Lenatheca Missarzhevsky, 1969
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publication ID |
https://doi.org/ 10.4202/app.2012.0004 |
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persistent identifier |
https://treatment.plazi.org/id/03C3891D-1537-C26C-FFF5-FA0ACD4FFABF |
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treatment provided by |
Felipe |
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scientific name |
Lenatheca Missarzhevsky |
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Genus Lenatheca Missarzhevsky in Rozanov et al., 1969
Type species: Hyolithus (Orthotheca) bayonet var. groenlandicus Poulsen, 1932 ; lower Cambrian , northeast Greenland .
Remarks.—According to Malinky and Skovsted (2004), the genus name Lenatheca is inadequately founded by Missarzhevsky (in Rozanov et al., 1969) on poorely preserved type material of Hyolithus (Orthotheca) bayonet var. groelandicus Poulsen, 1932 . Investigation by Malinky and Skovsted (2004) revealed difference between Poulsen’s type material and available Siberian specimens from Missarzhevsky’s collection. Val’kov (1975: 77) attributed, however, such forms found by him in the uppermost Emyaksin Formation to Lenatheca
Fig. 26. Hyolith conchs from lower Cambrian Emyaksin Formation, Bol’shaya Kuonamka River, Anabar Uplift, Siberia; sample B-247 (F) and sample → /70 (A–E, G–L). A–E. “ Lenatheca groenlandica ( Poulsen, 1932) ”, internal moulds. A. SMNH X 4635; apical (A
1
), ventral (A
2
), and lateral (A
3
) views.
B. SMNH X 4636; apical (B 1) and dorsal (B 2) views. C. SMNH X 4637; dorsal (C 1), apertural (C 3), and lateral (C 4) views; C 2, cross-section of apical part. D. Internal mould with septum, SMNH X 4638; transversal view from the apical end. E. Internal mould with septum, SMNH X 4639; transversal view from the apical end. F–H. Tetratheca clinisepta ( Sysoev, 1960) . F. Internal mould with flared apertural end, SMNH X 4643; oblique apertural view.
G, H. Partly phosphatised conchs. G. SMNH X 4641; G
1
, longitudinal view; G
2
, oblique transversal view on the septum from the apical end. H. SMNH
X 4642; H
1
, longitudinal view; H
2
, oblique transversal view from the apertural end. I, J. Orthothecida ? sp. indet. 2. I. SMNH X 4644; lateral (I
1
), dorsal
I
2
), apical (I
3
), and apertural (I
4
) views. J. SMNH X 4645; dorsal view of a smaller mould. K. Conotheca cf. C. mammilata, SMNH X 4628; apertural
K
1
), lateral (K
2
), and dorsal (K
3
) views. L. Internal mould of a hyolith conch with septa (not discussed in the text), SMNH X 4662; L
1
, transversal view of the septa; L
2
, oblique view of a septum. Scale bar: A, B, C
1
, C
3
, C
4
, 2 mm; D–H, 600 μm; I–L, 1200 μm.
groenlandica ( Poulsen, 1932) . Taking into account inappropriate designation to the genus and species, the fossils are described herein under “ Lenatheca groenlandica ( Poulsen, 1932) ” to refer to their definition by Val’kov (1975).
“ Lenatheca groenlandica ( Poulsen, 1932) ”
Figs. 25B View Fig , 26A–E.
Material.—Twenty phosphatised internal moulds, including SMNH X 4635–4639, from sample 7/70 and probably six more, including SMNH X 4640, from sample 7/36.7. Emyaksin Formation, Bol’shaya Kuonamka River; Calodiscus -Erbiella Zone, lower Botoman Stage and Delgadella anabara Zone, Atdabanian Stage (respectively).
Description.—Conch straight (Fig. 26A) or slightly curved laterally (Fig. 26C). In dorsal view the apical angle is ca. 30°. Cross-section drop-shaped (Fig. 26C 2) or rounded triangular at the juvenile conch (Fig. 26A 1), acquiring ventral invagination at later stages (Fig. 26B 1, C 3, E). Arched dorsal side with median longitudinal ridge on top and inflated flanks. Antero-lateral edges bluntly rounded. Ventral side contains a broad median depression with a flattened bottom. Septa are oval in outline, with two radial folds diverging at ca. 40º on the dorsal portion (Fig. 26D, E).
| SMNH |
Department of Paleozoology, Swedish Museum of Natural History |
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