Mosaics from the heritage of ELTE – January 2022

Object of the month - Fossil remain of a European green toad

Fossil remain of a European green toad from the Middle Miocene, i. e. approx. 13 million years old diatomaceous earth beds of Szurdokpüspöki (Mátra Mountains, Hungary). The slab is 9 cm high.

The specimen is a near complete skeleton of a frog identified, although tentatively, as a fossil representative of the extant species European green toad (Bufo viridis Laurenti, 1768, also known as Bufotes viridis), living in Central and Eastern Europe as well as on the Balkan Peninsula. Most of the bones, including those of the skull, have been preserved on the diatomaceous earth (or diatomite) slab available, and only a few can be inferred merely from their imprints. Presumably it has been left by a young specimen.

Fossil remains of green toad were described from beds geologically more or less coeval with the Szurdokpüspöki diatomaceous earth from Austria, Germany, Italy, Romania and Spain as well. The latter occurrences, however, have yielded exclusively isolated bones (vertebrate skeletons disaggregate before the final burial as a rule). Thus, the Szurdokpüspöki specimen is rightly considered as an exceptional one.

Its excellent preservation is due to the peculiar depositional environment of the diatomite succession. Associated to the nascent volcanoes now forming the Mátra Mountains, silica-rich solutions entered the surrounding water bodies during the Middle Miocene, creating favourable living conditions for diatoms and resulting in the deposition of the diatomite succession. As indicated by the finely laminated structure of some beds as well as by the mode of preservation of vertebrate fossils of which fish are the most frequent, the bottom was free of bottom-dweller organisms, including scavengers. The lifeless nature of the environment was most probably due to harmful algal blooms poisoning the bottom waters at times.


István Szente, chief museologist
ELTE Geologist Garden, Tata

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