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. 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 ''Namacalathus'' is a problematic metazoan fossil occurring in the latest Ediacaran. The first, and only described species, ''N. hermanastes'', was first described in 2000 from the Nama Group of central and southern Namibia. A U–Pb zircon age ...

''.

Affinity

The affinity of melanosclerites is uncertain; algal has been proposed, but hydrozoan (cnidarian) is preferred, though not conclusively established. ''Melanoscleritoites'' Eisenack, 1963 is interpreted as a hydrozoan, 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, and the preservation of the material raises some

taphonomic Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov t ...

problems. The composition resembles that of chitinozoans,

scolecodonts A scolecodont is the jaw of a polychaete annelid, a common type of fossil-producing segmented worm useful in invertebrate paleontology. Scolecodonts are common and diverse microfossils, which range from the Cambrian period (around half a billi ...

, graptolites, and

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

– though at least one species of extant cubomedusan hydroid does produce a similarity resilient "chitinous" 'wall'.

Occurrence

They have been reported in shallow marine

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s and

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

s, as well as upper slope and open marine sediments, in strata from the Lower Cambrian to Upper Devonian. 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

References

Incertae sedis Ordovician fossil record {{ordovician-animal-stub