Metzgeriothallus

Metzgeriothallus; Temporal range: Givetian–Lower Mississippian PreꞒ Ꞓ O S D C P T J K Pg N
	Light micrograph of a thallus
Scientific classification
Kingdom:	Plantae
Clade:	Embryophytes
Division:	Marchantiophyta
Class:	Jungermanniopsida
Order:	Metzgeriales
Genus:	†Metzgeriothallus; Walton, 1928
Species
	M. metzgerioides Walton, 1928 (type) ; M. sharonae VanAller Hernick et al., 2008;

Metzgeriothallus sharonae is the oldest known liverwort fossil, dating to the Middle Devonian.^[1] It is a simple, thalloid organism. M. metzgerioides is known from more fragmentary material dating to the Carboniferous of Scotland.^[1] A defining feature of these fossils is the presence of dark, scattered cells that closely resemble oil body cells of modern liverworts, suggesting evolutionary homology^[2] and implicating these structures in the chemical defense of liverworts against arthropod herbivory^[3]. Dark cells are distributed more or less evenly throughout the thallus wings, often forming characteristic 'salt-and-pepper' patterns, a spatial arrangement associated with the phenomenon of lateral inhibition^[4].

References

1 2 Hernick, L.; Landing, E.; Bartowski, K. (2008). "Earth's oldest liverworts—Metzgeriothallus sharonae sp. nov. from the Middle Devonian (Givetian) of eastern New York, USA". Review of Palaeobotany and Palynology. 148 (2–4): 154–162. Bibcode:2008RPaPa.148..154H. doi:10.1016/j.revpalbo.2007.09.002.
↑ Tremblay, S.; Mercadal, J. (2026). "Homology of the dark cells of Paleozoic liverworts with the specialized oil body cells of modern liverworts (Marchantiophyta)". New Phytologist nph.71332. doi:10.1111/nph.71332. PMID 42260898.
↑ Labandeira CC, Tremblay SL, Bartowski KE, VanAller Hernick L (April 2014). "Middle Devonian liverwort herbivory and antiherbivore defence". The New Phytologist. 202 (1): 247–258. Bibcode:2014NewPh.202..247L. doi:10.1111/nph.12643. PMID 24372344.
↑ Mercadal, Josep; Tremblay, Susan; Kraska, Leonie; Hutten, Martin A.; Formosa-Jordan, Pau (2026-07-21). "Lateral inhibition governs ancestral cellular patterning in fossil and extant liverworts". Development. 153 (14): dev205696. doi:10.1242/dev.205696. ISSN 0950-1991.

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[Hernick2008-1] 1 2 Hernick, L.; Landing, E.; Bartowski, K. (2008). "Earth's oldest liverworts—Metzgeriothallus sharonae sp. nov. from the Middle Devonian (Givetian) of eastern New York, USA". Review of Palaeobotany and Palynology. 148 (2–4): 154–162. Bibcode:2008RPaPa.148..154H. doi:10.1016/j.revpalbo.2007.09.002.

[2] Tremblay, S.; Mercadal, J. (2026). "Homology of the dark cells of Paleozoic liverworts with the specialized oil body cells of modern liverworts (Marchantiophyta)". New Phytologist nph.71332. doi:10.1111/nph.71332. PMID 42260898.

[3] Labandeira CC, Tremblay SL, Bartowski KE, VanAller Hernick L (April 2014). "Middle Devonian liverwort herbivory and antiherbivore defence". The New Phytologist. 202 (1): 247–258. Bibcode:2014NewPh.202..247L. doi:10.1111/nph.12643. PMID 24372344.

[4] Mercadal, Josep; Tremblay, Susan; Kraska, Leonie; Hutten, Martin A.; Formosa-Jordan, Pau (2026-07-21). "Lateral inhibition governs ancestral cellular patterning in fossil and extant liverworts". Development. 153 (14): dev205696. doi:10.1242/dev.205696. ISSN 0950-1991.

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