Melanosclerite Explained

The Melanosclerites are a group of problematic microfossils obtained by palynological processing.

Morphology

The form-taxon contains a wide array of rod-like fossils, 100 μm to some mm long, that culminate in a broad bulbous 'head', often separated from the stalk by a constriction.^[1] The bulbous end may bear broad 'prongs', giving the appearance of the end of a human femur where the prongs are paired, although the prongs often occur in higher number – five, six, a dozen – with some resemblance to Namacalathus.^[2]

Affinity

The affinity of melanosclerites is uncertain; algal has been proposed, but hydrozoan (cnidarian) is preferred, though not conclusively established.^[1] Melanoscleritoites Eisenack, 1963 is interpreted as a hydrozoan,^[3] with other taxa not attributable to that particular class, on the basis of a broad morphological similarity – though the distinguishing features are far from unequivocal,^[1] and the preservation of the material raises some taphonomic problems. The composition resembles that of chitinozoans, scolecodonts, graptolites, and fungi – though at least one species of extant cubomedusan hydroid does produce a similarity resilient "chitinous" 'wall'.^[3]

Occurrence

They have been reported in shallow marine sandstones and limestones, as well as upper slope and open marine sediments, in strata from the Lower Cambrian to Upper Devonian.^[1]

Taxa include:

• Eichbaumia Schallreuter, 1981
  • Eichbaumia incus Schallreuter, 1981
• Melanoarbustum Górka, 1971
  • Melanoarbustum balticum Górka, 1971
• Melanoclava Eisenack, 1942
  • Melanoclava betaotda Eisenack, 1942
• Melanocyathus Eisenack, 1942
  • Melanocyathus dentatus Eisenack, 1942
• Melanoporella Górka, 1971
  • Melanoporella polonica Górka, 1971
  • Melanoporella bulla
  • Melanoporella clava Schallreuter, 1981
• Melanorhachis Eisenack, 1942
  • Melanorhachis regularis Eisenack, 1942
• Melanoscleritoites Eisenack, 1963
• Melanosteus Eisenack, 1942
  • Melanosteus acutus Eisenack, 1942
• Melanostylus Eisenack, 1963
  • Melanostylus coronifer Eisenack, 1963
• Menola Schallreuter, 1981
  • Menola os Schallreuter, 1981
• Mirachitina Eisenack, 1963
  • Mirachitina quadrupedis Eisenack, 1963
• Semenola Schallreuter, 1981
  • Semenola semen Schallreuter, 1981

Notes and References

1. Winchester-Seeto. T.M.. McIlroy. D.. Lower Cambrian melanosclerites and foraminiferal linings from the Lontova Formation, St. Petersburg, Russia. Review of Palaeobotany and Palynology. May 2006. 139. 1–4. 71–79. 10.1016/j.revpalbo.2005.07.012.
2. Comunicações Geológicas . 2007 . 94. 93–107 . Melanosclerites from the Öjlemyr Cherts, Gotland. C. TRAMPISCH.
3. 1305842. Melanosclerites: First North American report of these problematic microfossils and discussion of their affinity. P. B. Cashman. Journal of Paleontology. 66. 4. July 1992. 563–569 . 10.1017/S0022336000024434. 89141723 .