Animals of the Past

by Frederic A. Lucas

shaped cross ridges, covered with enamel, while in the elephants the enamel takes the form of narrow, pocket-shaped plates, set upright in the body of the tooth. Moreover, in the mastodons the roots of the teeth are long prongs, while in the elephants the roots are small and irregular. A glance at the cuts will show these distinctions better than they can be explained by words. Back in the past, however, we meet, as we should if there is any truth in the theory of evolution, with elephants having an intermediate pattern of teeth.

Fig. 38.—Tooth of Mastodon and of Mammoth.

There is usually, or at least often, another point of difference between elephants and mastodons, for many of the latter not only had tusks in the upper, but in the lower jaw, and these are never found in any of the true elephants. The lower tusks are longer and larger in the earlier species of mastodon than in those of more recent age and in the latest species, the common American mastodon, the little lower tusks were usually shed early in life. These afford some hints of the relationships of the mastodon; for in Europe are found remains of a huge beast well called Dinotherium, or terrible animal, which possessed lower tusks only, and these, instead of sticking out from the jaw are bent directly downwards. No perfect skull of this creature has yet been found, but it is believed to have had a short trunk. For a long time nothing but the skull was known, and some naturalists thought the animal to have been a gigantic manatee, or sea cow, and that the tusks were used for tearing food from the bottom of rivers and for anchoring the animal to the bank, just as the walrus uses his tusks for digging clams and climbing out upon the ice. In the first restorations of Dinotherium it is represented lying amidst reeds, the feet concealed from view, the head alone visible, but now it is pictured as standing erect, for the discovery of massive leg-bones has definitely settled the question as to whether it did or did not have limbs.

There is another hint of relationship in the upper tusks of the earlier mastodons, and this is the presence of a band of enamel running down each tusk. In all gnawing animals the front, cutting teeth are formed of soft dentine, or ivory, faced with a plate of enamel, just as the blade of a chisel or plane is formed of a plate of tempered steel backed with soft iron; the object of this being the same in both tooth and chisel, to keep the edge sharp by wearing away the softer material. In the case of the chisel this is done by a man with a grindstone, but with the tooth it is performed automatically and more pleasantly by the gnawing of food. In the mastodon and elephant the tusks, which are the representatives of the cutting teeth of rodents, are wide apart, and of course do not gnaw anything, but the presence of these enamel bands hints at a time when they and their owner were smaller and differently shaped, and the teeth were used for cutting. Thus, great though the disparity of size may be, there is a suggestion that through the mastodon the elephant is distantly related to the mouse, and that, could we trace their respective pedigrees far enough, we might find a common ancestor.

This presence of structures that are apparently of no use, often worse than useless, is regarded as the survival of characters that once served some good purpose, like the familiar buttons on the sleeve or at the back of a man's coat, or the bows and ruffles on a woman's dress. We are told that these are put on "to make the dress look pretty," but the student regards the bows as vestiges of the time when there were no buttons and hooks and eyes had not been invented, and dresses were tied together with strings or ribbons. As for ruffles, they took the place of flounces, and flounces are vestiges of the time when a young woman wore the greater part of her wardrobe on her back, putting on one dress above another, the bottoms of the skirts showing like so many flounces. So buttons, ruffles, and the vermiform appendix of which we hear so much all fall in the category of vestigial structures.

Where the mastodons originated, we know not: Señor Ameghino thinks their ancestors are to be found in Patagonia, and he is very probably wrong; Professor Cope thought they came from Asia, and he is probably right; or they may have immigrated from the convenient Antarctica, which is called up to account for various facts in the distribution of animals.[18]

[18] During the past year, 1901, Mr. C. W. Andrews of the British Museum has discovered in Egypt a small and primitive species of mastodon, also the remains of another animal which he thinks may be the long sought ancestor of the elephant family, which includes the mammoth and mastodon.

Neither do we at present know just how many species of mastodons there may have been in the Western Hemisphere, for most of them are known from scattered teeth, single jaws, and odd bones, so that we cannot tell just what differences may be due to sex or individual variation. It is certain, however, that several distinct kinds, or species, have inhabited various parts of North America, while remains of others occur in South America. The mastodon, however, the one most recent in point of time, and the best known because its remains are scattered far and wide over pretty much the length and breadth of the United States, and are found also in southern and western Canada, is the well-named Mastodon americanus,[19] and unless otherwise specified this alone will be meant when the name mastodon is used. In some localities the mastodon seems to have abounded, but between the Hudson and Connecticut Rivers indications of its former presence are rare, and east of that they are practically wanting. The best preserved specimens come from Ulster and Orange Counties, New York, for these seem to have furnished the animal with the best facilities for getting mired. Just west of the Catskills, parallel with the valley of the Hudson, is a series of meadows, bogs, and pools marking the sites of swamps that came into existence after the recession of the mighty ice-sheet that long covered eastern North America, and in these many a mastodon, seeking for food or water, or merely wallowing in the mud, stuck fast and perished miserably. And here to-day the spade of the farmer as he sinks a ditch to drain what is left of some beaver pond of bygone days, strikes some bone as brown and rugged as a root, so like a piece of water-soaked wood that nine times out of ten it is taken for a fragment of tree-trunk.