Eucalyptocrinites sp. 1
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publication ID |
https://doi.org/ 10.4202/app.2010.0094 |
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persistent identifier |
https://treatment.plazi.org/id/BF03720D-FFCE-FFFD-BF24-FBE5279BFE85 |
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treatment provided by |
Felipe |
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scientific name |
Eucalyptocrinites sp. 1 |
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Fig. 3F View Fig .
Material.—TUG 1375−2, Janni Formation, Undva Cliff; TUG 1375−3, Janni Formation, Undva Cliff; TUT 1395−10, Ninance Member, Janni Formation, Liira Cliff; TUT, 1395−11, middle Äigu Beds, Kaugatuma Formation (Pridoli) at Kaugatuma Cliff. All are from Saaremaa Island.
Description.—The calyx is small to medium size for the genus. It has a low cone to bowl shape, and the base of calyx is convex with basals not visible in lateral view. Calyx plate sculpturing is smooth. The basal circlet is in a small basal concavity and is hidden by the proximal columnal. The radial circlet is 16–20% of the calyx height. The five radial plates are pentagonal. In smaller specimens the radial plate is 1.4 times wider than high, but in medium−sized specimens it is approximately as wide as high. Normal interrays are in contact with tegmen partition plates. The first interradial plate is decagonal, higher than wide, somewhat larger than radial plate, and much larger than first primibrachial. The second range has two plates that are sutured to the interradial tegmen partition plates. The posterior interray is indistinguishable from normal interrays. The first primibrachials are tetragonal, approximately 1.3 times wider than high, smaller than radial plates, and approximately the same size as the primaxil. The second secundibrachial is axillary in all rays. There are four arms per ray. One fixed intrabrachial is sutured distally with a partition plate, and in smaller specimens the fixed intrabrachial is approximately two times higher than wide.
In the smallest specimen (TUG 1375−2), the tegmen is comprised of ten partition plates that extend to base of the anal tube and rise to the full height of the arms. In the smallest specimen (TUG 1375−2) the distal partition plates expand slightly and curve inward toward the anal tube and the distal tegmen is narrow convex. A short anal tube is framed by two five−plate circlets (the distal tegmen may be different in the larger specimens assigned to this taxon). The largest specimen (TUG 1395−11) has partition plates of equal width along the entire length ( Fig. 3F View Fig ).
Free arms are 20 in number, atomous, pinnulate, cuneate uniserial through first six primibrachials, and thereafter biserial. Arms reach to distal extent of partition plates.
The proximal column is circular, heteromorphic, but other details are unknown.
Discussion.— Four specimens with both smooth calyx plate sculpturing and partition plates of uniform width throughout or slightly expanded do not correspond to any Angelin (1878: pl. 5: 1) illustration. The only Gotland species with these characters is E. ovatus , which has a much flatter base than the Estonian specimens. However, only one juvenile and three partial adult specimens are known, so description of a new species is considered premature. Therefore, this taxon is referred to herein as Eucalyptocrinites sp. 1 .
The most complete specimen is the smallest (TUG 1375−2), and it is not clear what aspects of this specimen reflect only juvenile characters. This specimen is a very slightly compressed, nearly complete crown with arms attached. Of intermediate size are TUG 1395−10 and TUG 1375−3. Specimen TUG 1395−10 is a crushed and mostly buried crown with a column mostly buried, calyx crushed with missing plates, and a few arms and partition plates partially visible. Specimen TUG 1375−3 is nearly one half of a crushed and fractured crown. The largest specimen (TUG 1395−11) is one half of a crushed crown with the lower half of the calyx missing.
As noted above, without a more complete understanding of the morphology of this smooth−sculptured form from Estonia and definitive diagnoses of Eucalyptocrinites species from Gotland, Eucalyptocrinites sp. 1 cannot be described as a new nominal taxon, if appropriate. Below we assign the majority of Eucalyptocrinites specimens to Eucalyptocrinites sp. ; however, we suspect that most of the Estonian specimens may be Eucalyptocrinites sp. 1 , potentially making this the most abundant taxon from the Silurian of Estonia, except perhaps locally, such as at Kaugatuma Cliff where Enallocrinus holdfasts are very abundant.
Measurements.—TUG 1375−2: crown height, 22.0; calyx width, 13.7*; calyx height, 8.0. TUG 1375−3: crown height, 39.8*; calyx width, 21.0*; calyx height, 11.3. TUG 1395−11 crown height, 40.0* (at least one half of calyx and distal tegmen missing).
Geographic and stratigraphic range.—In older collections, this taxon is known from the Jaani Formation (Ninase Member), Wenlock, Silurian, at Undva Cliff. New collections from the present study are from the Ninase Member of the Jaani Formation at Liiva Cliff and the middle Äigu Beds of the Kaugatuma Formation at Kaugatuma Cliff. All are from the Saaremaa Island, Estonia.
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