| abathochroal |
eyes with compound lenses,
each with separate cornea, each lens separated from others by shallow scleral
walls; corneal membrane ends at lens edge. see holochroal, schizochroal. |
| adaxial |
toward the axis (center line). |
| articulating facets |
see facets. |
| axial |
pertaining to the axis. |
| axis |
central lobe running the length
of the trilobite body; the glabella is the main expression of the
cephalic
axis. |
| cephalic |
pertaining to the cephalon. |
| cephalon |
frontmost trilobite part;
head. |
| coaptation |
close interlocking of opposing surface during enrollment |
| conterminant |
hypostome attached
to anterior doublure via suture. see impendent, natant. |
| dorsal |
referring to the top or back
surface, as opposed to ventral. |
| doublure |
shell continuation under the
trilobite, typically as a ventral cephalic and/or pygidial
rim. |
| effacement |
loss of detail. |
| enrollment |
bending of the body to enclose vulnerable ventral
organs in a protective clam-like or spheroid capsule formed by the cephalon,
pygidium
and thoracic segments. |
| facets |
flat surfaces, typically where
two adjoining body parts meet and articulate (move); e.g., articulating
facets on thoraxic pleural segments. |
| fixigena |
"fixed cheek" cephalic
shell surrounding glabella inside of facial sutures. see
gena,
librigena. |
| fulcrate |
referring to thoraxic segments
with a geniculation (bend) separating a horizontal inner portion from an
inclined outer portion. |
| gena (pl., genae) |
cephalic shell of the
cephalon
surrounding the glabella, usually divided by sutures into
fixigena
and librigena. |
| genal angle |
angle formed by the meeting
of the lateral (side) and posterior (rear) margins of the cephalon;
sometimes expressed as a genal spine. |
| genal
spine |
a spine anywhere on the gena
(cheek) of the cephalon, typically at the genal angle. |
| glabella |
middle (axial) portion of
cephalon,
typically convex and lobed. |
| gonatoparian |
facial sutures ending
at the tip of the genal angle. |
| granulate |
bearing granules or similar
sculpturing on the outer exoskeleton. |
| holaspis |
final developmental stages
beyond meraspis, attaining a certain number of thoraxic segments
considered typical of "adult" individuals, and typically with cephalic
and pygidial characters of adult. |
| holochroal |
eyes with compound lenses
directly in contact, all covered by a single continuous smooth corneal
surface. see abathochroal, schizochroal. |
| hypertrophy |
grown well beyond normal size. |
| hypostomal |
pertaining to the hypostome. |
| hypostome |
a piece of exoskeleton on
the venter (underside) of the cephalon, thought of as a mouthpart.
Typically the anterior edge of the hypostome lies directly under the anterior
edge of the glabella. |
| impendent |
type of conterminent hypostomal
attachment, but doublure underlies anterior glabellar edge, so anterior
hypostomal border does not match anterior glabellar border. see conterminant,
natant. |
| isopygous |
cephalon and pygidium
similar in size. see micropygous, macropygous. |
| konservat-lagerstatten |
special category of fossil deposits (fossil-lagerstatten)
where soft tissue features have been conserved particularly well (as in
the Burgess Shales). see lagerstatten. |
| lagerstatten |
geological deposit, especially fossil-lagerstatten
(fossil beds), konzentrat-lagerstatten (concentrations of fossil
parts) and konservat-lagerstatten (fossil beds with remarkably conserved
soft body detail - see above) - more |
| librigena |
"free cheek" cephalic
shell to the right and left of the glabella outside of facial sutures,
often lost during molting or after death. see fixigena, gena. |
| macropygous |
pygidium larger than
cephalon.
see isopygous, micropygous. |
| meraspis |
developmental stage following
protaspis,
bearing more than one segment, but with fewer than adult number of thoraxic
segments. see protaspis, holaspis. |
| micropygous |
pygidium much smaller
than cephalon. see isopygous, macropygous. |
| natant |
hypostome free, not
attached to the cephalic doublure. |
| occipital |
pertaining to the occiput. |
| occiput |
posterior portion of cephalon,
the axial portion is considered part of the glabella (occipital
ring). |
| opisthoparian |
facial sutures ending
along the rear margin of the cephalon adaxial to the genal
angle. see gonatoparian, proparian. |
| opisthothorax |
posterior, narrower portion
of thorax when it is divided into wider, anterior prothorax
and opisthothorax. |
| palpebral |
portion of fixigena
associated with the eye. |
| perrostral |
along the edge of the rostrum. |
| pleura
(pl., pleurae) |
lateral (side) part of thoraxic
segment or lateral (non axial) part of pygidium. |
| pleural |
referring to pleurae. |
| postaxial |
extending from the end of
the axis. |
| preglabellar
field |
portion of cephalon
in front of glabella. |
| proparian |
facial sutures ending
forward of the genal angle. |
| protaspis |
developmental stage lacking
segments. see meraspis, holaspis. |
| prothorax |
anterior and wider portion
of thorax when it is divided into prothorax and narrower, posterior opisthothorax,
as seen in some Redlichiida. |
| pygidial |
pertaining to the pygidium. |
| pygidium |
hindmost segment; tail. |
| pyriform |
pear-shaped, typically referring to
the glabella |
| rostral
plate (rostrum) |
middle portion of the ventral
cephalic doublure, typically where the hypostome attaches. |
| schizochroal |
eyes with compound lenses,
each with separate cornea, each lens separated from others by deep scleral
walls; corneal membrane extends downward into sclera. see
abathochroal,
holochroal. |
| spinose |
bearing a spine or spines. |
| subisopygous |
pygidium large, but
not quite as large as cephalon. |
| subparallel |
nearly parallel in arrangement,
slightly diverging or converging. |
| suture |
linear break in exoskeleton,
typically along which parts separate during molting. |
| thorax |
middle, segmented body portion
between cephalon and pygidium. see prothorax, opisthothorax |
| thoracic |
pertaining to the thorax. |
| tuberculate |
bearing tubercles or similar
sculpturing on the outer exoskeleton. |
| ventral |
referring to the underside. |
| vincular
furrow |
a groove along the anterior and/or lateral cephalic
doublure to accommodate the edge of the pygidium and thoracic
pleurae during enrollment (e.g., a feature of some Phacopida). |
