Reticulosa is an extinct order of sea sponges in the class Hexactinellida (glass sponges) and the subclass Amphidiscophora.^[1][2] Reticulosans were diverse in shape and size, similar to their modern relatives, the amphidiscosidans. Some were smooth and attached to a surface at a flat point, others were polyhedral or ornamented with nodes, many were covered in bristles, and a few were even suspended above the seabed by a rope-like anchor of braided glass spicules.^[2][3]

Quick Facts Scientific classification ...

Reticulosa Temporal range: Cambrian–Jurassic PreꞒ Ꞓ O S D C P T J K Pg N
Fossils of Hydnoceras, a large dictyospongiid from the Upper Devonian
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Porifera
Class:	Hexactinellida
Subclass:	Amphidiscophora
Order:	†Reticulosa Reid, 1958

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Reticulosans comprise the vast majority of Paleozoic hexactinellid diversity, though only a few species survived up to the Mesozoic.^[2][3] They may include the oldest sponge body fossil in the world: Palaeophragmodictya, from the late Ediacaran (~555 Ma), was originally described as a reticulosan based on its mesh-like surface texture.^[4] Ediacaran-type preservation has obscured any information about spicule structure, and some authors doubt that Palaeophragmodictya is a sponge in the first place.^[5][6][7] Regardless, unambiguous reticulosans appear in the fossil record not much later, in the early Cambrian.^[2]

Like most other glass sponges, reticulosans had a skeleton of unfused macroscleres reinforced with microscopic microscleres. Their macroscleres are often stauractines (four-rayed spicules, + shaped), though pentactine (five-rayed) or hexactine (six-rayed) spicules may be predominant in certain regions of the skeleton. The outer layer of the skeleton forms a regular mesh-like pattern, with incrementally smaller spicules filling in the gaps between larger spicules in a fractal pattern. The microscleres, when present, are simple bundled rods (paraclavules).^[2][3]

The living glass sponge Sclerothamnus is sometimes compared to the reticulosan family Titusvillidae,^[2][8] though it is more commonly placed in the family Tretodictyidae of the order Sceptrulophora.^[9]

From the Treatise on Invertebrate Paleontology (2004), unless otherwise noted:^[2]

• Superfamily †Dictyospongioidea Hall & Clarke, 1899
  • Family †Dictyospongiidae Hall & Clarke, 1899 [Ediacaran?–Middle Permian (Roadian)]
  • Family †Docodermatidae Finks, 1960 [Silurian (Ludlow)–Permian]
  • Family †Stereodictyidae Finks, 1960 [Carboniferous (Visean)–Upper Triassic (Carnian)]
• Superfamily †Dierespongioidea Rigby & Gutschick, 1976
  • Family †Aglithodictyidae Hall & Clarke, 1899 [Upper Devonian–Carboniferous (Visean)]
  • Family †Amphispongiidae Rauff, 1894 [upper Silurian]
  • Family †Dierespongiidae Rigby & Gutschick, 1976 [Middle Ordovician–Lower Permian (Artinskian)]
  • Family †Hydnodictyidae Rigby, 1971 [middle Cambrian–Upper Ordovician]
  • Family †Multivasculatidae Laubenfels, 1955 [upper Cambrian]
  • Family †Titusvillidae Caster, 1939 [Upper Devonian–Lower Mississippian, Holocene?]
• Superfamily †Hintzespongioidea Finks, 1983
  • Family †Hintzespongiidae Finks, 1983 [lower Cambrian–Middle Devonian (Givetian)]
  • Family †Teganiidae Laubenfels, 1955 [upper Cambrian (Furongian)–Upper Mississippian]
• Superfamily †Protospongioidea Hinde, 1887
  • Family †Asthenospongiidae? Botting, 2004^[10] [Ordovician]
  • Family †Protospongiidae Hinde, 1887 [lower Cambrian–Jurassic]
  • Family †Triactinellidae? _{Botting, 2005}^[11] [Ordovician]