Ornatifilum

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Ornatifilum
Temporal range: Late
Wenlock) – Early Devonian (Lochkovian)[1]
Tortotubus closely resembles Ornatifilum. 250 μm long.
T. protuberans from the Silurian of Kerrera, Scotland. 200 μm long.
Scientific classification
Genus:
Ornatifilum

Burgess & Edwards 1991
Species
  • O. granulatum Burgess & Edwards, 1991 (type)

Ornatifilum (Latin ornatus + filum, Ornamented filament) is an artificial

form genus
, which is used to categorise any small, branched filaments with external ornamentation.

It has been applied to microfossils of Devonian age with fungal affinities, though these taxa have since been recognized as an early growth form of Tortotubus.[2]

Background

The form genus Ornatifilum was erected by Burgess and Edwards in 1991 to describe tubular fossils retrieved by

acid maceration from the late Silurian.[1] It was originally intended as a form genus, to facilitate stratigraphy and environmental reconstruction; the fossils do not display enough features to classify them confidently, even at a kingdom level.[1]

The organisms comprise tubes of around 10 μm diameter, with an ornamented, granular surface texture. These fossils were compared to late Silurian (

Burgsvik beds by Sherwood-Pike and Gray,[3] and the genus was used when similar fossils were recovered from the Scottish island of Kerrera by Charles Wellman ten years later.[4]
Similar, unornamented filaments are known from the USA.[5] However, these latter fossils have now been assigned to Tortotubus.[2]

Ornatifilum granulatum

The type species of the genus consists of flattened filaments – perhaps an artefact resulting from post-burial pressure. Their branching is typically at obtuse angles; the irregularly sized grana, which ornament their surfaces, are concentrated at branching points.

convergent feature, found for example in liverwort rhizoids
and some fungi, so does not help in classification. The specimens recovered are most common in near-shore environments; however, they are never abundant.[1]

Ornatifilum lornensis

Ornatifilum lornensis is a junior synonym of Tortotubus protuberans. It has a more complex appearance than O. granatum. For a start, its surface ornament – which covers most of the surface uniformly – takes an array of forms, with "grana, coni, spinae verrucae and occasionally plia"[note 1] present.[4] Further, side-branches and the flask-shaped protuberances occasionally protrude from the tubes, on which the ornament is larger (2.5 μm rather than ~1 μm).[4] Such branching typically occurs in pairs across the main thread.[4]

Timeline

↓Rhynie chert
 Ornatifilum
 ___
│
−600
│
−550
│
−500
│
−450
│
−400
│
−350
│
−300
│
−250
│
−200
│
−150
│
−100
│
−50
│
0
Million years ago

Footnotes

  1. ^
      • grana: small grains
      • coni: small cones
      • spinae verrucae: Spiny warts
      • plia: small streaky knobs.

References

  1. ^
    doi:10.1111/j.1095-8339.1991.tb02282.x
    .
  2. ^
    doi:10.1111/boj.12389
    .
  3. doi:10.1111/j.1502-3931.1985.tb00680.x
    .
  4. ^
    doi:10.1016/0034-6667(94)00115-Z
    .
  5. doi:10.1016/0034-6667(78)90034-9
    .

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