Paleontology - Fossils

Benthonic

organisms that live on or within the seafloor

• crabs, starfish, worms, snails, clams, etc…

Bilateral symmetry

divided into two essentially identical halves

Bivalved symmetry - across the valves

divided where the left and right shells are different in shape/appearance but the shells themselves are bilaterally symmetrical

Bivalved symmetry - between the valves

divided where the individual valves are not symmetrical although each shell strongly resembles the other one

Carbonization

fossil is reduced to a thin sheet of carbon, outline and remains of cells get preserved

Cast

a shape produced by filling a cavity; preserves the shape of the organism, but not the internal details

Chemical fossil

organic residues in rocks that indicate the presence of now-vanished animals and plants

Colonial organism

where many individual animals share common walls and structures

Conispiral coiling

the interior of an animal’s shell contains an elongate spiral tube that tapers, spiraling upward

Coprolite

the preserved excrement/feces of now-vanished animals

External mold

ex. impression of an animals spine or growth lines, no actual fossil present

Internal mold

ex. impression of details of muscle attachment or shell hinges, actual fossil may not be present

Leaching

chemical activity that corrodes or bleaches the surfaces of fossils

Nektonic

organisms that can freely move about within the habitat of the sea floor

• fish, squid, jellyfish, arthropods, and mammals

Paleontology

the study of the naturally preserved remains or traces of once-living organisms (plants and animals)

Pentameral symmetry

divided into five portions radiating around some midpoint

Permineralization

minerals transported by water fill in all the open spaces of an organism or organic tissue

What is planispiral coiling?

a type of shell structure in which the shell is coiled in a flat, spiral shape, forming a single plane

Planktonic

organisms that either float or swim so weakly that they are essentially at the mercy of waves and currents

• phytoplankton & zooplankton

Pseudofossil

mineral or rock features that resemble fossils, but are actually formed by non-biological processes

Radial symmetry

divided into a pattern resembling the spokes of a bicycle wheel

Recrystallization

the original body materials are removed and new materials displace them, fine details look different, different composition

Replacement

the original body materials are removed and new materials displace them, looks the same but different composition

Solitary organism

when only a single animal occupies a structure

Steinkern

a type of fossil formed when sediment fills the internal cavity of a hollow object, like a shell, and then hardens, leaving a stony cast after the original shell has dissolved

Trace fossil

fossils of the tracks, trails, burrows, borings, and body impressions of an organism

What is trilobate symmetry?

a form of symmetry seen in certain organisms, characterized by three distinct lobes or sections along the body

Unaltered hard parts

the preservation of the dead organisms minerals

Unaltered soft parts

the preserved original tissues of a dead organism