Calceocrinus balticensis, Ausich & Wilson & Vinn, 2012
|
publication ID |
https://doi.org/ 10.4202/app.2010.0094 |
|
persistent identifier |
https://treatment.plazi.org/id/BF03720D-FFC4-FFF8-BC7D-FBAC2057F95E |
|
treatment provided by |
Felipe |
|
scientific name |
Calceocrinus balticensis |
| status |
sp. nov. |
Calceocrinus balticensis sp. nov.
Figs. 4B View Fig , 5F View Fig .
Etymology: Named in recognition of its occurrence in the Baltics. Holotype: GIT 405−212.
Type locality: Heltermaa on Hiiumaa, Estonia .
Type horizon: Juuru Stage, Llandovery, Silurian.
Material.— Holotype only.
Diagnosis.— Calceocrinus with adorally−aborally compressed aboral cup, smooth aboral plate sculpturing. Trapezoidal radial plate circlet, radial circlet higher than wide. (Condition of ligament pit unknown.) E arm unbranched through primibrachial 6. Main axil brachials not constricted. (Condition of anal tube unknown.)
Description.—The crown is recumbent on the column ( Fig. 5F View Fig ). The aboral cup is medium in size, adorally−aborally compressed, and with smooth plate sculpturing. The four basal plates are all in the column concavity and are all part of distal margin of basal circlet. The radial circlet is widest proximally and trapezoidal in shape; (ligament pit condition unknown). A and D radials occupy majority of radial circlet. The E−ray inferradial and superradial are inferred to have short sutural contact. The E superradial is triangular; the E inferradial is narrow, elongate; and the E superradial occupies 100% of the distal aboral cup margin. The distal facet of the D radial supports a lateral arm. The proximal facet articulates with the C inferradial and superradial (presumably analogous relationship of A radial and B inferradial). Anal plates are wider than high, and the anal sac is slender ( Fig. 4B View Fig ).
Only the D and E arms are visible; the A−ray arm is concealed. Arms are slender with aborally convex brachials. The main axil has nonaxillary brachials, divisions are heterotomous, and the first brachial is wedge−shaped. The E−ray arm is unbranched through six brachials, and it is poorly preserved but may branch higher. E−ray brachials are wider than high proximally. The main axils are well developed. Three axillaries are present, each one separated by one nonaxillary brachial ( Fig. 4B View Fig ). The lateral arms have few heterotomous divisions. The primaxil arm bifurcates at least through the axillary alphabrachial, and four nonaxillary brachials occur below the alphabrachial. One division is preserved on the betaaxil arm with four nonaxillary brachials before the bifurcation. The tertaxil arm and the omega ramule are slender and unbranched as known.
The column is homeomorphic, although near the aboral cup the columnals are very thin ( Fig. 5F View Fig ). Beneath the aboral cup columnals are approximately five times wider than high and wedge shaped. More distal columnals are parallel sided with more convex latera, and columnals are approximately less than 2.5 times wider than high. A pentalobate lumen occupies the central 30% of the column diameter, but details of columnal articular facets are unknown.
Discussion.—The calyx and proximal arms of Calceocrinus balticensis sp. nov. are reasonably well preserved on a bedding surface with only the D−ray side visible. Late Ordovician and Llandovery species of Calceocrinus were diagnosed in Ausich and Copper (2010). Calceocrinus balticensis is the sixth known Llandovery species of Calceocrinus , including C. incertus Foerste, 1936 ; C. ontario ( Springer, 1919) ; C. pustulosus Johnson in Brower, 1966; C. tridactylus Eckert, 1984 ; C. turnbulli Donovan, 1993 ; and this new species from Estonia. Calceocrinus turnbulli is from southwestern Wales, and the other previously known species are from North America. Thus, C. balticensis is the first Llandovery Calceocrinus from Baltica. With smooth aboral cup sculpturing, C. balticensis is most similar to C. insertus ; however, it is distinct because the aboral cup shape is rectangular in C. insertus and trapezoidal in C. balticensis . Both C. pustulosus and C. turnbulli have a trapezoidal aboral cup shape.
Measurements.—GIT 405−212: preserved crown height, 13.0*; calyx height, 4.5; calyx width, 3.0; calyx depth, 4.1; preserved columnal height, 11.1*.
Geographic and stratigraphic range.—This new species is only known from the Juuru Stage from Heltermaa, Hiiumaa Island.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.