the order; the former includes the gavials, of course, and the latter the crocodiles, alligators, and caimans.

Though “doctors disagree” thus in regard to the scientific classification of this small group of animals, this fact does not in the least diminish the intense interest in the individual members of the order.

ANCESTRY

Although the huge dragon-like dinosaurs or “terrible reptiles,” some of which were probably more than one hundred feet long, became extinct during the Mesozoic epoch, perhaps millions of years before man made his appearance upon earth, we have one group of reptiles still living in certain parts of the earth of which the Mesozoic lords of creation need not feel ashamed. While most of the living Crocodilia are mere pigmies in size, compared to the Atlantosaurus, there are a few representatives of the living group, to be discussed later, that are said to reach a length of thirty feet, which length makes pigmies, in turn, of most of the other living reptiles.

Considering the extinct as well as the living Crocodilia, Gadow says it is very difficult to separate them from the Dinosauria. In the Mesozoic Crocodilia the fore limbs were much shorter and weaker than the hind limbs, as was often the case with the dinosaurs; they were almost entirely marine, but gave indications of descent from terrestrial forms.

Various facts point, thinks Gadow, “to some Theropodous Dinosaurian stock of which the Crocodilia may well form an aquatic, further developed branch” (Cambridge Natural History, p. 432).

Skull of =Belodon=. A, from above; B, from below. A, orbit; Bo, basi-occipital; Ch, internal nares; D, pre-orbital fossa; Exo. exoccipital; Fr. frontal; Ju. jugal; La. lacrymal; Mx. maxilla; Na. nasal; Pa. parietal; Pl. palatine; Pmx. pre-maxilla; Por. post-orbital; Prf. pre-frontal; Pt. pterygoid; Qu. quadrate; S, lateral temporal fossa; S′, superior temporal fossa; Sq. squamosal; Vo. vomer. (From Zittel.)

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