Part 4 (1/2)
_Diplodocus._ The _Diplodocus_ nearly equalled the Brontosaurus in bulk and exceeded it in length. A skeleton in the Carnegie Museum at Pittsburgh measures 87 feet in total length; although the mount is composed from several individuals these proportions are probably not far from correct. The skull is smaller and differently shaped and the teeth are of quite different type. In the American Museum of Natural History, a partial skeleton is exhibited in the wall case to the left of the entrance of the Dinosaur Hall, and in an A-case near by are skulls of _Diplodocus_ and _Morosaurus_ and a model of the skull of _Brontosaurus_. The Diplodocus skull is widely different from the other two in size and proportions and in the characters of teeth.
When the first remains of these amphibious Dinosaurs were found in the Oxford Clays of England, they were considered by Richard Owen to be related to the Crocodiles, and named Opisthocoelia. Subsequently the finding of complete skeletons in this country led Cope and Marsh to place them with the true Dinosaurs and the latter named them Sauropoda.[13] Remains of these animals have also been found in India, in German East Africa, in Madagascar, and in South America, so that they were evidently widely distributed. In the Northern world they survived until the Comanchic or Lower Cretaceous Period, but in the southern continents they may have lived on into the Upper Cretaceous or true Cretacic. Some of the remains recently found in German East Africa indicate an animal exceeding either _Brontosaurus_ or _Diplodocus_ in bulk.
[Ill.u.s.tration: Fig. 24.--The Largest Known Dinosaur. Sketch reconstruction of _Brachiosaurus_, from specimens in the Field Museum in Chicago, and the Natural History Museum in Berlin.]
At the date of writing this handbook only preliminary accounts have been given of the marvellous finds made near Tendaguru by the expedition from Berlin. From these it appears that in length of neck and fore limb this East African Dinosaur greatly exceeded either _Brontosaurus_ or _Diplodocus_. The hinder parts of the skeleton however, were relatively small. The proportions and measurements given tally closely with the American _Brachiosaurus_, a gigantic sauropod whose incomplete remains are preserved in the Field Museum in Chicago and to this genus the Berlin authorities now refer their largest and finest skeleton. If the Berlin specimens are correctly referred to _Brachiosaurus_ they indicate an animal somewhat exceeding _Diplodocus_ or _Brontosaurus_ in total bulk but distinguished by much longer fore limbs and an immensely long neck--a giraffe-like wader adapted to take refuge in deeper waters, more out of reach of the fierce carnivores of the land.[14]
FOOTNOTES:
[Footnote 11: The mounted Skeleton of Brontosaurus, by W.D. Matthew, Amer. Mus. Jour. Vol. v, pp. 63-70, figs. 1-5.]
[Footnote 12: Professor Williston makes the following criticism of this theory:
”I cannot agree with this view--the animals _must_ have laid their eggs upon land--for the reason that reptile eggs cannot hatch in water. S.W.W.”
But with deference to Williston's high authority I may note that there is no evidence that the Sauropoda were egg-laying reptiles. They, or some of them, may have been viviparous like the Ichthyosaurus.]
[Footnote 13: European palaeontologists, especially Huxley and Seeley in England, had also recognized their true relations.h.i.+ps, and Seeley's term Cetiosauria has precedence over Sauropoda, although the latter is in common use.]
[Footnote 14: It is of interest to observe that in this group of Sauropoda, the Brachiosauridae, the neural spines of the vertebrae are much simpler and narrower than in the Brontosaurus and Diplodocus. The attachments were thus less extensive for the muscles of the back, indicating that these muscles were less powerful. This difference is correlated by Professor Williston with the longer fore limbs of the Brachiosaurus, as signifying that the animal was less able, as indeed he had less need, to rise up upon the hind limbs, in comparison with Diplodocus or Brontosaurus in which the fore limbs were relatively short.]
CHAPTER VI.
THE BEAKED DINOSAURS.
ORDER ORTHOPODA (ORNITHISCHIA OR PREDENTATA.)
The peculiar feature of this group of Dinosaurs is the h.o.r.n.y beak or bill. The bony core sutured to the front of the upper and lower jaws was covered in life by a h.o.r.n.y sheath, as in birds or turtles. But this is not the only feature in which they came nearer to birds than do the other Dinosaurs. The pelvic or hip bones are much more bird-like in many respects, especially the backward direction of the pubic bone, the presence of a prepubis, in the number of vertebrae coossified into a solid sacrum, in the proportions of the ilium and so on. Various features in the anatomy of the head, shoulder-blades and hind limbs are equally suggestive of birds, and it seems probable that the earliest ancestors of the birds were very closely related to the ancestors of this group of Dinosaurs. But the ancestral birds became adapted to flying, the ancestral Predentates to terrestrial life, and in their later development became as widely diversified in form and habits as the warm-blooded quadrupeds which succeeded them in the Age of Mammals.
[Ill.u.s.tration: Fig. 25.--Skulls of Iguanodont and Trachodont Dinosaurs. _Iguanodon_ and _Camptosaurus_ of the Jura.s.sic and Comanchic; _Kritosaurus_ and _Corythosaurus_ of the Middle Cretacic (Belly River); _Saurolophus_ of the late Cretacic (Edmonton); _Trachodon_ of the latest Cretacic (Lance). The Iguanodon is European, the others North American. All 1/25 natural size.]
These Beaked Dinosaurs were, so far as we can tell, all vegetarians.
Unlike the birds, they retained their teeth and in some cases converted them into a grinding apparatus which served the same purpose as the grinders of herbivorous quadrupeds. It is interesting to observe the different way in which this result is attained. In the mammals the teeth, originally more complex in construction and fewer in number, are converted into efficient grinders by infolding and elongation of the crown of each tooth so as to produce on the wearing surface a complex pattern of enamel ridges with softer dentine or cement intervening, making a series of crests and hollows continually renewed during the wear of the tooth. In the reptile the teeth, originally simple in construction but more numerous and continually renewed as they wear down and fall out,[15] are banked up in several close packed rows, the enamel borders and softer dentine giving a wearing surface of alternating crests and hollows continually renewed, and reinforced from time to time, by the addition of new rows of teeth to one side, as the first formed rows wear down to the roots. This is the best ill.u.s.trated in the _Trachodon_ (see fig. 27); the other groups have not so perfect a mechanism.
A. THE IGUANODONTS: IGUANODON, CAMPTOSAURUS.
_Sub-Order Ornithopoda or Iguanodontia._
In the early days of geology, about the middle of the nineteenth century, bones and footprints of huge extinct reptiles were found in the rocks of the Weald in south-eastern England. They were described by Mantell and Owen and shown to pertain to an extinct group of reptiles which Owen called the Dinosauria. So different were these bones from those of any modern reptiles that even the anatomical learning of the great English palaeontologist did not enable him to place them all correctly or reconstruct the true proportions of the animal to which they belonged. With them were found a.s.sociated the bones of the great carnivorous dinosaur _Megalosaurus_; and the weird reconstructions of these animals, based by Waterhouse Hawkins upon the imperfect knowledge and erroneous ideas then prevailing, must be familiar to many of the older readers of this handbook. Life size restorations of these and other extinct animals were erected in the grounds of the Crystal Palace at Sydenham, London, and in Central Park, New York. Those in London still exist, so far as the writer is aware, but the stern mandate of a former mayor of New York ordered the destruction of the Central Park models, not indeed as incorrect scientifically, but as inconsistent with the doctrines of revealed religion, and they were accordingly broken up and thrown into the waters of the Park lake. Small replicas of these early attempts at restoring dinosaurs may still be seen in some of the older museums in this country and abroad.
[Ill.u.s.tration: Fig. 26.--SKELETON OF CAMPTOSAURUS, AN AMERICAN RELATIVE OF THE IGUANODON.]
The real construction of the Iguanodon was gradually built up by later discoveries, and in 1877 an extraordinary find in a coal mine at Bernissart in Belgium brought to light no less than seventeen skeletons more or less complete. These were found in an ancient fissure filled with rocks of Comanchic age, traversing the Carboniferous strata in which the coal seam lay, and with them were skeletons of other extinct reptiles of smaller size. The open fissure had evidently served as a trap into which these ancient giants had fallen, and either killed by the fall or unable to escape from the pit, their remains had been subsequently covered up by sediments and the pit filled in to remain sealed up until the present day. These skeletons, unique in their occurrence and manner of discovery, are the pride of the Brussels Museum of Natural History, and, together with the earlier discoveries, have made the _Iguanodon_ the most familiar type of dinosaur to the people of England and Western Europe.
[Ill.u.s.tration: Fig. 27.--Teeth of the duck-billed dinosaur _Trachodon_. The dental magazine has been removed from the lower jaw and is seen to consist of several close-set rows of numerous small pencil-like teeth which are pushed up from beneath as they wear off at the grinding surface.]