E Sarcophaga. This is the last section of the existing Marsupials, and includes a number of predaceous and rapacious forms, which fill the place held elsewhere by the true Carnivora. They are distinguished by the fact that the intestine is destitute of a caecum, and by their strictly carnivorous dentition, the canines being strong, long, and pointed, whilst the molars and praemolars have cutting edges furnished with three cusps (fig. 364, C). The best-known species of this section are the Thy-lacinus cynocephalus and the Dasyums ursinus. The former of these is the largest of the rapacious Marsupials, being about as big as a shepherd's dog. It is a native of Van Diemen's Land, and is known to the colonists as the "hyaena." Its head is very large, and the back exhibits several transverse black bands. The marsupial bones are peculiar in being represented only by permanent cartilages, and the marsupium opens backward. It lives in caverns and amongst the rocks in the wildest parts of the colony, and its numbers have been very much reduced by the constant war waged upon it by the settlers. The Dasynrus ursinus is also a native of Van Diemen's Land, where it is known as the "native devil." Though smaller than the Thylacine, the Dasyurus is extremely ferocious, and is capable of committing great havoc amongst animals even as large as sheep. The dental formula of Dasyurus is:
4 - 4
1 - 1
2 - 2
4 - 4
3 - 3
1 - 1
2 - 2
The praemolars and molars are remarkable in the fact that they, all of them, possess sharp, serrated, cutting edges.
As regards their distribution in time, the Marsupials are probably the oldest of Mammals hitherto discovered; but owing to the detached and fragmentary condition of almost all Mammalian remains - consisting mostly of the ramus of the lower jaw, or of separate teeth - it is not possible to state this with absolute certainty. The Microlestes of the Trias, the oldest, or nearly the oldest, of the Mammals, known only by its molar teeth (fig. 369), was probably a Marsupial; but the evidence upon this point is not conclusive. In the Triassic rocks of America, also, perhaps at a lower horizon than that at which Microlestes occurs in Europe, has been found the jaw of a small Mammal, which is probably Marsupial, and has been named Dromatherium (fig. 368).
Fig. 367. - Myrmecobius fasciatus.
Fig. 368. - Lower jaw of Dromatherium sylvestre. Trias, North Carolina. (After Emmons.)
Fig. 369. - a Molar tooth of Micro-lestes antiquus, magnified; b Crown of the same, magnified still further. Trias, Germany.
In the next mammaliferous horizon, however - namely, that of the Stonesfield Slate in the Lower Oolites - there is no doubt but that some of the Mammalian remains, if not all, belong to small Marsupials (fig. 370). From this horizon the two genera, Phascolotherium and Amphitherium are almost certainly referable to the Marsupialia; the latter seeming to be most nearly related to the living Myrmecobius, whilst the former finds its nearest living ally in the Opossums of America. The Stereo-gnathus of the Stonesfield Slate is in a doubtful position. It may have been Marsupial; but, upon the whole, Professor Owen is inclined to believe that it was placental, hoofed, and herbivorous.
In the middle Purbeck beds (Upper Oolite), where fourteen species of Mammals are known to exist, it is probable that all were Marsupial. All the Purbeck Mammalia were of small size, the largest being no bigger than a polecat or hedgehog. They form the genera Plagiaulax, Triconodon, and Galestes, of which Plagiaulax is believed to be most nearly allied to the living Kangaroo-rat (Hypsiprymnus) of Australia.
Fig. 370. - Oolitic Mammals, natural size. 1. Lower jaw and teeth of Phascolotherium 2. of Triconodon; 3. of Amphitherium; 4. of Plagiaulax.
In the Tertiary series of rocks Marsupials are of rare occurrence; but Opossums, closely allied to the existing American forms, have been discovered in the Miocene and Eocene rocks of Europe, and have been referred to a distinct genus under the name of Peratherium. It is also interesting to note that the Upper Jurassic beds have recently yielded to the researches of Professor Marsh the first fossil Marsupials which have been detected in the North American continent in beds older than the Post-pliocene, and that these belong to an extinct type of the at present exclusively American family of the Didelphidae.
The next occurrence of Marsupials is in the later Tertiary (Pliocene) and in the Post-tertiary epoch; and here they are represented by some very remarkable forms. The remains in question have been found in the bone-caves of Australia - the country in which Marsupials now abound above every other part of the globe; and they show that Australia, at no distant geological period, possessed a Marsupial fauna, much resembling that which it has at present, but of forms comparatively of a much more gigantic size. In the remains from the Australian bone-caves almost all the most characteristic living Marsupials of Australia and Van Diemen's Land are represented; but the extinct forms are usually of much greater size. We have Wombats, Phalangers, Flying Phalangers, and Kangaroos, with carnivorous Marsupials resembling the recent Thyla-cinus and Dasyurus. The two most remarkable of these extinct forms are Diprotodon and Thylacoleo. In most essential respects Diprotodon resembled the Kangaroos, the dentition, especially, showing many points of affinity. The hind-limbs, however, of Diprotodon were by no means so disproportionately long as in the Kangaroos. In size Diprotodon must have many times exceeded the largest of the living Kangaroos, since the skull measures three feet in length (fig. 371). The affinities of Thylacoleo are disputed. The great feature in the dentition is the presence in either jaw of one huge, compressed, and trenchant praemolar. This is regarded as corresponding to the great cutting praemolar of the Kangaroo-rats (Hypsiprymnus). Upon the whole, therefore, Professor Flower concludes that "Thylacoleo is a highly modified and aberrant form of the type of Marsupials now represented by the Macropodidae and Phalangistidae, though not belonging to either of these families as now restricted," and he believes that its diet was of a vegetable nature. On the other hand, Professor Owen is of opinion that Thylacoleo was probably carnivorous in its habits. This distinguished naturalist thus regards Thylacoleo as an ancient form of the Dipro-todont Marsupials (Kangaroos, etc.), adapted for carnivorism, but not anatomically related to the true Carnivorous or Poly-protodont Marsupials (such as Thylacinus and Dasyurus). Under any view of its habits, Thylacoleo is a very remarkable type of the Marsupials; and it must have attained a very great size, since the length of the crown of the great praemolar is not less than two inches and a quarter.
Fig. 371. - Skull of Diprotodon australis.