NAME Laevitubulus crassus
AGE Late Ordovician to Early Devonian.   AGE span: 460.9...397.5 mya
K&J CLASSIFICATION (2000) Fungi Imperfecti, Mycelia sterilia.
FIGURE(S)
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Pl.30fig.13.jpg
FIGURE REFERENCE Burgess ND, Edwards D. 1991. Classification of uppermost Ordovician to Lower Devonian tubular and filamentous macerals from the Anglo-Welsh Basin; Botanical Journal of the Linnean Society, v. 106, p. 41-66.
SPECIES, AUTHORITY L. crassus Burgess & Edwards 1991, p. 48, fig. 6.
LOCATION Anglo-Welsh Basin, Great Britain.
ORIG DESCRIPTION* Tubes 6.5-30 µm in diameter, straight or helical and unbranched. Wall 3-10 µm thick and opaque. The longest specimen is 800 µm long and incomplete. All tubes are unbranched, have thick walls (fig. 7) and are rigid. Specimens remain opaque even after prolonged oxidation in Schulze's solution. They are usually straight and stick-like, but may be helical with individual gyres 50-200 µm apart (figs. 5, 6). Rare specimens taper to a closed end (fig. 6).
COMMENTS* Laevitubulus tenuis is thinner-walled and never helical. Other members of the genus are thinner-walled, translucent and may be branched.

Edwards (1982; figs. 76, 77) illustrated similar tubes from the late Ludlow of Wales. These were regarded as melanosclerites and thus of probable animal origin. However, the Melanoscleritoidae, a group of Problematica first described by Eisenack (1942), were diagnosed as: "Axially symmetric, often polar and occasionally ramifying remains". As in Eisenack's illustrations most species appear closed at both ends, and are perhaps not hollow (Eisenack, 1942; 1963), they are unlikely to be of the same origin as ours. Similar tubes are seen in tube-wefts of nematophytales, but whether they derive solely from the Nematophytales or a number of sources cannot be decided.

Derivation: crassus-thick, refers to tube wall.
PUBLICATION REFERENCE Burgess ND, Edwards D. 1991. Classification of uppermost Ordovician to Lower Devonian tubular and filamentous macerals from the Anglo-Welsh Basin; Botanical Journal of the Linnean Society, v. 106, p. 41-66.
K&J REMARKS Melanosclerites are presently considered juvenile (planula and early polyp) stages of certain coelenterates (Cashman, 1996).
TYPE
ALL NAMES (Including synonyms) Laevitubulus crassus
SERIAL NUMBER 882
PUBLIC COMMENTS
 *For source, see Publication Reference.