# The Osteology of the Reptiles/Chapter 12

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CHAPTER XII
THE SUBCLASS DIAPSIDA
Two temporal openings, the upper bounded by the parietal above, the postorbito-squamosal arch below; the lateral by the postorbito-squamosal arch above, the jugal, or jugal and quadratojugal, below. A single coracoid on each side; no cleithra. Pelvis with pubo-ischiatic opening. Quadrate fixed or partly movable, never streptostylic.
The phyletic unity of this great division of reptiles and their descendants, the birds, admits of little or no doubt. In much probability they were derived from the single-arched type with the lateral opening, by the simple separation of the postorbital and squamosal from the parietal. Until recently it was confidently believed that the most primitive and oldest representative of the subclass was Paleohatteria, from the Lower Permian. In all probability, if not certainty, this form did not have the upper temporal opening, and must therefore be included in the more primitive group, the Theromorpha. At present the oldest known form referable to the subclass is Youngina, from the Upper Permian of Africa, an intermediate type peculiar in its retention of certain skull bones lost in all other members. It is, however, yet very imperfectly known. Doubtless many other forms from the Permian with these and yet other primitive characters await discovery.
12. ? ORDER PROTEROSUCHIA
Skull elongate, with palatal teeth; an antorbital vacuity. Skull only known.
[Triassic. Proterosuchus Broom, South Africa.]
13. ORDER "EOSUCHIA"
Family Younginidae. Skull with interparietals and tabulars (? supratemporals). Skull short; no antorbital vacuity; probably with palatal teeth. Skeleton otherwise unknown.
Upper Permian. Youngina Broom, South Africa.
A. SUPERORDER DIAPTOSAURIA
Teeth on some or all the palatal bones, acrodont or protacrodont. No antorbital opening; no interparietals or tabulars. Vertebrae amphicoelous. Dorsal ribs holocephalous, articulating in part or chiefly to centrum. Two or three sacral vertebrae. Fifth tarsale absent. Phalangeal formula never reduced. Parasternal ribs present.
In the absence of more complete information as to the structural details of some of the forms included under this group name, and in the differences of opinion, as usual, as to the value of the groups, the tribe or superorder Diaptosauria has a present use. Several groups formerly placed under it are now relegated to other divisions.
14. ORDER RHYNCHOCEPHALIA
Terrestrial or littoral lizard-like reptiles of small or moderate size. Palate primitive, with teeth on some or all the bones. Pectoral girdle complete. Dorsal ribs holocephalous, articulating in intercentral space and arch.
The three groups of reptiles here considered suborders are by some authors given a family rank, by others ordinal. Except the living Sphenodon, most of the genera are yet incompletely known. The differences between them seem hardly greater than among the Lacertilia with the inclusion of the Pythonomorpha.
A. Suborder Rhynchosauria
Skull more or less depressed and broad, with a strong, decurved, and edentulous beak, formed by the premaxillae. Temporal openings relatively large, their boundaries as in the Sphenodontia. No parietal foramen. Nares undivided. Palate with small interpterygoidal opening. Dorsal intercentra absent or unknown. About seven or eight cervicals and twenty-three presacrals; two sacrals. A small pubo-ischiatic vacuity. Humerus without epicondylar foramina.
A small group of terrestrial, perhaps in some cases subaquatic, shore-dwelling and shell-eating reptiles from three to six feet in length. The complete skull, tail, and mesopodials are known in none. In Howesia a distinct intermedium tarsus is figured; if not an ​error, it is the only known example among reptiles. The palatal teeth are confined to the palatines in two or three rows, save in Howesia, where they occur on the pterygoids only. However, the
Fig. 185. Skeleton of Rhynchosaurus (Rhynchocephalia). After Woodward. Five sixteenths natural size.
​anterior part of the skull of this genus is poorly known, and its immediate relationships with the other genera are still in doubt.
Upper Triassic. Rhynchosaurus Owen, England. Hyperodapedon Huxley, Scotland, India. Stenometopon Boulenger, Scotland. Howesia Broom, South Africa.
B. Suborder Sphenodontia (Rhynchocephalia vera)
Upper temporal opening bounded by parietal, squamosal, postfrontal, and postorbital. A single row of acrodont teeth on maxillae, dentaries, and palatines. Premaxillae with a decurved beak, usually with teeth. Frontals and parietals paired. No lacrimals. A parietal foramen. Humerus with an entepicondylar foramen, sometimes also with an ectepicondylar foramen. Pelvis with large pubo-ischiatic vacuity. Carpus primitive. Twenty-three to twenty-five presacral vertebrae, the neck with not more than eight. Parasternal ribs present.
Two genera only, the living Sphenodon and the Jurassic Homœosaurus, can be located with certainty in this suborder. Sphenodon has long enjoyed the reputation of being the most primitive of living reptiles, as evidenced by the persistent dorsal intercentra, deeply amphicoelous vertebrae, and the single-headed ribs of primitive type. So far as known Homœosaurus agrees closely, except that it has no uncinate process on the ribs, a character in which Sphenodon is almost unique among reptiles. Probably it has dorsal intercentra, but this remains to be determined. It has also no ectepicondylar foramen present in Sphenodon. Palacrodon and Opisthias are known only from mandibles. The former, however, is said to have teeth quite like those of Ardeosaurus which, according to Nopcsa, is a near relative of Acrosaurus. Nor is the temporal region of Ardeosaurus as well known as one could wish. Brachyrhinodon has two temporal arches, but is poorly known otherwise. Of Eifelosaurus the skull is wholly unknown.
Middle and Upper Triassic. ? Eifelosaurus Jaekel, ? Polysphenodon Jaekel, Germany. Palacrodon Broom, South Africa. Brachyrhinodon Huene, Scotland.
Upper Jurassic. Homœosaurus, v. Meyer, Ardeosaurus v. Meyer, Germany.
​Lowermost Cretaceous. Opisthias Gilmore, Wyoming.
Recent. Sphenodon Gray, New Zealand.
Fig. 186. Skeleton of Homœosaurus (Rhynchocephalia). After Lortet. Natural size.
C. Suborder Choristodera
Elongate, subaquatic reptiles, with a very slender face, terminal undivided nares, with small teeth on all palatal bones. No parietal foramen. Internal nares posterior. Teeth labyrinthine in structure. Vertebrae shallowly amphicoelous without dorsal intercentra. Twenty-six presacral, two or three sacral, and a long, flattened tail. Dorsal ribs holocephalous, broad, and heavy. Parasternals stout. Pelvis without pubo-ischiatic opening. Humerus with ectepicondylar foramen. Mesopodials imperfectly known.
This small group of water reptiles, animals reaching a length of eight feet, is of interest because of the retention of several primitive characters, otherwise unknown in the Diapsida, especially the labyrinthine teeth and the absence of a pubo-ischiatic opening. The arrangement of the bones of the temporal region is doubtful. The legs are essentially terrestrial in structure, with but slight aquatic adaptations, but the heavy flattened ribs and the elongate flattened tail decisively indicate bottom-crawling aquatic habits. The relationships between the known genera are very close.
Uppermost Cretaceous and Paleocene. Champsosaurus Cope (Nothosaurops Leidy), North America. Simœdosaurus Gervais, France, Belgium.
D. ? Suborder Thalattosauria
Marine reptiles with elongate face, posterior[ly placed external] nares, sclerotic plates, and paddle-like extremities. Premaxillary, anterior, mandibular, and pterygoidal teeth conical; those of the prevomers, and posterior part of maxillae and mandibles low-crowned. A parietal foramen. Vertebrae rather deeply biconcave; intercentra unknown. Dorsal ribs holocephalous, articulating chiefly with centra. Parasternal ribs slender. Humerus short, without foramina.
These small reptiles of but three or four feet in length are still imperfectly known; nor is it quite certain that they have two temporal openings. The upper opening occupies a peculiar position. The limbs, so far as known, resemble those of the mosasaurs. The habits of the thalattosaurs must have been similar to those of the mosasaurs; the dentition intermediate between that of the Mosasauridae and that of the Globidentidae.
​Middle and Upper Triassic. Thalattosaurus Merriam, Nectosaurus Merriam, California.
AA. SUPERORDER ARCHOSAURIA
Dorsal ribs attached exclusively to the arch, at least anteriorly, by two articulations, the cervicals to arch and centrum. Usually an antorbital vacuity. The quadratojugal is well developed and usually enters the border of the lateral temporal opening. No parietal foramen, tabulars, or [dermo]supraoccipitals, and doubtfully, [if] ever, the interparietals. Teeth thecodont, confined to jaws, rarely absent. Vertebrae never notochordal, nor the dorsal intercentra persistent.
15. ORDER PARASUCHIA
From small to rather large, crawling or leaping reptiles, characterized especially by the normal pelvis, absence of a secondary palate, and a large antorbital opening. Body usually with dermal armor. Roof bones of skull always paired; postfrontals present. Vertebrae amphicoelous or platycoelous. Clavicles and interclavicle present, the corocoid not elongate. Parasternal ribs generally present. Mesopodials imperfectly known; phalanges not reduced.
The Parasuchia in the present sense were long united with the Crocodilia as two suborders, the Parasuchia, sens, str., and the Pseudosuchia or Aetosauria, but the marked differences in skull and pelvis justify their ordinal separation. By some authors the three suborders here recognized are each given ordinal rank. Sclerotic plates are known in a single genus of Pseudosuchia.
A. Suborder Pseudosuchia
Typically a group of small, slender, climbing or leaping reptiles with more or less elongated hind legs. The external and internal nares are near the extremity of the more or less pointed skull; the lateral orbits are large, as are also the antorbital openings. The epipodials are long, the clavicles and interclavicle slender.
None of the forms referred to this suborder is completely known, and among the known forms there is a considerable diversity of structure, some departing so widely, perhaps, that their location here is provisional. Of the more typical, Scleromochlus has no dermal ​armor, and Euparkeria alone has sclerotic plates; the latter has been accredited with an interparietal bone.
With the inclusion of the doubtful forms there are but few constant characters to distinguish the group from the Rhynchocephalia; typically, however, the absence of palatal teeth, and the attachment of the dorsal ribs are decisive. As a whole, however, the group is one of wide genetic possibilities and [may] have had a close genealogical relationship with all the other members of the Archosauria, and especially the Saurischia. Nearly every known genus has been accredited with family rank.
Family Aetosauridae. Twenty-five presacrals; two sacrals. Humerus a little longer than radius and ulna; hind legs a half longer than the front. Dorsal scutes transversely elongate, covering the whole back; abdomen with small plates.
Triassic. Aetosaurus Fraas, Dyoplax Fraas, Germany. Stegomus Marsh, Connecticut.
Family Ornithosuchidae. Scapula slender, coracoid short and broad. Legs very slender, the epipodials a little longer than the propodials. Two rows of dermal plates, each longer than broad.
Euparkeria is accredited with an interparietal, the only member of the group.
Triassic. Ornithosuchus Newton, ? Erpetosuchus Newton, England. Euparkeria Broom, Sphenosuchus Haughton, South Africa.
Family Scleromochlidae. Premaxillae united. Twenty-one presacrals, three sacrals. Scapulae slender, coracoid long. Tubes long and slender, expanded at extremity; calcaneum with tuberosity; feet as long as tibia, the epipodials longer than propodials. Slender parasternal ribs. No dermal armor.
Triassic. Scleromochlus Woodward, England.
B. Suborder Pelycosimia
Large, heavily built, terrestrial or marsh reptiles. External and internal nares near extremity of triangular skull. Antorbital openings large, the orbits relatively small. Upper temporal opening not depressed below level of [parietals]. Palatines approximated or ​contiguous, without respiratory canal. Teeth compressed, curved, and sharply pointed. Legs short and rather stout.
This group, proposed as a separate order, is based almost exclusively upon Erythrosuchus. In the structure of the skull it is somewhat intermediate between the Pseudosuchia and the Phytosauria.
Triassic. Erythrosuchus Broom, South Africa. ? Scaponyx Woodward, South America.
C. Suborder Phytosauria
Large, crawling, subaquatic reptiles, reaching a length of twenty or more feet, especially characterized by the elongate face, composed chiefly of the premaxillae, the posterior nares, and the deep respiratory canal, formed by the underarching of the palatines. Skull rugose, the lateral, temporal, and antorbital openings large, the supratemporal opening small and more or less depressed below the plane of the parietals. Tip of premaxillae decurved, with two or three very long, cylindrical teeth on each. Teeth either cylindrical throughout, or the posterior ones more or less flattened and separated. Neck, body, and tail covered with four or more rows of strong dermal bones; the pectoral region and abdomen with smaller, bony scutes. Tail long and flattened, compressed. Feet probably webbed. Vertebrae platycoelous; two sacrals.
Family Phytosauridae. Ilium with postacetabular process; pubis not dilated at extremity.
Triassic. Phytosaurus Jaeger, Mystriosuchus Fraas, Mesorhinus Jaekel, Germany. Parasuchus Lydekker, India. Paleorhinus Williston, Angistorhinus Mehl, Lophoprosopus Mehl, Rocky Mts. Rutiodon Emmons (Rhylidodon), Carolina, New York, Connecticut.
Family Stagonolepidae. A supracoracoid foramen. Ilium without postacetabular process; pubes dilated at extremity.
Triassic. Stagonolepis Huxley, England.
[D. Suborder Desmatosuchia]
[Large, long-tailed reptiles reaching a length of perhaps sixteen feet, especially characterized by the probably secondary absence of the upper temporal opening. Cervical and anterior dorsal bony plates bearing long horn-like outgrowths. Skull with large antorbital ​opening and dorsal anterior nares, snout not greatly produced. Teeth thecodont. Distinguished from the Phytosauria especially by the absence of the upper temporal opening, which may have been secondarily lost as in the caimans. Von Huene refers Desmatosuchus to the Phytosauria.
Triassic. Desmatosuchus Case, Texas.]
16. ORDER CROCODILIA
[Loricata]
Internal nares carried far back in the mouth by the union of the maxillae and palatines, and in the later forms the pterygoids also. Premaxillae never much elongate, the external nares terminal. Acetabulum formed by ilium and ischium only, the so-called pubes (? prepubes) excluded and not meeting in a median symphysis. Phalanges of fourth and fifth digits reduced; calcaneum elongate. Two sacral vertebrae.
The Crocodilia are at once distinguished from all other reptiles by the structure of the palate and pelvis. There is not a very great diversity of structure among the known forms. All are lizard-like in form, with a long, flattened tail, very predaceous, with conical thecodont teeth, and more or less water-loving in habit. In size they vary from less than one foot to about fifty feet in length. The vertebrae were platycoelous in all till about the beginning of the Lower Cretaceous; procoelous in all since the early part of the Eocene. Some have a relatively broad skull; others a more or less elongated face, sometimes very slender, as in the ancient teleosaurs and the modern gavials. In such forms the nasals do not reach the external nares, and the splenials meet in a symphysis. The upper temporal openings in the modern forms are smaller, very small in the broad-faced types. In the early types the arch between the orbit and lateral temporal opening was covered immediately by the skin; since Wealden times the bar is more cylindrical and more deeply placed. The amphibious crocodiles have a strong dermal, osseous armor along the back and tail, sometimes also on the under side. Both the carpus and tarsus are peculiarly modified, suggesting, v. Huene thinks, a primitive, more upright-walking gait.
A. Suborder Eusuchia
An antorbital opening primitively present but lost in many ancient and all modern forms. Mandible with an external vacuity posteriorly. Nine cervical vertebrae, twenty-three or twenty-four presacrals. No sclerotic plates in orbits. Body with dermal bones. Feet partly webbed, clawed, not paddle-like.
Until within recent years, and still by some authors, the Eusuchia comprised only those crocodilians with procoelous vertebrae, amphicoelian forms comprised in the suborder Mesosuchia. It is now known that the change in the form of the vertebrae was a relatively unimportant one and may have occurred in different lines of descent.
Family Teleosauridae. Vertebrae platycoelous. Internal nares large, situated at posterior end of palatines. Face very long and slender. An antorbital opening sometimes present. Postorbital bar not modified. Upper temporal opening large. A nearly complete dermal armor. Front feet much smaller than hind. From two to ten feet in length.
Jurassic. Pelagosaurus Bronn, Teleosaurus Geoffroy, Teleidosaurus Deslongchamps, Suchodus Lydekker, Aeolodon Meyer, Crocodilemus Jourdan, Gnathosaurus Münster, Europe. Steneosaurus Geoffroy, Europe, Madagascar.
Cretaceous. ? Teleorhinus Osborn, Wyoming.
Family Pholidosauridae. Vertebrae platycoelous. Internal nares opening in palatines and pterygoids. Face long; the nasals reach to the premaxillae. Upper temporal opening smaller than orbits. Postorbital bar modified. Front legs larger than in the Teleosauridae. Dorsal and ventral armor present.
Upper Jura and Lowermost Cretaceous. Pholidosaurus Meyer (Macrorhynchus), Pterosuchus Owen, Europe.
Family Atoposauridae. Vertebrae platycoelous. Posterior nares not reaching pterygoids. Head short, broad. Upper temporal openings much smaller than orbits. Dermal armor composed of two rows of quadrilateral plates, probably extending on tail. Probably no ventral scutes. Tail long. Small reptiles from eight to sixteen inches in length. ​Upper Jurassic. Atoposaurus Meyer, Alligatorellus Jourdan, Alligatorium Lortet, Germany.
Family Goniopholidae. Vertebrae platycoelous. Internal nares bounded by pterygoids and palatines. Face rather broad, not long. Postorbital bar subdermal. A dorsal armor of two or more rows of plates.
Lowermost Cretaceous. Goniopholis Owen, Europe, North and South America. Nannosuchus Owen, Theriosuchus Owen, Machimosaurus Meyer, Bernissartia Dollo, Europe.
Upper Cretaceous. Coelosuchus Williston, Teleorhinus Osborn, Wyoming. Notosuchus Woodward, Cynodontosuchus Woodward, South America.
Family Dyrosauridae. Vertebrae platycoelous; internal nares between palatines and pterygoids. Face very slender. Postorbital bar subdermal. From fifteen to eighteen feet in length.
Lower Eocene. Dyrosaurus Pomel, Africa.
Family Hylaeochampsidae. Vertebrae probably procoelous. Internal nares surrounded by pterygoids. Palate with large foramen between ectopterygoid and maxillae. Skull short, broad.
Wealden Cretaceous. Hylcœochampsa Owen, ? Heterosuchus Seeley, England.
Family Gavialidae. Vertebrae procoelous. Posterior nares surrounded by pterygoids. Face very slender. Postorbital bar subdermal. Upper temporal openings large. Nasals remote from nares. Dorsal but no ventral scutes. From ten to fifty feet in length.
Pleistocene, Recent. Gavialis Oppel, Rhamphosuchus Owen, Paleosuchus Falconer and Cautley, India.
Family Tomistomidae. Vertebrae procoelous. Posterior nares surrounded by pterygoids. Face less elongated, gradually merging into cranium. Postorbital bar subdermal. Nasals extend into nares. Sometimes an antorbital opening. From six to forty or more feet in length.
Upper Cretaceous. Thoracosaurus Leidy, Holops Cope, United States.
Eocene. [Tomistoma, Europe, Africa.] Eosuchus Dollo, Belgium.
Pliocene. Tomistoma (?) [Gavialosuchus], Florida. ​Pleistocene. Tomistoma, Hungary.
Recent. Tomistoma, Borneo.
Tertiary. Leptorhamphus Ameghino, Oxydontosaurus Ameghino, Argentina.
Family Crocodilidae. Vertebrae procoelous. Posterior nares surrounded by pterygoids, single or divided. Upper temporal openings small. Postorbital bar subdermal. Face never slender. Teeth stout, anisodont. Dorsal plates in two or more rows, the ventral armor present or absent. The nasals usually reach the external nares. From four or five to more than forty feet in length.
Uppermost Cretaceous. Deinosuchus Holland, Bottosaurus Leidy [Agassiz], Brachychampsa Gilmore, Leidyosuchus Lambe, ? Polydectes Cope, North America. Crocodilus Laurenti, Italy.
Eocene. Crocodilus Laurenti, Diplocynodon Pomel, Europe, North America. Limnosaurus Marsh, North America.
Oligocene. Caimanoidea Mehl, South Dakota.
Miocene. "Crocodilus" [?], [Alligator], North America.
Pleistocene. Crocodilus Laurenti, Europe, India, Africa, North America. [Alligator, North America.]
[Recent. Crocodilus, Osteolaemus, Osteoblepharon, Alligator, Caiman, Jacare.]
Incertae Sedis. Lower Jurassic. Notochampsa Broom, South Africa.
B. Suborder Thalattosuchia
Marine crocodiles, without bony armor, and with limbs more or less modified as paddles, without claws. Vertebrae platycoelous. Face more or less elongated. Nares at posterior end of palatines. Prefrontals large, protuberant. Supratemporal openings large. Bones of skull smooth. Orbits with sclerotic plates. No antorbital or mandibular openings. Seven cervical, twenty-five presacral, vertebrae. Tail long, with distal fin-like dilatation.
​Family Metriorhynchidae.
Upper Jurassic. Dacosaurus Quenstedt, Geosaurus Cuvier, Europe. Metriorhynchus Quenstedt, Europe, Patagonia.
Lowermost Cretaceous. Neustosaurus Raspail, ? Enaliosuchus Dollo, Europe.
[DINOSAURIA]
17. ORDER SAURISCHIA
More or less upright-walking reptiles. The normal pubes and ischia meet in a ventral symphysis, the acetabulum perforated. No predentary or rostral bones. One or more antorbital openings. No dermal bones.
A. Suborder Theropoda
Carnivorous or secondarily herbivorous in habit. More or less bipedal in gait, the hind feet more or less digitigrade, the front legs more or less reduced. Pubes meeting in a long ventral symphysis, with a distal dilatation.
Family Plateosauridae. Teeth less compressed, not recurved and somewhat thickened, their anterior and posterior borders denticulated. Anterior vertebrae platycoelous; twenty-three presacrals, three sacrals. Front legs a little longer than the femora, preaxonic, their phalangeal formula 2, 3, 4, 5, (?), the first claw large. Hind feet more mesaxonic, the first and fifth toes reduced. Feet digitigrade or semiplantigrade. Astragalus without ascending process.
Upper Triassic. Plateosaurus Meyer, Gressylosaurus Rütimeyer, Pachysaurus Huene, Teratosaurus Meyer, Europe. Euskelosaurus Huxley, Gryponyx Broom, South Africa.
This, the most primitive family of the Theropoda, is thought by some to have an ancestral relationship with the Sauropoda. The characters drawn chiefly from Plateosaurus may not and probably do not apply to all the genera listed in the family. The reptiles were clearly bipedal in gait, though of rather heavy build. Jaekel thinks that the hind feet were purely plantigrade, but this was improbable since the mesaxonic structure distinctly indicates the elevation of the ankle from the ground. Plateosaurus attained a length of about fifteen feet.
​Family Anchisauridae. Smaller and more slender theropods. Vertebrae amphicoelous. Teeth compressed, more or less recurved. Astragalus without ascending process.
Upper Triassic. Anchisaurus Marsh, Megadactylus Hitchcock, Ammosaurus Marsh, Connecticut Valley. Thecodontosaurus Riley and Stutchbury, England, Africa, Australia. Massospondylus Owen, South Africa. Zanclodon Plieninger, Sellosaurus Huene, Europe.
Fig. 187. Skeleton of Gorgosaurus (Saurischia). After Lambe. One thirty-sixth natural size.
[No MS. was found for (1) the Coelurosauria, containing several families and numerous genera of light-limbed saurischian dinosaurs, including the Ornithomimidae, (2) the Megalosauria group of the Jurassic, and (3) the Deinodont group of the Cretaceous. For group 1 see papers by Osborn 1917 (Bulletin, Amer. Mus. Nat. Hist., vol. XLIII), von Huene 1921 (Acta Zoölogica, Bd. II); for groups 2 and 3 see Matthew and Brown, 1922 (Bulletin, Amer. Mus. Nat. Hist., vol. XLVI).—Ed.]
B. Suborder Sauropoda (Opisthocoelia, Cetiosauria)
Quadrupedal, semiplantigrade, herbivorous dinosaurs, with long neck and tail and small skull. Postfrontal sometimes present. Teeth subcylindrical, with a thickened, spoon-shaped crown, in a single row, and more or less restricted to anterior part of jaws, the premaxillae with teeth; no predentary. No coronoid process to mandible. The anterior, sometimes all, presacral vertebrae opisthocoelous, with a more or less developed hyposphene-hypantrum articulation, and with hollow, lateral cavities in centra. Four or five sacrals, twenty-six or ​twenty-seven presacrals. The pubes are massive and meet in a large ventral symphysis. Carpals and tarsals reduced, feet preaxial. Limb bones cancellous in structure. From about fifteen to about ninety feet in length.
Family Cetiosauridae. Spines of dorsal vertebrae simple, not furcate. Front limbs as long as the hind. Scapulae dilated distally. Pubes not constricted.
Upper Jurassic. Cetiosaurus Owen (Cardiodon Owen), England.
Lower Cretaceous (Morrison). Haplacanthosaurus Hatcher, Brachiosaurus Riggs, Rocky Mts. Gigantosaurus Fraas (non Seeley), (? Brachiosaurus Riggs), South Africa. Pelorosaurus Mantell, Europe, Madagascar.
Family Camarasauridae. Spines of dorsal vertebrae furcate. Front limbs distinctly shorter than hind. Scapulae distally expanded. Ischia slender.
Lower Cretaceous. Camarasaurus Cope (Morosaurus Marsh), Pleurocoelus Marsh, North America. Titanosaurus Lydekker, Europe, Madagascar, India.
Upper Cretaceous. Titanosaurus Lydekker, France, Patagonia.
Family Atlantosauridae. Spines of presacral vertebrae furcate. Front legs much shorter than hind. Scapulae narrow distally. Ischia expanded at extremity.
Lower Cretaceous (Morrison). Atlantosaurus Marsh, Apatosaurus Marsh (Brontosaurus Marsh), Amphicoelias Cope, Rocky Mts.
Family Diplodocidae. Spines of presacral vertebrae furcate. Front legs shorter than hind. Teeth slender, confined to anterior part of jaws. External nares near top of skull, remote from extremity. Ischia not expanded distally, the pubes constricted in middle. More slender sauropods.
Lower Cretaceous (Morrison). Diplodocus Marsh, Rocky Mts.
Genera Incertae Sedis: ? Jurassic. Dystrophaeus Cope, Rocky Mts.
Upper Jura and Wealden. Bothriospondylus Mantell, Chondrosteus Owen, Chondrosteosaurus Owen, Eucamerotus Hulke, Ischyrosaurus ​Hulke, Nesodon Mousaye, Oplosaurus Gervais, Ornithopsis Seeley, Europe.
Lower Cretaceous (Morrison). Barosaurus Marsh, Caulodon Cope, Elosaurus Peterson and Gilmore, Epanterias Cope, Symphyrophus Cope, ? Astrodon Leidy, Rocky Mts.
Lower Cretaceous. Dinodocus Owen, Hypselosaurus Matheron, Aepysaurus Gervais, Morinosaurus Sauvage, Europe.
Algaosaurus Broom, South Africa.
Upper Cretaceous. Argyrosaurus Lydekker, Microcoelus Lydekker, South America.
18. ORDER ORNITHISCHIA
[ORTHOPODA, PREDENTATA]
Quadrupedal or bipedal dinosaurs, especially characterized by the presence of a predentary bone in the mandible and by the structure of the pelvis. Premaxillae rarely with teeth. Antorbital openings small or absent. Vertebrae amphicoelous or amphiplatyan, the anterior ones often opisthocoelous. Pubes not meeting in a median symphysis, with an anterior, more or less spatulate, prepubis, and a posterior, usually long, postpubis, underlying the ischium. Front limbs always shorter than hind, never functionally pentadactylate, rarely with as many as four phalanges in any digit. Hind limbs usually functionally tridactylate, more or less digitigrade. Ungual phalanges short and broad.
A. Suborder Ornithopoda
Bipedal in habit, digitigrade. External nares near extremity of face, divided. Postpubis complete, slender. Antorbital opening sometimes small.
Family Nanosauridae. Premaxillae edentulous. Teeth in a single row, compressed and pointed. Vertebrae amphicoelous; three sacrals. Femur shorter than tibia. Bones very hollow. Of the size of a cat.
Lower Jurassic. Nanosaurus Marsh, Colorado.
Family Hypsilophodontidae. Premaxillae with teeth. Teeth in a single row. Anterior vertebrae opisthocoelous. Femur longer than ​tibia. Body covered with dermal ossifications. Five sacral vertebrae. Manus with five, the pes with four, digits, the fifth vestigial.
Wealden. Hypsilophodon Hulke, England.
Family Iguanodontidae. Premaxillae edentulous. Teeth in a single row. Anterior vertebrae platycoelous or opisthocoelous. No dermal ossifications. Four or five sacral vertebrae. Femur longer or shorter than tibia. Four functional fingers, three functional toes.
This family has been sometimes divided into three, the Laosauridae with platycoelous vertebrae, the Camptosauridae, and Iguanodontidae with opisthocoelous vertebrae; but the differences seem to be of minor importance.
The Scelosaurus, though its teeth are unknown, has been located with the Hypsilophodontidae. Its vertebrae are plano-concave or nearly amphiplatyan. It is the latest of known Ornithopoda and may eventually, perhaps, find its proper location in a distinct family.
Lower Cretaceous (Morrison, Wealden). Camptosaurus Marsh, Laosaurus Marsh, Rocky Mts. Iguanodon Mantell, England.
Family Trachodontidae. (Hadrosauridae.) Teeth in many rows, forming a tessellated pavement in use. Premaxillae edentulous. Cranium often with crest. Extremity of face more or less dilated. Cervical vertebrae opisthocoelous, about fifteen in number; seven or eight sacrals. Tail flattened. Femur longer than tibia; phalanges reduced; four functional fingers and three functional toes. Subaquatic in habit; sclerotic plates in orbits.
Upper Cretaceous. Cheneosaurus Lambe, Claosaurus Marsh, Hadrosaurus Leidy, Hypacrosaurus Brown, Kritosaurus Brown, Gryposaurus Lambe, Prosaurolophus Brown, Saurolophus Brown, Stephanosaurus Lambe, Corythrosaurus Brown, Trachodon Leidy.
B. Suborder Stegosauria
[Quadrupedal, with dermal armor of plates and spines; skull small; bones solid. Jurassic to close of Cretaceous. No MS.]
C. Suborder Ceratopsia
Secondarily quadrupedal dinosaurs, with large skull, armed with horns and protuberances, located on nasal, postorbitals, and the margin of a greatly extended "frill" or extension of the skull over ​the neck. Lateral temporal openings small. Teeth with divided roots in a single functional row. No teeth on premaxillae, the upper jaws terminating in a distinct "rostral" bone. Vertebrae platycoelous, the first three or four cervicals coössified. Sacrum composed of numerous vertebrae. Ilium with long preacetabular and postacetabular process. Ischium slender, curved, the postpubis more or less vestigial. Carpus and tarsus reduced, but two carpalia. Astragalus firmly united with tibia, the calcaneum free; fifth toe vestigial.
Uppermost Cretaceous. Anchiceratops Brown, Brachyceratops Gilmore, Ceratops Marsh, Chasmosaurus Lambe, Centrosaurus Lambe, Diceratops Lull, Eoceratops Lambe, Leptoceratops Brown, Monoclonius Cope, Triceratops Marsh, Styracosaurus Lambe, Torosaurus Marsh, Agathaumas Cope, Western North America.
19. ORDER PTEROSAURIA
Volant reptiles with highly ossified, pneumatic skeleton. Skull elongated, more or less pointed, the external nares remote from the tip. No parietal foramen. Orbits with sclerotic plates. Neck elongate; eight or nine cervicals, ten or more dorsals, four to ten sacrals, and about twelve to forty caudals; the presacrals procoelous, the caudals amphicoelous. No supracoracoid foramen, clavicles, or interclavicle. Sternum large, well ossified; parasternals present. Humerus shorter than forearm, with large lateral process; carpus more or less reduced; a pteroid bone articulating with carpus. First three fingers small, with claws; fourth greatly elongated for support of patagium; fifth digit absent. Prepubes articulating with pelvis. Femora shorter than tibia; fibula reduced or absent; first tarsal row more or less fused with tibia; feet long, pentadactylate, the fifth toe more or less reduced.
A. Suborder Pterodermata (Rhamphorhynchoidea)
Fig. 188. Skeleton of Rhamphorhynchus (Pterosauria). One third natural size.
​Family Rhamphorhynchidae.
Jurassic. Rhamphorhynchus Meyer, Scaphognathus Wagner, Dimorphodon Meyer, Dorygnathus Orpel, Campylognathus Plieninger, Europe.
B. Suborder Pterodactyloidea
Wing metacarpal, longer or but little shorter than forearm. Tail very short. No cervical ribs. Fifth toe more or less reduced.
Family Pterodactylidae. Nares and antorbital vacuity more or less coalescent. Teeth in anterior part of jaws. Anterior dorsal vertebrae not fused. All metacarpals articulating with carpus. Prepubes not band-like. Smaller.
Upper Jurassic. Pterodactylus Cuvier (Ornithocephalus Sommering, Diopecephalus Seeley, Cycnorhamphus Seeley, Pterodracon Lydekker), Europe.
Family Ornithocheiridae. Skull more elongate. A supraoccipital crest. Scapula with enlarged distal end articulating with notarium. Jaws with teeth in front. Skeleton imperfectly known.
Wealden. Ornithocheirus Seeley, Ornithodesmus Seeley, England.
Family Pteranodontidae. Skull much elongated, toothless. A long supraoccipital crest. Orbits small. No antorbital opening. No fibula; fifth toe without phalanges. First three metacarpals splint-like. Upper end of scapula articulating with notarium. Prepubes band-like. From twelve to twenty-five feet in expanse of wings.
Upper Cretaceous. Pteranodon Marsh, North America. Ornithostoma (? Pteranodon) Seeley, England.
Family Nyctosauridae. Like the Pteranodontidae, but no occipital crest, and the upper end of scapula flat, not articulating with notarium. Eight-foot wing expanse.
Cretaceous. Nyctosaurus (Nyctodactylus) Marsh, Kansas.
Genera Incertae Sedis. Doratorhynchus Seeley, Paleornis Mantell, England.
Fig. 189. Skeleton of Pterodactylus. Four thirds natural size.
Fig. 190. Skeleton of Nyctosaurus (Pterosauria). One eighth natural size.
Fig. 191. Restoration of Nyctosaurus (Pterosauria) by Herrick E. Wilson.
* ↑ [An antorbital vacuity is present, according to Broom.—Ed.]
* ↑ [But cf. page 268 above. According to C. L. Camp (1923), Ardeosaurus is related to the geckos.—Ed.]
* ↑ [For recent morphological and taxonomic treatment of the Crocodilia, see numerous papers by C. C. Mook, 1921–, Bulletin, Amer. Mus. Nat. Hist.—Ed.]
* ↑ [Williston here includes the genera Alligator and Caiman under the Crocodilidae, and places Tomistoma in a separate family, but Mook (op. cit.) has shown that Alligator, Caiman, and Jacare are more distinct from Crocodilus and its allies (Osteolaemus, Osteoblepharon) than is Tomistoma. — Ed.]
* ↑ [Belongs in Diplodocidae. — Osborn and Mook.]
* ↑ [Belongs in the Diplodocidae. — Lull.]
* ↑ [Belongs in the Camarasauridae. — Osborn and Mook.]