Obolella crassa

Overview

Obolella crassa was a small brachiopod with two convex valves and a shell slightly longer than wide. Specimens from northern Greenland preserve growth lines. Its small shell reveals traces of growth and the outline from front to back.^[1]

Key facts

A small illustrated specimen is reported as about 0.6 mm. Even shells smaller than 1 mm were studied for their surface and internal forms. Very small fossils can convey detailed information for comparing organisms.^[1]

Time and place

Material from the Aftenstjernesø Formation at Navarana Fjord in present-day northern Greenland has been studied. It belongs to the early Cambrian context of Series 2, Stage 4. The Cambrian as a whole spans approximately 540–490 million years ago.^[1][2]

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

Size, form and skeleton

The shell is described as having two convex valves, being slightly longer than wide, and having a pointed posterior end. Surface growth lines form a step-like outline near the anterior margin. The overall outline and small changes along the margin can be examined together.^[1]

Habitat and reproduction

What different information do a shell’s outer and inner surfaces provide? This material includes studies of external surfaces, internal surfaces, and molds of the interior. Even the hard body of one organism conveys different information depending on which surface is preserved.^[1]

Fossil discovery

The study separately described dorsal and ventral valve exteriors, internal surfaces, and molds from the same sample. Different specimens add clues for examining each region. This research explores tiny fossils from several directions and modes of preservation.^[1]

References

1. Peel 2021 — Selected species description of Obolella crassa and Fig. 6 caption
2. International Commission on Stratigraphy (2024) — Geological time chart
3. Zhan et al. (2010) — Late Cambrian brachiopods from Jingxi

Research questions

Where are the step-like growth lines on the shell surface most visible? Following changes along the anterior margin reveals traces of growth in the tiny shell. Reading the overall form together with its surface record is part of its fascination.^[1]

Observation

Move your gaze from the pointed posterior end to the two convex valves and anterior margin. Examining the small growth lines reveals the different stories told by the outline and surface.^[1]