Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: June 21, 2025
These sands repose upon the Upper Lias clays in the south and west of England. The Collyweston slate, formerly classed with the Great Oolite, and supposed to represent in Northamptonshire the Stonesfield slate, is now found to belong to the Inferior Oolite, both by community of species and position in the series.
As most of the Placentals have not this process, we can, with some probability, recognise the Marsupial from this feature alone. Most of the mammal remains that we have from the Jurassic and Cretaceous deposits are merely lower jaws, and most of the jaws found in the Jurassic deposits at Stonesfield and Purbeck have the peculiar hook-like process that characterises the lower jaw of the Marsupial.
So far as the imperfect materials which exist enable a judgment to be formed, the same law appears to have held good for all the earlier Mesozoic Mammalia. Of the Stonesfield slate mammals, one, Amphitherium, has a definitely Australian character; one, Phascolotherium, may be either Dasyurid or Didelphine; of a third, Stereognathus, nothing can at present be said.
The jaw would thus be deposited immediately, while the rest of the body would float and drift away altogether, ultimately reaching the sea, and perhaps becoming destroyed. The jaw becomes covered up and preserved in the river silt, and thus it comes that we have such a curious circumstance as that of the lower jaws in the Stonesfield slates.
Small quadrupeds frequenting trees, and feeding on insects, would be those most likely both to be drifted away from their native lands and to find fit food in a new one. Insectivorous mammals, like in size to those found in the Trias and the Stonesfield slate, might naturally be looked for as the pioneers of the higher vertebrata.
Between forty and fifty pieces or sides of lower jaws with teeth have been found in oolitic strata in Purbeck; only five upper maxillaries, together with one portion of a separate cranium, occur at Stonesfield, and it is remarkable that with these there were no examples in Purbeck of an entire skeleton, nor of any considerable number of bones in juxtaposition.
But a reptile about two feet long, called Compsognathus, lately found in the Stonesfield slate, makes a much greater approximation to the class Aves than any Dinosaur, and therefore forms a closer link between the classes Aves and Reptilia than does the Archaeopteryx.
These observations are made to prepare the reader to appreciate more justly the interest felt by every geologist in the discovery in the Stonesfield slate of no less than ten specimens of lower jaws of mammiferous quadrupeds, belonging to four different species and to three distinct genera, for which the names of Amphitherium, Phascolotherium, and Stereognathus have been adopted. Tupaia tana.
Next anterior in age are the mammalia of the Lower Oolite of Stonesfield, of which four species are known, also very small and probably marsupial, with one exception, the Stereognathus ooliticus, which, according to Professor Owen's conjecture, may have been a hoofed quadruped and placental, though, as we have only half of the lower jaw with teeth, and the molars are unlike any living type, such an opinion is of course hazarded with due caution.
Stonesfield Slate. Fossil Mammalia. Fuller's Earth. Inferior Oolite and Fossils. Northamptonshire Slates. Yorkshire Oolitic Coal-field. Brora Coal. Palaeontological Relations of the several Subdivisions of the Oolitic group.
Word Of The Day
Others Looking