Ordovician – Early Silurian
Heterospongia is an extinct genus of stationary epifaunal suspension feeders
Identification in Hand Sample:
- Branching, twiglike to lobate sponges without a central spongocel
- Exteriors may be smooth or somewhat nodose
- Pores may be circular, polygonal or elongate of irregular size
- Few oscula, distinguished by their larger size and surrounded by radiating channels
Fossils of Ohio (1996):
- The genus Heterospongia Ulrich includes branching, twiglike to lobate sponges without a central spongocel. Their exteriors may be smooth or somewhat nodose and may have circular, polygonal or elongate skeletal pores of irregular size and distribution. Larger pores appear to be openings of excurrent canals and smaller ones of incurrent canals. The skeletal net generally consists of subvertical principal fibers along the axial region that curve upward and outward toward the outer surface. These fibers are connected in an irregular way by fibers essentially normal to the principal ones. Both types of fibers are composed of closely packed heloclonid monaxial spicules and perhaps other smooth monaxons, arranged basically parallel to the fiber surface , although the skeletal structure is not well defined.
- Heterospongiaappears similar to Dystactospongia Miller but differs in having a finer textured skeleton, a more twiglike growth form, and the possible possession of oxeas or styles (monaxons with one blunt end and one pointed end) in the skeleton. Heterospongiaoccurs in Upper Ordovician rocks of Kentucky, Ohio, and Minnesota.
Treatise on Invertebrate Paleontology, Part E (1955):
- Like Dystactospongia, sublobate.
- Sponge sublobate or of compressed branches, surface showing mouths of branching, more or less tortuous canals which curve outward from the center. A few oscula present, distinguished by their larger size and surrounded by radiating channels. Sponge skeleton between the canals of variable thickness, sometimes appearing nearly solid, at others of loosely interwoven spicules.
- Sub-lobate, or with irregularly divided, compressed branches.
- “Entire surface exhibiting the mouths of branching and more or less tortuous canals, which begin near the center, where they are nearly vertical, and proceed toward all portions of the surface in a curved direction. A limited number of ‘oscula’, distinguished from the ordinary canals by being larger and surrounded by radiating channels, occasionally present. Sponge skeleton between the canals of variable thickness, sometimes appearing nearly solid, at other times composed of loosely interwoven spicule fibers. None of the specimens show the spicules in a satisfactory manner. From the traces seen it would appear that they are mostly very small, and of the three rayed type” -Ibid, p. 239, 240
- Mr. Ulrich considers this genus related to the preceding, Dystactospongia, remarking that the four or five species of Miller’s genus known to him are parasitic, or form amorphous masses. But two species of Dystactospongia have so far been described.