Ambyploda (Extinct Herbivorous Mammals)

Skeletal components of the now obsolete Order of extinct mammals the Amblypoda showing:  Coryphodon skulls (1 & 2), feet (3 & 4) and cheek teeth (5 & 6); Dinoceras skulls (7 & 8), feet (9 & 10) and cheek teeth (11 & 12).  Note the similar structure of the feet which was incorrectly used to define this obsolete group (ambly – dull or blunt; poda – feet) from fossil evidence.

Sedentary Sea Squirts (Ascidians)

Initially this group was divided into those that lived solitarily and those that lived colonially.  Now considered as a single class the Ascidians are typical tunicates often referred to as sea squirts.  Their developmental forms (11 – 13) maintain the four main characteristics of chordates (blue; dorsal hollow nerve chord, gold; notochord, pharyngeal gill slits and post anal tail both not represented here) however as an adult many of these have been reduced or lost to suit their sedentary, filter feeding niche.  The large majority of space is taken up by the pharynx (4 & 10) which is used to filter particulate organic matter from water moved through the siphons by cilia.  Ascidians have a closed circulatory system (2, red) with a heart that can switch direction.  Gametes and feaces are transported from the base of the adult to the outside of the  pharynx (10, r & a) where they are carried by water currents out of the ex-current siphon.

Free Floating Sea Squirts

Anatomy of members of the Class Thaliacea showing:  internal structures through transluscent bodies, variation of individual body plans (1, 3, 4, 6, 7 & 8′) and arrangements of colonies (5 & 10).  The general body plan is of seiving structures held within a tubular pharynx where water is funnelled for food, respiration and propulsion.  Note the muscle banding used to create water flow and the centralisation of nervous tissue (labelled N) which is indicative of their place within the Chordata.


The Foraminifera are single celled, mainly benthic, marine to brackish water protozoans that are amoeboid in shape (1A) but produce mainly calcareous tests (3 & 4) (some aggregate sediment particles in a hardened mucus (2)) through which extensions of the ectoplasm form parapodia (2, 3, 6 & 9).  These extensions are used for motility, anchoring to the sediment and to capture prey (diatoms and bacteria).  The taxonomy of this group is disputed as they are possibly grouped with radiolarians and cercazoans in the Infrakingdom Rhizaria.  All of these groups are important in carbon recycling as their tests sink carbon to the ocean floor from the atmosphere.


Radiolarians are a group of marine protozoa (single celled eukaryotes) which have intricate siliceous skeletons (blue structures).  The skeletons both seperate the cell into two distinct inner and outer regions (7) (endo/ecto-plasm) and create long pseudopodia which increase surface area and aid in buoyancy.  The endoplasm usually contains the nucleus (n)  and other organelles whilst the ectoplasm often utilises gas filled vacuoles and lipid deposits to increase buoyancy (2).  The ectoplasm also often have symbiotic algae (Gz) which photosynthesise to produce food for the radiolarian (2 & 3).  The taxonomy of this group is disputed as they are possibly grouped with foraminiferans and cercazoans in the Infrakingdom Rhizaria.  All of these groups are important in carbon recycling as their tests sink carbon to the ocean floor from the atmosphere.


The old phylum of Protozoa is recognised to be a paraphyletic group containing a diverse range of taxa grouped together only because of their simple body plan lacking complete tissues and being somewhat heterotrophic.  As such the clade Protozoa is now considered to be a paraphyletic kingdom containing meany phyla which are both related and un-related.  The phylum Ciliophora contains many large complex protozoans which utilise the beating of hair like structures called cilia to create movement of either themselves or the medium which carries their food to them.

Polychaete Worms

Vermes is an obsolete taxon used to group all non-arthropod invertebrates together.  Here the Class Annelides has now been promoted to the Phylum Annelida.  The order Polychaetae errantes is now classified as the Class Polychaeta.  The Annelida are the segmented worms (arguably some memberts have lost segmentation) with the polychaetes being the bristle-worms, both the formal and informal names refer to the many rigid bristles which extend from each segment’s parapodia.  This chart shows adult sand worms (1, 2, 3 & 9) but the group also include burrowing and tube building worms.  Annelids have a closed circulatory system which is highlited in the by the vessels (red), a partitioned through-gut (yellow) and cephalisation (concentration at the anterior end) of sensory organs (6 & 8).

Peanut Worms (Sipunculids and Echiurans)

The now obsolete taxon of Vermes once encompassed all non-arthropod invertebrates.  This wall chart compares two different phyla of worm; sipunculids and echiurans.  Both groups have previously been classified with in the Annelida despite their lacking the segmentation and bristled parapodia characteristic of this group. They are now both classified as seperate phyla within a group known as the Lophotrochozoa based on both larval development (14 & 15) and ribosomal DNA evidence.  A typical sipunculid (peanut worm) has an introvertible anterior region often with a crest of tentacles (1, 2, & 3). Different species burrow into sediments, rocks or calcified organic structures with the anterior end protruding. Echiurans are found in soft sediments with a long proboscis extending to the surface of the sediment where organic particles settle down onto a ciliated gutter which moves food to the mouth via the proboscis (10).