Marsupium

“ An animal born so premature as the little opossum must necessarily perish from exposure, were it not for the curious provision for its protection and the constant supply of milk afforded in the pouch of the female. The internal cavity of the adult female marsupium seems to be formed by an infolding of the external skin. ”

“ When those phalanges are clad with hoofs or covered by a nail they end in a rounded and flattened termination. On the other hand, when they bear a claw they are themselves sharpened at the extremity and often grooved above.
The Marsupium.—It may appear to be unnecessary at this juncture to speak of the marsupial pouch, which is so usually believed to be a characteristic of the group Marsupialia. Rudiments of this structure have, however, been recently discovered in the higher mammals, and, as Dr. ”

“ Marsupials are also found in America; but, with this exception, they now exist only in Australia and in the adjacent islands New Guinea and Tasmania, which is evidence that the latter islands were at one time united with Australia.
The marsupials are so called from their having a pouch (marsupium) for carrying the immature young. The young are born without much development, and they are at once transferred to the pouch, where they continue to grow until they are able to take care of themselves. The pouch is supported by the marsupial bones, which are equally developed in both sexes. ”

“ The first definite proof of the occurrence of a pouch in any mammal not a Marsupial or a Monotreme was made by Malkmus, who found this structure in a Sheep. It seems, however, that the structures found in the higher mammals are not always comparable to the marsupium of the Marsupials, but sometimes to the mammary pouch of the Monotreme. That the Marsupials are a side line, and not involved in the ancestry of the Eutheria, is an opinion which is at present widely held. ”

“ In standard works on natural history the animals under consideration are classed as mammiferous Didelphæ. They are brought forth in an imperfect state, and during their transitional condition are suckled in a pouch supported by bones called marsupial, which are attached by their extremities to the pelvis, and serve to support the marsupium, whence the animals provided with these provisions for bringing up their progeny are called Marsupial Mammals. The Opossum, Kangaroo, and Ornithorhynchus are existing representatives of this group. ”

“ The majority live parasitically in the marsupial pouches of female Amphipods, Isopods, Mysidae, and Cumacea, e.g. Sphaeronella and Stenochotheres in the marsupia of Gammarids; but Choniostoma occurs in the branchial cavity of Hippolyte, Homoeoscelis is common in the branchial cavity of Diastylis and Iphinoe, and Aspidoecia on the outside of the body of the Mysid Erythrops. The males and females live together in the same marsupium, but the adult males retain the power of roving about, and do not feed so much as the females, though their mouth-parts are similarly constructed (Fig. 47) . ”

“ The pupil is horizontal, the tongue can be protruded but little; the tympanum is free, and the adhesive discs of the fingers and toes are well developed. These "marsupial frogs," of which about half-a-dozen species are known, live chiefly in the tropical forest-region of South America, notably from Peru to Venezuela.
N. marsupiatum is green with darker blue-green spots, or with longitudinal patches which are each surrounded by a whitish or yellow seam of little dots. The limbs have cross-bars. Total length about 21⁄2 to 3 inches. The eggs of this species are comparatively small and numerous. ”

“ All ten are absent in other mammals, significantly confirming the monophyly of marsupials (p = 2.0×10−5; [10 0 0] [15] ) .
The other 43 phylogenetically informative retroposon markers provide significant support for most of the basal splits within marsupials. The earliest marsupial divergence was previously impossible to resolve based on sequence data, which could not distinguish between Paucituberculata and Didelphimorphia as the sister group to Australidelphia [14] , [16] – [17] . ”

“ In the higher Eocene deposits, this group is more abundant, but still represented by small animals, most of them insectivorous, or carnivorous in habit, like the existing opossum. From the Miocene and Pliocene, no remains of Marsupials have been described. From the Post-Tertiary, only specimens nearly allied to those now living are known, and most of these were found in the caves of South America.
The Edentate [3] Mammals are evidently an American type, and on this continent attained a great development in numbers and size. ”

“ As this inferior condition of living Marsupialia shows this order to hold an intermediate place between viviparous and oviparous animals, forming, as it were, a link between Mammalia and Reptiles; the analogies afforded by the occurrence of the more simple forms of other classes of animals in the earlier geological deposites, would lead us to expect also that the first forms of Mammalia would have been Marsupial. ”

“ In the "Animal Kingdom" of the great naturalist just named, the marsupiata, or pouched animals, are made to occupy the fourth place among the nine orders of the Mammalia; but should they not rather occupy a place intermediate between the placental mammals and the birds? and does not nature indicate their true position by the position which she assigns to them in the geologic scale? The birds are oviparous; and between the extrusion of the egg and the development of the perfect young bird they have to hatch it into life during a long period of incubation. ”

“ Returning now to our subject from this geological digression—which will hardly be deemed unprofitable, since I have given you in few words the results of a great deal of my own hard mountain work—let us consider the Tertiary mammals, as we know them front the remains already discovered, and attempt to trace the history of each order down to the present time. We have seen that a single small Marsupial, from the Trias, is the only mammal found in all the American rocks below the Eocene; and yet in beds of this age, immediately over the Chalk, fossil mammals of many different kinds abound. ”

“ But the marmose is smaller, and his snout sharper; the female has no pouch under the belly, she has only two loose skins near the thighs, between which the young fix themselves to the teats. The parts of generation of the male and female marmose resemble, by their form and their position, those of the opossum. When the young are brought forth, and fix themselves to the teats, they are not so big as small beans. ”

“ The monotremes or egg-laying types of mammals such as the duck-bill and spiny anteaters which now inhabit Australia are almost unknown as fossils. Marsupials, the next higher living group, which includes the opossum and kangaroo, appeared at the end of Cretaceous time along with the placentals or higher mammals which dominate the history of the Cenozoic era. Nevertheless, there are a few teeth and jaws from rocks of Triassic and Jurassic age to indicate that small mammals, from the size of mice to slightly larger than rats, existed throughout most of the Age of Reptiles. ”

“ The four Australasian orders share a single origin with Microbiotheria as their closest sister group, supporting a clear divergence between South American and Australasian marsupials. In addition, the new data place the South American opossums (Didelphimorphia) as the first branch of the marsupial tree. The exhaustive computational and experimental evidence provides important insight into the evolution of retroposable elements in the marsupial genome. Placing the retroposon insertion pattern in a paleobiogeographic context indicates a single marsupial migration from South America to Australia. ”

“ The Eocene period has been defined in the last chapter as that in which the existing orders and families of the placental mammalia appear for the first time. The Eocene marsupials, however, are, as may be expected from their class having appeared in the Secondary age, in a far more advanced stage of evolution, being represented by a living genus, [3] the opossum, as well as by other forms intermediate between the marsupials and the true placental mammals. ”

“ I have not failed to observe much disparity in size in the Marsupiata; they seem to be always growing; for the males get larger and still larger for years, even long after they have commenced the duty of reproduction, and hence individuals of all sizes occur, and occasionally one extraordinarily large may be met with. I have observed this in all the Marsupials, but particularly among the Kangaroos. The great herds of the grey species, Macropus major, are frequently headed by an enormous male, or Boomer as he is called. ”

“ The three sub-classes of Mammalia—as we have already seen—stand in such a relation to one another that the291 Marsupials, both as regards their anatomy and their ontogeny and phylogeny, form the direct transition from the Monotrema to Placental animals (p. 247) . Consequently, human ancestors must also have existed among Marsupials. They originated out of the Monotrema—which include the primary Mammalia, or Promammalia—by the division of the cloaca into the rectum and the urogenital sinus, by the formation of a nipple on the mammary gland, and by the partial suppression of the clavicles. ”

“ We had a glimpse of the museum, by courtesy of the American gentleman who is curator of it. It has samples of half-a-dozen different kinds of marsupials— [A marsupial is a plantigrade vertebrate whose specialty is its pocket. In some countries it is extinct, in the others it is rare. The first American marsupials were Stephen Girard, Mr. Astor and the opossum; the principal marsupials of the Southern Hemisphere are Mr. Rhodes, and the kangaroo. I, myself, am the latest marsupial. Also, I might boast that I have the largest pocket of them all. But there is nothing in that.] ”

“ You lie!" screamed Bram. "I have shown to all the world that phascalotherium, amphitherium, amblotherium, spalacotherium, and many other orders are to be found in the Upper Jurassic rocks of England, Wyoming, and other places. You—you are the man who denied the existence of the nototherium, of the marsupial lion, in pleistocene deposits! You denied that the dasyuridae can be traced back beyond the pleistocene. And you stand there and lie to me, when you are at my mercy!"
"For God's sake don't aggravate him," whispered Tommy to Dodd. "Don't you see that he's insane? ”

“ This pouch is supported by two characteristic marsupial bones, also existing in Cloacal animals, but not in Placental animals. The young Marsupial animal is born in a much more imperfect form than the young Placental animal, and only attains the same degree of development which the latter possesses directly at its birth, after it has developed in the pouch for some time. ”

“ Side by side with this wonderful outgrowth of the mammalian type, in the first plasticity of its vigorous youth, the older marsupials die away one by one in the geological record before the faces of their more successful competitors; the new carnivores devour them wholesale, the new ruminants eat up their pastures, the new rodents outwit them in the modernized forests. At last the pouched creatures all disappear utterly from all the world, save only Australia, with the solitary exception of a single advanced marsupial family, the familiar opossum of plantation melodies. ”

“ Owen in 1846 to prove that the inflection of the angular process of the lower jaw was not sufficiently marked to entitle the osteologist to infer that this quadruped was marsupial, as the process is not bent inwards in a greater degree than in the mole or hedgehog. Hence the genus amphitherium, of which there are two species from Stonesfield, must be referred to the ordinary or placental 139 type of insectivorous mammals, although it approximates in some points of structure to the myrmecobius and allied marsupials of Australia. ”

“ The order of living marsupials presents remarkable diversity of structure and habits, containing herbivorous, insectivorous, and carnivorous species; yet we find all these traits combined in one and the same species, the opossum. It is probable that, by adaptation to similar modes of life, the marsupials have developed groups parallel to those of the placental mammals. However, it is certain the Quadrumana seem represented by the Phalangers, the Carnivora by the Dasyuri, Insectivora by the Phascogales, Ruminantia by the kangaroos, and Edentata by the Monotremes. ”

“ That the young opossums stick to the teats of the mother till they have acquired strength, and a sufficient growth to move with ease, is a fact not to be doubted; nor is it peculiar to this species only, since we have seen it in that of the marmose. The female marmose [246] has not, like the opossum, a bag under the belly; it is not, therefore, in consequence of the assistance which the young receive from the pouch that they stick so long to the teats, and increase in that immoveable situation. ”

“ Professor Leidy describes, besides Omomys above referred to, some other fossils from the Eocene of Wyoming, which he seems to regard as Insectivorous in habit, but Marsupial in structure; and the Stonesfield Mammals, although plainly Marsupial, have Insectivorous tendencies, so that the derivation of the type Insectivora from the Marsupials, or at all events the near affinity of the two orders, perhaps at several points of contact, may be looked upon as established. ”

“ As all the above-mentioned Purbeck marsupials, belonging to eight or nine genera and to about fourteen species, insectivorous, predaceous, and herbivorous, have been obtained from an area less than 500 square yards in extent, and from a single stratum no more than a few inches thick, we may safely conclude that the whole lived together in the same region, and in all likelihood they constituted a mere fraction of the mammalia which inhabited the lands drained by one river and its tributaries. ”