Morganucodon

Morganucodon is an extinct early mammaliaform known from Late Triassic and Early Jurassic fossils. Its anatomy combines mammal-like teeth and jaw joints with features retained from earlier synapsids.

Mammaliaformes: Mammaliaformes are mammals and their closest extinct relatives, defined by shared anatomical features. Morganucodon belongs to this group, broader than crown mammals.
Tribosphenic molar: A tribosphenic molar combines shearing surfaces with a basin that crushes or grinds food. Morganucodon molars were not tribosphenic, showing that this later design was not universal early on.
Triassic–Jurassic extinction event: The Triassic–Jurassic extinction event was a major loss of biodiversity around 201 million years ago. Morganucodon fossils span this boundary, placing its history amid major ecological change.
Pant-y-ffynnon Quarry: Pant-y-ffynnon Quarry is a fossil site in South Wales known for Mesozoic vertebrate remains. Its deposits have yielded Morganucodon fossils alongside other small vertebrates.
Synapsid: Synapsids are amniotes whose skulls typically have one temporal opening behind each eye. Morganucodon inherited its deep evolutionary history from this lineage.
Molar: Molars are posterior teeth specialized for crushing, grinding, or shearing food. Morganucodon’s distinctive molars provide evidence about its diet and chewing.
Early Jurassic: The Early Jurassic is the first epoch of the Jurassic Period, following the Triassic. Many Morganucodon fossils come from rocks of this epoch.
Morganucodon watsoni: Morganucodon watsoni is a species of Morganucodon named from fossil material found in Wales. It is the best-known species used to characterize the genus.
Dentary: The dentary is the main tooth-bearing bone of the lower jaw in vertebrates. Its enlarged dentary participates in the jaw transition visible in Morganucodon.
Mammalian middle ear: The mammalian middle ear transmits sound through the malleus, incus, and stapes. Morganucodon retained jaw-associated bones that later became part of this hearing system.

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