Acaenoplax Temporal range:
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Scientific classification
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Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Mollusca |
Class: | incertae sedis |
Family: | † Heloplacidae |
Genus: | † Acaenoplax |
Species: | †A. hayae
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Binomial name | |
†Acaenoplax hayae Sutton et al, 2001
|
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]
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]
Heloplax, Enetoplax and Arctoplax are genera of shell that are closely related to Acaenoplax, but whose soft tissue is not preserved. [1]
Acaenoplax Temporal range:
| |
---|---|
Scientific classification
![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Mollusca |
Class: | incertae sedis |
Family: | † Heloplacidae |
Genus: | † Acaenoplax |
Species: | †A. hayae
|
Binomial name | |
†Acaenoplax hayae Sutton et al, 2001
|
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]
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]
Heloplax, Enetoplax and Arctoplax are genera of shell that are closely related to Acaenoplax, but whose soft tissue is not preserved. [1]