SMALL SCALED GROWTH FORM FEATURES 
OF FOSSIL CORALLINE ALGAE
by Michael Rasser

As several biologists use the growth form for taxonomic identification of coralline algae, Woelkerling (1993, Aust. Syst. Bot., 6:277-293) summarised and defined them for present-day material.

This homepage aims to provide some images of growthforms from Recent and fossil material, and thus to test the applicability of this feature to fossil material. Click on the blue-framed thumbnails on the left to see images (if available).

Everybody is welcome who wishes to contribute his knowledge or some images!
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The problem appears, that the recognition of several growthforms depends on the kind of preservation. If a coralline flora is only known from well cemented limestones, and thus only from thin sections, some growth forms cannot be recognised with confidence.

Definitions of Growth Forms after Woelkerling:

First of all some definitions: filaments - probuberances - lamellate branches - branched (in fruticose plants) - lamella

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1. Unconsolidated:
Plants composed partly or entirely of unconsolidated (free) filaments.

This growthform is not known from fossil material.


2. Encrusting:
Plants crustose and flattened, attached ventrally, and devoid of protuberances and lamellate branches.

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3. Warty:
Plants with warty protuberances that are usually <3 mm long and unbranched.

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4. Lumpy:
Plants with lumpy, usually swollen protuberances that may vary in length, usually crowded, rarely branched.

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5. Fruticose:
Plants with cylindrical to compressed protuberances that are mostly >3 mm long, not lumpy, usually branched.
6. Discoid:
Plants each consisting of an unbranched and largely unattached disc-like lamella of varying shape.

This growthform is apparently not known from fossil material. It cannot be recognised in thin sections.


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7. Layered:
Plants consisting of several to many flattened, lamellate branches arranged in horizontally orientated layers. Often terraced appearance in surface view.
8. Foliose:
Plants consisting of several to many lamellate branches (like 7, but:) arranged at various angles to one another.

This growthform is apparently not known from fossil material.

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9. Ribbon-like:
Plants composed of flat, ribbon-like (taeniform) branches and lacking a distinct holdfast and stipe

This growthform is apparently not known from fossil material.

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10. Arborescent:
Plants more or less tree-like, composed of a distinct holdfast and a stipe bearing flattened, ribbon-like to fan shaped branches.

This growthform is apparently not known from fossil material.

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