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Daohugouthallus

Daohugouthallus is a monotypic genus of lichen, known from fossils found in the Jurassic Haifanggou Formation near Daohugou village, Ningcheng County, China. The genus contains a single species, D. ciliiferus. Although Daohugouthallus shows some relationships to the family Parmeliaceae, it is distinct enough for scientists to suggest its classification into its own family, Daohugouthallaceae. Dated at approximately 165 million years ago, this macrolichen is thought to be the earliest fossil example of an epiphytic macrolichen, indicating it likely grew on gymnosperm plants.

Discovery
Five specimens of Daohugouthallus ciliiferus have been found so far. These were collected from the fossiliferous beds of the Jurassic Haifanggou Formation in China (Callovian–Oxfordian boundary interval, Middle Jurassic), More specifically, the site of discovery can be found about 80 km to the south of Chifeng City, within the Inner Mongolia Autonomous Region (lat.119°14.318′E, long. 41°18.979′N). D. ciliiferus fossil specimens are currently kept in Beijing, at the Key Lab of Insect Evolution and Environmental Changes within the College of Life Sciences and Academy for Multidisciplinary Studies at Capital Normal University. Etymology Daohugouthallus ciliiferus fossil specimens were found near Daohugou village in Ningcheng County. The village lends its name to the first part of the genus "Daohugou" while the second part "thallus" is a Latin term which refers to a plant-like body without typical differentiation into parts such as roots, stems and leaves. "Ciliiferus" comes from the Latin for bearing cilia, referring to the presence of cilia present in this macrolichen. == Description ==
Description
The thalli of Daohugouthallus ciliiferus are approximately 5 cm high and 3 cm wide and foliose to subfruticose. The slender lobes have tapering tips and are approximately 5 mm long and between 0.5 and 1.5 mm wide. Their branching pattern is irregular, and in some places lateral cilia and lobules are present. Aggregated, punctiform black spots are regularly visible on the surface of the lichen remnants, and the upper cortex is approximately 1 μm thick and described as conglutinate, i.e. stuck together. The fungal hyphae of the mycobiont component are filamentous and septate with a diameter of less than 1.25 μm. Both the photobiont cells and fungal hyphae are narrower than those of extant macrolichen species which could be due to drying during the fossilisation process which caused shrinkage. Alternatively, the photobiont algae species could have been naturally smaller in size in this lichen species. The external morphology could be closely correlated to the extant lichen species Everniastrum cirrhatum. However, several key diagnostic features which would allow for a more accurate classification are missing including hamathecia, asci, and ascospore structures. Phylogeny A simplified cladogram for D. ciliiferus, following the phylogeny of Wang, Krings & Taylor (2010); Yang et al. (2023). {{Clade|style= == Palaeoenvironment ==
Palaeoenvironment
The Middle Jurassic palaeoenvironment of the Daohuguo area can be visualised as temperate, humid and seasonal, with variations in precipitation. This period is partially characterised by diverse gymnosperm forests which may have provided the ideal environment for the adaptation of epiphytic macrolichens. Forest ecosystems similar to these recovered again following the end-Triassic mass extinction (200 Mya). This makes it possible for the existence of gymnosperm epiphytic lichens during the middle-Jurassic from which D. ciliiferus is dated. However, there is no empiric fossil evidence to support this evolutionary path nor the potential transition of epiphytic lichens from gymnosperm to angiosperm substrates. Insect-lichen mimesis A moth lacewing genera – Lichenipolystoechotes – may have been associated with D. ciliiferus via a mimetic relationship. Two new species of moth lacewing were described from fossils found at Daohugou 1 (near Daohugou Village, China) at the Jurassic Jiulongshan Formation, close to the site in which D. ciliiferus fossils were found. They were given the genus Lichenipolystoechotes (family Ithonidae) to indicate their possible association with D. ciliiferus lichen. Structural similarities between the branching patterns on the wings of the insect fossil specimens of Lichenipolystoechotes and thalli of D. ciliiferus could indicate the earliest known example of insect-lichen mimesis. Additionally, black spots present on the wings of one fossil species, Lichenipolystoechotes ramimaculatus, resemble the black spots found on D. ciliiferus specimens. It has been hypothesised that these moth lacewings could have camouflaged themselves effectively against a backdrop of D. ciliiferus lichen, providing them with a survival advantage. However, evidence of the evolution of insect-lichen mimesis is largely missing in the fossil record and this potential lichen-insect mimesis requires further investigation. == References ==
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