Английская Википедия:Acaenoplax

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Acaenoplax is an extinct worm-shaped mollusc known from the Coalbrookdale Formation of Herefordshire, England. It lived in the Silurian period. It was a couple of centimetres long and half a centimetre wide, and comprises serially repeated units with seven or eight shells, and rings of 'spines'.[1][2]

Some of its characters are reminiscent of the polychaete worms, and the character combinations do not place it obviously in the stem of any modern mollusc group,[3] but although it was originally interpreted as a polychaete,[1] this position is untenable for a number of reasons.[4]

Morphology

The organism resembles a bristled worm, but bears a number of shells on its upper surface. The first shell is cap-like, whereas the others are saddle-shaped. The rearmost shell is almost rectangular, whereas the others are more circular, with spines on the rear surface of the third to sixth shells. The originally-aragonitic shells do not overlap.[1] There are eighteen rows of spines projecting from ridges in the body surface, which encircle the body except for its bottom surface,[1] which presumably bore a molluscan foot. Its straight gut was preserved in phosphate.[2]

Affinity

Heloplax, Enetoplax and Arctoplax are genera of shell that are closely related to Acaenoplax, but whose soft tissue is not preserved.[1]

See also

  • Kulindroplax, a possibly related seven-shelled mollusk from the same Lagerstätte.

References

Шаблон:Reflist

Шаблон:Taxonbar


Шаблон:Paleo-mollusc-stub