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Isograptus caduceus imitatus
Taxonomy
Isograptus caduceus imitata was named by Harris (1933).
It was corrected as Isograptus caduceus imitatus by Cooper and Fortey (1982); it was recombined as Isograptus imitatus by Wagner (2020).
It was corrected as Isograptus caduceus imitatus by Cooper and Fortey (1982); it was recombined as Isograptus imitatus by Wagner (2020).
Sister species lacking formal opinion data
Synonymy list
| Year | Name and author |
|---|---|
| 1933 | Isograptus caduceus imitata Harris p. 92 figs. 55-59 |
| 1982 | Isograptus caduceus imitatus Cooper and Fortey pp. 252 - 253 figs. 54a-d |
| 2020 | Isograptus imitatus Wagner |
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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.
†Isograptus caduceus imitatus Harris 1933
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| R. A. Cooper and R. A. Fortey 1982 | Rhabdosome is V -shaped rather than U-shaped, the dorsal stipe margins flexing sharply upwards rather than smoothly as in /. victoriae victoriae. The sicula ranges from 3-4 to 4-2 mm in length and is about 0-7 mm wide at the aperture. The ventral notch between the free ventral walls of the sicula and theca I 1 is, in most specimens, narrower and deeper than in /. victoriae victoriae. The outline of the ventral margin is deeper in the proximal region than it is in I. victoriae victoriae, resulting from the ventrally extended sicula and proximal thecae. This feature is most marked in the specimen from the 125 m level (Fig. 54a) in which the ventral margins of the sicula and first theca project outwards in prominent ventral processes. The specimen is preserved as a flattened rhabdosome in black calcareous shale, in contrast to specimens from the 128-129 m level which are preserved in full relief in limestone. In the absence of an adequate population from the 125 m level it is not possible to assess the significance of this difference except to point out that the feature is one that is unlikely to be greatly enhanced by the flattening process.
The stipes are widest at their origin and gradually taper throughout their length. Proximal stipe width ranges from 2-1-2-3 mm, and maximum stipe length observed is 8 mm. Pendent thecae number 6-8. Thecae midway along the length of the stipe are inclined initially at about 30; they curve strongly so that their free ventral walls are inclined at about 110. |
Measurements
No measurements are available
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| Source: o = order, c = class | |||||
| References: Aberhan et al. 2004, Aberhan 1992 | |||||
Age range: Yapeenian or 470.30000 to 467.30000 Ma
Collections (10 total)
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Yapeenian | New Zealand | Isograptus caduceus (63202 63279 63281 63362 63363 63367 63368) | |
| Castlemainian | New Zealand | Isograptus caduceus (63284 63285) | |
| Castlemainian - Yapeenian | USA (Idaho) | Isograptus caduceus (145326) |