Miscellaneous Groups
MORPHOLOGY
Image modified from Moore and Harrington, 1967
The image below shows the external characteristics of conularids.
MORPHOLOGY
Images from Berry in Boardman, Cheetham, and Rowell, 1987
The images below show examples of the principle soft part anatomy of graptolites and the hard exterior morphology (which is commonly preserved).
TERMINOLOGY
Definitions of terms from Bulman, 1970
Adnate thecae Thecae that have adhered together during growth.
Amplexograptid theca Strongly geniculate theca with deep and long, rounded apertural excavations, generally with infragenicular selvage and typically with low rounded apertural lappets.
Apertural spine Projection originating on margin of aperture; commonly single, less commonly paired.
Aseptate Biserial rhabdosome lacking median septum (a partition in biserial graptoloids separating two series of thecae).
Axillary angle Angle at the base of V-shaped bifurcation of dichotomously branched rhabdosomes, and especially bifurcation of dicranograptids.
Biserial Scandent (stipes growing erect and enclosing or including the nema/virgula) graptoloid rhabdosome with two series of thecae enclosing nema.
Branch See stipe.
Climacograpid theca - strongly geniculate theca with straight or slightly convex supragenicular wall parallel to axis of rhabdosome and relatively short (narrow) apertural excavation.
Dicalycal theca Graptoloid theca giving rise to two buds ( c.f. normal asexual reproduction in which single bud is produced by each zooid.
Everted Plane of aperture facing outward (cf. introverted, retroverted)
Geniculum Angular bend in direction of growth of graptoloid theca, especially climacograptid or lasiograptid; hence supragenicular, infragenicular.
Geniculate Has an angular bend in direction of growth of theca.
Introverted Plane of aperture facing inward (dorsally), resulting from excessive growth of ventral wall of theca usually accompanied by sigmoidal curvature of thecal axis.
Isolation Separation of distal (metathecal) portions of thecae from stipe.
Mesial Middle portion of free ventral wall (supragenicular wall) of theca; hence mesial spine.
Metatheca distal portion of graptoloid theca, morphologically equivalent to autotheca of dendroids, etc.
Nema Threadlike extension of apex of prosicula, extending embryonic nema prosiculae ; probably solid in adult rhabdosomes. May have served for attachment or may terminate in disc of attachment or vanelike float structures. Known as virgula in scandent (stipes growing erect and enclosing or including the nema/virgula) graptoloids.
Orthograptid theca Straight, parallel-sided, tubular theca of biserial graptoloid.
Periderm Horny substance of scleroproteic composition forming skeleton of Graptolithina, comprising inner (fusellar) layer with growth bands and growth lines and outer (cortical) layer of finely laminated tissue.
Prosicula Proximal, initially formed part of sicula, apparently selected as single conical unit with faintly marked spiral thread; at later stage longitudinal fibers are added.
Rhabdosome Sclerotized exoskeleton of entire graptolithine colony.
Selvage Thickened margin, especially of aperture.
Septate Rhabdosome having a median septum.
Sicula Skeleton of initial zooid of colony, comprising conical prosicula and tubular distal metasicula.
Stipe One branch of a branched rhabdosome or entire colony of unbranched rhabdosome.
Subapertural spine See apertural spine.
Th 11, 12, 21, etc. Th 11 is the technical term for the first formed theca in the branching series of thecae that make up many graptolite exoskeletons. The following thecae are consecutively numbered in the same manner.
Theca (pl., thecae) Sclerotized tube or cup (other than sicula) enclosing any zooid of rhabdosome.
Uniserial Rhabdosome or stipe of graptoloid consisting of single row of thecae only.
Virgella Spine developed during growth of metasicula (distal portion of sicula), embedded in sicular wall and projecting freely from its apertural margin.
Zooid Soft-bodied individual inhabiting theca.
MORPHOLOGY
Images from Adrain, 1992
The sketch below illustrates two different kinds of Machaeridian body plans.
