Pleuroceras, Geist & Weis & Schlögl & Košťák & Mazuch, 2025
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publication ID |
https://doi.org/10.1186/s13358-025-00366-5 |
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persistent identifier |
https://treatment.plazi.org/id/6B11FC53-C265-4877-FF31-FB519037FA55 |
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treatment provided by |
Felipe |
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scientific name |
Pleuroceras |
| status |
n. sp. |
Pleuroceras View in CoL n. sp. ( aff. spinatum (Bruguière, 1789)
( Figs. 3N, O View Fig , 4A, B View Fig ).
Material: Two fragments of large specimens (Ge 33511 and Ge 33512).
Description: Despite morphological differences, we consider both fragments as belonging to the same species. Rather evolute coiling with equidimensional and slightly trapezoidal whorl section. Bituberculate, radiate ribs which are strongly curved forward on the latero-ventral edge, gradually fading, but reaching the base of a well-developed crenulated keel ( Fig. 3N, O View Fig ), or bifurcating or trifurcating, and passing on to the venter as chevrons
( Fig. 4A, B View Fig ). Lower row of blunter tubercles is situated near the umbilico-lateral edge and the upper row of more pointed but still rather low tubercles on the latero-ventral edge. Ribs are already well-developed on the umbilical wall. Tere are no tubercles on specimen figured on Fig. 4A, B View Fig . Tis fragment probably represents a terminal part of an adult body chamber with adult modifications such as lateral ribs diminishing in relief, disappearance of tubercles, and more elevated keel with forward inclined chevrons. We can roughly estimate the adult size of the complete specimen to 18–20 cm of D.
Remarks: As the mature modifications of the large-size Pleuroceras are not known, we can compare only the densely ribbed fragment of a body-chamber ( Fig. 3N, O View Fig ). Apart of the probably slightly less evolute coiling and higher density of the ribs, their individual morphology, as well as the morphology of the keel are very similar to P. spinatum figured by Howarth (1958, pl. 7, fig. 2). Pleuroceras gigas Howarth, 1958 is another large form described in the same publication (Howarth, 1958), however this ammonite differs from our specimen in more compressed whorl section, ribs morphology without tubercles and thinner and less crenulated keel which can even disappear in larger sizes. Numerous large-size Pleuroceras were recently published by Bohain et al. (2023) from Vendée in France. Here, the similarly densely ribbed forms are ranged among P. quadratum Howarth, 1957 , however in a comparable diameter this species is more evolute, the section is subquadratic and the ventral projection of ribs can be less developed or even absent. Moreover, the ribs seem to be less pronounced on both umbilical wall and on the flanks (Bohain et al., 2023 pl. 52). Te crenulated keel is strong as on our specimens. Other large specimens are attributed to P. cf. apyrenum (Buckman, 1911) and P. elaboratum ( Simpson, 1884) and differ from our specimens in subrectangular compressed whorls for the first species (Bohain et al., 2023, pl. 57, fig. 1) and more evolute coiling with subparallel flanks for the second species (Bohain et al., 2023, pl. 54, fig. 4).
Occurrence: Spinatum Zone (without precision) of the Outer Western Carpathians in Czech Republic.
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