Snow Hill Island Formation
The Snow Hill Island Formation is an Early Maastrichtian geologic formation found on James Ross Island, James Ross Island group, Antarctica. Remains of a paravian theropod Imperobator antarcticus have been recovered from it, as well as the elasmarian ornithopods Trinisaura santamartaensis, "Biscoveosaurus" and Morrosaurus antarcticus, the ankylosaurian Antarctopelta oliveroi, and the shark Notidanodon sp. Alongside these described genera are also the remains of indeterminate elasmosaurids, lithostrotian titanosaurs and an indeterminate pterosaur.
In the Herbert Sound Member of the Snow Hill Island Formation, bivalves, ammonites, and fish were found.
Plants
During the Campanian–Maastrichtian, the Antarctic Peninsula supported temperate, humid forests dominated by podocarps, araucarian conifers, and a diversifying group of angiosperms. Key angiosperm families included Nothofagaceae, Monimiaceae, Cunoniaceae, Proteaceae, Myrtaceae, Lauraceae, Atherospermataceae, Winteraceae, and extinct Sassafras-like forms. Another important group is Asteraceae, with Dasyphyllum-like pollen, the oldest fossils ever found for the family. At The Naze area, Podocarpaceae-Nothofagus rainforests thriving in lowland areas under cool-temperate, frost-free, and high-rainfall conditions, with understories rich in other angiosperms and ferns. Smaller components, likely endemic, included lycophytes, bryophytes, Proteaceae, Liliaceae, Palmae or Microthyriaceae, and various herbaceous or shrubby dicotyledons. Forests were structurally similar to modern Valdivian temperate forests. These plants were primarily found in riparian floodplains, with bryophyte-lycophyte rich swamps and Chlorophyta-rich lake margins, while influence of marine waters can be seen by Dinoflagellates. The climate was highly humid and seasonal, as evidenced by distinct growth rings in Agathoxylon fossil wood from Lachman Crags and The Naze, indicating a temperate but variable environment. The flora reflects a transition from gymnosperm-dominated to mixed angiosperm-conifer ecosystems under polar greenhouse conditions.