Topic
Halysis
About: Halysis is a research topic. Over the lifetime, 2 publications have been published within this topic receiving 18 citations.
Papers
TL;DR: interpretation of Halysis as a coralline-like alga strengthens the likelihood that a variety of corallines was present in the Ordovician, more than 300 Ma prior to the currently recognized major diversification of this important group of red algae in the Cretaceous.
Abstract: The systematic position of the Ordovician calcareous microfossil Halysis Hoeg, 1932 has long been uncertain. Only known from thin sections, its morphology has been suggested to be either a single chain of cells or a series of tubes and it has been regarded as a green alga or cyanobacterium. Here we propose that Halysis represents a single sheet of cells. This new morphological interpretation accounts for Halysis's appearance in thin section as an extended flexuous series of cells, some of which are not seen to be in mutual contact, exhibiting nonlinear cell-size variation. It is also consistent with the absence of tubiform sections unequivocally attributable to Halysis. This reassessment suggests comparisons between Halysis and Mesozoic–Cenozoic thin laminar unistratose coralline red algae. Halysis cells are relatively large (40–210 μm), but their lower range is comparable to cells of corallinaceans such as Lithoporella (Foslie) Foslie, 1909. Applanate thallus morphology in Halysis resembles that...
13 citations
TL;DR: In this paper, a 3D computer model of Halysis has been constructed in order to set up planes sectioning the model and the results show that Halysis represents a microfossil with a morphology consisting of parallel juxtaposed, partly branching tubes.
Abstract: Halysis is a microfossil found in Ordovician to Devonian shallow-marine carbonates. Up to now, it is only known from thin-sections, and therefore its three-dimensional shape and its systematic position are controversial. Halysis is described as a chain-like microfossil with a shape of the single “chain links” ranging from circular to rounded rectangular. Given that Halysis commonly co-occurs with calcareous algae, it is assumed to also be an alga. Interpretations of the anatomy propose a filiform or tubiform shape. Even a unistratose sheet of cells has been discussed. Since Halysis is comparatively rare, its shape has not been resolved up to now. For the present study, 52 out of several hundred specimens from an Upper Ordovician shallow-water limestone of South China have been investigated in detail, which for the first time offers the opportunity to analyze a great number of sections through Halysis. A three-dimensional computer model of Halysis has been constructed in order to set up planes sectioning the model. These simulated sections have been compared to those from Halysis in thin-sections. The results show that Halysis represents a microfossil with a morphology consisting of parallel juxtaposed, partly branching tubes. A single sheet of cells, which was recently proposed as shape of Halysis, can clearly be excluded.
8 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2013 | 1 |
| 2005 | 1 |