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258 Cards in this Set
- Front
- Back
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How old must a specimen be to be a fossil? |
10,000 years |
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What substrates are fossils more likely to be preserved on? |
muddy |
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Direct preservation & common organisms |
Preserved w.o any changes, except the removal of soft tissue - Corals & sponges |
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Indirect preservation & 3 types |
Original organic material is partially or fully changes into a new material - carbonization, petrification, dissolution&replacement |
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Indirect preservation: carbonization |
- Water transforms organism into a thin film of carbon, H2, and O2, leaving a carbon outline of the organism
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Indirect preservation: Petrification |
Groundwater percolates through cores, supersaturating calcium carbonate or silica in pore spaces. Fossil becomes a solid rock partially composed of the original material
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Indirect preservation: Dissolution and replacement |
Groundwater dissolves original material, leaving a void that is filled w/ sediment or minderals. Can have an external mold + cast, or an external mold, internal mold, + a cast |
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Pelagic |
Organisms that live up in the water column
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Nektonic |
pelagic organisms that swim freely independent of currents |
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Planktonic |
pelagic organisms that float/drift in the current |
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benthic |
organisms that live in or on substrate (epifaunal & infaunal) |
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Epifaunal |
Benthic organisms that live on the substrate (cementers or vagrants) - Radially symmetric or assymetric
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Infaunal |
Benthic organisms that live in substrate - bilaterally symmetrical, tend to have a head |
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2 types of infaunal living |
- Burrowing - Boring (bioeroders)
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Organosedimentary build-ups |
bioherms (reefs) and Mounds |
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Bioherms (reefs) |
- rock-like structures produced by the cementing together or organisms w/ secreted skeletons to produce a community of sessile benthic organisms |
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What do the organisms in a reef cause in the environment? |
Higher rate of carbon production than in surrounding environments |
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Mounds |
Steep cone-like piles or flat lenses of relatively small size that form in quiet water - Made of mud, lack macroscopic skeletal structure |
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Where do reefs grow best? |
clear, shallow, tropical waters - limited to photic zone - best in 25-29deg, can grow 18-36 - Salinity 22-40 ppt - Low sediment rates |
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4 Walker-Alberstadt model of reef succession stages & level of species diversity: |
1) Stabilization: low 2) Colonization: low 3) Diversification: high 4) Domination: low to moderate |
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Reef succession: Stabilization |
Accumulation of piles of skeletal debris from echinoderms or algae - Living organisms accumulate around the piles & stabilize the substrate w/ roots and holdfasts |
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Reef succession: colonization |
- Incoming of reef-building organisms - Cementers stabilize, massive branching growth forms framework, builds the crest |
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Reef succession: Diversification: |
reef reaches air/waiter inferface - lateral diversity occurs -- diverse niche spaces for organisms that live in crevices/crack - increase in debris-producing organisms
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When does lateral diversity of reefs occur? |
Diversification stage |
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Reef succesion: Domination |
- Reef dominated by only a few species - typically encrusting growth habits |
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4 parts of the reef |
lagoon, back reef, reef crest, fore reef zone
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when is a lagoon present? |
When the sea level is rising (transgression) - If sea level is stable or regressing, the lagoon will be full of sediment |
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substrate of lagoon |
- High % of organic material due to boring organisms & wave action that breaks off pieces of skeletons - small loose grains that shift easily |
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Species of lagoon |
- Limited to some palegic scavengers and some infaunal bivalves and worms |
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Back reef conditions & what type of growth pattern does this cause? |
- shallow, high light-intensity, high temperatures, some may be exposed during high tide - causes radial growth patterns
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Organisms of back reef |
- stubby, branching, or massive forms that extend above the substrate to allow them to withstand mud & storms - sponges, mollusks, crustaceans, burrowers, infauna |
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Reef crest condigions |
- rigid lattice right up to water/air interface - High-energy, constant wave and wind action
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reef crest organisms |
- cementing organisms - calcerous algae & encrusting crustals |
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Fore reef conditions |
- furthest from shore, slopes steeply down - top part is high-energy due to waves - Lower part is quieter |
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Fore reef organisms |
- cement down to the substrate, or have arms that protrude into the current, reducing the chance of resistance & breakage - Lower part dominated by flat platy corals where flat morphology is ideal for capturing light |
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Which reef section has the highest diversity & number of niches? |
the Fore reef |
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Framework organisms in reefs |
- sponges, archaeocyathids, rudist bivalves, corals |
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Cementing organisms & role in reefs |
- algae, corals, stromatoporoids - fill in spaces left by framework, binding reef together |
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Bioeroding organisms |
- Bore into reef & take over skeletons - clinoid sponges, boring bivalves |
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Base of the carribean reef |
limestone & calcium carbonate skeletons
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Where are massive & branching corals found in the reef? |
- back reef, where light is abundant and sedimentation rates are high |
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Benefit of massive/branching coralshape |
- sediments are removed easier so they don't get buried |
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Where are encrusting corals found in a reef |
at the reef crest where waves break on them |
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Stromatolites |
layers of sedimentary rocks formed by mats of cyanobacteria in the photic zone of the sea floor |
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How stromatolites are formed |
cyanobacterial mats covered in sediment, cyanobacteria migrate up towards light, leads to buildup of extensive layered mounds |
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Where do stromatolites form? |
on stable substrate (rock), not on shifting substrate (sand) |
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Modern conditions that support stromatolite growth & modern example |
- extreme conditions that deter growth of competitors or grazers - Shark Bay, australia (Hamelin pool): narrow opening to the pool limited flow of seawater and caused very high evaporation rate, so very saline --> typical grazer snails are absent |
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What depth are stromatolites restricted to in hamelin pool and why? |
- 4m because below that calcification can't occur |
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What roles do stromatolites play for other organisms? |
- Colonized by intertidal microbial mats - provide shelter for small organisms, a substrate for marine plants, a source of food for crustaceans & fish |
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Are sponges symmetric? |
No, most are asymetric |
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Shape of: -Deep water sponges vs. shallow water |
- Deep: stalk-shaped - Shallow: broad and flat |
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Unique thing about sponge cells |
- are independent of one another: if separated and put back together, will recombine, clump, and reform the organism |
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When did sponges first appear? |
Cambrian |
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Mesolgea |
jelly separating 2 layers of cells in sponges and between outer and inner layers of polyps |
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Sponge skeleton |
Within the mesoglea, and made of spongin: a flexible network of protein fibers
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Spicules function |
reinforce the mesoglea |
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Paragaster |
sponge central cavity, opens at top through the operculum |
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Ostia |
small openings on the outside of the sponge which mark entrance into tiny canals |
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3 types of sponge cells |
- Epithelial: Line outside of sponge & canals - Choanocytes: occupy internal chamber & assist w/ moving water through sponge - Amoebocytes: digestive, reproductive, and skeletal roles --> secrete spicules |
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Feeding processes of sponges |
- Draw water through ostia --> pumped along canals by beating of choanocyte flagella, food gets stuck in sticky collars --> inside paragaster, O2 and organic matter adhere to choanocytes, where nutrients are ingested --> wastewater & CO2 exit through operculum
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Sponge: Absorption/breakdown of food |
- Choanocytes phagocytose food into a food vacuole --> picked up by amoebocytes --> complete the digestion -> move through mesolgea to distribute the nutrients |
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Calcerous sponges |
- Calcium carbonate spicules - Monaxon, straigh or slightly curved or shaped like a tuning fork |
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Common sponges |
- Spicules made of silica - Monaxon or tetraxon - Some have desmas spicules: lumpy, irregular |
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Hexactinellid sponges |
- Spicules made of silica - Rays diverge at right angles, usually triaxon (6 rays) joined to adjacent spicules to form a skeleton |
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Important hexactinellid sponge |
Hydenoceras, important framework organism in Devonian reefs |
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3 SA:V solutions of sponges |
1) Increased complexity of body chamber 2) Bumps on exterior of chamber |
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3 levels of complexity of sponges |
- Asconoid: simple, small, unconvoluted walls - Scyonoid: Partially convoluted, little chambers - Leuconoid: Highly convoluted walls, lots of sycon-like chambers |
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Sponges that acted as bioeroders & when |
- Clionid sponges in the Jurassic |
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How did clionid sponges kill cora? |
Larva attach to coral, grow into adults branching into coral, damage it |
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Evidence of clionid corals in fossil record |
- Clionid chips (40% debris in Jurassic age) - Clionid burrows in host skeleton fossils |
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Why can sponges live so deep in the water? |
- Not dependent on sunlight like corals are |
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What do sponges eat? |
Marine snow: dead bodies and waste |
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Archaeocyathids |
- sessile, exclusively-marine filter-feeders commonly lived in 20-30m deep water |
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Morphology of archaeocyathids |
- calcium carbonate skeleton made of exterior & interior cone - Joined by septae
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Intervallum |
Space between two cones of archaeocyathids |
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How did archaeocyathids feed? |
Draws water through pores in outer wall, filters nutrients through intervallum, expels waste through pores in inner wall out the top |
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Were archaeocyathids solitary or colonial? |
Both |
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Stromatoporoids |
- Sessile benthic filter-feeders
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When & where were stromatoporoids common? |
- In shallow water in ordovician --> devonian communities |
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How do stromatoporoids grow? |
by secreting calcerous sheets |
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Skeleton of stromatoporoids |
- Composed of laminae parallel to substrate & pillars vertical to the substrate |
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Mamelons |
swellings on surface of stromatoporoids with astorhizae/canals radiating from the centre |
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How do stromatopodoids feed |
Filter-feed through pores at the base of the animal --> passes through astorhizae canals, waste excreted out mamelons |
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2 morphologies of stromatoporoids & their respective roles |
- Domes: framework - Sheets: cementing organisms that filled cracks in reefs |
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Corallite |
- calcium carbonate coral cup that polyp sits in |
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Where is coral poly mouth & what does it do? |
- at top, surrounded by 8 or more tentacles - It is the only opening, so it intakes food and exretes waste |
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Polyp outer cell layer |
secrete skeletal parts, have muscle cells that control movement, sensory and nerve cells, and cnidocytes |
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Polyp inner cell layer |
- Assimilates food
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Polyp mesoglea cell layer |
- Jelly circulates fluids between outer & inner - Amoeboid cells suspended here
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Cnidocytes |
- Stinging cells mostly on polyp tentacles, each one has a nematocyst with a coiled barbed threat |
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How does polyp digest the food brought into the body cavity by the tentacles |
- Gland cells in the inner layer secrete enzymes to digest the food, and special cells engulf & digest the food, then nutrients diffuse from cell to cell |
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Corralite septa |
- occur in a radial arrangement - sometims septal grooves occur where septa join the skeletal wall - converge @ centre of corralite, creating a central axial structure |
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Calice |
area at top of the corallite where the polyp is attached |
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Coral growth stages |
- Free-swimming larvae - Grow on a basal plate & secrete radial septa - Too big for corralite: secrete dissepiments to push the body up higher in the corralite to make room for growth, and tabula for it to sit on |
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Dissepimentarium |
- Concentrated area of dissepiments: small angled plates that push the poly up higher in the corralite to make more room for growth
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Tabularium |
- Concentrated area of tabula: Horizontal sheets for polyps to sit on |
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Coral: solutions to SA:V problem |
1) Internal soft tissues protrude into digested cavity in vertical folds 2) Grow septa on the corralite which protrude up beyond the base of the soft polyp, creating folding of soft tissues |
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How is the rate of earth's rotation changing? how can we tell? |
- Decreasing by 2 seconds/100,000 years - Growth bands on corals |
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What type of algae are zooxanthellae |
dinoflagellates |
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equation for production of calcium carbonate by corals |
Ca + 2HCO3- --> CO2 + H2O + CaCO3 |
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equation for photosynthesis by zooxanthellae |
CO2+H2O + Light --> organics + O2 |
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Algae/coral symbiosis: - Advantages to coral |
- photosynthesis removes CO2 from system, driving the production of calcium carbonate (can grow up to 3X faster) - recieves addtional food & oxygen from organics produced by algae |
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Algae/coral symbiosis: - Advantages to algae |
- habitat - increased CO2 to use for photosynthesis - protection from coralnematocyts |
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Algae/coral symbiosis: - disadvantages to coral |
- restricted to photic zone (100m), and temps > 20C b/c those suit the algae |
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Algae/coral symbiosis: - disadvantages to algae |
- could be eaten |
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Tabulate coral |
- Well developed tabulae - reduced or absent septa - colonial - calcite skeleton - Had zooxanthellae, found in shallow water |
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3 most common genera of tabulate coral |
- Favosites (honeycomb) - Halysites (chain) - Syringopora (organ pipe) |
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Favosite tabulate coral |
- colonial, packed together in long narrow tubes - coral head grows by asexual budding |
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Halysite tabulate coral |
- corrallites linked in chains that loop back, leaving gaps - sediment accumulates in the holes |
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Syringopora tabulate coral |
- organ pipe coral - loosley bundled linked by calcium carbonate rods - appear noticeably seperate |
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Rugose corals |
- wringled outside edges - colonial (hexagonal) & solitary (HORN) - calcite skelton - usually have tabulae - Probs didn't have zooxanthellae
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Scleractinian corals |
- colonial or solitary - aragonite skeleton - no tabulae, but dissepiments are developed
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Hermatypic scleractinian corals |
- framework organisms in modern reefs - have zooxanthellae - Basal plate seperates polyp from substratum, permitting anchorage of animal to substrate - secrete aragonite on exterior to attach to adjacent corals |
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ahermatypic scleractinian coral - |
non reef-building - can live in cold waters down to 6000m - lack zooxanthellae |
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2 theories of scleractinian evolution |
1) arose from rugose corals 2) Arose from sea anemones |
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Rugose coral septal patterns |
- Originally 2: cardinal & counter septum - Then inserted in 4s - Have fossula: gaps between septa in up to 4 areas - new septa branch off of old ones |
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Scleractinian coral septal patterns |
- Originally: 6, then 6 each time - No fossula - Septa are parralell
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When did Brachiopods first exist? when did they dominate? |
- Arose in cambrian - Diversified and dominated in paleozoic
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Brachiopod symmetry
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- In one valve: bilaterally symmetric/equilateral - Between valves: Inequivalved |
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Where are the 2 shells of a brachiopod attached? |
at the hinge |
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Lophophore |
Organi in brachiopods: - Series of tentacles lined w/ cilia that cause a current to sweep food and oxygenated water towards the mouth - Assist with food gathering and respiration |
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Pedicle |
Organ in brachiopods: - fleshy stalk that protrudes through one of the valves and attaches the animal to the substrate |
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Articulate brachiopods |
- Hinges have teeth on one valve that fit into sockets of other valve - Shell open & closed via an antagonistic muscle system |
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What to brachiopod adductor muscles do? |
- Close valve by contracting: quick fibres permit quick closing, slow fibres help them stay closed |
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What do brachiopod diductor muscles do? |
Contract, pulling valves open to 10 deg. |
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What do brachiopod adjustor muscles do? |
Move the animal with respect to the pedicle to reorient in the water column |
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What limits the size of brachiopods? How do they solve this? |
- Size of lophophore (SA:V) |
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Inarticulate brachiopods |
No formal hinge with tooth/socket system |
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How do inarticulate brachiopods open? |
Muscles squeeze the body cavity so it expands around margins and opens shell by 10 deg |
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Modes of life of brachiopods (4) |
attached, cementing, free-lying, burrowing |
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Attached brachiopods |
Attached to substrate via pedicle |
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Pedicle foramen |
Opening that pedicle petrudes from |
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Cementing brachiopods |
One valve is cylindrical & cements to substrate, the other forms a cap on top - Mimic solitary corals - formed framework component in Permian reefs
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Free-lying brachiopods |
Juveniles attached by pedicle --> lose pedicle, foramen is sealed off - Large, can sit under their own weight - Spiral brachida to fix SA:V problem |
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What one group of brachiopods used the burrowing lifestyle? |
Lingulids |
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Burrowing brachiopods |
- Tongue-shaped shell & long pedicle - Burrow head-first using valves in scissor-like motion, produces U-shaped burrow |
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What limits the deepness of burrowing brachiopods? |
- Lophophore not supported by brachidia, instead respire using cilia - Lateral cilia form an inhalant pseudo-siphon, generating current of water in towards mouth - Frontal cilia form exhalant pseudo-siphon to expel water |
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Brachiopods through time: Early camprian, middle cambrian, ordovician, devonian, end-devonian mass extinction, permian |
- Early camb: Large, complex, abundant. Inarticulate abundant - Mid camb: Articulate/inarticulate equal - Odovician: Articulates more diverse & #s - End-devonian mass extinction: many groups went extinct - Permian: moderate diversity |
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What phylum do bivalves belong to? |
Mollusca |
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Common examples of bivalves |
clams, mussels, oysters |
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When did bivalves first arise? When did they dominate benthos? |
- Arose in cambrian, but sidelined by brachiopods - Dominated benthos after the end-permian extinction |
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What type of feeders are bivalves |
- mostly filter. some deposit & carnivores - some parasitic, living in gut of sea cucumbers |
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Symmetry of bivalves |
- Equivalved: valves are bilaterally symmetric - Inequilateral: Individual valve isn't symmetric |
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Distinguishing features of a bivalve |
large foot + gills, muscle scars, teeth and sockets on both valves |
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Monomyarian |
Bivalve with a single adductor muscle scar - usually epifaunal |
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Dymarian & 2 types |
Bivalve w/ 2 adductor muscle scars - Isomyarian: both same size - Anisomyarian: posterior adductor muscle is enlarged |
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How are bivalve shells held together |
attached at top by an elastic protein ligament |
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Describe muscle system of bivalve |
- Natural state = open - To close, uses adductor muscles to draw valves together - To open, adductor muscles relax and it springs open |
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Mantle |
In bivalves, the thin membrane that surrounds the soft parts and secretes valves, ligament, and hinge teeth
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Pallial line |
In bivalves, where the mantle attaches to the shell - circular mark near external portion of inside of shell |
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Bivalve foot |
Byssal threads secreted from foot permanently anchor animal to substrate |
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Functions of bivalve gills |
- Gas exchange - Good filtered from water & passed via streams of mucus to the mouth |
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6 modes of life of bivavels (4 epifaunal, 2 infaunal) |
- Epifaunal: Bysally-attached, cementing, free-lying, swimming - Infaunal: Burrowing, boring |
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Where are byssally-attached bivales found? Common example |
- Attached to firm substrates (rocks) - High energy environments b/c hairs act as rudders, reducing force on shell - mussels |
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Rudists |
cementing bivalves: one valve is larger & moe conical, cements onto substrate. Cone shaped, mimic corals - important framework for cretaceous reefs |
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Free-lying bivalves & modern examples |
- Originally cemented via beak - thicken bottom of shell by secreting calcium carbonate --> sit under own weight - Giant clams, devil's toe nails |
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How do swimming bivalves jet propel? |
Take water into mantle cavity --> seal cavity by contracting adductor muscles --> creates pressure --> cavity opened --> water squirts out |
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Infaunal bivalve features |
- Siphons: protrude up through sediment - Have a pallial sinus: inward bend in posterior portion of pallial line where animal stores its siphon when it moves - Have a gape: permanent opening that allows siphon to protrude - Dimyarian |
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How do burrowing bivalves burrow? |
By rhythmically contracting their 2 adductor muscles |
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A small group of bivalves feed by: - why is this inefficient? |
Deposit feeders: scavenge sediment surface w/ inhalant siphon to pick up particles - b/c organic content of sediment is very low |
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How to boring bivalves bore? |
- Chemically using weak acids - or mechanically by open/closing valves or grinding back & forth - Some of gouging apparatus w/ knobs or serrations |
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When did true siphons evolve? |
Permian |
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What was the turning point for the evolution of bivalves? |
The end-permian extinction: competing groups went extinct, more niche space - 95% of brachiopods went extinct, only 60% of bivalves |
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Muscle systems: brachiopods & bivalves |
- Brachiopods: 2 muscle system - Bivalves: 1 muscle system |
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Advantages of Bivalves over brachiopods |
- More diverse (there are no swimmer/borer brachiopods) - 1 muscle-system is more efficient - Foot can be used to move and dig (vs. brachiopod pedicle which is stationary) - Gills have enormous SA:V (vs. lophophore, relatively low ration) - Siphons allow them to live lower in substrate |
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how do organosedimentary communities react to extinction events? |
slow to recover & very eeffected b/c of complex diversity interactions |
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Precambrian domating organisms |
stromatolites |
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Cambrian dominating orgainsms |
stromatolites & archaeocyathids (both mounds) |
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Ordovician dominating organisms |
- Reefs: stromatoporoids/corals - Mounds: sponges |
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Silurian dominating organisms |
Reefs: stromatoporoids/corals Mounds: Stromatoliites |
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Devonian dominating organisms |
stromatoporoids/corals (reefs) |
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Mississipian & Pensylvanian dominating organisms |
Algae (mounds) |
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Triassic dominating organisms |
Reefs: corals/stromatoporoids/sponges Mounds: Stromatolites |
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Jurassic |
Reefs: corals, stromatoporoids, sponges |
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Cretaceous |
Reefs: rudists,corals, stromatoporoids |
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Cenozoic dominating organisms |
reefs: corals |
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What environments did tribolites live in? |
Entirely marine |
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When did tribolites evolve & go extinct? |
-Evolved: early cambrian - Extinct: end of permian |
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Tribolite symmetry |
bisymmetrical: symmetric on either side when divided down the middle |
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Tribolite exoskeleton |
- hard, jointed - calcium carbonate - divided into cephalon, thorax, pygidium |
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Cephalon |
Tribolite head. Contains concentrated sensory system, eyes, glabella |
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Glabella |
tribolites: raised area in centre of cephalon with ridges (glabellar furrows) - may have been digestive chamber or egg sac |
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Thorax |
Tribolites - 2-61 articulating body segments |
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Pygidium |
Tribolites 1-30 fused segments |
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Some tribolites had spines. What were their functions? |
-protection, asssistance w/ molting, help w/ shallow burrowing, stabilize, spread body weight out |
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What are compound eyes? |
Each eye has many lenses, and the c-axis is perpendicular to the surface of each eye |
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Holochroal eyes |
- more primitive & widespread - small, closely-packed hexagonal lenses - entire eye covered in a single membrane - Double refraction causes fuzzy images |
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Schizochroal eyes |
- Large thick lenses, onlya few per eye - Round seperated lenses - Each lense covered by its own membrane - Biconvex lenses -- curved organic inner interface, outer calcium carbonate - 2 materials have different refractice indexes, corrects double refraction, perfectly focused |
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Theory of evolution of schizochroal eyes |
- Juvenile holochroal eyes look like schizochroal eyes, so they were just retained in the adult form |
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4 unusual eye types |
No eyes, huge eyes, stalked eyes, columnar with eyeshades |
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Ecdysis |
Growth of triboltes by molting of exoskeleton |
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Facial structures |
- Lines where the 3 facial plates of tribolites join |
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Proprarian |
- most primitive tribolite face shape, found in larval stage |
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Gonatoparian |
tribolite face shape |
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Opisthoparian |
more complex tribolite face shape, intersects the middle of the base of the cephalon on each side |
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Tribolite feeding |
- Some Detritovores: fed on organic matter - Some filter feeders - Mostly carnivores or scavangers |
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Rusophycus |
impression of a resting tribolite in sediment |
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Cruziana |
impressions of a tribolite moving through mud |
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Diplichnites |
trace fossil created by tribolites walking freely across a harder surface |
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Unique mechanisms tribolites used to protect ventral side from predators |
- bring cephalon & pygidium together to roll into a ball - some had tooth & socket pairs on cephalon & pygidium to allow two parts to inerlock |
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Agnostid tribolites time period |
early cambrian --> ordovician |
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agnostid triboltes |
- Very small, no eyes or facial structures, unsegmented pygdium, 2-3 thoracic segments - crawled, swam, or planktonic |
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Polymerid tribolites timeline |
- early cambrian - permian |
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Polymerid tribolides |
- well developed compound eyes - all 3 types of faial structures, 5-61 thoracic segments, segmented pygidium - often micropygous |
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Micropygous |
in tribolites, when the pygdium is smaller than the cephalon |
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what was different about tribolites when they first evolved? what evidence is there of this? |
- Lacked a mineralized exoskeleton - tracks slightly predate body fossils |
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When did tribolites first exist? |
early Cambrian |
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What caused extinction of the tribolites? |
Global drop in sea level during the middle permean, which reduced shelf and reef habitats |
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3 Broad trends in tribolited morphology through time |
1) Reduction in # of thoracic segments 2) Development of a distinct pygidium: due to fusion of lowest segments, then a weakening of the borders between the segments to fuse them 3) Weakening of glabellar furrows |
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What phylum do cephalopods belong to, and who are they related to? |
- mollusks - related to bivalves |
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Nautiloids & ammonoids |
exclusively marine cephalopods that have shells |
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timeline of nautiloids |
- Ordovician --> still extant
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timeline of ammonoids |
devonian --> end cretaceous extinction |
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Cephalopods shell morphology |
- Planispiral: coil in a single horizontal plane - Whorl: each 360 deg revolution - Venter: Outside edge of each whorl L |
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Living chamber |
- houses soft body of tribolites - |
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soft body |
Tribolites: - 90 tentacles that help gather good and reproduce - hyponome: folded flat tube for jet propulsion - digestive system, gills, reproductive organs |
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Aperture |
Tribolites: opening in shell through which the soft body projects |
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Phragmocone |
Tribolites: A series of gas-filled chambers separated by septa |
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Siphuncle |
Tribolites: a soft-tissue organ that runs through the center of the phragmocone chambers and connects themto the mantle cavity - contains bloodvessels, nerves, cells |
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5 subtypes of Polymerid tribolites |
-olenellus, paradoxides, phacops, isotelus, eoharpes |
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Modern cephalopod analouge (still living) |
- Nautilus - Found in 15deg water along equator of pacific ocean |
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Nautilus feeding |
- reef predators & scavengers - sticky tentacles grab prey --> pass food to mouth (middle of tentacles) --> mouth has beak-like jaw to crack shells and tear food --> processed by hard radula --> swallowed |
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Nautilus locomotion- |
- Jet propulsion by drawing water into mantle cavity then opening hyponome - can direct water at any angle by moving the hyponome |
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How do cephalopods control their buoyancy |
- Shell 3x less denser than water - Need to lower density by filling phragmocone chambers with gas |
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Cephalopod buoyancy control during growth |
- adds new chambers to phragmocone behind soft body as it grows - Fills new chamber with liquid, but as animal gets heaviers, removes liquid & replaces w/ air |
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How do growing cephalopods remove water from their phragmocone chambers? |
- By usingthe siphuncle, which connects the mantle cavity to the chambers - Water remains in chambers until septum is 1/2 full thickness, and strong enough to withstand hydrostatic pressure |
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Osmotic pressure vs. hydrostatic pressure in cephalopods - |
- Water only empties out of the chamber if the osmotic pressure between chamber liquid & blood in siphuncle is larger than the hydrostatic pressure difference between chambers and sea water - As animal goes deeper, osmotic difference must be increased to exceed the hydrostatic pressure |
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How does nautilus change its depth in the water column? |
- Never completely empties phragmocone chambers, allowing it to empty/refill chambers - needs to alter [salt] on chamber side of siphuncle to do this - Wants to go deeper: pumps salt out of chamber so chambers don't flood with liquid |
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Why do nautilus max out at 600 m depth |
- Water pressure keeps increasing, while phragmocone pressure remains below 1 - shell & septa must be strong enough |
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Why do nautilus often bump into things while moving through the water column? |
- travels shell-first, can't see where its going |
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How do nautilus detect predators and prey? |
- tentacles have highly developed chemical sensors |
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Earliest nautiloids |
- Main scavenging & predatory animals of the early paleozoic - straight-shelled cones facing down towards hte gound - longicones or brevicones |
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Apical end |
pointed end of nautiloids |
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Apical end of longicones vs. brevicones |
- longicones: 10-15 deg. long & thin cone(slow growing) - brevicones: 20-25 deg, short & fat shell (fast growing) |
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Degree of stability of straight-shelled cephalopods |
- The further apart center of mass and center of buoyancy are, the mre stable |
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Center of buoyancy |
- 3/4 down shell as measured from apicall end
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Center of mass |
displaced towards body chamber, where heavy mass is |
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Advantages of brevicone nautiloids |
- More stable: soft body near aperture, further from center of buoyancy |
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Disadvantage of brevicones |
- face down with wide-open aperture, open to predators
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Time limitation of brevicones |
limited to early - middle ordovician |
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Counterweight principle (success of longicones) |
- Add weight to the apical end which tips soft body away from substrate, enhanced protection from predators & lowered drag |
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Longicone orthocerids |
- Cameral calcium carbonate deposists at apical end for counterweight principle, but not in siphuncle so it could stll function - some used crytoconic coiling (cytocones): slight bend in the shell |
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Longicone actinoceratoids |
- siphuncle deposits of calcium carbonate - siphuncle remained connected to phragmocone chambers via narrow pore, so still able to control buoyancy |
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Longicone ebdiceratoids - |
huge siphuncle set off from center of shell for the counterweight principle - infilled cones of calcium carbonate at apical end |
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Coiled nautiloids |
- planispiral shells - Silurian --> today - reduces drag & adds strength to shell b/c spherical shape produces a more even distribution of hydrostatic forces |
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5 differences in nautiloids vs. ammonoids |
- position of siphuncle - concave vs. convex septa - shell thickness -diversity of shell shape - structural complexity |
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Position of siphuncle: ammonoids vs nautiloids |
- Nautiloids: runs through middle of septal faces in center of chambers of phragmocone - Ammonoids: Ventral - runs along outer edge of chambers, just under the shell |
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Concave/Convex speta, ammonoids vs. nautiloids
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- Nautiloids: Septa concave to body chamber -- make slast eptum weak - Ammonoids: Convex to body chamber & more complex on outer edges |
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Shell thickness, ammonoids vs. nautiloids |
- Nautiloids thicker than ammonoids
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Diversity of shell shape, ammonoids vs. nautiloids |
- Ammonoids: Variable: compressed/depressed - Nautiloids: mostly globular |
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Suture line |
Cephalopods: the junction where each septum meets the animal'sshell: look like lines on the outside of the inernal mould |
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Structural complexity ammonoids vs nautiloids |
- Nautiloids: No weak flat areas, so suture lines are simple - Ammonoids: Sometimes have flat areas, so septa can be complex |
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How to septa increase ammonoid shell strength
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- pillars that splay on the roof, transmitting the weight - Compressed ammonoids: buttresses are horizontal - Depressed ammonoids: buttresses are vertical |
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Saddles |
septal suture lines closer to animal |
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Lobes |
septal suture lines further from animal |
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Ammonoid goniatities |
simple saddles & lobes |
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Ammonoid ceratites |
simple saddles & frilled lobes |
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Ammonoid ammonites |
frilled saddles, frilled lobes |
