Littorina muricata

Jurassic

Phylum: Mollusca
Class: Gastropoda
Genus: Littorina

Coiled shell (helical)
Spire
Body whorl

External mould and external casts

Cambrian to Carboniferous

Phylum: Hemichordata
Class: Graptolithina
Order: Dendroidea

Numerous branching stipes
Colonial
Thecae

Flattened

In this specimen we cannot see the size of a potential holdfast. Because of this we cannot say if this is a planktonic or benthic animal.

Dendroid graptolites began as benthic organisms attaching to the seafloor with a holdfast, but some diversified as planktonic animals, with a reduced holdfast.

Ordovician

Phylum: Hemichordata
Class: Graptolithina
Order: Graptoloidea

Thecae
Stipes
Rhabdosome
Nema

Flattened
Carbon film
Red colour from iron in sediment seeping into fossil

The number of stipes decreased over time, from 4 to 3 to 2. This specimen has 3 stipes, placing it between four stiped animals such as Tetragraptus and two stiped animals such as Didymograptus in time.

Ordovician

Phylum: Hemichordata
Class: Graptolithina
Genus: Didymograptus

Stipes (2)
Thecae
Rhabdosome
Nema
'sawtooth'

Flattened
Carbon film
Pale colourisation from chlorine inclusion into the fossil

The 'sawtooth' faces are facing each other. This is therefore a relatively old two stiped graptolite from the Ordovician. One specimen shows two graptolites with nemas overlapping. At first glance this could be mistaken for a four stiped graptolite, such as Tetrapgraptus, but close examination reveals that there are two animals, squashed on top of each other.

Phylum: Hemichordata
Class: Graptolithina

Stipes (2)
Nema
Horizontal
Thecae
Rhabdosome

Compressed
Carbon film
Red colour from iron in sediment seeping into fossil

The position of the nema tells us that there are two horizontal stipes and not one stipe. This allows identification as a Didymograptid and not as a Monograptid.

Ordovician

Phylum: Hemichordata
Class: Graptolithina
Order: Graptoloidea

Stipes
Rhabdosome
Thecae
'sawtooth'

Flattened
Red colour from iron in sediment seeping into fossil

You can see a range of geometries on this specimen: scandent, horizontal and pendent.

Silurian to Devonian

Phylum: Hemichordata
Class: Graptolithina

Spiral stipes
Rhabdosome
Thecae
'sawtooth'

Flattened
Carbon film

You can see various preservational geometries in these slabs.

Cambrian to Permian

Phylum: Mollusca
Class: Cephalopoda

Straight
Chambers
Septa

Manmade internal cast

Nautiloids originated in the Cambrian and radiated during the Ordovician. Straight nautiloids went extinct in the Permian, but planispirally coiled nautiloids, for example the nautilus, live in the sea today.

Ellipsocephalus hoffi

Cambrian

Phylum: Arthropoda
Class: Trilobita
Order: Ptychopariida
Genus: Ellipsocephalus

Cephalon
Thorax
Pygidium
No eyes

Cast of a mould (manmade)
External moulds of trilobite hard parts

Ellipsocephalus hoffi was a blind species of trilobite. It likely lived in deep, poorly lit, aphotic environments.

Mount Stephen, Brisith Columbia, Canada

Cambrian

Phylum: Arthropoda
Class: Trilobita
Order: Corynexochida
Genus: Ogygopsis

Glabella
Eye ridges
Cephalon
Thorax
Pygidium

External mould (manmade cast)