Porpoceras, Buckman, 1911

Jattiot, Romain, Fara, Emmanuel, Brayard, Arnaud & Vennin, Emmanuelle, 2016, Revised stratigraphic range of the Toarcian ammonite genus Porpoceras Buckman, 1911, Geodiversitas 38 (4), pp. 505-513 : 508-512

publication ID

https://doi.org/ 10.5252/g2016n4a3

publication LSID

urn:lsid:zoobank.org:pub:BC8394F4-9DF1-458A-B9A1-4293D82962EE

persistent identifier

https://treatment.plazi.org/id/504C4F13-FFC8-FFDB-7DA2-9F33FD54FB20

treatment provided by

Felipe

scientific name

Porpoceras
status

 

Porpoceras View in CoL gr. vortex ( Simpson, 1855) - verticosum Buckman, 1914

( Figs 4 View FIG B-H; 5)

Ammonites vortex Simpson, 1855: 60 View in CoL .

Porpoceras vortex View in CoL – Buckman 1911: pl. 29A. — Géczy & Szente 2007: pl. 8, fig. 4.

Porpoceras verticosum Buckman, 1914 : pl. 91.

Porpoceras gr. vortex - verticosum – Rulleau et al. 2013: 101, pl. 29, fig. 2; pl. 30, figs 1, 2; pl. 31, figs 1, 3, 5; pl. 32, figs 1, 3-6; pl. 33, figs 1, 2; pl. 34, fig. 1.

Porpoceras vortex View in CoL – Kovàcs 2014: 50, pl. 2, figs 2, 7; pl. 4, fig. 5. DESCRIPTION

Very evolute shell with a cadicone whorl section on inner whorls, becoming quadratic to depressed on mature whorls. Every two, three or four primary ribs, one primary rib bears a ventro-lateral tubercle. Ribs are often grouped by two on the same tubercle. This ornamentation is constant throughout ontogeny. Each tubercle bears a very developed spine leaning on the following whorl and not visible on internal molds. Suture lines not visible on the specimens from the Airvault quarry.

MEASUREMENTS

See Table 1. View TABLE

STRATIGRAPHIC AND PALAEOGEOGRAPHICAL OCCURRENCES From the uppermost part of the Serpentinum Zone (?) to the Variabilis Subzone; found in NW Europe, Siberia, Spitsbergen, North and South America.

DISCUSSION

According to Rulleau et al. (2013), it is extremely difficult to distinguish P. vortex from P. verticosum , even with a large number of specimens. They therefore decided to include these two species within the same group and we concur with this taxonomic opinion. Porpoceras differs from Catacoeloceras and Mucrodactylites by its well-developed ventro-lateral tubercles and ribs generally grouped by two on the same tubercle. The resembling genus Peronoceras is older and does not exhibit tubercles on inner whorls ( Rulleau et al. 2013).

TABLE 1. — Measurements (in mm) of Porpoceras gr. vortex (Simpson, 1855) -verticosum Buckman, 1914 specimens from Airvault quarry (UBGD 279076, UBGD 279077), from Belmont quarry (UBGD 279075), from Anduze, Gard (France, 1665 F-2) and of the holotypes of Porpoceras vortex (WM 153a) and Porpoceras verticosum (WM 220a) from Whitby, Yorkshire (England). Abbreviations: D, Diameter; H, whorl height; W, whorl width; U, umbilical diameter.

Genus Species Specimen D H W U H/D U/D Remarks
Porpoceras vortex-verticosum UBGD 279076 59 13.3 34.8 0.23 0.59
Porpoceras vortex-verticosum UBGD 279077 57.3 11.5 35.2 0.20 0.61
Porpoceras vortex-verticosum UBGD 279075 74.7 18.7 43.5 0.25 0.58
Porpoceras vortex-verticosum 1665 F-2; Rulleau et al. (2013: pl. 32, fig. 1) 78 17 20.5 47 0.22 0.60
Porpoceras vortex WM 153a; Buckman (1911: pl. 29A) 83 15 26 53 0.18 0.64 Holotype
Porpoceras verticosum WM 220a; Buckman (1914: pl. 91) 71 15 18.5 43 0.21 0.61 Holotype

Kingdom

Animalia

Phylum

Mollusca

Class

Cephalopoda

Order

Ammonoidea

Family

Dactylioceratidae

Loc

Porpoceras

Jattiot, Romain, Fara, Emmanuel, Brayard, Arnaud & Vennin, Emmanuelle 2016
2016
Loc

Porpoceras vortex

KOVACS A. 2014: 50
2014
Loc

vortex

SIMPSON M. 1855: 60
1855
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