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INVERTEBRATE PALEONTOLOGY 2014/2015DR. IKHLAS ALHEJOJ, UNIVERSITY OF JORDAN,
PALAEONTOLOGYThe study of fossils
Gastropod (snail) fossil
A fossil is an original material, impression (mold), cast, or track of any animal or plant that is preserved in rock after the original organic material is transformed or removed.
PALEONTOLOGY
- Paleozoology : study of fossil animals a. Invertebrate paleontology - study of
fossil invertebrates (animals without a vertebral column).
b. Vertebrate paleontology - study of fossil vertebrates (animals with a vertebral column).
PALEONTOLOGY
- Paleobotany : study of fossil plants. Palynology : study of pollen and spores (some also
include marine one celled "plants"; i.e. acritarchs, dinoflagellates, tasmanites, silicoflagellates, diatoms, ebridians, calcareous nannoplankton/coccoliths).
- Micropaleontology : study of small fossils (includes many groups mentioned under palynology and also foraminifera, radiolaria, chitinozoa, graptolites, pteropods (gastropods), ostracods (crustaceans), conodonts .
Evolution and the fossil record
Age of Earth is ~4.6 billion yearsAtmosphere had little free O2
Included CO2, H2O, CO, H2, N2, NH3, H2S, CH4.
Fossils range in age from the youngest at the start of the Holocene Epoch to the oldest from the Archaean Eon, up to 3.48 billion years old.
Evolution and the fossil record
Stromatolites 3.4 Ga from Western Australia
Types of Fossils
• Body Fossils - the actual body or body parts of an organism, whether altered or not.
•Trace Fossils - any evidence of past life that is not a body fossil; examples: tracks, trails, burrows borings, impressions, molds, casts.
WHY STUDY FOSSILS?
Fossils give clues about organisms that lived long ago. They help to show that evolution has occurred.
They provide evidence about how Earth’s surface has changed over time.
Fossils help scientists understand what past environments may have been like.
Hard Parts: Common mineral componentsCalcium carbonate CaCO3 Principal mineral components of most
seashells. Two common calcareous minerals in seashells:Aragonite – unstable over geological time.
Aragonitic shells commonly are dissolved (preserved as moulds) or transform to calcite (poor preservation of primary textures).
Calcite – stable over geological time. Consequently calcitic (e.g. brachiopod) shells tends to be well-preserved.
Silica SiO2 – Usually amorphous hydrated silica (Opal A) which commonly transforms to quartz and other silica minerals following death. Opal may be well preserved in pelagic sediments, if deeply buried.This is the principal “mineral” component of the skeletons of some sponges, and micro-organisms such as diatoms and radiolarians. Skeletons may be lost or degraded through opal dissolution and obliteration of the original amorphous structure through quartz crystallization.
Calcium phosphate (apatite) Ca3(F.Cl.OH)(PO4)3 –stable over geological time (tends to be well-preserved). Principal mineral component of bones, teeth and some shells.
The process of fossilization (taphonomy).
HOW IS A FOSSIL FORMED?
1. SedimentAn animal is buried by sediment, such as volcanic ash or silt, shortly after it dies. Its bones are protected from rotting by the layer of sediment.
2. LayersMore sediment layers accumulate above the animal’s remains, and minerals, such as silica (a compound of silicon and oxygen), slowly replace the calcium phosphate in the bones.
3. MovementMovement of tectonic plates, or giant rock slabs that make up Earth’s surface, lifts up the sediments and pushes the fossil closer to the surface.
4. ErosionErosion from rain, rivers, and wind wears away the remaining rock layers. Eventually, erosion or people digging for fossils will expose the preserved remains.
WHAT ARE THE CONDITIONS THAT ARE FAVORABLE FOR PRESERVATION?
*Hard body parts such as skeletal bones or exoskeletons
*Rapid burial and/or lack of oxygen
BODY FOSSILS Body Fossils are the actual body or body
parts of an organism that has been preserved. These fossils may or may not be altered (fossils that have gone through a chemical change or physical change). The two main types of body fossils are (A) unaltered remains and (B) altered remains…
Unaltered remains of fossils means that the remains have gone through little or no chemical or physical change.
A. UNALTERED REMAINS Original skeletal material: this means that the
hard parts of the organism are preserved as the original
material.- Tar impregnation- Amber Entombment- Refrigeration
Tar impregnation: tar pits are excellent areas to preserve life as a fossil. La Brea tar pits in California is one of the most famous areas because of the large number of preserved life forms found in it.
TAR IMPREGNATION
Fossilized water beetle, Hydrophilus sp., preserved in oil-impregnated sands of a late Pleistocene (roughly 35, 000 years old) tar seep in the vicinity of the Kettleman Hills.
REFRIGERATION
Refrigeration--During the Pleistocene glaciations, when ice sheets cover much of the Northern Hemisphere, some animals (mammoths, for example) fell into crevasses in frozen terrain or became trapped in permanently frozen soil. Some of these animals have been discovered perfectly preserved.
Mammoths
They lived from the Pliocene epoch (from around 5 million years ago) into the Holocene at about 4,500 years ago
Ice Age wooly mammoths from the Pleistocene Epoch have been found frozen in Siberia and Alaska. Skin, hair, and soft tissue have been preserved in frozen soil.
AMBER ENTOMBMENT-- Amber-preserved fossils are organisms that become trapped in tree resin that hardens after the tree is buried. Small insects and other minute organism may become trapped in this resin, which after burial may harden into amber. Certain parts of the Baltic Sea coast and some of the islands in the West Indies are well known for occurrences of insects preserved in amber
Body Fossils, Altered remains
Altered remains of fossils means that the organisms have gone through chemical or physical change and must be at least ten thousand years old.The types of altered remains of fossils are…
-
Recrystallization Replacement PermineralizationCarbonization
PERMINERALIZATION
Many bones, shells, and plant stems have porous internal structures. These pores may become filled with mineral deposits. In the process of permineralization, the actual chemical composition of the original hard parts of the organism may not change
Permineralized Wood
- Carbonization
- Carbonization preserves soft tissues of plants or animals as a thin carbon film, usually in fine-grained sediments (shales). Fine details of the organisms may be preserved. Plant fossils, such as ferns, in shale generally are preserved by carbonization. Soft-bodied animals such as jellyfish or worms may also be preserved as carbonaceous films in black shales
(leaf)
DISSOLUTION/REPLACEMENT
Dissolution/Replacement -- Groundwater (especially acidic groundwater) may act to dissolve a hard structure in an organism trapped in sediments and may, simultaneously deposit a mineral in its place--molecule by molecule.
Silicification(replacement by silica)
Fossil calcareous sponge(originally calcitic, now siliceous)
Depending on the chemistry of pore waters within sediment, a number of minerals can replace the original material. These transformations may occur at earlier (before or during lithification), or later (after lithification) stages of fossilization.
Calcareous (calcitic and aragonitic) shells are commonly replaced by silica minerals (silicon dioxide), pyrite (iron sulphide), or calcium phosphate minerals.
Pyritization(replacement by pyrite)
Pyritized brachiopod
MOLD& CAST Mold - impression of skeletal (or skin) remains in an
adjoining rock External mold = impression of outer side Internal mold (steinkern) = impression shows form or
markings of inner surface Cast - original skeletal material dissolves and cavity
(mold) fills with material Endocast- natural infilling of cranial cavity (may study
brain evolution in fossil mammals)
CAST
A cast may be produced if a mold is filled with sediment or mineral matter. A cast is a replica of the original. Casts are relatively uncommon. (A rubber mold of a fossil can be filled with modelling clay to produce a replica or artificial cast of the original object.)
Molds
External mould
Internal mould
External mould
Internal mould
Clam Fossil clam
Fossil snailSnail
Fossil snail
2.Shell is dissolved
1 .Sediment surrounding the shell and filling the shell cavity
hardens
2.Shell is dissolved
1 .Sediment surrounding the shell and filling the shell cavity
hardens
A mold (below) and cast (above) of a trilobite..
Ichnology - study of trace fossils (Ichnofossils = tracks, trails and burrows of organisms).
Burrows or borings – Spaces dug out by living things and preserved as is or filled in
Ichnology
Trace Fossils -Burrows: These trace fossils show how an animal
such as a worm (an annelid) moved through the soft sediment.
This worm tube trace fossil is
hollow (the hole goes all
the way through it).
Trace Fossils2 .Trace Fossils
-Tracks: can show how an animal moved and what its footprint looked like. These tracks can tell us a lot
about the animal that made them in the geologic past.
(trilobite)(trilobite tracks)
(Dinosaur tracks)Do you see the people?
Cruziana: produced by a trilobite “plowing” along the sediment surface.
Diplichnites: produced by a trilobite walking over the sediment surface.
grazing
crawling
tracks resting
living
feeding
Trace fossils
Ziegler (1972)
Bodyfossils
Trace fossils and water depth
Frey and Pemberton, in Walker (1884)
Hardground borings• Condensation• gaps, hiati
Firmground bioturbation (lower part)• softground• continuous sedimentation
Borings and bioturbation
Ziegler (1972)
Trace Fossils Trace Fossils
- Coprolite: -fossil excrement of animals; may contain undigested remains of food. usually preserved by replacement.
MORE ON TRACE FOSSILS
Gastroliths – smooth stones from abdominal cavity of dinosaurs
MORE ON TRACE FOSSILS
Tracks – impressions of
passage of living things
Pseudofossils
Pseudofossils (meaning “fake fossils”) many rocks and rock structures look like fossils, but aren't!.
(fossilized raindrops that hit
soft sediment)
PSEUDOFOSSILS
The following represent a few sedimentary features that may be confused for fossils:
1. Differential Weathering- weathering of rock and mineral surfaces often yield fossil-looking
features 2. Nodules- formed by filling voids in the sediment and incorporation of
sedimentary materials within the sedimentary body a. Chert Nodules - microcrystalline quartz; typically found along bedding planes in
limestone
b. Septaria - large nodules with radial and concentric cracks in their
centers - Melikaria are boxwork patterns of material filling septarian
cracks; may be all that is left after weathering of the septaria
c. Rosettes - radiating macrocrystalline bodies of discoidal or spherical
shape, consisting essentially of one mineral (typically pyrite, marcasite, barite, or gypsum)
3. Concretions- mineral growth within sediment often
forms structures that resemble bones, turtle shells, logs, etc.
4. Dendrites precipitation of manganese oxide along bedding planes creates fern-like patterns
(dendrite made by a mineral)
Different types of Trace Fossils
Do you remember what the five types of trace fossils are?
-Mold
-Cast
-Burrow
-Track
-Coprolite
Competition - two species vie for limited environmental resources
Autotrophs (Producers) = manufacture their own food; "plants"; form lowest trophic level and constitute the base of the biomass "pyramid"
Heterotrophs (Consumers) = feed on other organisms; consist of "animals" (much energy is lost cycling through higher trophic levels, and therefore with fewer organisms)
Herbivores = feed on producers Predation = effect of a predator on a prey
species Carnivores = feed on other consumers by
predation Parasites = derive nutrition from other
organisms without killing them
Scavengers = feed on dead organisms Commensalism = biological
association beneficial to one but does not hurt the host
Symbiosis = mutual benefit to both
participants
ORGANISM DISTRIBUTION (ESPECIALLY MARINE) DEPENDS UPON THE FOLLOWING:
a. Seawater Properties - Density and Viscosity
Density of aquatic organisms typically equals water density
Viscosity - influences shape and feeding (there are many "filter feeders" in aquatic environments, due to the viscosity of water allowing food to be held in suspension)
b. Salinity - usually measured in parts per thousand (0/00); average
seawater salinity is 35 0/00 but varies from 0 to 270 0/00
- in Geochemical Studies of Paleosalinity use boron (greater in saltwater); other trace elements; type of organic matter; carbon and oxygen isotopes [freshwaters depleted in heavy carbon (C-13) and heavy oxygen (0-18)]
- in Biological Studies use stenohaline (restricted by salinity; organisms internal "salinities" equals surrounding water salinity; if rapid change cells may not function) versus euryhaline (salinity tolerant) organisms
C. TEMPERATURE
- water moderates temperature - in cold-blooded organisms, an increase in temperature of 10°C often
causes metabolic activity to double - in warm-blooded organisms there is little metabolic change with
temperature change - temperature influences reproductive cycles - in Geochemical Studies of Paleotemperature use 18O/16O (less with
greater temperature; most important for determining paleotemperatures); boron and bromine greater if greater temperature; Calcium/Magnesium and Calcium/Strontium ratios are less if the temperature is increased
- in Biological studies of paleotemperature use stenothermal (temperature intolerant) versus eurythermal (temperature tolerant) organisms; also may look at species diversity (greater in warmer environments) or morphology (body form reflects environmental factors)
d. Dissolved Gases - concentrations depend on atmospheric concentration;
solubility of gas; water temperature and salinity d1. Nitrogen (N) - most abundant dissolved gas;
required by plants in ionic form d2. Oxygen (O) - enters sea by photosynthesis, river
water, atmosphere; all organisms use oxygen during respiration; oxygen at maximum near surface, minimum at about 700-1,000m Oxygen; approximately 6 to 10 ppm; warmer, saltier or organic debris-rich water with less oxygen
d3. Carbon Dioxide (CO2) - enters sea from organism respiration, atmosphere and rivers; removed by plants for photosynthesis and used by organisms to make shells; increases to approximately 1,000m; increased CO2 leads to Greenhouse Effect (increase temperature)
d4. Hydrogen Sulfide (H2S) - produced by anaerobic bacteria e. Light - Photic zone = zone of light penetration Euphotic zone = upper illuminated layers of water in the photic
zone; receive sufficient light to support photosynthesis; usually 10-60 meters but clear tropical waters may be greater than 100 meters
- Aphotic zone = zone in which light does not penetrate
f. Pressure - pressure increases approximately 1 atmosphere per 10 meters - affects vertical migration of organisms, bacterial decomposition, production of
shells (CCD = carbonate compensation depth) g. Depth - deep water stores carbon, nitrate, phosphate Paleobathymetry - the ancient water depth may be determined by type of body
fossils and trace fossils present h. Water energy, turbidity and sedimentation rates - affects distribution of food and nutrients; types and morphology of organisms
present - amount of suspended sediment especially affects filter-feeders - nature of substrate affects type of infauna (live in substrate) or epifauna (live
on substrate; sessile or vagile benthonic) present
Biostratigraphy ("Stratigraphic Paleontology") 1. Biostratigraphic distributions are controlled by: a. Evolution b. Paleoecology - no organism inhabits all
environments b1. Facies-controlled organisms = restricted to
particular sedimentary environments (often with slow evolutionary change)
b2. Biofacies = facies distinguished on the basis of their fossils (Ex. = reef biofacies - may have corals, coralline algae, stromatoporoids, rudist bivalves)
2. Biostratigraphic Units- body of rocks delimited from adjacent rocks by their fossil content - often use fossils for Correlation (matching stratigraphic sections of the same
age) a. First appearances of fossils may be due to 1) evolutionary first
occurrence 2) immigrationFAD = First appearance datum FOD = First occurrence datum
b. Last appearance of fossils may be due to 1) extinction event 2) emigrationLAD = Last appearance datum LOD = Last occurrence datum
Biozone - basic unit of biostratigraphic classification - based on the distribution of Index Fossils
(fossils characteristic of key formations; should have short time span, wide geographic range, independent as possible of facies, abundant, rapidly changing and with distinctive morphology)
Biological Classification of Fossils
As fossils clearly represent the the remains of ancient biological organisms, it only makes sense that they should also be classified in the same manner as living organisms.
The fundamental unit of biological classification is the species. Members of a species are able to interbreed and give rise to fertile offspring. Palaeontologists, lacking evidence of reproductive isolation of ancient “species”, focus on morphological definitions of species. Above the species level are increasingly more inclusive groups which are defined by certain characteristics possessed by all their members. These various groupings are as follows:
Kingdom: (e.g. Animalia)Phylum: (e.g. Chordata)Class: (e.g. Mammalia)Order: (e.g. Primates)
Family: (e.g. Hominidae)Genus (e.g. Homo)
Species: (e.g. Homo sapiens)
This classification heirarchy applies mainly to body fossils. As you will see, trace fossils classification is more limited in this respect.
INVERTEBRATE GROUPS
Sponges (Phylum Porifera) Cnidarians (Phylum Cnidaria) Phylum Brachiopoda: (both articulates and
inarticulates)Bryozoans Mollusks (Phylum Mollusca): - Class Bivalvia-Class Cephalopoda (Subclass Nautiloidea)-Class Gastropoda-Class Monoplacophora
INVERTEBRATE GROUPS
Arthropods (Phylum Arthropoda):-Class Crustacea (Subclass Ostracoda)-Class Trilobita Echinoderms (Phylum
Echinodermata)-Starfish-Echinoids (sea urchins sand dollars, and sea
biscuits)
Phylum Mollusca (Kingdom Animalia
PHYLUM MOLLUSCA
The molluscs include bivalves (or pelecypods, Lamellibranchia), gastropods (snails), cephalopods (ammonoids, belemnoids, squids, etc.), and a few other groups.
Molluscs diversified following the Permian extinctions, and became more diverse than in the Paleozoic. During the Mesozoic, the molluscs surpassed the brachiopods (which had dominated the Paleozoic seafloor).Class. CephalopodaClass. GastropodaClass. Bivalvia
The body of mollusca are divided into: Head Hard Body : ShellMantelFoot
MOLLUSCA: CLASS CEPHALOPODS
CephalopodsThe cephalopods include the ammonoids,
nautiloids, belemnoids, and squids. Most were nektonic (swimmers). the cephalopods extinct groups are ammonites and belemnites).
Environments: Marine (Shallow and deep) Predatory animals Geological age : Cambrian to present -
MORPHOLOGY OF FOSSIL CEPHALOPOD SHELLS
The structure secreted by the mantle of cephalopods for protection or neutral buoyancy is called the Shell or Conch (except octopus). The complete shell is basically a hollow cone with two major parts, the Body Chamber, or Living Chamber, and thePhragmocone. The opening on the large end is called the Aperture, and the Apex is at the tip of the small end. The shell orTest that forms the cone is called the Shell Wall.
Orientation : Lateral is between ventral and dorsal. Longitudinal is in an anterior to posterior direction, and Transverse is in a dorsal to ventral direction.
Body Chamber: - Chambers- Septa- Siphuncle: extended from the mantel to apex-About 8-10 tentacles-Funnel
-The edge of the aperture is the Peristome.
Two lateral views of the shell of Nautilus, external on the left and internal on the right
Drawings of an imaginary coiled cephalopod shell
Phragmocone As the animal grew, it occasionally moved forward in the body
chamber and secreted a Septum at the back of the mantle. This created a series of Chambers, or Camerae, called the Phragmocone. Some septa are deposited a short distance along the shell wall, this part is called the Mural Part. The Free Part of the septum is between the mural part and the septal neck.
Parts of a Septal Suture line.
Septal Suture line types
The septum is attached to the shell wall along a Suture, seen as a series of simple to complex lines on internal molds. Parts of the suture line directed adorally are termed Saddles, and those directed adapically are termed Lobes.
Orthoceratitic Sutures are relatively simple having shallow lobes and saddles.
Agoniatitic Sutures have broad lobes and saddles with a narrow mid ventral lobe.
Goniatitic Sutures have strong, mostly angular lobes and angular to rounded saddles.
Ceratitic Sutures have strong rounded saddles and serrated lobes.
Ammonitic Sutures have complex lobes and saddles
Types of suture lines
SHELL SHAPE Nautiloid shells can be Planispirally Coiled (coiled
in one plane) or straight, curved, open spiral etc., ammonoids not Planispirally coiled or have an open spiral are termed Heteromorphs.
Curved or coiled shells are Exogastric if the ventral side, or Venter, is convex and on the outer side, and Endogastric if the dorsal side, or Dorsum, is convex and on the outer side.
The cross sectional shape, or Whorl Section, canbe Round, Oval, Square, Rectangular, Triangular, Lanceolate(shaped like a lance point), Fastigate (tapering towards the venter), Tabulate (with a flattened venter) or some variation of each.
Compressed shells are shorter laterally, and Depressed shells are shorter ventro-dorsally.
COMMON WHORL SECTION SHAPES
A Whorl is one complete volution of a coiled shell. The space enclosed on both sides by the last whorl is termed the Umbilicus.
Shells with a wide umbilicus are termed Evolute and shells with a narrow umbilicus are termed Involute.
Theumbilical Seam is where the shell wall attaches to the preceding whorl. The Umbilical Wall is between the umbilical shoulder and the umbilical seam. The Umbilical Shoulder is where the shell wall bends toward the preceding whorl.
The Ventrolateral Shoulder is where the shell bends toward the venter, and the Side or Flank, is between the ventrolateral shoulder and the umbilical shoulder.
Cross section of a coiled shell showing parts and common dimensions.
Straight shells are Orthocones, curved shells are Cyrtocones, either of these could be long, Longiconic, or short,Breviconic. Curved shells that make at least one volution are termed Gyrocones. Coiled shells that touch or are just barely impressed by the preceding whorl are Tarphycones. Serpenticones are very evolute with many subcircular or depressed whorls. Involute to moderately involute shells with subrectangular, compressed whorls are termed Platycones. Shells that are involute with subtriangular, compressed whorls are Oxycones. Discocones have involute shells with an oval whorl section. Spherocones are subglobular with a small umbilicus and subcircular whorls. Cadicones are subglobular with an open, angular, umbilicus. Planorbicones are evolute with relatively few subcircular depressed whorls. Ancylocones have open or closed, planispiral or helical early whorls followed by a hook. Torticones have helical whorls. Shells that form two or more straight shafts are called Hamiticones. Irregular, worm like shells are termed Vermicones.
IRREGULAR OR HETEROMORPHIC SHELL SHAPES
PLANISPIRAL SHELL SHAPE
ORNAMENTATION
All cephalopod shells are ornamented with at least Growth Lines, each one representing a former position of the peristome. Ribs are usually radial folds of the shell so they are equally apparent on internal molds, sometimes they are thickenings of the outer part of the shell and don’t show on internal molds. Ribs directed radially are Rectiradiate, those inclined forward areProrsiradiate, and those inclined backward are Rursiradiate. Ribs can be Dense, closely spaced, or Distant, widely spaced. Sinuous ribs snake across the flanks, Falcate ribs are sickle-shaped, Falcoid ribs are generally falcate, Projected ribs are inclined forward on the outer portion. Branching ribs have Secondary Ribs that branch from Primary Ribs. Virgatotone ribshave other ribs branching from a single inclined rib. Intercalated Ribs are ribs not connected to other ribs. Bundled ribs are connected at one dorsal point. Zigzag ribs are alternately connected at the dorsal and ventral ends. Looped ribs are connected at both ends.
TYPE, DIRECTION AND SPACING OF RIB
Constrictions are internal shell thickenings and usually only show on the internal mold as sinuous transverse grooves. Lirae are small, usually longitudinal, raised portions of the shell separated by striae, small grooves. If they are strong enough they will show on internal molds. Tubercles and other Nodes are present on some shells. Nodes on internal molds are commonly the bases of Spines. Spines were usually formed hollow on the peristome and sealed later as the shell grew. Tubercles elongated radially are termedBullae, and those elongated longitudinally are termed Clavi. A raised longitudinal ridge on the venter is called a Keel. Keels can be Entire (smooth), Serrated or Clavate. Sometimes a Furrow or groove can be found on each side of the keel. A large, deep, longitudinal groove is called a Sulcus, and can be found on the venter or in a lateral position.
Ornamentation other than ribs
Ornamentation other than ribs
MOLLUSCA: CEPHALOPODS, AMMONOIDS
Ammonoids:Ammonoids were among the dominant
swimming invertebrates in Mesozoic seas. Ammonoids were so abundant and varied that the Mesozoic could be called the "Age of Ammonoids".
The geologic range of ammonoid cephalopods is Devonian to Cretaceous.
MOLLUSCA: CEPHALOPODS, AMMONOIDS
Ammonoids are useful in biostratigraphy and worldwide correlation of Mesozoic rocks because they were abundant, morphologically variable, widely distributed, and had short geologic ranges (evolved rapidly).
One of the most distinctive features of the ammonoids is the character of the sutures seen on the outside of the fossils. Sutures are the seam where internal partitions called septa intersect the outside wall of the shell.
In the ammonoid cephalopods, the septae are convoluted or wrinkled, and the sutures make more complex patterns.
MOLLUSCA: CEPHALOPODS, AMMONOIDS
The three suture patterns of the ammonoids are goniatite, ceratite, and ammononite.
HTTP://HIGHEREDBCS.WILEY.COM/LEGACY/COLLEGE/LEVIN/0471697435/CHAP_TUT/CHAPS/CHAPTER14-04.HTML
MOLLUSCA: CEPHALOPODS, NAUTILOIDS
Nautiloids Unlike ammonites, some nautiloids are still alive today.
Nautiloids are the only cephalopods with an external shell that are still alive today. The living animal, Nautilus, is housed in a coiled shell, exposing only its head and tentacles to the outside world. Much of the shell is divided into chambers that are filled with gas. By adjusting the levels of gas the animal may live in the depths of the ocean and move to shallow water at night time to feed.
In contrast, the nautiloid cephalopods have smoothly curved septa.The geologic range of nautiloid cephalopods is Cambrian to Recent.
.
MOLLUSCA: CEPHALOPODS, BELEMNITES
Belemnites died out at the same time as ammonites and dinosaurs.
Belemnites are an extinct group of cephalopod that probably looked like a squid.
Unlike nautiloids and ammonites, belemnites have an internal soild calcareous shell (which resembles a cigar in size, shape, and color) called a rostrum. Many people will be familiar with belemnite rostra, they are straight, and look rather like bullets.
The front part of this shell is chambered, as in the nautiloids and ammonoids. The rostrum is made of fibrous calcite, arranged in concentric layers.
Geologic range: Belemnites first appeared about 360 million years ago. Along with ammonites and dinosaurs, they died out at the end of the Cretaceous period 65 million years ago.
- all extinct. The belemnites were highly successful
during the Jurassic and Cretaceous.
MOLLUSCA: CEPHALOPODS, BELEMNITES
Apart from their shells, palaeontologists have also found some belemnite fossils that show their internal structure and soft parts.
These fossils tell us a great deal about the way these animals lived. Belemnites had large eyes, and swam quickly using a form of jet propulsion.
Drawing of an orthoconic cephalopod shell and internal mold.
PHYLUM MOLLUSCA, CLASS BIVALVIA
Bivalves (Class Bivalvia) include clams, mussels, oysters, and scallops
The body of bivalves is laterally compressed (flattened sideways) and consists of 2 hinged valves that are mirror images of one another
94
Phylum Mollusca Class. Bivalvia
Soft parts and life cycleIn bivalves the soft parts are partially or
completely enclosed between two hinged valves. Most of the soft parts are to be found close to the back of the enclosed space, adjacent to the hinge. A mantle lines both valves almost as far as their outermost edges, and is responsible for secreting the shell.The body does not occupy all the space inside the valves even when closed. The residual space is taken up by the mantle cavity, into which hang the respiratory gills and the muscular foot. The gill create currents using the cilia with which they are covered.
PHYLUM MOLLUSCA, CLASS BIVALVIA
Strong muscles, the adductor muscles, are used to close the valves
Two siphons, an incurrent and an excurrent siphon, draw water into and out of the mantle cavity, respectively
Since many clams burrow into the sediment, these siphons allow the clam to feed and breathe
. . / 03 / .www marinebio net marinescience ecology mfunder htm
PHYLUM MOLLUSCA, CLASS BIVALVIA
Not all bivalves are burrowers; mussels secrete strong byssal threads to attach to rocks and other surfaces
Oysters cement themselves to hard substances including other oysters!
Scallops are unattached and can swim for short distances by rapidly ejecting water from the mantle cavity and flapping their valves
In bivalves, the mantle forms a thin membrane that lines the inside surface of the shellThis creates a mantle cavity, within which the entire body of the bivalve lies
CLASS BIVALVIA (BIVALVES)
Body contained between 2 hinged shells (valves)
Foot hatchet-like, modified for burrowing in sand/mud
Little cephalization: no head
CLASS BIVALVIA (BIVALVES) Adductor muscles (2 in most bivalves)
close Cilia on gills pull water into and out of
shell through siphons. Brings oxygen, food particles
CLASS BIVALVIA (BIVALVES) Importance:
human food (clams, oysters, scallops, mussels)
clams
mussels
oysters
CLASS BIVALVIA (BIVALVES) Importance:
jewelry (pearls)
PHYLUM MOLLUCSA , CLASS GASTROPODA Most diverse group (~60,000 species) >15,000 described fossil species Most extensive adaptive radiation of
any mollusc group Single shell, mostly right handed
sprial. some gastropods have lost their shells
altogether (slugs for example).
Torsion Fresh and salty environments but
marine loving environment. Geological age (Camb.-Rec.).
Gastropods have a well-developed head foot, upon which are found the eyes and a mouth containing the radula.
In front of and above the mantle cavity lies the visceral mass, which contain a simple heart, the kidneys and the gut.
The Gut opens anteriorly at the mouth, in which there is a rasp-like tongue bearing sharp, inward pointing teeth. It is called radula, and is used for grazing food (typically algal films) off the substrate.
Digestion takes place in an out-pouching of the gut called the digestive gland, and waste is expelled as discrete pellets via the anus.
The brain consists of a nerve ring surrounding the oesphagus, and two pairs of nerves arise from it. One pair serves the gut and another serves the large, muscular foot. The head is situated anteriorly, bearing primitive eyes.
Other sense organs include simple balancing organ, called statocysts (in the foot) and a pairs of osphradia, which may be sensitive to water chemistry and monitor the sediment content of the inhalent currents.
SHELL FORM
Gastropods shells are mainly made of calcium carbonate (96/) aragonite or calcite.
Mainly are dextral (right handed sprial, right aperture ) but a few rare cases are sinistral.
MAJOR CHANGES FROM GENERALIZED MOLLUSC
Development of head Dorsoventral elongation Shell – from shield to retreat Torsion Conispiral coiling and asymmetry
Monoplacophoranancestor
Planispiral coiling
TORSION
Weight of shell over head, mantle cavity posterior
Torsion – 180o counterclockwise rotation of visceral mass, shell, mantle, mantle cavity
Occurs in larvae not adult First gastropods Detorsion
COSTS OF CONISPIRAL SHELL
Loss of a gill, nephridium, atrium Mantle cavity (anus and
nephridiopore) now anterior and near mouth
Compensation - changes in water flow or shell structure
See Figure 12-20 (mantle cavity evolution) and 12-21A (abalone)
SHELL
Apex, whorl, columnella, aperature, siphonal canal
Spire, body whorl, outer lip, inner lip
operculum
LOCOMOTION
Most move using foot Most have ciliated sole and
secretory glands (mucus producing)
Hard-bottom dwelling and terrestrial, and large soft-bottom snails - undulating wave of muscle contractions
FEEDING
Most often thought of as algal scrapers (radula)
Deposit feeders Suspension feeders Scavengers Predators Parasites
CLASS GASTROPODA
Three “groups” – phylogeny revision Prosobranchs – most common members
when think of snails Terrestrial, freshwater, and marine* Common feature – operculum
Opisthobranchs Sea slugs, sea hares Many members lost shell
Pulmonates Many terrestrial species, also freshwater, a
few marine
MARINE GASTROPODA
Patella
Littorina Buccinum Turritella
PATELLA
Patella is a genus of sea snails with gills, typical true limpets, marine gastropod mollusks in the family Patellidae, the true limpets.
or cap like (Eocene to present ), cone like shell, oval aperture e.g, Limpet, attached beach rocks.
BUCCINUM(Pliocene to present) oval shell shaped with large last whorl
LITTORINA
Littorina is a genus of small sea snails, marine gastropod
molluscs in the family Littorinidae, the winkles or periwinkles.
These small snails live in the tidal zone of rocky shores.
Jurassic to
present )circul
ar hard shell
and rounded
aperture.
TURRITELLA
Turritella (Cretaceous to
present )multi whorls shell, shallow
water environments.
Turritella is a genus of medium-sized
sea snails with an operculum, marine
gastropod mollusks in the family
Turritellidae. [2]
They have tightly coiled shells, whose
overall shape is basically that of an
elongated cone.
NATICA
Natica is a genus of small to medium-sized predatory sea snails, marine gastropods in the family Naticidae, the moon snails
FRESH WATER GASTROPDA:
Planorbis is a genus of air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails, or planorbids. All species in this genus have sinistral or left-coiling shells.
Planorbis
ECHINODERMS (PHYLUM ECHINODERMATA) (THE SPINY SKINNED ANIMALS)
Echinodermata means "spiny" (echinos) + "skin" (derma).
Marine animals. Echinoderms have radial
symmetry, 5-part symmetry, many having five or multiples of five arms.
They lack body segmentation.
They have a shell, made mainly of calcium carbonate, which is covered by skin.
ECHINODERMS (PHYLUM ECHINODERMATA)
Exclusively marine. Some are attached to the seafloor by a stem with "roots" called holdfasts; others are free-moving bottom dwellers.
Geologic range: Cambrian to Recent.
ECHINODERMS (PHYLUM ECHINODERMATA)
water vascular system. Seawater is taken into a system of canals and is used to extend the many tube feet. These have suckers on their tips and aid the animal in attaching itself to solid surfaces.
About 6,000 species — all of them marine. There are 5 classes of echinoderms:Sea urchins
and sand dollars (Echinoidea), Sea lilies (Crinoidea), Sea Stars (aka "Starfish") (Asteroidea), Brittle stars (Ophiuroidea), Sea cucumbers (Holothuroidea)
THE DIFFERENT GROUPS OF ECHINODERMS
CLASS CRINOIDEA (CRINOIDS OR "SEA LILIES") Crinoids are animals which
resemble flowers - they consist of a calyx with arms, atop a stem of calcite disks called columnals. The crinoid is attached to the seafloor by root-like holdfasts. Some living crinoids are swimmers.
Geologic range: Middle Cambrian to Recent. Especially abundant during the Mesozoic.
Diagram illustrating the major body parts of a crinoid.
Fossil Crinoidea
Modern Crinoidea
CLASS ECHINOIDEA (SAND DOLLARS AND SEA URCHINS)
Echinoids are disk-shaped, biscuit-shaped, or globular.
Have five-part symmetry. There are two types of echinoids, the
regulars and the irregulars. Geologic range: Ordovician to Recent.
TYPES OF ECHINODERMS
Lack arms eat algae or are detritus eaters usually have spines
ECHINODERMS:
Phylum: Echinodermata
Class: Echinoidea
(sea urchins)
Order:Regular Irregular
REGULAR ECHINOIDS
Regular echinoids have five-fold radial symmetry
Mouth and periproct at opposite poles. Regular echinoids are mostly epifaunal
mobile grazers that sometimes occur in rocky subtidal and intertidal environments
IRREGULAR ECHINOIDS
Irregular echinoids have bilateral symmetry;
Mouth toward anterior on ventral side, and periproct in posterior interambulacral area.
Irregular echinoids occur primarily in infaunal environments.
The depths at which individuals lived can sometimes be deduced by their external morphology
CLASS: ECHINOIDEA They are exclusively
marine in shallow depths to the abyssal planes.
MORPHOLOGY: They have a hard shell
which when alive is covered by a very thin skin and therefore they have an ENDOSKELETON.
ECHINOID MORPHOLOGY 2
The skeleton (TEST) is made of calcite with tiny interlocking plates which protect and enclose most of the soft parts inside.
The test is usually hemispherical, the interlocking plates are arranged in 10 double columns radiating out from the top of the upper surface (CORONA).
. There are two types of plate:
AMBULACRUMINTERAMBULACRUM
ECHINOIDS MORPHOLOGY 3
Ambulacrum: These occur where the TUBE FEET are positioned.
These feet are connected to the WATER VASCULAR SYSTEM (system of hydraulic tubes) through which water is circulated around the body and can be used to extend the tentacles through the test and can act like feet.
ECHINOID MORPHOLOGY 4
Towards the top (APEX) of the test is the APICAL SYSTEM which is made up of about 10 small plates that are interconnected.
· One plate has a special
function: it is porous and allows sea water into the body = MADREPORITE.
· This water then passes through the RADIAL CANALS and into the tube feet.
ORDERS OF ECHINOIDS: Echinoidea are divided into 2
orders which can be achieved by looking at their symmetry:
REGULAR ECHINOIDS: They are usually circular
when viewed from above. They show a 5-fold
symmetry. Therefore they have a regular pattern.
The apical system is situated on the top and contains the anus in the centre surrounded by the PERIPROCT (membrane).
REGULAR ECHINOIDS 2
The mouth is situated on the underside (ORAL SURFACE) usually in the centre.
JAWS are present although they are rarely preserved.
The upper surface is called the ABORAL SURFACE.
IRREGULAR ECHINOIDS: Look at Page 190
(Black) Micraster and copy the diagram.
· These are not circular but are either flattened
or heart shaped.
They still have 5 rows of ambulacrum and
interambulacrum plates but instead of 5-fold
symmetry they show a bilateral symmetry .
IRREGULAR ECHINOIDS 2
The ANUS is not enclosed within the apical system.
Instead it lies either:1) On the aboral side half way
up the side (Posterior). Sometimes in a groove.
2) On the oral surface towards the posterior.
The MOUTH is found on the oral surface either:
1) In the centre with jaws.2) Closer to the front (anterior)
without jaws.Therefore it is easier to define
anterior and posterior.
IRREGULAR ECHINOIDS 3 Frequently the two rows of pores
within the double ambulacrum plate can diverge from each other and then converge lower down the test forming a distinctive pattern called PETALS or PETALOID.
Sometimes the posterior interambulacrum area can extend down across the oral surface, this usually occurs when the mouth is posterior closer to the anterior end.
This forms a flatish ridge on the oral surface called the PLASTRON.
This may project like a lip across part of the mouth: LABRUM.
ECHINOIDS’ MODE OF LIFE
Varies depending on whether the echinoid is regular or irregular.
All are benthonic, can move and are
gregarious.
REGULAR ECHINOIDS They are usually mobile, moving about
looking for food and protection. Many are capable of living on hard rocks:
anchor themselves to the rocks via tube feet even in relatively shallow water.
Common between the sub littoral zone down to 100 m.
Can also use the tube feet to climb steep rock surfaces.
On sand they use their spines to support them and move themselves using the spines on the oral surface and low down on the aboral.
Could move in any direction. They eat sea weed but also partly
carnivorous: bryozoa and sponges in particular.
Have strong jaws e.g. Echinus lives on rocks.
IRREGULAR ECHINOIDS MODE OF LIFEA) FLATTENED TEST:
Clypeaster lived partially or completely buried in loose sediment and moved forward by moving spines to plough through soft sediment.
The tube feet extract organic matter from sediment and transfer to food tubes.
Lives in shallow water 0.5 - 5 m.
IRREGULAR ECHINOIDS 2B) HEART SHAPED:
Micraster and Echinocardium which could be completely buried.
Common down to 50 m but can survive down to 200 m below sea level.
Lived in burrows of soft sediment (Micraster in fine lime mud).
. Burrows forwards using spines and tube feet
(Mucus can be secreted to help stabilise the sediment to stop collapsing.
IRREGULAR ECHINOIDS 3 Sand etc. is pushed aside and backwards. Organic matter is extracted from the
sediment and the waste disposed behind. Some food is also obtained from the sea
water via a FUNNEL which extends from the burrow.
The tube feet in the upper areas extend out of the burrow.
Water is drawn into the animal and CILIA help waft it into the tube feet respiratory system.
All are gregarious.
ECHINOID HISTORY Upper Ordovician to Recent: Began in the Upper Ordovician but only a small
number. In the Carboniferous the numbers peaked briefly but
reduced during the Permian. During the Mesozoic (Triassic) the numbers increased
again with new species due to a major adaptive radiation after the Permian extinction provided new niches.
They are very rarely found as Palaeozoic fossils as they did not burrow and plates of test not well fused therefore broke up.
Those preserved are usually found in limestone.
ECHINOID HISTORY 2 Irregular appear in the Upper Jurassic and increase
quickly in numbers. They increase so quickly because they were more efficient
food grazers and had improved sanitation with anus removed from the apical system.
Common in limestone particularly chalk. Still abundant today. Micraster was a very important fossil as it evolved quite
quickly and palaeontologists were able to show it changing its mouth and anus positions over time.
This added proof to Darwin’s theory of evolution.
STARFISH (ASTEROIDEA)
STARFISH (ASTEROIDEA)
Carnivores – clams, mussels, bivalves
Motile by way of tube feet
endoskeleton made of calcareous plates (ie. Calcium carbonate)
breathes through dermal “skin gills”
STARFISH ARM
Each arm contains a digestive gland and gonads
The top of the tube feet are called ampulla, like a medicine dropper that is squeezed to create pressure
STARFISH
The eye of the starfish is at the end of the arms. (It is often red coloured)
The anus of the starfish is on the top (aboral side)
The mouth piece of the starfish is called “Aristotle’s Lantern”.
SEA STAR ANATOMY
STAR FISHThe water
vascular system’s opening is called a madreporite. It
opens into a radial canal. The radial canal then
goes out to the arms in radial
canals. The radial canals then feed
water to the tube feet.
Ring Canal
Digestive Gland in Arm
Anus
TRILOBITES: ARTHROPODS PHYLUM
Trilobites are remarkable, hard-shelled, segmented creatures that existed over 520 million years ago in the Earth's ancient seas
TRILOBITES: INTRODUCTIONTrilobites first evolved in the
Lower Cambrian and became extinct by the end of the
Permian.They are most common during
the Cambrian, Ordovician and Silurian.
Therefore they have no modern equivalents and an
understanding of their soft parts has to be based on
modern day arthropods that show some similarity i.e.
crustaceans.They are marine animals.
THE NAME "TRILOBITE," WHICH MEANS "THREE LOBED ",
all trilobites bear a long central axial lobe, flanked on each side by right and left pleural lobes (pleura = side, rib). These three lobes that run from the cephalon to the pygidium are what give trilobites their name, and are common to all trilobites despite their great diversity of size and form.
The main body parts: a cephalon (head), a segmented thorax, and a pygidium (tail piece).
The body can be divided into segments:
Laterally:A central or axial segment.Bounded by two lateral
segments.Transversely into three regions:
Cephalon - “head” area.Thorax - “body” with hinged
segments.Pygidium - “tail” with fused
segments.
PALEOECOLOGY AND LIFE HABITS Trilobites are very common in marine limestones
and shales of the early Paleozoic, especially from the Cambrian Period.
Most trilobites were epifaunal crawlers. Although they occupy a wide variety of
exclusively marine habitats, specific life habits are difficult to discern by morphology alone.
Nonetheless, several aspects of trilobite morphology can indeed provide some clue as to the life habit or activity.
Examples include the elongated cephalic shield of the example which may have aided in ploughing through sediments.
Although most trilobites are considered to have been benthic, the small size and non-descript morphology of agnostid trilobites suggests that these (along with some others) may have been nektonic or nekto-benthic.\
Enrolling of trilobites may certainly have been a defensive mechanism.
TAXONOMY
According to some texts, trilobites are considered to have phylum status and are divided into eight Orders. A less radical classification treats trilobites as a Superclass or Class with two orders: the Polymerida and the Agnostida.
The Polymerida are by far the most diverse of the two in regards to species diversity and also morphologic and ecologic types.
The Polymerids can be identified by their larger size, a well defined cephalic region with eyes and facial sutures, and a large number of thoraxic segments. An easier way to identify Polymerids is by default; if its not a agnostid (easy to identify) then it's a Polymerid. All of the images you have seen thus far are Polymerids, here is another example from this diverse group.
Agnostid trilobites are easily recognizable by their small size, few thoraxic segments (usually around two), and a cephalon without eyes which is superficially similar in morphology to the pygidium. Furthermore, agnostids lack facial sutures.
