Organism · Molluscs
Platyceras erectum
Source time context (not species duration) · ≈ 420–359 Ma
Inferred life reconstruction
Platyceras erectum
Overview
Platyceras erectum was an unusual gastropod of Devonian seas. Its shell widens rapidly below a tightly coiled apex. The obliquely flared opening reveals an outline unlike familiar sea snails.[1][2]
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Key facts
The shell opening is not a regular circle. Its edge flares in an undulating outline. Curved bands below it reveal the form in which the shell grew.[1]
Time and place
It is associated with North American Devonian seas around 400–380 million years ago. Records come from formations in present-day New York, United States, and near the Falls of the Ohio on the Kentucky side. Rocks beside today’s river reveal a much older sea.[1][2]
The time range describes source context, not the complete duration of this species.
Size, form and skeleton
The apex was described as tightly coiled for about one and a half whorls. Below it, the body whorl expands rapidly and curves gently overall. Closely spaced lamellar striae and narrow curved bands on the lower part are also visible.[1][2]
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Habitat and reproduction
The fossils are associated with limestone deposited in ancient seas. Kentucky records also describe the gastropod from Devonian limestone. One small shell helps reveal a regional seascape different from that of today.[2]
Fossil discovery
Hall’s nineteenth-century research recorded the shell apex, opening, and surface striae in detail. Nettelroth described the same species and its locality again while cataloging Kentucky fossils. Old descriptions allow fossils from different regions to be compared.[1][2]
References
- Hall1879 — Devonian gastropod fossils from New York
- Nettelroth1889 — Silurian and Devonian fossils of Kentucky
- Hall1879 — Devonian gastropod fossils from New York
- Nettelroth1889 — Silurian and Devonian fossils of Kentucky
- Dockery1977 — Mollusks of the Moodys Branch Formation, Mississippi
- Mississippi DEQ — Fossils and ancient seas of Mississippi
- USGS Professional Paper306A — Natica permunda
Research questions
How did the opening change as the shell grew? Surface layers and bands can be compared with the present aperture edge. A shell that looks like a simple curve retains several stages of growth.[1][2]
Observation
Follow the outline from the tightly coiled apex to the expanding body whorl and oblique opening. After examining the broad curve, look for closely spaced surface striae.[1]
Related organisms
Natica permundaMolluscsSource time context (not species duration) · ≈ 56–33.9 MaMarine gastropods from different periods
Devonian Platyceras and Eocene Natica were marine gastropods from very different times. Compare a rapidly expanding shell with a rounded shell and examine the shape of each opening and apex.