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Helotholus
Taxonomy
Helotholus was named by Jørgensen (1905) [Sepkoski's age data: T Eo R]. It is extant. It was considered unknown by Jørgensen (1905).
It was assigned to Plagiacanthidae by Jørgensen (1905); and to Nassellaria by Sepkoski (2002).
It was assigned to Plagiacanthidae by Jørgensen (1905); and to Nassellaria by Sepkoski (2002).
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
G. Helotholus Jørgensen 1905
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| E. Jørgensen 1905 | The four primary spines with the ventral, sagittal one. All five protrude as single spikes, the dorsal one, A, down on the thorax, the ventral, sagittal one in the neck stricture, the one marked D, on the cephalis as an apical spine. The lower part of this latter spine is inside the wall of the cephalis, while it a little higher up runs in the very wall. It is therefore no genuine columella. There;is also an axial spine, as in the other species here mentioned of the Cyrtoidea group. This axial spine starts as usual from the ventral end of the central rod, in the interior of the lattice shell, a little below the neck stricture, and is in elder individuals of Helotholus histricosa divided in two.
The thorax is broadly campanulate, nearly semispherical. |
Measurements
No measurements are available
No ecological data are available
Age range: base of the Early/Lower Miocene to the top of the Pleistocene or 23.04000 to 0.01170 Ma
Collections (43 total)
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Early/Lower Miocene | Southern Ocean | H. haysi (253176 253177 253178 253179 253181 253182) | |
| Middle Miocene | Southern Ocean | H. vema, H. haysi (253173) | |
| Late/Upper Miocene | Southern Ocean | H. haysi (247625 247626 247627 247628 247920 258880 258881 258882 258883 258885 258886 259940 259943) H. vema (259939) | |
| Pliocene | Southern Ocean | H. haysi (252118) H. vema (247910 247912 247913 247914 247917 252120 252123 252125 252133 252134 258876 258877 258878 259937) H. vema, H. haysi (252127) | |
| Pleistocene | Southern Ocean | H. vema (247619 250733 250739 252116 252117 258874) |