AGGLUTINATED OR PORCELANEOUS TESTS: WHERE TO DRAW THE LINE?

摘要

The simple, tubular foraminifer Glutameandrata vallieri n. gen., n. sp. is formally described from Spring Creek, one of the most fossiliferous Late Triassic localities of North America (Martin Bridge Formation, Wallowa terrane, Oregon, USA). Uncoiled in the final stage, this new benthic form displays an initial meandrospiroid arrangement, a coiling mode typically observed in coeval porcelaneous foraminifers. Yet, we demonstrate through a comparative study of diagenetic results that the wall of G. vallieri n. gen., n. sp. is, in fact, finely agglutinated. Agglutinated meandrospiroid foraminifers, here encompassed by the family Glutameandratidae n. fam., are sporadically but continuously observed in Triassic-Recent rocks. Their potential phylogenetic relationships and their significance to define the relative taxonomic importance of wall characteristics versus coiling mode are discussed.