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Atavograptus atavus
Taxonomy
Monograptus atavus was named by Jones (1909) [Lectotype, by subsequent designation by Pribyl & Spasov (1955), p. 195, figured by Jones (1909), text-fig. 18b;]. Its type specimen is GSM 23710 and is a 3D body fossil. It is the type species of Atavograptus.
It was recombined as Atavograptus atavus by Rickards (1974) and Bjerreskov and Koren' (1997).
It was recombined as Atavograptus atavus by Rickards (1974) and Bjerreskov and Koren' (1997).
Sister species lacking formal opinion data
Synonymy list
| Year | Name and author |
|---|---|
| 1909 | Monograptus atavus Jones p. 531 figs. 18a-d |
| 1974 | Atavograptus atavus Rickards |
| 1997 | Atavograptus atavus Bjerreskov and Koren' pp. 10 - 11 figs. 5A, B; 6,7A-D, F |
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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.
†Atavograptus atavus Jones 1909
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| M. Bjerreskov and T. Koren' 1997 | Rhabdosome more than 100 mm long, proximally with gentle dorsal curvature becoming straight distally. The maximum dorso-ventral width is 1.2-1.4 mm. The most proximal fragments are 0.4- 0.5 mm wide, in the mesial part of the rhabdosome the dorso-ventral width increases to 0.2 mm within a distance of about 40 mm. However, the extreme distal fragments, 30 mm long, have uniform width.
Thecae are simple tubes which increasing overlap from 1/5 proximally to 1/2 distally. The straight thecal apertures are everted throughout. The proximal thecae have a smooth geniculum, which becomes slightly more pronounced in mesial and distal parts of the rhabdosome. The angle of thecal inclination increases from 5° to 10°-15° towards the distal end. The maximum length of the distal thecae is 2 mm, the width of apertures is 0.5-0.6 mm. The thecal count increases from 6-7 to 9-10 in 10 mm distally. |