Helicoconchus elongatus, Wilson & Vinn & Yancey, 2011
|
publication ID |
https://doi.org/ 10.4202/app.2010.0086 |
|
persistent identifier |
https://treatment.plazi.org/id/03FF7E56-FFCD-7147-FCD5-9F3582C3A3EC |
|
treatment provided by |
Felipe |
|
scientific name |
Helicoconchus elongatus |
| status |
sp. nov. |
Helicoconchus elongatus sp. nov.
Figs. 1–8 View Fig View Fig View Fig View Fig View Fig View Fig View Fig View Fig .
Etymology: Refers to the elongated nature of the late growth tube.
Holotype: NHM PI AN 1183 , aggregation of tubes.
Type locality: Roadcut on Farm−to−Market Road 1929 (Ray Stoker Jr.
http://dx.doi.org/10.4202/app.2010.0086
Highway) on the south side of Ivie Reservoir on the Colorado River , Concho County, Texas (coordinates: N 31.48454 °, W 99.69368 °) GoogleMaps .
Type horizon: Base of the Bead Mountain Formation (Lower Permian, Artinskian), Wichita−Albany Group; 3.9 meters above the top of a massive gypsum unit.
Material.— Holotype NHM PI AN 1183 . Paratypes NHM PI AN 1184–1189 . Topotypes also deposited at The University of Texas, Texas Natural Science Center.
Diagnosis.—As for genus, by monotypy.
Description.—Tube small, dextrally coiled and attached at its base and then extended as an erect, free helical tube, elongated many times its attachment diameter. Attachment portion consists of one to two slightly overlapping whorls, circular to elliptical in outline. Well−developed umbilicus absent in planispiral portion of juvenile attached tube. Tube origin is closed, bulb−like; tube diameter increases rapidly through whorls to erect portion, where it then maintains a consistent diameter ( Figs. 1–5 View Fig View Fig View Fig View Fig View Fig ). Two types of budding present. Erect portion of the tube has frequent lateral budding, producing daughter tubes that grew parallel to the parent tube and at least started as helical ( Fig. 6 View Fig ). Tubes also show budding by distal fission that produced daughter tubes of equal diameter ( Fig. 7 View Fig ). When tubes become closely packed in mature colonies their helical nature is lost and they are more or less straight.
Tube interior walls are smooth. Diaphragms are common in the erect portion of the tubes, roughly one every two mm of length, and planar, convex or concave toward the distal end. The diaphragms are microlamellar like the tube walls, with about half their thickness. The diaphragms have small openings in their centers formed by invaginated diaphragm shell structure. The living chamber (portion of the tube from the last diaphragm to its aperture) is between 5 and 7 mm long.
Tube exteriors have fine growth lines, about 4 per 0.1 mm. They often form incomplete rings and merge on parts of the tube.
Tube walls are thin (0.03–0.05 mm) and microlamellar with no punctae or pseudopunctae ( Fig. 8 View Fig ). There are roughly 4–5 microlamellae in the walls of erect tubes. The junction between a parent tube and a daughter tube shows no internal connection (no pore or other canal).
Often forming an integrated colony of tubes with a radial growth habit of spreading laterally over substrate and growing upward in closely packed array of tubes. Large colonies have closely packed tubes; loose arrangement of tubes allows helical coiling to develop ( Figs. 1 View Fig , 2 View Fig ).
Dimensions.—The planispiral coiled attachment base of H. elongatus ranges from 0.8 to 1.9 mm in outline diameter; the proximal bulb within it is about 0.6 mm at its widest. The erect portion of the tube ranges from 0.9 mm (where it emerges from the coiled attachment) to 1.5 mm in diameter and up to 5.0 cm in length and probably extended much longer. (Individual tube length is difficult to estimate because of the budding and closely packed nature of mature aggregations.) Mature aggregations form small reefs up to 2.0 meter in diameter and at least 0.5 meters high.
Stratigraphic and geographic range.—As for the genus.
| PI |
Paleontological Institute |
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.