Middle Jurassic

The Middle Jurassic is the most poorly represented epoch in mammalian history. Most of the known record comes from Britain, where several faunules and localities have been reported. Several isolated occurrences ofprobable or possible Jurassic age are known from China; and the La Boca Formation, Mexico (discussed earlier), has yielded three mammals that may be Early or Middle Jurassic in age. A single specimen recently described from Madagascar is Bathonian in age. Middle Jurassic mammalian assemblages include both primitive (Morganucodontidae) and advanced ("Amphilestidae") "triconodonts," aberrant "symmetrodontans," and, notably, the first appearance of "eupantotherians"—a group that possibly gave rise to northern tribosphenic mammals. Docodonta, possibly present as early as the Late Triassic, are surely represented in Middle Jurassic assemblages of Britain. Of Allotheria, the Late Triassic-Early Jurassic haramiyids and thero-

teinids are no longer present (though haramiyids survived in Africa [see chapter 8] until at least the Late Jurassic); instead, the group is represented by the enigmatic eleutherodontids (known only from the Middle Jurassic) and, possibly, Multituberculata, a group that achieved prominence by the Late Jurassic and remained as an important element of terrestrial faunas through the Mesozoic, well into the Tertiary.

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