Eldredgeops rana

Overview

Eldredgeops rana is a trilobite whose eyes and segmented exoskeleton have been studied. A central body axis and lateral regions form its broad construction. Observation can shift from the overall outline to the small lenses of the eyes.^[1][2]

Key facts

Museum specimen PRI49811 is introduced as having a preserved length of about 3cm. Divisions into head, trunk, and tail remain within the small fossil.^[1]

Time and place

It is known from Devonian trilobite material. The Devonian was roughly 420–360 million years ago. Historical morphological descriptions and studies of eye lenses convey different features of this animal.^[1][4]

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

Size, form and skeleton

A central axis and long regions on either side can be distinguished on the back. The occipital ring behind the head is a different structure from the trunk segments. Segmentation within the tail shield can also be examined separately from the trunk.^[1][3]

Habitat and reproduction

What small structures survive in trilobite eyes? Research addressed separate calcite lenses and issues of preservation and alteration. This is a case of narrowing observation from the whole exoskeleton to the eye’s small components.^[2]

Fossil discovery

In 1888, Hall and Clarke described its form under the old name Phacops rana. In 2014, this material was compared in research on eye lenses. Connecting an old name with new research reveals its small structures.^[2][3]

References

1. Devonian trilobites
2. Torney et al. (2014) — Lenses of trilobite eyes
3. Hall·Clarke (1888) — Morphological description of Phacops rana
4. International Commission on Stratigraphy (2024) — Geological time chart
5. Morzadec (2001) — Devonian trilobites of the Anti-Atlas

Research questions

How can the ring behind the head be distinguished from trunk segments? First reading the major boundaries between head, thorax, and tail, then following subdivisions within them, reveals the structures. Similar repetitions represent different parts depending on their body positions.^[3]

Observation

Move your gaze from the eyes on the head to the ring behind it and the trunk. Examining subdivisions of the tail shield separately helps you read large regions and small repetitions together.^[1][3]