Popular Science Monthly/Volume 40/March 1892/The Australian Marsupial Mole
|THE AUSTRALIAN MARSUPIAL MOLE.|
By Dr. E. TROUESSART.
THE discovery of a new mammal with distinct enough characteristics to constitute the type of a new family, possibly of an order, in the class of Didelphæ or Aplacentariæ, is, at this age, a zoölogical event of great importance. The discovery is still ÷ more interesting in the case of an animal presenting so curious a form and organization as the one about to be described. The account we give of it is taken from the original memoir of Mr. E. C. Stirling, Director of the South Australian Museum and professor in the University of Adelaide, who found the animal in the central desert of Australia. The researches of English naturalists, especially of the ornithologist Gould, have made us so well acquainted with the fauna of New Holland that the announcement of the existence in that country of a living mammal that fills what has long been recognized as a gap in it is a real surprise.
The Notoryctes, as Prof. Stirling has named it, is a marsupial mole presenting remarkable analogies at once with the Chrysochlores, or moles, of the Cape of Good Hope, placentary insectivores peculiar to South Africa, and with the primitive mammals of the Secondary period and the beginning of the Tertiary, of which only the dentition is known to us. The name, Notoryctes typhlops, means blind burrower of the South.
The first individual of this species, of which Prof. Stirling saw the remains in very bad condition, was captured in 1888 by Mr. Coulthard, a cattle-raiser of northern South Australia. Following the tracks of the animal, he found it at the foot of a tuft of porcupine-grass (Spinifex or Triodia irritans). Although he had lived many years in the country, he had never seen or heard of it before. The region where it was found is about a thousand miles north of Adelaide; is bounded on the northeast by the dry bed of Finke River, and is a country of dunes and red sand, with spots of vegetation composed exclusively of Spinifex and Acacia. It rarely rains there. The species does not seem to be very abundant, and the natives appeared to have no knowledge of the animal when a figure of it was shown them. Much interested in his discovery. Prof. Stirling visited the South Australian desert and procured six specimens of the Notoryctes, four female and two male, and preserved them in alcohol for dissection on his return to Adelaide.
It was only with the assistance of the natives, and their surprising gifts in following the tracks of an animal, that it was possible to procure the precious specimens. The rainy season of the short semitropical summer of the country is the most favorable time for this kind of investigation. The tracks of the animal are then preserved in the ground, while the soil is at other times too friable to retain any mark. The Notoryctes is essentially a burrower, and never comes out from under the sand except to run a few feet in a slow and tortuous gait, dragging its belly along the ground. It walks, clinching the outer edges of its claws in the ground, leaving a triple, often interrupted, sinuous track, the lateral lines of which are drawn by the feet, the middle line by the tail, on which the animal supports itself by beating it on the ground. The track resembles those of some Australian lizards, which Prof. Stirling was apt at first to mistake for them.
The Notoryctes burrows obliquely in the sand, going two or three inches under the ground, and never betraying its passage except by a slight undulation of the soil. In digging it uses its conical nose, which is protected by a horny plate, and the strong, mattock-shaped claws of its fore feet. The hind feet, which are wider and spade-shaped, throw the sand back so that no trace is left of the tunnel which it hollows. It comes to the surface a few yards farther on, and then buries itself again, all without making any noise. It is prodigiously agile and swift, a property on which Mr. Benham, who lived for some time at Idracowra, says: "Everybody here can tell you how soon one of these animals will get away by digging in the sand. I had brought a live one to the house and we were talking of its agility in digging. Mr. Stokes desired to see it at work. After spading and turning over the ground near the house, we set the animal down; I held it in my hands till it was nearly hidden, and then tried to overtake it by scratching the ground behind it, but it was quicker than I. I took a shovel and tried to find it, but without success. Another man came to my help with a second shovel, and also a native woman used to digging in the ground with her hands. But all three of us could not find it."
The Notoryctes are hard to keep alive, even if large tubs full of sand are provided. Night and day can be heard the slight sound they make in digging in this friable soil. They would not touch the ants which Mr. Stirling gave them, although ants were found in their stomachs. On the other hand, they readily ate the large white grubs of long-horned beetles and Lepidoptera; one "of them even ate bread, but it died the next day. They did not try to bite when taken in the hand. The natives call them oor-quamata, and seem to have a superstitious fear of them, arising perhaps from the animal's being almost unknown. They have never seen the young ones. The intestines of different individuals dissected by Mr. Stirling contained ants and other insects.
At first sight, the animal looks very much like the Chrysochlores, or golden moles of the Cape, but differs from them by its strong tail (the Chrysochlores have none), in the shape of its incisors, and in the presence of a pouch in the female. It is smaller than the European mole. Its pelage is yellowish, golden at some points, and silvered at others. It has no distinct neck, but the cheeks merge into the . It results that the body
Fig. 1.—The New Mammal, Notoryctes typhlops (slightly reduced).
is strongly arched. The nose, the feet, and the tail only are in the same plane. The nostrils are pierced through the horny plate which protects the muzzle, and which is divided in two by a transversal furrow. The mouth is underneath. The tongue is broad and shaped like a man's tongue.
There are no outside traces of eyes. Those organs are not even indicated by a pigmentary spot visible under the skin. The external ear is represented by a small roundish hole. The tail is singular, having the form of a truncated cone; is bare, ringed. hidden to a considerable extent by the hairs of the back, but fully visible from below, It is swelled out near the middle by two considerable lateral tuberosities. The fore feet are similar to those of the Chrysochlores. The two large arched and compressed nails of the third and fourth digits conceal the others, with the exception of the obtuse and corneous nail of the fifth digit, which is turned back and inserted at the base of the fourth. On examining the narrow palm of this paw, we can discover the thin, atrophied nails of the thumb and second finger. The palm is cleft, and the fingers form two groups: the outer, consisting of the third, fourth, and fifth; and the inner, of the first and second. The hind paws are likewise short and very thick, more robust than those of the Chrysochlores, spade-shaped, have the sole turned outward, are deeply grooved, and bare to the metatarsus. The first four toes are subequal; the fifth is represented by a short nail, much like that of the hand, and flanked by a large, broad, and flat sesamoid bone. The tibia is thick.
The dentition of the Notoryctes comprises forty teeth—ten in each branch of the jaws. The molars resemble those of the Chrysochlores,
|Fig. 2.—Feet of the Notoryctes. 1, 2, and 3, fore foot seen in front, in profile, and from beneath; 4 and 5, hind foot, from above and from beneath.||Fig. 3.—Details or the Skeleton (enlarged). 1 and 2, skull, profile and from beneath; 3 and 4, feet.|
having, like them, V-formed crowns; but the front teeth, especially the incisors, are much smaller than those of the Chrysochlores. This fact is remarkable, considering that the general form of the skull is also strikingly like that of the Chrysochlores. The median incisors are, like those of the Musaraignes and most of the placentary insectivores, scalpriformed, or thick and hooked like the teeth of rodents, and constitute strong organs of prehension which touch on the median line. On the other hand, the front teeth, of the Notoryctes are small, hardly more than pegs, and leave a considerable gap on the median line, a disposition like that observed in some of the edentates. It might be well to compare this dentition with that of the Myrmecobia, which is also Australian, and with that of some of the types of Eocene fossil mammals which have recently been discovered in
Fig. 4.—Notoryctes. (View of the under side; two thirds the natural size.)
South America. The angular apophysis of the lower jaw is markedly bent within, a tolerably constant characteristic of the opossums. The marsupial bones, on the other hand, are but little developed. They are represented only by two small osseous nodules diverging forward and united in the tendon of the oblique external muscle of the abdomen at its insertion on the symphysis of the pubis. They are hardly visible with the lens, and might easily pass undetected in a hasty or superficial dissection. Nothing is yet known of the method of reproduction of the Notoryctes.
As a whole, we are struck by the resemblances exhibited between the Notoryctes and the African Chrysochlores; the forms of the skull, of the molar teeth, and of the fore limb are such as to lead us to suppose something more than a simple secondary adaptation depending on an identical mode of life. The unlikeness, on the contrary, between the incisors and the canine teeth of the two types is deserving of closer study. It is of interest to recollect that these two genera are not the only ones which establish by their outer forms a bond of relationship between the South African and the Australian fauna. The Pedetes (Helamy), or great jerboa of the Cape, exhibits absolutely the forms of the Australian kangaroos, although it is a placentary rodent. There are also well-known relations between the South African and the Australian flora.—Translated for The Popular Science Monthly from La Nature.
[Mr. J. Douglas Ogilby has reached the conclusion, after a careful study of Mr. Stirling's accounts of this animal, that in it we have at last obtained a definite connecting link between the Monotremes (Ornithorhyncus) and the Marsupials (kangaroos and opossums). At the present state of our knowledge it would, he thinks, be presumptuous to class Notoryctes among the Monotremes proper, although several naturalists incline to the opinion that its affinities are closer to those animals than to the Marsupials.—Ed. P. S. M.]
- From an examination of the osteology, we should say that the hind feet of the Notoryctes are similar in form to the fore feet of the real moles.