Stethacanthus altonensis

Overview

Stethacanthus altonensis is a cartilaginous fish known for its unusually modified first dorsal fin. A structure combining a spine and a brush-like part has been studied. It invites us to imagine a construction unlike the familiar dorsal fin of a shark.^[1][3]

Key facts

The specialized structure is studied under the name “spine-brush complex.” It is an example of one fin becoming distinctive within the outline of the whole body.^[3][4]

Time and place

The museum introduces this species in the context of Carboniferous sharks. The Carboniferous was roughly 360–300 million years ago. Its unusual dorsal fin and material from the pectoral fins have been compared in different studies.^[1][5]

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

Size, form and skeleton

The first dorsal fin is described as a structure combining a spine and a brush-like part. The internal supports of the pectoral fins have also been discussed in comparative research. The outer outlines and internal frameworks of the fins offer different perspectives.^[3][2]

The total body length of Stethacanthus altonensis is summarized as about 1.5m. This is the adult size compared from the literature in a 2015 study of vertebrate size.^[16]

Habitat and reproduction

What function might the unusual first dorsal fin have served? Studies of this structure have asked about its form, function, and differences among related groups. It is a case of exploring constructions beyond familiar fin shapes.^[4][3]

Fossil discovery

The spine-brush of Stethacanthus altonensis was a subject of research in 1984. A 2008 comparison discussed differences in pectoral-fin supports, and a 2009 research abstract discussed the modified first dorsal fin. Different questions arise from different fins on the same body.^[4][2][3]

References

1. Smithsonian Ocean guide — Carboniferous sharks
2. Maisey (2008) — Comparison of Denaea and early cartilaginous fishes
3. Maisey (2009) — The spine-brush of early cartilaginous fishes
4. Zangerl (1984) — Study of the specialized dorsal fin of Stethacanthus
5. International Commission on Stratigraphy (2024) — Geological time chart
6. The Naturalist (1924) — Historical morphological illustration of Megalichthys
7. International Commission on Stratigraphy (2024) — Geological time chart
8. Smithsonian Ocean guide — Carboniferous sharks
9. Maisey (2009) — The spine-brush of early cartilaginous fishes
10. International Commission on Stratigraphy (2024) — Geological time chart
11. Stahl (1980) — Jaw and head skeletons of Carboniferous cartilaginous fishes
12. Smithsonian Ocean guide — Carboniferous sharks
13. Maisey (2009) — The spine-brush of early cartilaginous fishes
14. International Commission on Stratigraphy (2024) — Geological time chart
15. Maisey (2008) — Comparison of Denaea and early cartilaginous fishes
16. Sallan·Galimberti (2015) — Changes in vertebrate size before and after the end-Devonian extinction

Research questions

Do fin remains assigned to the same name all show the same construction? Comparative research has also discussed differences in the internal supports of the pectoral fins. This research considers other body parts alongside one conspicuous feature.^[2]

Observation

Move your gaze from the unusual first dorsal fin to the pectoral fins. Thinking about both the large external shapes and the internal supports helps you compare different fins on one body.^[1][2]