MT1 Flashcards
Fossils
lithified remains of once living organisms
Body fossils
-hard body parts (teeth, shells, bones, wood, etc)
-soft body parts are much harder to preserve – much rarer
Trace fossils
-record behaviour of fossils
-tracks, trails, burrows, etc.
Biomineralization
-process by which organisms produce hard skeletons
Basal Skeleton
-protective base to which a soft body is attached
-like corals, bryozoans
5 types of skeletal material
-Calcium carbonate – invertebrates, corals, sea urchins, clams
-Calcium phosphate – vertebrate bones
-Silica – some sponges
-Cellulose – plants
-Chitin – arthropods
3 Types of Calcium Carbonate
-low magnesium calcite
-high magnesium calcite
-aragonite
Silica
-not common
-diatoms
-some types of sponges
-Radiolarians
Calcium Phosphate
-only common in 2 main groups
-vertebrates
-linguliformean bachiopods
Cellulose
-long polysaccharide chains
-form strong fibers
-resistant to decomposition
-found in plants - cell walls
Chitin
-modified polysaccharides
-common in arthropod exoskeletons
4 Main types of Trace Fossils
-tracks – discrete footprints formed by arthropods or vertebrates
-trails – continuous traces left by invertebrates
-burrows – variety of structures that penetrate soft sediment surface
-borings – like burrows but penetrate hard rock or shell surface
Coprolites
-trace fossil
-mineralized shit of animal
-can tell us about diet or ecosystem
Gastroliths
-common in birds & reptiles
-animals eat stones to help their stomachs grind food
-might have helped some aquatic species
Trace Fossil Pros & Cons
Pros
-can give clues on environment & ecology, animal behaviour, sediment concentrations
Cons
-producer not often preserved
-multiple organisms can make same kind of trace or several different kinds
-same structure can be preserved differently depending on substrate
-long stratigraphic ranges
Environments that favour fossilization
-anaerobic, nutrient poor, hypersaline
-little to no transportation
-rapid burial
-little to no diagenesis
Taphonomy
-study of all the processes that occur between death of organism & it’s final state
-disarticulation
-fragmentation
-abrasion
-bioerosion
-corrosion & dissolution
-flattening – happens after burial
-diagenesis – happens after burial
Raup’s Taphonomic Filters
a fossil must make it through each of these processes to be discovered by paleontologists
-anatomic
-biological
-ecological
-sedimentary
-preservation
-diagenetic
-metamorphic
-vertical movement
-human
Types of preservation
-complete
-soft-tissue
-carbonizatin
-unaltered hard parts
-recrystallization
-replacement
-molds & casts
concretions
Complete Preservation
-original material is still present in it’s original form
Soft Body Fossils
-soft-bodied organisms are generally rare in fossil record
-decomposition usually occurs before burial
-occurs under exceptional circumstances
-called Lagerstatten
Carbonization
-volatile compounds driven off by pressure/heat
-only carbon film remains
Unaltered preservation
-soft parts decay away & hard parts remian
-hard parts retain original composition & structure
Recrystallization
-less stable mineral forms change into more stable crystal forms
-change in structure of fossil
Permineralization
-addition of new minerals into pore spaces of original fossil
-original tissue often replaced
-tissue structure preserved
Replacement
-shell replaced by another mineral
-often preserves gross morphology but obscures fine detail
-silicification
-pyritization
-phosphatization
Molds & Casts
-internal mold shows internal features of organism
-external mold shows exterior of organism
-cast of organism is from infilling of mold
Concretions
-form early during diagenesis as minerals that precipitate around a nucleus
-nucleus is commonly organic
-harder than surrounding rock, protects fossil from weathering
Taxonomy
-science of classifying living organisms
Biological Species
-a group that is reproductively isolated from other groups
-generally distinct.
Morphological Species
-species that share similar morphological characteristics
-can be quantified statistically
-commonly applied in paleontology
Gradualism
-slow but sustained evolution over time
-gradual introduction of new species through time
-relatively constant
Punctuated equilibrium
-sudden pulses of evolution in short intervals
-often occurs during environmental changes
Niche of species limiting factors
-environmental – temp, salinity, precipitation
-competition – competing with other species
-predation – species is predator or prey
Population
-single group of individuals of single species
Community
-multiple species that live in an area
Ecosystem
-organisms within a community & physical environment
Pelagic
-lives in water column
planktonic –floating in water column
nektonic – swimming through water column
Benthic
-lives on sea floor
vagile – able to move under it’s own power
sessile – settles ont seafloor (libro=free-lying, fixo=attached)
epifaunal – above the sea floor
infaunal – below the sea floor
Photic Zone
-region of marine habitat that can get light
Aphotic Zone
-region of marine habitat that can’t get light
-most of marine environment
Supratidal
-above high tide
Intertidal
-between high & low tide
Subtidal
-below tidal zone (continental shelf)
Bathyal
-continental slope
Abyssal
-ocean floor
-basin floor is more commonly used now
Hadal
-ocean trenches
Why do organisms burrow?
-protection from predators, environment
-easier access to resources
Types of Trace Fossils
-dwelling structure – Domichnia
-sediment feeding structure – fodinichnia
-grazing on sediment surface – pascichnia
-locomotion – repichnia
-resting & hiding – cubichnia
Diplocraterion
-dwelling structure
-U shaped curves
-maintain ideal burrow depth through erosion & sedimentation
Skolithos
-dwelling structure
-vertical worm burrows
-like diplocraterion but straight up & down, no curves
Thalassinoides
-dwelling structure/feeding burrow
-branching, Y-shaped
unlined burrows, built in cohesive muddy sand
Zoophycos
-feeding structure
-corkscrew mine
Planolites
-feeding structure
-random tunneller following a food-rich layer
-not efficient
Teichichnus
-feeding structure
-back & forth miner
-either mine sediment upwards or downwards
Chondrites
-feeding structure
-branch miner
Rosselia
-feeding structure
-muddy sediment & organic matter is trapped in cone by mucous lining
-encourages growth of bacteria
-re-mined by worm
-cone shaped
Phycodes
-feeding structure
-originates from central base point & fans outwards in pattern of individual burrows
Grazing Structures
-mainly just spirals on ocean floor made by large worms
Cruziana & Diplichnites
-locomotion traces
Lockeia & Rusophycus
-resting traces
Graptolites
-colonial organism
Rhabdosome
-entire colony of a graptolite
Stipe
-an individual branch of a graptolite
Theca
-an individual chamber of a graptolite
Sicula
-joins the Nema (top spiky point) with the stipes
-turns into stipes as it goes down
Zooid
-small colonial animals that live in individual theca
-use cilia like projections to filter for food
Skeleton of Graptolites
-organic skeleton reinforced by a chitin like substance (like arthropods)
-goes through carbonization process
-tough but flexible
-insoluble in most acids
-usually preserved in deep-water fine-grained rocks as carbon film
Time Period of Graptolites
-range from middle cambrian to late carboniferous
-most abundant in ordovician & silurian
Orders of Graptolites
-Dendroidea
–benthic, stuck around the longest
–cambrain to carboniferous
-Graptoloidea
–planktonic
–ordovician to denovian
Dendroidea
-multibranched colonies
-stipes connected together laterally
-some genera may have become planktonic in late cambrian
Graptoloidea
-stipes less interconnected
-increasing degree of symmetry throughout evolution
-planktonic lifestyle drifting with ocean currents
-locomotion is uncertain
–thought to be attached to floating mats of algae
–some theories that they had a membrane like structure, like jellyfish
–now thought to have drifted on ocean currents like a net
–zooids may have used wing-like appendages
–may have been able to rotate the colony to move up & down water column, spinning like a helicopter - might explain spiral morphology
Graptolite Evolutionary Trends
-benthic to planktonic transition
–helped to protect from benthic predators
–Anisograptid fauna: late cambrain to early ordovician
-3 main graptolite evolutionary faunas
–Dichograptid fauna: early & middle ordovician
–Diplograptid fauna: late ordovician
–Monograptid fauna: Silurian
Dichograptid fauna
-reduction in number of stipes
Diplograptid fauna
-change in flexure, pendant to V shaped
-evolved straight median septum & short, angular theca
Monograptid fauna
-reduction in number of stipes & theca
-thought to offer more stable hydrodynamics
-some developed spiraling structures
-thought to be able to swim via coordinated movement of zooids
Anisograptids
-evolution of planktonic graptolite forms
Extinction of planktonic graptolites
-early devonian
Extinction of dendroid graptolites
-late carboniferous
Why are graptolites excellent index fossils?
-rapid evolution
-wide distribution
-easy to identify
-distinct characteristics restricted to specific time period
Planktonic graptoloids
-all graptoloidea
-suspension filter feeders
-zooids living in the theces extract nutrients from water column
Nektonic graptolites
-some graptolites may have been capable of active swimming
Fixosessile-epifaunal graptolites
-dendroideans
-suspension filter feeders
Phylum: Porifera
-sponges
-multicellular eukaryotes
-specialized cells for specific functions
-variety of forms (vase-shaped, bulbous, cylindrical, branching less common)
-mostly marine & fixosessile (fixed to marine floor)
-filters - filter water
-body walls enclose central body cavity (spongocoel) that opens to external environment via osculim
-small pores in body wall (ostia) allow seawater to enter sponge
-paragaster - internal cavity of sponge
Archaeocytes
-sponge cells for digestion, nutrient transport
-develop into sex cells, contained within mesohyl (gelatinous matrix within body of sponge)
Choanocytes
-sponge cell
-flagellate cells that line the inner wall of the body cavity (spongocoel)
Porocytes
-sponge cell
-form ostia to allow water into sponge
Sclerocytes
-sponge cell
-secrete spicules (minute skeletons)
Pinacocytes
-sponge cell
-protect the outside of sponge
Spongocytes
-sponge cell
-contained within mesohyl, secrete spongin protein
Leucon
-most common type of sponge
-most complex
-lots of ostia, 1 big osculum
Sponge Reproduction
-can be asexual or sexual
-asexual reproduction is budding
-sexual reproduction is jizzing into water & fertilizatioin
–sexual sponges ar hermaphrodites
Sponge Skeleton
-made of either spongin or calcareous/siliceous spicules
-spongin – hardened organic material, make up body wall
-calcareous or siliceous spicules – secreted by specialized cells called sclerocytes, may be seperate elements within sponge or interwoven into complex structures
Megascleres
-classification of spicules
-comprise structural skeleton of sponge
Microscleres
-classification of spicules
-scattered throughout sponge
-less likely to be preserved
Spicules are grouped by shape & number of?
Rays/axes/appendages
-monoaxon - 1 ray
-tetraaxon - 4 rays
-triaxon - 3 rays
-desmas - oddly shaped ones
-polyaxons - irregular shaped ones
-microscleres - minute in scale
Demosponges
-class demospongea
-skeletons are made up of siliceous spicules
–1 ray or 4, and/or spongin
-can be freshwater along with marine
-cambrian to present
Calcareous Sponges
-class calcarea
-skeletons entirely comprised of calcareous spicules packed in dense networks
-cambrain to recent
-important reef formers in mid-paleozoic
-mostly limited to shallow, warm seas
–firm substrates for attachment
–supersaturation of CaCO3 for biomineralization
Glass sponges
-class Hexactinellida
-skeletons of opaline, silica spicules, 5-6 rays
-abundant in paleogene & neogene on continental shelf
-today, only common at bathyl & abyssal depths.
-ordovician to recent
-live below 200m
-very slow growing
Heterotrophic Sponges
-filter water to gather food particles & microscopic organisms for food
Autotrophic Sponges
-have photosynthetic symbionts living in their body
Carnivorous sponges
-trap parine invetebrates
-located in deep sea
Sponges good index fossil?
-no
-long range, so not good
2 Fossil sponge groups
-Archaeocyatha
-Stromatoporoids
Archaeocyatha
-calcareous skeletons with body walls
-first reef forming organisms of early cambrian
-some debate to affinities but most likely a type of sponge
-found worldwide
-commonly solitary, also some branching colonial forms
-early to middle cambrian
Stromatoporoids
-calcareous skeletons with parallel lamellae intersected by vertical pillars
-ordovician through devonian
Laminar & Dorsal sponges
-forms in higher energy settings
Dendroid & Columnar sponges
-forms in lower energy settings
