Dictyonema sensu stricto Dictyonema is a genus of
callograptid which can reach large sizes, with a specimen of
D. retiforme having dimensions of roughly 120 × 130 mm. The genus is distinct because of its mesh-like structure, formed by
thecal bridges that occur when one or multiple
thecae on one
stipe cross over to an adjacent stipe.
Dictyonema, like other callograptids, has ropy-looking compound stipes formed by multiple tubular thecae. However, unlike
Ordovician callograptids, the thecae of
Dictyonema do not extend laterally to form 'twigs,' making differentiating between true callograptid
Dictyonema and
dendrograptid Dictyonema with simple stipes extremely difficult. The thecal apertures of
Dictyonema are isolated and oriented ventrally (towards the center of the colony). Triad budding is possible, but there is no morphological differentiation between
autothecae and '
bithecae'.
"Dictyonema" sensu lato There are several species of
Dictyonema with simple
dendrograptid thecae and dissepiments (e.g. '''D'. cotyledon
, 'D'. peltatum
, and 'D'. rarum'') that will need to be moved to a different genus. In these taxa, bithecae are easily determined from autothecae and dissepiments are constructed from fusellar and cortical material secreted by the zooids of adjacent bithecae without any thecae crossing over to adjacent stipes. ==Species==