Provanna fortis, Hybertsen & Kiel, 2018

Hybertsen, Frida & Kiel, Steffen, 2018, A middle Eocene seep deposit with silicified fauna from the Humptulips Formation in western Washington State, USA, Acta Palaeontologica Polonica 63 (4), pp. 751-768 : 760-761

Provanna fortis sp. nov.

Fig. 14 .

Etymology: From Latin fortis , reinforced; referring to the appearance of the shell.

Type material: Holotype: NRM Mo 185028 with one intact whorl of protoconch and distinct nodes on the teleoconch . Paratype: NRM 185027 with distinct spiral cords on the base and aperture with siphonal notch .

Type locality: Satsop Weatherwax seep deposit, Washington State, USA .

Type horizon: Basal Humptulips Formation, middle Eocene.

Material.— Type material and 5 other specimens. Two specimens deposited in the Burke Museum ( UWBM 108854–55 ) .

Dimensions. — Holotype is approximately 2.3 mm in height and 1.7 mm in width.

Diagnosis. —Sturdy, high-spired shell with prominent, angular whorls with spiny nodes at intersection of the axial and spiral ribs, apical angle of approximately 45° reaching at least 2.3 mm in height and 1.7 mm in width.

Description.—Protoconch: at least one whorl; maximum diameter 0.5 mm; sculptured by reticulate pattern, ~24 prominent, slightly sinuous axial ribs, ~16 fine spiral cords; transition to teleoconch unknown. Teleoconch: up to three whorls, sculptured by reticulate pattern, 14 orthocline axial ribs, two prominent and equally strong spiral ribs, blunt, short spines at intersections; spines more prominent on lower whorls; axial ribs start at the upper suture and fade below the lower spiral rib; irregularly spaced, fine spiral treads on whorl flank, fine axial growth increments; basal margin marked by distinct spiral rib, without spines; two spiral ribs of decreasing strength on base of the whorl; aperture broadly oval; short siphonal notch bordered by low ridge; columella smooth, thin callus on inner lip.

Remarks.—The strong angulation and spiny appearance of Provanna fortis can also be seen in other provannids such as for example Provanna ios Warén and Bouchet, 1986 and Provanna muricata Warén and Bouchet, 1986 from the East Pacific region ( Warén and Bouchet 1986). Where the first one has one distinct spiral keel, P. muricata has developed two ribs on the spire which can also be seen in the P. fortis sp. nov. The protoconch of P. muricata was not recovered from the specimen described by Warén and Bouchet (1986) which aggravates a distinction between these two species. Provanna antiqua Squires, 1995 from Eocene and Oligocene seep deposits in western Washington shows a reticulate pattern but lacks spines and has rounded whorls instead of the prominent angulation seen on P. fortis . Provanna alexi Amano and Little, 2014 and Provanna hirokoae Amano and Little, 2014 from the middle Miocene of Japan ( Amano and Little 2014) both lack the strong angulation seen on P. fortis . Provanna marshalli Saether, Little, and Campbell, 2010 from early to middle Miocene of New Zealand is similar to P. antiqua , also lacks strong angulation and has more spiral ribs on the whorls than P. fortis . Provanna urahoroensis Amano and Jenkins, 2013 reported from Oligocene deposits in Japan does not have the distinct reticulate pattern or anything resembling the spines on P. fortis . Provanna nakagawensis Kaim, Jenkins, and Hikida, 2009 from the Upper Cretaceous of Japan is sculptured by a distinct reticulate pattern, lacks the spines and does not have the shelf-structure made up by strong angulation as seen on the lowermost whorl of P. fortis . Kaim et al. (2008) also report Provanna tappuensis Kaim, Jenkins, and Warén, 2008 from the Cretaceous of Japan, which shows strong axial and spiral sculpture, although the spiral base has an increasing number of spiral ribs; up to five, beneath the spiral base where the P. fortis only has up to three spiral ribs in adult specimens and is therefore described as a new species.

Stratigraphic and geographic range.— Type locality and horizon only.

Figures

Fig. 14. The provannid gastropod Provanna fortis sp. nov. from the middle Eocene Satsop Weatherwax seep deposit, Washington State, USA. A. NRM Mo 185027, teleoconch with 2.5 whorls (A1); basal view showing spiral cords and aperture with siphonal notch (A2). B. NRM Mo 185028 (holotype); part of protoconch and teleoconch with 3 strongly angular whorls with spines (B2); close-up on protoconch (B1); spiral suture and fading axial rib (B3); growth increments (B4).