Echiura, Sedgwick, 1898
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publication ID |
https://doi.org/ 10.4202/app.01107.2023 |
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persistent identifier |
https://treatment.plazi.org/id/8165B75B-FFAA-E97D-75E0-5030FBCFF829 |
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treatment provided by |
Felipe |
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scientific name |
Echiura |
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Echiura View in CoL gen. et sp. indet.
Fig. 6 View Fig .
Material.— NMW.2021.3G.102, complete specimen in lateral view, from level A3–A4 at the type locality and horizon for Llwygarua suzannae gen. et sp. nov .
Description.—A single specimen preserved in lateral view. Length 2.1 mm, of which 1.3 mm is the trunk, and 0.8 mm the more flexible, wrinkled proboscis (which is otherwise preserved with similar appearance to the trunk). Maximum dorsoventral width 0.3 mm, constant in anterior half then gradually tapering to sharply rounded tip. Caudal apex showing three or four possible blunt projections, up to 0.08 mm long, directly obliquely backwards on the ventral surface ( Fig. 6A View Fig 3 View Fig , A 4 View Fig ).
Proboscis maximum width almost as wide as trunk, sinuous, narrowing immediately above junction with trunk, but then expanding slightly to 0.3 mm, before narrowing to apex that is truncate and 0.2 mm wide ( Fig. 6A View Fig 1 View Fig ). Proboscis marked by irregular reticulation (slightly elongated longitudinally) of polygonal cells up to 0.07 mm long ( Fig. 6A View Fig 2 View Fig ). Margins of proboscis with fine serration or tuberculation. Apical margin apparently slightly frayed, with diverging strands from reticulation. No setae or muscles preserved.
Remarks.—No categorically diagnostic echiuran characters are visible in this specimen, but it shows close similarity to Llwygarua suzannae gen. et sp. nov. in most features, including the preservation, body shape and reticulation of the proboscis, and is presumed to be closely related to that species. Nonetheless, it differs in several key features. In particular, the proboscis is proportionally much longer and more sinuous. This is a fundamental difference and may well indicate its status as a separate species. The projections in the anal region also appear to differ significantly from Llwygarua suzannae gen. et sp. nov., but this would need to be confirmed from additional specimens.
Aside from being difficult to describe as a new species based on only a single specimen, the small size of this worm compared with the material of Llwygarua suzannae gen. et sp. nov. makes possible an interpretation as a juvenile of the latter. This interpretation would require allometric growth of the proboscis and trunk, with the proboscis being relatively long in juveniles. Such changes can occur in the related sipunculans ( Schulze and Rice 2009), so this hypothesis is not unreasonable; however, the reticulation of the proboscis is on a similar scale to (and slightly coarser than) that in the much larger Llwygarua suzannae gen. et sp. nov. specimens, and this is difficult to reconcile with a growth difference. The anal structures, if confirmed, would also be compelling evidence of this being a distinct species.
| NMW |
Naturhistorisches Museum, Wien |
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