Abyssochrysos? giganteum, Kiel & Campbell & Elder & Little, 2008
|
publication ID |
https://doi.org/ 10.4202/app.2008.0412 |
|
persistent identifier |
https://treatment.plazi.org/id/03DC9B54-FFEC-3370-FF43-46E37DB3CF1E |
|
treatment provided by |
Felipe |
|
scientific name |
Abyssochrysos? giganteum |
| status |
sp. nov. |
Abyssochrysos? giganteum sp. nov.
Fig. 5J, K View Fig .
2006 Large, high−spired abyssochrysid; Campbell 2006: 382, fig. 6B.
Etymology: After its extremely large size compared to other abyssochrysids.
Type material: Holotype: UCMP 555095 View Materials , large specimen with five−and−a−half sculptured whorls preserved; paratypes: one specimen from East Berryessa (site 12; UCMP 555096 View Materials ).
Type locality: East Berryessa , Napa County, California, USA (site 12) .
Type horizon.— Seep carbonates, Lower Cretaceous , Great Valley Group .
Diagnosis.—Large, high−spired cerithiform shell with at least five−and−a−half evenly convex whorls; juvenile sculpture of strong ribs and densely spaced spiral cords; spiral sculpture fades on later whorls and a subsutural constriction may develop. Basal margin well rounded, aperture simple, round, siphonal notch not apparent.
Description.—Largest available fragment has five−and−a−half whorls and incised suture; early whorls sculptured by 14–16 strong opisthocline ribs crossed by 18 densely spaced spiral cords of variable strength, spirals crossed by numerous fine growth increments, giving them a plaited appearance; on later whorls spiral sculpture becomes weaker or disappears. Last whorl up to 30 mm wide, largest specimen at least 73 mm high.
Discussion.—As with many of the gastropods described here, the lack of protoconch data makes it difficult to place this species. On the basis of teleoconch characters alone this species is indistinguishable from Abyssochrysos . It has the same type of spiral and axial ornament that is often reduced on late whorls, the same opisthocline growth lines, and a similar base and simple aperture ( Houbrick 1979; Bouchet 1991; Killeen and Oliver 2000). However, extant species of Abyssochrysos are only up to 40 mm high and 10 mm wide, whereas Abyssochrysos? giganteum sp. nov. reached at least three times that size. Therefore our new species is only tentatively assigned to Abyssochrysos .
In size and whorl profile Abyssochrysos? giganteum resembles the presumed zygopleurid Zebalia suciaensis ( Packard, 1922) from Late Cretaceous sediments of western North America ( Squires and Saul 2003), but in that species the ribs are blade−like near the upper suture, a feature not seen in Abyssochrysos? giganteum or other Abyssochrysos species. Remarkable are the similarities between Abyssochrysos? giganteum and some extant potamidids (hypersaline and brackish−water cerithioideans) such as some large species of Cerithidea Swainson, 1840 in respect to ornament, or Telescopium Montfort, 1810 regarding the opisthocline growth line ( Houbrick 1991). Superficially similar is a species that was originally described as Abyssochrysos raui Goeder and Kaler, 1996 from a seep carbonate in the middle Eocene Humptulips Formation in Washington State, USA ( Goedert and Kaler 1996). Subsequent collection of better preserved material by James L. Goedert and the senior author at the type locality showed that this species has two very deep sinuses in the outer lip of its aperture, a feature that is not found in extant Abyssochrysos ; the species belongs to the new genus Humptulipsia (Kiel 2008) .
Stratigraphic and geographic range.—Early Cretaceous, restricted to seep carbonates in the Great Valley Group, California, USA.
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.