Dictyonema

Dictyonema retiforme, photographed by K. Carlson at the Peabody Museum of Natural History.

Belongs within: Dendroidea.

Dictyonema is a genus of dendroid graptolites known from the Upper Cambrian to the Carboniferous, characterised by a conical, net-like colonial structure. Branches of the colony are connected by transverse threads (dissepiments) that are extrathecal in origin and composed of cortical tissue. In members of the Upper Silurian subgenus Pseudodictyonema, the thecae are elongate, giving the stipe a somewhat 'ropy' appearance; members of the subgenus Dictyonema have thecae with a more standard length ratio (Bulman 1970).

Characters (from Bulman 1970): Rhabdosome conical, varying from almost cylindrical to almost discoidal, with thecate or nonthecate stem or rarely attached by nema; branching dichotomous, stipes straight, subparallel to parallel, united by transverse dissepiments, anastomosis rare; authothecae denticulate, commonly spined, rarely tubular and isolate; bithecae normally inconspicuous.

<==Dictyonema Hall 1851 (see below for synonymy) B70
    |--D. (Dictyonema) B70
    |    |--*D. (D.) retiforme (Hall 1843) (see below for synonymy) B70
    |    `--D. (D.) crassibasale B70
    `--D. (Pseudodictyonema Bouček 1957) B70
         `--D. (*P.) graptolithorum Počta 1894 B70

Dictyonema incertae sedis:
  D. campanulatum B70
  D. canadense B70
  D. cavernosum B70
  D. cervicorne B70
  D. cotyledon B70
  D. estlandicum K48
  D. falciferum B70
  D. furciferum Ruedemann 1904 [=*Airograptus furciferum] B70
  D. inconstans B70
  D. longilingue Kozłowski 1948 K48
  D. parabola J79
  D. peltatum B70
  D. rarum B70
  ‘*Nephelograptus’ rectibrachiatus Ruedemann 1947 B70
  D. rectithecale Kozłowski 1948 K48
  D. rhinanthiforme B70
  D. scitulum B70
  D. vinculosum Sherrard 1956 F71
  D. wimani K48
  D. wysoczkianum Kozłowski 1948 K48
    |--D. w. wysoczkianum K48
    `--D. w. macrothecale Kozłowski 1948 K48

Dictyonema Hall 1851 [=Dictyodendron Westergård 1909, Dictyograptus Hopkinson 1875; incl. Airograptus Ruedemann 1916, Damesograptus Jahn 1892, Nephelograptus Ruedemann 1947] B70

*Dictyonema (Dictyonema) retiforme (Hall 1843) [=Gorgonia retiformis, *Dictyodendron retiforme, *Dictyograptus (sensu Hopkinson) retiformis] B70

*Type species of generic name indicated

REFERENCES

[B70] Bulman, O. M. B. 1970. Graptolithina with sections on Enteropneusta and Pterobranchia. In: Teichert, C. (ed.) Treatise on Invertebrate Paleontology pt V 2^nd ed. pp. V1–V149. The Geological Society of America, Inc.: Boulder (Colorado), and the University of Kansas: Lawrence (Kansas).

[F71] Fletcher, H. O. 1971. Catalogue of type specimens of fossils in the Australian Museum, Sydney. Australian Museum Memoir 13: 1–167.

[J79] Jaanusson, V. 1979. Ordovician. In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A136–A166. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[K48] Kozłowski, R. 1948. Les graptolithes et quelques nouveaux groupes d’animaux du Tremadoc de la Pologne. Palaeontologica Polonica 3: i–xii, 1–235.