Poriferans And Cnidarians

Front 1

Back 1

Kingdom, Animalia

Phylum, Porifera

Class, Demospongea

(Cambrian - Recent)

Hint 1

Sponges with skeletons of spongin, spongin and siliceous spicules, or a skeleton of fused opaline silica. When present, spicules are commonly monaxon, tetraxon, or polyaxon, but never triaxon. Here is an example of a modern demosponge with spongin. Here is a good example of a fossil demosponge. Note in this specimen the canals in the siliceous walls.

Front 2

Back 2

Kingdom, Animalia

Phylum, Porifera

Class, Hexactinellida

(Cambrian - Recent)

Hint 2

Sponges with siliceous spicules that are usually triaxons and commonly fused to form a net or box-like pattern. They are often called glass sponges.

Front 3

Back 3

Kingdom, Animalia

Phylum, Porifera

Class, Calcarea

(Cambrian - Recent)

Hint 3

Sponges that have calcareous spicules as in Astaeospongia or more commonly, non-spicular porous chambers.When spicules are present, they are not fused and are typically monaxons and/or tetraxons.

Front 4

Back 4

Kingdom, Animalia

Phylum, Porifera

"Class, Stromatoporoida" (Ordovician - ?Recent)

Hint 4

Although some texts treats this group as a member of the demospongea, some paleontologists consider stromatoporoids not as true sponges, but belonging to their own phylum. The middle road is taken in this course, treating the stromatoperoids as a separate class within the Porifera. The sheet-like or hemispherical skeletons of stromatoporoids are of two types. The first type have small mounds called mamelons from which canals called astorhizae radiate. This group has horizontal partitions called laminae and vertical partitions called pillars. The space between the laminae and pillars is called the gallery. Compare the image with the accompanying figure below.

Front 5

Back 5

Kingdom, Animalia

Phylum, Archaeocyatha

(Cambrian)

Hint 5

The Archaeocyathids are predominantly an Early Cambrian phylum with no living representatives. They generally have skeletons that formed a porous calcareous cup or cone that resembles later Paleozoic corals. In fact, the archaeocyathids where the reef builders of the Early-Middle Cambrian. The cone-shaped skeletons are commonly constructed of two perforate walls separated by radially arranged vertical blades called septa. As shown in the accompanying figure, the skeletons of archaeocyathids come in two varieties: (i) regulars that have both septa and tabulae but lack dissepiments (small curved plates), and (ii) irregulars that lack septa, but have dissepiments and rod-like bars similar to sponge spicules. This similarity has led some to believe that archaeocyathids belong with the Phylum Porifera. See the diagram below for a representation of an archaeocyathid.

Front 6

Back 6

Kingdom, Animalia

Phylum, Cnidaria

Class, Anthozoa

Order, Tabulata

(Ordovician-Permian)

Hint 6

The exclusively colonial Tabulate corals occur only in the Paleozoic. Their calcite skeletons typically have a lateral wall (epitheca) that separates each rather small corallite. Each of the corallites typically have a tabula that serve as the floor for the polyp. Septa in tabulate corals are either absent or inconspicuous. Although their growth forms vary, they often occur in "honeycomb" or chain-like morphologies.

Front 7

Back 7

Kingdom, Animalia

Phylum, Cnidaria

Class, Anthozoa

Order, Rugosa

(Ordovician-Permian)

Hint 7

The Paleozoic rugosan corals can be either solitary or colonial. Although they may have originally had aragonitic skeletons, all are now calcite. Rugosa corals are distinguished from the other Paleozoic group, the Tabulata, by having dissepiments and well developed septa in addition to the tabulae. As shown in the accompanying figure (Figure 3.1), rugosan corals have six primary septa and new septa are added in only four of the resulting six spaces with none added in the remaining two spaces. This septal arrangement is well illustrated in the external mold where the septa are preserved as gaps.For examples of solitary forms which typically exhibit a cone or horn morphology (hence the informal name "horn corals")

Front 8

Back 8

Kingdom, Animalia

Phylum, Cnidaria

Class, Anthozoa Subclass, Octocorallia

(Precambrian-Recent)

Hint 8

Although octocorals are very abundant in modern oceans, they do not have a good fossil record at all because of their lightly calcitized skeletons. Among the more common octocorals are sea whips and sea fans such as shown by these specimens. - - Other groups of octocorals have even a poorer fossil record because they have only calcitic spicules or non-calcified skeletons. One of the latter group are the sea-pens which have soft, feather-like skeletons.

Front 9

Back 9

Kingdom, Animalia

Phylum, Cnidaria

Class, Hydrozoa

(Precambrian-Recent)

Hint 9

Hydrozoans are a diverse group of cnidarians that inhabit a variety of marine and fresh-water environments. The more important groups (in terms of paleontology) construct their skeletons of calcite. These critters can sometimes superficially resemble corals in skeletal morphology and growth habits, or they can also occur as encrusting sheets or erect blades. Some hydrozoa such as the fire coral Millipora have thick calcareous lamellar skeletons with vertical tubes and cross partitions.

Front 10

Back 10

Kingdom, Animalia

Phylum,Cnidaria

Class, Scyphozoa

(Precambrian-Recent)

Hint 10

Scyphozoa (jelly fish) only occur in marine environments. The are typified by a reduced polyp stage and an extended free-swimming medusae stage. As one might imagine, fossil scyphozoans are rarely preserved as fossils; yet surprisingly they are probably represented in the famous Ediacara fauna of the Precambrian. Almost all fossil remains of scyphozoans occur as molds and less commonly casts. Some workers would place the Conularia as a Subclass of the Scyphozoa.