Order Leucosolenida Hartman, 1958

Abstract

Leucosolenida Hartman (Calcarea, Calcaronea) is emended here to include nine families, and 42 genera. Leucosolenida seems to have evolved from the olynthus grade, a form that is probably present in the early stages of ontogenesis of all Leucosolenida, and subsists at the adult stage in Leucosolenia. Leucosolenida comprises a diverse group with several pathways of progressive complexity of form, starting with sponges of a simple sycettid organization and leading to sponges with a complex aquiferous system and skeleton. Increase in size from the sycettid grade of organization may occur by two different processes: (1) the growth and elongation of radial tubes increasing the thickness of the sponge body (seen in the Sycettidae-Grantiidae line and the Heteropiidae), or (2) the growth of the central tube containing the atrial cavity which increases the length of the sponge body (seen in the Jenkinidae and the simple forms of Amphoriscidae).