Loriolaster mirabilis

Overview

Loriolaster mirabilis is a Devonian brittle star with a broad disc and five arms. The disc extending between the arms gives it a distinctive overall appearance. This illustration was constructed by following the outline preserved on the underside, or ventral surface, of a single fossil.^[1]

Key facts

The species name mirabilis means 'wonderful.' The article explains that this broad-disc species served as the emblem of a special exhibition of slate fossils in 1997. The distinctive appearance of a fossil thus became a face for presenting the region's ancient sea.^[1]

Time and place

The source presents a specimen from the Untereschenbach Mine at Bundenbach in present-day Germany. The Hunsrück Slate of this area is described as a record of an Early Devonian sea. Here we encounter traces of a star-shaped animal left in the mud of that ancient sea.^[1]

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

Size, form and skeleton

Five arms extend from a single center, and the broad disc between them reaches almost to the arm tips. Along the undersides of the arms, rows of skeletal plates remain that have been compared to boots and spoons in shape. Examine the connections between the bent arms and the disc in the specimen.^[1]

Habitat and reproduction

The article presents the Hunsrück Slate as a record of varied muddy sediments deposited in an ancient sea. It explains that different fossil assemblages were preserved in areas with different depositional processes and habitats. Both the shape of a specimen and the locality and strata from which it came provide clues to the world of ancient organisms.^[1]

Fossil discovery

The specimen featured in the 2021 article is numbered HM2020.181, and its caption records a maximum diameter of 147 mm. The article identifies it as material from the Wouter Südkamp collection at the Hunsrück Museum in Simmern. Connecting its Bundenbach locality with the collection allows us to trace the record of this individual specimen.^[1]

References

1. Ikonen des Hunsrückschiefers
2. Ohmden study — Pentacrinites quenstedti

Research questions

The article also includes a record of Rudolf Opitz's work exposing a separate Loriolaster specimen. Gradually removing the covering slate to find the boundaries of the body was a process of making the fossil available for observation. It shows the importance of fossil preparation in distinguishing preserved structures from the surrounding rock.^[1]

Observation

The illustration centers on the observed arrangement of the broad disc and five arms preserved on the ventral surface of HM2020.181. Follow the outlines of the bent or obscured arms, then move your gaze to the disc and rows of plates connecting them. The colors and shallow relief are explanatory treatments intended to make the surviving structures easier to read.^[1]