Baltica data makes it difficult to locate the margin in the Arctic. Ordovician faunas indicate that most of Svalbard, including Bjørnøya, was part of Laurentia, but Franz Josef Land and Kvitøya (an eastern island of the Svalbard archipelago) most likely became part of Baltica in the Timanide Orogeny. The Taymyr Peninsula, in contrast, never was part of Baltica: southern Taymyr was part of Siberia whilst northern Taymyr and the Severnaya Zemlya archipelago were part of the independent Kara Terrane in the early Palaeozoic. The eastern margin, the Uralide orogen, extends from the Arctic Novaya Zemlya archipelago to the Aral Sea. The
Severnaya Zemlya to a survey of prior observations by De Korte, Volkov, and Gavrilo, thirty-two bird species have been observed on Severnaya Zemlya, 17 of which are known to breed on the islands. Eight species are widespread across the archipelago: five of which are colonial seabirds: little auk ("Alle alle"), black-legged kittiwake ("Rissa tridactyla"), black guillemot ("Cepphus grylle"), ivory gull ("Pagophila eburnea"), and glaucous gull ("Larus hyperboreus"); and three species of tundra bird: the snow bunting ("Plectrophenax nivalis"), purple sandpiper ("Calidris maritima"), and brent goose ("Branta bernicla"). The most common mammal on Severnaya Zemlya is the collared lemming ("Dicrostonyx torquatus"), also known