MULTITUBERCULATA  , a

group of extinct mammals, mostly of small size, whose remains are met with in strata ranging from the Trias to the Eocene, both in Europe and in North America . They are mostly known by their lower jaws, and take their name from the fact that the grinding teeth (fig . 2, m . 1 and 2; and fig . 3 a. b. c.) bear two or three longitudinal rows 0f tubercles, or are provided with tubercles round the edges . From this feature these otherwise unknown animals are believed to be related to the existing egg-laying mammals (duck-billed platypus and spiny ant-eater), constituting the order Monotremata, and are therefore provisionally placed near that group . The largest representative of the Multituberculata is Polymastodon from the Lower Eocene of New Mexico; the same beds also yield the smaller Ptilodus; while from corresponding strata at Rheims, in France, has been obtained the nearly allied Neoplagiaulax . The latter takes its name from its resemblance to Plagiaulax (figs . 1 and 2) from the Purbeck bras . m strata of Swanage, Dorsetshire, which was one of the first-known members of the group . These have cutting teeth in front and multituberculate molars behind . Allodon and Ctenacodon represent the group in the Cretaceous of North America; and the English Purbeck genus Bolodon, in which all the cheek-teeth are multituberculate, also belongs here .

Stereognathus (fig . 3) is another English Upper Oolitic type . Single teeth from the

Rhaetic of England and Wurttemberg described as Microlestes apparently indicate the earliest member of the group . A skull from the Upper Triassic Karoo beds of South Africa described as Tritylodon longaevus, which has multituberculate molar teeth, was also at first placed in this group, but has been subsequently regarded as a reptile, although Dr R . Broom considers that the Fig . 2.-Lower Jaw of Plagiaulax FIG . 3.-Fragment of Jaw of minor, from Swanage. p . 1-4 Stereognathus oolithicus in premolars ; m . 1 and 2 molars. matrix. a b c, molars . original determination is correct . Possibly a fore-limb from the same formation described as Theriodesmus phylarchus indicates a similar or allied animal . Not improbably Tritylodon indicates a direct link between the multituberculate mammals and the anomodont reptiles of the Permian and Trias .

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