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FOSSIL MORPHOLOGY Jurassic Dinosaur footprint, Cloughton Wyke, Scarborough.

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Presentation on theme: "FOSSIL MORPHOLOGY Jurassic Dinosaur footprint, Cloughton Wyke, Scarborough."— Presentation transcript:

1 FOSSIL MORPHOLOGY Jurassic Dinosaur footprint, Cloughton Wyke, Scarborough

2 Fossils A fossil is a feature which records organisms or plants in rocks. Fossils can include hard parts of the organism such as skeletons, bones, plant material, pollen or shells. Trace fossils record the activities of animals or plants, but do not include any hard parts. Trace fossils include burrows, footprints and feeding tracks.

THICK SHELL EVIDENCE FOR MODE OF LIFE? High energy, intertidal shorelines: Thick shell, large muscle scars, strong teeth and socket arrangements.

The line of symmetry of bivalves runs BETWEEN the two valves.

5 Pecten (scallop) Thin, light shell for floating Mode of life: Pectens float/swim between periods on the sea bed EARS Strong ribs to live in high energy water This bivalve is nearly symmetrical but the ears are not the same and the umbo leans slightly to the left.

6 Bivalves in their life positions (life assemblage)
St Bees sandstone, St Bees, Lake District Flags on the Pennine Way Mussels beds on a present day shore

7 Burrowing bivalves TEETH AND SOCKETS UMBO 5cm GROWTH LINES MUSCLE SCARS Bivalves which burrow are likely to be more elongated than those which live on the top of the sea-bed. They may also have a gape (the valves do not meet at one end) so that the siphons which enable them to feed can reach the surface of the sea-bed.

PEDICLE OPENING Brachiopods differ from bivalves in that they have a sessile mode of life – they live attached to the sea-bed by a pedicle, which is a tough ligament which emerges from the pedicle opening.

9 Rhynchonella is a very common Jurassic brachiopod, with heavily ribbed valves.
UMBO PEDICLE OPENING LINE OF SYMMETRY RIBS Rhynchonella has two valves which close together very tightly, suggesting that they lived on intertidal shorelines which had high energy breaking waves.

10 Jurassic brachiopods Picture from the Palaeontological Association

11 Carboniferous brachiopods in black shales
These valves of the brachiopod Productus are not broken up, but they are separated. That suggests that they have been transported by gentle waves or currents into the area of muds without being fragmented. Carboniferous brachiopods in black shales

12 CORALS In this Silurian coral, Halysites, the individual corallites have been linked together to form a coral colony, which would have been firmly attached to the sea-bed.

13 These Carboniferous corals also form a colony, preserved in limestone in their position of growth.
Septa are radiating plates of calcite that held the soft body of the coral animal (polyp) firmly inside the corallite. Corals live in high energy conditions with breaking waves where there are plenty of other organisms from which to feed. SEPTA Picture from the Palaeontological Association

14 Solitary corals lived with the pointed end stuck into the sea-bed
Solitary corals lived with the pointed end stuck into the sea-bed. The coral animal could reach food in the sea with its many tentacles. SEPTA

15 CORAL ENVIRONMENTS Coral reef growth is only possible if these requirements are met: Marine conditions Warm water (over 25oC) Clear water Shallow water (photic zone) High energy (breaking waves) Present coral reefs

16 Coral reefs in the Red Sea
Photos from Ellen Spencer

17 GRAPTOLITES The first graptolites were colonies of animals attached to each other on branches (stipes) and attached to the sea-bed by a hold-fast. They extracted their food from sea-water. STIPES HOLD-FAST

18 Tetragraptus STIPE As time passed, it became more efficient for graptolite colonies to float freely in the oceans to find food (pelagic floating). The number of stipes reduced and the trilobite animals on each colony decreased in number. Their chambers (thecae) became larger and are clearly seen in this picture. THECAE

19 Didymograptus murchisoni
TWO STIPES In the Ordovician period the number of stipes per colony reduced to two. Often the thecae became more complex in structure. THECA

20 Monograptus Later, in the Silurian period the two stipes of Didymograptus united and became one, but with thecae on both sides. Monograptus is only found in Silurian rocks and is therefore an excellent zone fossil to correlate rocks of this age. THECAE ON BOTH SIDES OF THE STIPE SINGLE STIPE

21 TRILOBITES Trilobites had segmented exoskeletons which allowed some species to roll up to protect themselves. Picture from the Palaeontological Association

PYGIDIUM – fused segments COMPOUND EYE – hidden in shadow Trilobite exoskeletons were made from protein and therefore were slightly flexible. The soft parts, like brain, breathing gills, guts and reproductive organs were protected by the exoskeleton.

23 Calymene cephalon GLABELLA
COMPOUND EYES These were made of many crystals of calcite, like present-day insect eyes. SEGMENT OF THE THORAX

24 Spiny trilobite Some trilobites developed elaborate spines, perhaps to protect themselves from predators or to stop their exoskeletons from sinking into soft sea-bed muds.

25 Trinucleus Trinucleus had long genal spines (broken off in this fossil) which probably helped it to balance in soft mud. Trinucleus had no eyes. But the ribbed headshield is thought to be a sensitive organ which could enable Trinucleus to feel its way through mud to find its food by touch.

26 Angelina sedgwickii This Lower Ordovician trilobite is always found in slates so has been deformed by metamorphism. It is therefore used by geologists as an indicator of the direction and size of pressure during mountain building periods which metamorphosed the shales, in which Angelina is found, into slates.

27 AMMONITES WHORLS KEEL This specimen has very few ribs or growth lines on its shell. BODY CHAMBER Ammonite shells were made of calcite.

28 Ammonite morphology RIBS WHORLS BODY CHAMBER KEEL

29 Ammonite interior Each chamber is separated from the next by a calcite septum secreted by the animal as it grows larger. These chambers have been filled with coarse calcite crystals when the shell was covered with sediments. SEPTA

30 Detail of inside whorl

31 Outer shell and whorls original shell of the ammonite
Shell broken away to show the infilling of the chambers by sediment

32 Suture lines in ammonites developed very frilly edges to give the shell more strength. This allowed ammonites to become much larger and more competitive. 6cm SEPTUM

33 Ammonite suture lines FRILLY SUTURE LINES
Both lobes and saddles developed frills. On this specimen it is not easy to see which is which because the fossil does not include the body chamber. SURFACE OF THE SEPTA

34 GONIATITES Goniatites are the ancestors of the ammonites and were common in the Carboniferous period. They have simple suture lines and are usually small with very few whorls.

35 Goniatites have simple suture lines

36 PLANTS This tree trunk was found in its position of growth (in situ) in Appleton Quarry, Shepley. The tree grew in a swamp and became covered with fine muds, which are now laminated fissile black shales. The trunk has become carbonised and there is a thin black layer of carbon around the outside of the tree. 4m

37 Carbonised leaves in white sandstone

38 Jurassic Gingko tree leaves fossilised in pale grey shale

39 Plant branch fossils Lepidodendron has leaf scales which give it a diamond-shaped pattern. Calamites has a strongly ribbed trunk.

40 Branches in Millstone Grit sandstone
Flagstones on the Pennine Way Sandstone in Ratten Clough, Todmorden

41 Rootlets The thin coal seam represents the plants which have become compressed and carbonised as water and gases have been driven off as the rocks became lithified. Carbonised rootlets growing in a silica-rich soil, which would have developed in a tropical climate.

42 THE END THE END Jurassic ammonite moulds and casts, Dorset

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