Mikhail Dmitrievich Zalessky (russian: Михаил Дмитриевич Залесский, ''Mikhail Dmitrievich Zalesskiy''; 15 September 1877 – 22 December 1946) was a Russian

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

and

paleobotanist Paleobotany, which is also spelled as palaeobotany, is the branch of botany dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments (paleogeogr ...

. His main focus was an investigation of plant remains in

coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...

s and

oil shale Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitu ...

s. In 1911, Zalessky described a new type of

petrified wood Petrified wood, also known as petrified tree (from Ancient Greek meaning 'rock' or 'stone'; literally 'wood turned into stone'), is the name given to a special type of '' fossilized wood'', the fossilized remains of terrestrial vegetation. ' ...

from the

Donets Basin The Seversky Donets () or Siverskyi Donets (), usually simply called the Donets, is a river on the south of the East European Plain. It originates in the Central Russian Upland, north of Belgorod, flows south-east through Ukraine (Kharkiv, Don ...

Ukraine Ukraine ( uk, Україна, Ukraïna, ) is a country in Eastern Europe. It is the second-largest European country after Russia, which it borders to the east and northeast. Ukraine covers approximately . Prior to the ongoing Russian invas ...

. He called the wood ''Callixylon'', though he did not find any structures other than the trunk. In the 1960s, it was demonstrated that the fossil wood known as ''Callixylon'' and the leaves known as ''

Archaeopteris ''Archaeopteris'' is an extinct genus of progymnosperm tree with fern-like leaves. A useful index fossil, this tree is found in strata dating from the Upper Devonian to Lower Carboniferous (), the oldest fossils being 385 million years old, a ...

'' were actually part of the same plant. In 1917, he studied

kukersite Kukersite is a light-brown marine type oil shale of Ordovician age. It is found in the Baltic Oil Shale Basin in Estonia and North-West Russia. It is of the lowest Upper Ordovician formation, formed some 460 million years ago. It was name ...

oil shale from Kukruse stage in

Estonia Estonia, formally the Republic of Estonia, is a country by the Baltic Sea in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the sea across from Sweden, to the south by Latvia, and t ...

. Correspondingly he named that particular oil shale after the German name of the Kukruse manor. Zalessky described oval bodies of

kerogen Kerogen is solid, insoluble organic matter in sedimentary rocks. Comprising an estimated 1016 tons of carbon, it is the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. It ...

in kukersite which by his conclusion were the remains of an extinct microorganism, which he called ''Gloeocapsamorpha prisca''. This conclusion was criticized in the 1950s but later studies by using electron microscope confirmed Zalessky's observations.

References

{{DEFAULTSORT:Zalessky, Mikhail 1877 births 1946 deaths Paleobotanists Paleontologists from the Russian Empire Oil shale in Estonia Oil shale researchers Burials at Bogoslovskoe Cemetery