Marine faunal realms of the Mesozoic: review and revision under the new guidelines for biogeographic classification and nomenclature

Consensus among the Friends of Paleobiogeography produced tentative guidelines to the classification and nomenclature of marine biogeographic units, i.e. biochores. Based on these loose ‘rules’, the present paper is a critical review of all published Mesozoic marine Realms, Subrealms, and ?Superrealms (formerly called ‘climatic belts’).Biochores are defined by the overall endemism within geographic and time envelopes that include choro- and chrono-types, without consideration of facies or climate. The hierarchy of ranks or tiers is: ?Superrealm, Realm, Subrealm, Province, Subprovince (only ranks in italics are obligatory); ‘region’ is informal. These ranks scale with endemism, geographic range, and persistence in time. Biochores are named geographically, following nomenclatural guidelines (not strict rules) of synonymy and homonymy, with priority beginning with Uhligʹs paper of 1911. Uhligʹs two ‘climatic belts’ are tentatively accepted as optional, top-ranking ‘Superrealms’ for times of exceptional global endemism; available names for them are ‘Euroboreal’ (or ‘Panboreal’, new) and ‘Tethys–Panthalassa’. The validity of the 29 existing names for realm-group biochores (Realms, Subrealms and Superrealms) in the marine Mesozoic is discussed; 19 names are rejected for a variety of reasons, including synonymy, homonymy and usefulness. The most important realm-group biochores are: Arctic and Boreal–Atlantic in the Boreal/?Euroboreal Realm or ?Superrealm; and Tethyan, Mediterran–Caucasian, Indo-Pacific (Jurassic–Early Cretaceous) and Austral (Middle–Late Cretaceous) in the ?Tethys–Panthalassa ?Superrealm.