Thallophyca
Extinct genus of algae
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Thallophyca is a non-mineralized branching alga from the Ediacaran period of China. Two distinct species are known, T. ramosa and T. corrugata.
| Thallophyca Temporal range: Ediacaran ~ | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Clade: | Archaeplastida |
| Division: | Rhodophyta |
| Class: | Florideophyceae |
| Order: | Corallinales |
| Stem group: | Corallinaceae |
| Genus: | †Thallophyca Zhang, 1989 |
| Type species | |
| †Thallophyca ramosa Zhang, 1989 | |
| Species | |
| Synonyms | |
| |
Discovery
Fossil material of Thallophyca was found in the Doushantuo Formation, Guizhou Province of South China and formally described in 1989.[2]
Etymology
The generic name Thallophyca derives from a truncated Greek word Thallus, commonly used for algae; and phyc, to mean "seaweed".[2]
The specific name of T. ramosa derives directly from the Latin word of the same spelling, ramosa, to mean "branched", in reference to the appearance of its branching thallus.[2] The specific name of T. corrugata derives directly from the Latin words of the same spelling, corrugata, to mean "wrinkly", in reference to the wrinkly appearance of the thallus. And the specific name of T. phylloformis derives from the Greek word phyllo, to mean "leaf"; and the Latin suffix word -formis, to mean "shape", in reference to the leaf-like shape of its thallus.[3]
Description
Thallophyca are ellipsoidal alga growing up to 3.5 mm (0.14 in) in height and 20 mm (0.8 in) in width, with the outer portions of their thallus being enlarged, with notable differentiation into an outer cortex and an inner medulla. [4][5] The outer cells of the cortex are slightly elongated and spheroidal to polyhedral in shape, and oriented along the thallus, meanwhile the inner cells of the medulla diverge outwards in rows.[5] These inners cells are similar to pseudoparenchyma, due to their tightly packed nature.[5] Some specimens of Thallophyca also show possible reproductive cells within the thallus in the form of clustered islands of larger cells which may be cystocarps, sorus-like structures, and cavities, which are suggested to be similar to conceptacles.[4]
Due to the overall appearance of Thallophyca, it has been compared to extant forms of Coralline algae, and as such has been postured to be an early stem group corallinalean red alga.[4][5] It was also most likely a benthic alga, inferred from how its lobate protrusions and tissues grew, which can be seen in the large lobes of Thallophyca specimens, which radiate from a centre point.[5]
Taxonomy
To date, Thallophyca contains three valid species, and one invalid species, which are as follows:
| Species | Authority | Type locality | Notes | Refs | |
|---|---|---|---|---|---|
| Thallophyca ramosa | Zhang (1989) | Doushantuo Formation, South China | valid | Type species | [2] |
| Thallophyca simplicia | Zhang (1989) | Doushantuo Formation, South China | invalid | Synonym of T. ramosa. | [2][5] |
| Thallophyca corrugata | Zhang & Yuan (1992) | Doushantuo Formation, South China | valid | [3] | |
| Thallophyca phylloformis | Zhang & Yuan (1992) | Doushantuo Formation, South China | valid | [3] |