Iniopteryx rushlaui

Overview

Iniopteryx rushlaui is a cartilaginous fish known from Late Carboniferous North America. Examine its distinctive silhouette, with pectoral fins positioned high on the body and a continuation into the tail.^[1]

Key facts

This fish’s jaw articulation became an important clue in examining relationships between sharks and chimaeras. The research compares how jaws and skull fitted together alongside external appearance.^[1]

Time and place

Its age is Late Carboniferous, Pennsylvanian. New specimens examined in a 1980 study were collected from the Mecca Quarry Shale in present-day Parke County, Indiana, USA.^[1]

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

Size, form and skeleton

The author’s skeletal reconstruction shows a broad head and anterior body tapering toward the tail. The pectoral-fin supports extend high on the body, and the skeleton of a fan-like fin appears at the tail tip.^[1]

Large skeletal specimens of Iniopteryx rushlaui were introduced in a 1973 study as about 30–35cm in total length. Fossils with several body regions connected, such as type specimen PF6678 and comparative specimen PF6645, convey the size of this fish with unusual fins.^[7]

Habitat and reproduction

The research introduces a landscape in which diverse cartilaginous fishes inhabited shallow seas and brackish waters of Carboniferous central North America. Brackish water mixes freshwater with seawater. Fossils preserved in shale provide evidence for exploring that aquatic world.^[1]

Fossil discovery

The new specimens used in the study were collected by a Field Museum expedition in 1973. They remained in the museum’s collections in Chicago and enabled later research on the head skeleton.^[1]

References

1. Stahl (1980) — Jaw and head skeletons of Carboniferous cartilaginous fishes
2. Stahl (1980) — Jaw and head skeletons of Carboniferous cartilaginous fishes
3. Smithsonian Ocean guide — Carboniferous sharks
4. Maisey (2009) — The spine-brush of early cartilaginous fishes
5. International Commission on Stratigraphy (2024) — Geological time chart
6. Maisey (2008) — Comparison of Denaea and early cartilaginous fishes
7. Zangerl·Case (1973) — Iniopteryx and Carboniferous cartilaginous fishes

Research questions

The specimens were covered by shale, making it difficult to remove rock and expose bones. The researcher viewed X-rays from different angles stereoscopically to examine the skeleton inside the head and compare it with other specimens.^[1]

Observation

Inferred life reconstruction (male), based on Zangerl & Case (1973) and Stahl (1980). Colour, pattern, soft-tissue outline and pose are inferred.^[1][7]