Fossil Identification Flashcards
(22 cards)
1
Q
Sponges
A
- paraphyletic
- few types of cells, not organized into tissues
- no nervous system
- intermediate between single celled organisms and the more complex metazoans
- sessile benthic organisms and are all filter feeders.
- roughly vase shaped
- external shape of a ‘sponge’ is often determined more by the environment in which it lives than what type species it is)
- The central cavity is called the paragaster and it is usually open at the top via the osculum
- ostia>outer wall
- choanocytes>collared cells lining the chambers, which use their flagellum to generate the influent current
- outside the collar is sticky, which food particles get stuck on
- amoeboid cells>move the body and transport food
2
Q
what are the 3 basic groupings of sponges and talk about them
A
- classified based on their complexity
1. ascon grade>least complex, sac body, single chamber lined with collared cells
2. sycon>number of grouped ascon-like chambers with a central opening, somewhat complex
3. leucon>number of synconlike elements that open into a large central cavity. are more efficient feeders because the complex grades have more surface area in collared cells>rare, small size
The grades in ‘sponges’ is not related to taxonomy, so in other words ascon, sycon and leucon grades just describe the complexity of the body, not how they are related to each other
3
Q
how are the clades of sponges defined?
A
- defined by how their support structures are made. Sponges typically have support structures made up of spongin (a horny material) and/or a skeleton made up of calcareous or siliceous spicules.
- spicules vary in shape which is important
4
Q
what are the basic types of spicules sponges have?
A
monaxons, triaxons, tetraxons, polyaxons…refer to image
5
Q
discuss the ecology of sponges
A
- Sponges vary from cyclindrical and globular forms to low, tabular encrusting forms; some bore into rock substrates
- Desmsponges>most abundant living sponges, have a skeleton of spongin, and their mineral skeleton ) is made up of siliceous spicules that are never triaxonic, and occasionally a calcareous basal skeleton is present.
- the calcareous skeleton is preserved in the fossil record>the stromotoporoids
6
Q
tell me about stromotoporoids
A
- Cambrian to Oligocene, common in Ordovician to Devonian, where they were important reef builders.
- When the upper surface is preserved stromotoporoids usually have swellings, called mamelons, that groves that lead to the centre of the mamelons called astrorhize….refer to image
- These structures are believed to be exhalant canal systems
- They have a basal, laminated-to-vertically tubular, calcareous skeleton. Growth form is largely controlled by the environment. Often they have strong vertical elements called pillars joined at intervals and traversed by thin horizontal laminae. They grow as laminar sheets that can vary in form due to changes in the environment such as changes in sedimentation rate. The laminae are often grouped into sets, that resemble seasonal tree growth-rings called latilaminae. The galleries are the spaces between the laminae and in life were either filled with sea water or soft tissues, but in fossils are filled with calcite spar.
7
Q
tell me about Archaeocyatha (arKeeosyatha)
A
- Cambrian
- calcareous cone shaped organisms
- we will not put them into a group within the sponges because of disagreeance with which group they belong to.
- lower Cambrian and persist until the upper Cambrian
- earliest reef building organisms, but these early bioherms are usually dominated by stromatolitic algae with the archaeocyathids playing a secondary role
- one inverted cup inserted into another separated by vertical radial partitions (septa).
- inner and outer walls are perforated by pores allowing water to flow through the body
8
Q
tell me about Receptaculita (Reseptaculita)
A
- ordovician to permian
- They have been placed in the porifera, in the algae and in their own phylum.
- common in Lower Paleozoic carbonate rocks.
- found in calm marine waters
- They were radially symmetrical, globose calcareous marine organisms.
- distinctive mineralized element, the merom, arranged in whorls around the central axis of symmetry. The radiating pattern of the meroms usually gives then a honeycomb or sunflower look, because of this they are sometimes called Sunflower corals
9
Q
tell me about cnidarians
A
- simplest true mesozoans, cells are organised into tissues, unlike sponges
- included are jellyfish, corals, sea anemones and other colonial orgs
- two layers of tissue, outer ectoderm and the inner endoderm, separated by an acellular mesoglea or a mesenchyme (mezənˌkīm) containing some cells
- A single opening surrounded by tentacles leads to a single gastrovascular cavity (the enteron).
- All cnidarians have stinging cells on their tentacles called nematocysts that they use to capture their prey. Their life cycle typically has two alternating stages, the polypoid and medusoid stages. Usually sessile polyp asexually produces free-living medusa by budding. Medusae produce eggs and sperm. Fertilized embryo develops into ciliated planaria larva which settles onto the bottom and metamorphoses into a polyp.
10
Q
what are the two groups of cnidarians and why are they split up?
A
-based at least partially on which stages dominates, the Anthozoa which spend most of their lives as polyps and the Medusozoa that most members spend most of their lives in the medusoid stage (the hydrozoans are the exception).
11
Q
tell me about Class Scyphozoa, Conulariids
A
-ordovician to triassic
- possess a steeply pyramidal, four-sided, phosphatic skeleton
- Each face carries transverse ridges and was divided longitudinally by a narrow median groove. They bear a strong resemblance to chitinous skeletons of certain scyphozoan polyps.
-
12
Q
tell me about class anthozoa
A
- precambrian to recent
- exclusively marine cnidarians, mesusoid stage (free swimming stage) is absent
- colonial (asexual) or solitary
- sexual reproduction is also possible>have gonads on partitions (mesentaries) within the gastrovascular cavity
- external fertilization typicaly but sperm can be drawn into gastrovascular cavity
- The fertilized egg develops into a planktotrophic planula larvae that is often long-lived with high dispersal capability. The larva eventually settles and metamorphoses into a polyp.
- polyps are tubular shaped
- The mouth, which is surrounded by nematocyst-bearing tentacles leads to a muscular pharynx that extends into the inner gastrovascular cavity. The pharynx usually bears cilia that function in driving water into the gastrovascular cavity.
- gastrovascular cavity used for circulation and digestion, which is divided by partitions (mesentaries) which are projections of inner body wall. most mesentaries fuse with the pharynx
- Initial digestion of prey takes place inside the gastrovacular cavity and the product of this initial breakdown is a soupy broth, which is carried to the gastrodermis for further digestion.
- The edges of the mesentaries may be extended into long mesentarial filaments that function in defence and feeding (see diagram of a colonial scleractinian coral below). Corals secrete a skeleton of calcium carbonate that includes vertical partitions (septa) that act as supports for the mesentaries (septa are inserted beneath the spaces between the mesentaries)
13
Q
what are the most important subgroups within anthozoa?
A
-subgroups> corals and sea anemones(zoantharia)
14
Q
what are the 3 orders of corals? talk about them
A
- rugosa
- tabulata
- schleractinia
The skeletons of scleractinian and rugose corals are superficially similar to one another. The entire skeleton of a coral is termed the corallum, regardless of whether the animal is solitary or colonial.
- corallite>single polyp
- Thus, the corallum of a solitary coral (one polyp) consists of a single corallite, whereas the corallum of a colonial coral (many polyps) is composed of many corallites. Polyps occupy only the uppermost, cup-shaped surfaces of the corallites and, in modern species, the polyps can retract down into their cups for protection (most modern Carribean species emerge to feed only at night, whereas those living in the Pacific often feed during both day and night).
- epithica>outer wall of skeleton
- two elements in the corallite
1. septa>vertical partitions that support the mesentaries
2. tabulae>As the polyp grows, the skeleton is extended upwards. The bottoms of the corallites are periodically sealed off by horizontal these partitions. this becomes the new basal portion of the polyp. - dissepiments>additional support structures (cyst like plates), deposited in tabulae
15
Q
what are the two skeleton criteria for schleractinia and rugosa?
A
-Rugose and scleractinian corals may be separated by two skeletal criteria: the relationship between the septa and the corallite walls and the manner in which the septa are inserted into the corallite during growth.
16
Q
tell me more about schleractinian corals
A
- middle triassic to recent
- characterised by regular, radial pattern of septal insertion during growth
- septa are in multiples of 6
- Scleractinian septa are distinctive in commonly standing high above the rim of the corallite (exsert septa; see above) and continue along the epitheca as ridges or costae
- colonial and solitary
- individual polyps are connected by extensions of gastrovascular cavity
- mesenterial filaments in extending from the partitions (mesentaries) in the gastrovascular cavity. These are important in competitive interactions between modern species (competition is for living space). When polyps of different species come into contact, one species may extrude its mesentarial filaments (either through the mouth or through pores in the body wall) over the other, dissolving its tissues, much as it might digest food (refer to image)
17
Q
what do living schleractinian corals fall into?
A
- hermatypic>construct reefs. Hermatypic corals have evolved a mutually 13 beneficial relationship (symbiosis) with a group of single-celled, photosynthetic algae (termed zooxanthellae; zo. in the diagram above) which actually live in the cells of the body tissues (normally in the gastrodermis).
- zooxanthellae provide nutrients to coral hosts and influence rates of growth (imp bc rapid growth are important to reef development (as they are in competition with other corals I think).
- Because the algae need sunlight for photosynthesis, hermatypic corals are restricted to shallow, clear waters (typically less than 90 m). Modern hermatypic corals are also sensitive to water temperature and typically live in the range of 25°C-28°C. They cannot tolerate average minimum temperatures less than about 20°C. - ahermatypic> dont construct reefs
- Ahermatypic forms lack the algal partners, have lower rates of skeletal growth and do not construct reefs.
- Ahermatypic corals are environmentally more widespread, occurring at a wider range of depths (down to 6000 m) and water temperatures (down to 1°C).
18
Q
tell me about the order rugosa
A
- middle ordovician to permian
- colonial or solitary, and are characterized by a pattern of growth in which septa are inserted in distinct regions or quadrants of the corallite. Gaps between the quadrants are termed fossulae (sing. fossula).
- Unlike scleractinian corals, in which septal insertion occurs regularly around the margins of the corallite, rugose corals tend to have septa inserted in distinct quadrants.
- Initial growth involves a pair of septa inserted at the “north and south poles” (left diagram). Subsequent insertion is in 4 regions on each side of the initial pair of septa; gaps or fossulae are present in the “equatorial region”. One of the first formed septa is often reduced in size later in growth, producing an additional fossula (near the “south pole” of the diagram above). Thus, rather than radial symmetry, as in scleractinians, rugose coral skeletons commonly display bilateral symmetry
- Unlike scleractinian corals, septa of rugose corals are not extended beyond the outer epithecal walls (i.e. exsert septa and costa are not present). Rather, the intersection of each septum and the epitheca is marked by a shallow groove (septal groove).
- growth forms in rugosa include:
1. fasciculate (dendroid, phaceloid)
2. massive (cerioid, astraeoid
Cerioid: closely packed, polygonal corallites with distinct epithecal walls.
Asteroid: closely packed, polygonal corallites without distinct epithecal walls.
Dendroid: loose, irregularly branched corallites.
Phaceloid: subparallel coralites that may be joined by small lateral branches
19
Q
tell me the ecology of rugosa
A
- common in Paleozoic carbonate rocks, live in warm, shallow, clear waters.
- built primarily by other organims (notably the stromatoporoids).
20
Q
tell me about tabulata
A
- Paleozoic (mid Ordovician-Permian)
- colonial only
- corallum is made of polygonal, circular or elliptical, tubular corallites
- Within the corallites, tabulae are well developed but septa are greatly reduced in size or are absent altogether.
21
Q
what are the suborders of tabulata?
A
- Favostina(mid Ordovician-Permian)
- slender, polygonal to subcircular corallites
- Corallite walls are perforated with openings called mural pores, which presumably allowed correction between the soft tissues of adjacent polyps. - Aulaporina(mid Ordivician-Permian)
- Corallum of relatively few corallites characterized by creeping or encrusting branches (reptant growth form) - Halysitina(mid Ordovician-upper Silurian)
- Corallum with elliptical corallites in meandering chains (cateniform growth form). Mural pores absent - Syringoporina ( mid Ordovician-Permian)
- Fasciculate corallum with cylindrical corallites connected by horizontal tubules.
22
Q
tell me about the ecology of tabulata
A
-living environments similar to rugose corals, but like the rugose corals, are minor in reef building. dont know if they had algal symbionts
