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Palaeontology Crawler (Dalmanites + Catyines): tapering ends, eyes In both types of Cephalopods mentioned, the animal
on top of head for better vision, mouth on ventral side for lives in the last chamber of the shell, called the body
Kingdom Phylum Class Order Family Genus feeding and lots of legs for crawling around. chamber. The chambers within the shell are divided by
Species Burrower (trinucleus + encrinumrus): no eyes/eyes on Septa, which is perforated and a fleshy tube called the
stalks, large cephalon (head), reduced thorax (chest) Siphuncle passes through the Septal Neck during life.
Phylum: Mollusca Class: Bivalivia and lower number of legs. Is adapted for burrowing in The Siphuncle is responsible for the gas/water
The Bivalves mud. interchange which allows the cephalopod to rise or fall
Bivalves are equivalve, but are rarely bilaterally Swimmers (ogygias): rounded body, streamlined, by filling or emptying the vacant chambers.
symmetrical (BLS). The valves, which can be appendages (fins) for swimming and eyes on the side In nautiloids the Septal neck s backward facing and is
described as either left or right, are united on the dorsal for better all-round vision. in the centre while in ammonites the septal neck is
surface and separated along the other margins. forward facing and is near the Venter.
The muscle scars mark where the muscles, which are Phylum: Hemichordata Class: Graptolithina On internal moulds markings are left by the septum,
now decomposed, were attached to the shell. There are The Graptolites which on the outer surface is called a suture line.
called posterior muscle scars or anterior muscle Graptolites are the remains of extinct, colonel marine
scars depending on their position. organisms which are confined to the Lower Palaeozoic Phylum: Cnidaria Class: Anthozoa
The pallial line joins the two muscle scars together rocks during the periods of Cambrian, Ordovician and The Corals
where the soft body of the mollusc was joined to the Silurian. Corals are extremely good environmental indicators.
shell. These zone fossils because they have a rapid Modern corals are largely restricted to 30° N+S of the
*Uniformitarianism the present is the key to the evolutionary change, worldwide geographical equator. Corals grow in warm, shallow, clear, tropical
past* distribution and the fact that they are the only fossils and well oxygenised waters.
Fixed: no movement, so no pallial sinus. that can be preserved in black shales. Corals are also very good zone fossils and are
Burrower: posterior pallial sinus. Graptolites are commonly found in black shales as particularly important in the Lower Carboniferous era.
Crawler: anterior pallial sinus. carbonised impressions or whitish films which resemble In a coral the soft animal lives in or on a calcareous
hack-saw blades. skeleton. Solitary corals have a single polyp on a cup-
Phylum: Brachiapoda The skeleton of a graptolite is called a Rhabdosome like skeleton whilst colonial or compound corals have
The Brachiopods which originated in a tiny conical called a Sicula. From numerous polyps on complex and branching skeletons.
Brachiopods are not equivalve but are bilaterally the Sicula grew one or more branches known as The Rugose corals are solitary or compound Paleozoic
symmetrical. Stipes. corals with a calcareous skeleton which is called a
However, unlike the bivalves, the relaxed state of these The stipes are made up of a series of short overlapping corallum. This skeleton is divided by vertical radial
animals is with both valves closed. When the animal tubes called Theca which would have held an individual partitions called septa. They are bilaterally
dies, the valves are more likely to remain together, while member (Zooid) of the colony. symmetrical.
bivalves fall apart since their relaxed state is open.
All brachiopods are marine, and they range in size from Phylum: Mollusca Class: Cephalpoda Solitary Rugose Corals:
5-20mm. The Cephalopods The corallum is often rounded on the outside and often
Modern brachiopods are fixed to the floor, tilt towards These fossils are exclusively marine and range from has a wrinkled appearance. The upper surface is a cup-
the current and opens its valves to filter feed. shallow to deep waters. The modern forms are shaped hollow of varying depth called the Calice. This is
nautiloids, and the ammonites became extinct at the where the coral polyp sits during life. Septa run vertically
Phylum: Arthropoda Class: Trilobita same time as the dinosaurs, the end of the Cretaceous through the corallum, and the floor of the successive
The Trilobites period. calices is known as the tabulae. Dissepiments are
Trilobites were a group of extinct marine arthropods *K/T Boundary* plates which lie between the septa, and up the middle of
which resemble modern woodlice. They had the ability Most are bilaterally symmetrical, and the shell is the corallum there may be a space or a rod-like axial
to curl up as a defensive mechanism. always coiled, either in an Evolute or Ivolute style. structure or columella.
Trilobites range in time from the Cambrian period to the Ammonites are more useful than nautiloids because of
Permian period where they became extinct. They were their great value as zone fossils. Compound Rugose Corals:
of greatest significance in Ordovician and Silurian In six geological periods, swarms of these animals were Compound corals are build up from a number of
times and began to decline in numbers in the Devonian thrown off, and each group evolved rapidly before dying individual polyps, each of which is referred to as a
period, where the first signs of fish appeared. out. A new group arose before the extinction of the corallite. These may remain free of one another, or they
They range in size from 0.5-35cm. previous group to repeat a similar evolution. may be in contact (massive). The free forms may have
Many trilobite fossils are found broken up. This is There can be considerable variation in the rib type, most regular or irregular branching.
largely due to the fact that they shed their skin at important types include primary, secondary and
different growth stages, called Ecdysis and is similar to bifurcating. Sulcus and Keels can be seen on the
snakes shedding their skin today. Venter margin.