A Major Eocene Sponge Fauna (Castle Hayne Formation, North Carolina)

Abstract

Abstract The Castle Hayne Formation (Middle and Upper Eocene, North Carolina) contains a rich, diverse and well-preserved sponge fauna, equaled among known Tertiary faunas only by the Eocene fauna of Western Australia and the Miocene fauna of Algeria. It includes among Calcarea two genera of lithonines, (3 new species); among Demospongia one hadromerine, two genera of choristids (2 new species), one cephalorhaphiditid (new genus and species), and three genera and species of plinthosellid lithistids (2 new species); and among Hexactinellida four genera of hexactinosan hexactinellids (1 new genus, 1 new subgenus, 2 new species), two genera of lychniscosan hexactinellids (1 new genus, 2 new species), and a new genus and species of lyssacine hexactinellid. Noteworthy are whole fossil specimens of Geodia and Stelletta (Stolleya), two new genera (one of which is extremely abundant) of cup-shaped hexactinellids with radial fins, and the first fossil species of the Recent genus Verrucocoeloidea. Two faunal facies are recognized: a near-shore one dominated by demosponges and an off-shore one dominated by hexactinellids (with lithonine Calcarea), a pattern known from other published Cretaceous and Tertiary faunas. The off-shore facies is dated from associated fossils as late Claibornian (Auversian); the near-shore facies is probably of approximately the same age because of some common species. The prominence of the extinct plinthosellid lithistids and the absence of rhizomorines and megamorines is noteworthy. All the genera have close relatives in the Cretaceous; all but the plinthosellids have living relatives as well, and five genera are still extant. It is noteworthy that this Eocene fauna is richer than any known North American Cretaceous sponge fauna, even though the Cretaceous was elsewhere very sponge-rich.