Hexactinellida -  Also known as glass sponges, Hexactinellida are made up of tiny structures called spicules. Spicules are the tiny, filament like structures that make up a sponges "skeleton." The spicules of a Hexactinellida closely resemble a child's toy jack, with six spines jutting out from a common joint. Hexactinellida are often viewed as an early group, even within Porifera because they lack the ability to contract as many more common sponges do. Despite this lack, they still have an ability to react to external stimuli via electrical impulses. Demospongia -  Demospongia make up over 90% of the 5,000 species of sponges, making it by far the most diverse group. Like the Hexactinellida, Demosponges have skeletal structure made up of filamentous structures called spicules. The spicules of a Demosponge only consists of one to four spines. Demosponges are seen in every environment from coastal shelves to deep ocean abysses. The Demosponge is the creature most people think of when they think of sponges, they are porous and their bodies, due to their complex skeletal structure prove to be very absorbent outside of their aquatic environment. Calcarea -  Calcarea is the only sponge group to have calcium carbonate spicules, lading to the spicules to be hallow. Calcarea was first seen during the Cambrian Explosion and they're diversity peaked during the cretatious period. Today, Calcarea make up around 100 different species of sponge, with they're most diversity seen in tropical areas. |