Context:

• A fossilised skull of a small critter found in Utah underneath a dinosaur foot bone is providing insight into one of the most primitive mammalian groups and has scientists rethinking the timing of the break-up of Earth’s bygone supercontinent Pangaea.
• Scientists described the cranium of a small primitive Cretaceous Period mammal called Cifelliodon wahkarmoosuch, about the size of a small hare, that lived 130 million years ago, boasting traits suggesting it possessed a keen sense of smell and may have been nocturnal.

About Cifelliodon wahkarmoosuch

• It’s a plant eater, as we can tell from its herbivorous teeth.
• From the sediments in which it was preserved, likely it lived on the banks or flood plain of a small river.
• The three-inch skull was well preserved and nearly complete, unlike the usual scrappy fossils of the group to which Cifelliodon belonged, called haramiyidans.
• The earliest primitive mammals evolved during the Triassic Period, when dinosaurs also first appeared, from creatures that combined reptilian and mammalian characteristics.
• Haramiyidans appeared close to the dawn of the mammalian lineage, with the earliest-known representative living about 208 million years ago and the last-known member perhaps about 70 million years ago.
• The skull was unwittingly excavated at a site north of Arches National Park in eastern Utah. The palaeontologists from Utah Geological Survey did not know it was entombed in rock brought back to a lab for study until they looked under a foot bone of a two-legged plant-eating dinosaur called Hippodraco.
• Compared to modern mammals, Cifelliodon had a simple, tube-like brain, lacked complex bony structures usually associated with the front part of the brain case and nasal region, and had simple tooth roots, among other primitive features.
• The discovery of Cifelliodon, which had a close contemporaneous relative in Africa, suggests there were still connections between the northern hemisphere continents and those in the southern hemisphere 15 million years later than previously believed.

Source:TH