Complex sentence: In 2011, McMenamin reported the discovery of the oldest known adult animal fossils, Proterozoic chitons from the Clemente Formation, northwestern Sonora, Mexico, which has also received no acceptance from other palaeontologists and has not yet been published in a scientific journal following peer review.
Split into simpler sentences: In 2011, McMenamin reported the discovery of the oldest known adult animal fossils, Proterozoic chitons from the Clemente Formation, northwestern Sonora, Mexico. This discovery has not yet been published in a scientific journal following peer review.