Aulacoseira giraffensis

Overview

Aulacoseira giraffensis is a fossil diatom known from Eocene lake sediments. Its small siliceous shell, examined under a microscope, provides clues to its body. It introduces a world at a different scale from large animal fossils.^[1]

Key facts

Under a microscope, the shell resembles a small cylinder. Straight striations are described along its sides. Even a tiny fossil can be compared through its overall outline and surface pattern separately.^[1]

Time and place

It is known from Eocene lake sediments in present-day northwestern Canada. The Eocene spanned approximately 56–34 million years ago. Small shells provide evidence for studying communities of an ancient lake.^[1]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

The body’s evidence is a cylindrical siliceous shell. Siliceous refers to hard material composed of silica. Straight striations along the shell’s sides are also included in the morphological description.^[1][2]

The shells in the original description are approximately 3.6–12 µm in diameter. Small barrel-shaped cells connect like a chain.^[3]

Habitat and reproduction

Many fossils of this diatom were found in one core interval. Through this record of accumulated small shells, researchers examined an ancient lake’s diatom community. Small organisms contained in sediments tell the story of a past lake.^[1]

Fossil discovery

The original 2019 description treated diatoms from lake sediments in northwestern Canada. It introduced cylindrical shells, lateral striations, and a concentration in one core interval. Form seen under a microscope provided evidence for describing a new fossil species.^[1]

References

1. 2019 original description — Fossil diatoms from an Eocene lake in Canada
2. Siliceous shell morphology of Aulacoseira
3. Siver·Wolfe·Edlund (2019) — Original description of Aulacoseira giraffensis
4. Australian Biological Resources Study — Coscinodiscus marginatus
5. USGS1993 — Sancetta’s diatom descriptions and comparisons

Research questions

What can a tiny siliceous shell reveal? Cylindrical form and striations are compared to distinguish diatoms. Assemblages of several shells expand the view from one organism’s shape to an ancient lake.^[1][2]

Observation

Move your gaze from the outline of the small cylinder to the straight striations along its side. Remember that even inconspicuous fossils have distinguishing features under a microscope.^[1]