Schloenbachia lymensis SPATH , 1926

Košťák, Martin, Sklenář, Jan, Mazuch, Martin & Čech, Stanislav, 2019, Taxonomy And Stratigraphic Distribution Of The Ammonite Schloenbachia Neumayr, 1875 From The Bohemian Cretaceous Basin, Fossil Imprint 75 (1), pp. 64-69 : 65-67

Schloenbachia lymensis SPATH, 1926

Text-fig. 2a–g

1853 Ammonites varians var. subtuberculata ; Sharpe, p. 22, pl. 8, fig. 8.

non 1853 Ammonites coupei var. tuberculata MANTELL ; Sharpe, p. 24, pl. 8, fig. 4.

1926 Schloenbachia lymensis ; Spath, pp. 426, 430.

1971 Schloenbachia varians trituberculata SPATH ; Soukup, p. 77, figs 1–2, pl. 1.

1985 Schloenbachia varians trituberculata SPATH ; Svoboda, p. 26.

1998 Schloenbachia spp. ; Kaplan et al., p. 109.

2002 Schloenbachia lymensis SPATH ; Wright and Kennedy, p. 185, pl. 31, figs 3–4.

2004 Schloenbachia varians trituberculata ; Košťák et al., p. 515.

2005 Schloenbachia lymensis SPATH, 1926 a ; Gale et al., p. 466, fig. 12f.

2013 Schloenbachia lymensis SPATH, 1926 b ; Kennedy, p. 464, fig. 11.

2015 Schloenbachia lymensis S PATH; Wright and Kennedy, p. 450, figs 179–180, pls 141–145. (with complete synonymy)

M a t e r i a l. Two specimens No. NM-O 1801 (National Museum, Prague) and No. 2310/2819 (Chlupáč’s Museum of Earth History, Faculty of Sciences , Charles University, Prague) .

D e s c r i p t i o n. For detailed description of specimen S. lymensis from Plaňany quarry see Soukup (1971). The additional record from Slaný represents a larger adult specimen (?macroconch) with the majority of the body chamber preserved (internal mould) including the aperture. The preserved slightly compressed fragment consists of a 70 mm long and 30 mm high part of the whorl. The siphonal keel is well developed, connecting the chevronlike structures resulting from the constriction of the body chamber. The umbilical bullae are coarser and they give a rise to prorsiradiate ribs, coarser in the inner part. Unusual ventrolateral spines (i.e. modified ventrolateral clavi) are well developed in the last three main ribs of the body chamber. The suture line observable in Soukup’s original specimen from Plaňany ( Text-fig. 2d ) corresponds well to the specimen figured by Wright and Kennedy (2015: textfig. 180 B).

R e m a r k s. Spath’s (1926) holotype corresponds with our specimen from Plaňany in the majority of morphological aspects. The only difference are the remarkable coarser lateral tubercles in the second specimen (loc. Slaný; see Text-fig. 2e, g ). According to Wright and Kennedy (2015), S. lymensis is analogous to S. coupei forma trituberculata (= S. varians trituberculata sensu Soukup 1971 ) with some differences such as the larger adult size (specimen from Slaný), finer inner ribs, missing lateral and umbilical tubercles typical for S. coupei (compare with the specimen from Plaňany), disappearing of the lateral tubercles (partly seen in the Plaňany specimen) and loss of the ventrolateral clavi in adult specimens of S. lymensis . Sharpe’s specimen (1853: 24, pl. 8, fig. 4) included in the synonymy list by Soukup (1971) belongs to S. lymensis according to Wright and Kennedy (2015).

Wright and Kennedy (2015) recognized five forms of S. lymensis : lymensis sensu stricto, simplicosta, lautiforme, flexicosta and lissa based on differences in morphology. Both specimens from the BCB correspond to the forma lymensis sensu stricto. Additionally, in the specimen from Slaný, we observed unusual ornamentation consisting of markedly developed ventrolateral clavi slightly modified as spines. This morphological feature modifies to some extent the opinion ( Wright and Kennedy 2015) that the loss of the ventrolateral clavi occurred in mature specimens of S. lymensis .

The specimen from Slaný was originally labelled as “ Ammonites dentato-carinatus Roem. ”. A taxon corresponding to the Coniacian genera Barroisiceras DE GROSSOUVE, 1894 or Santonian Texasia REESIDE, 1932 . The keel in our specimen does not show any serration or clavi typical for these taxa. Moreover, no sediments of the same age have been recognized in the vicinity of Slaný town.

S t r a t i g r a p h i c a n d g e o g r a p h i c d i s t r i b u t i o n s. According to Kennedy (2013) and Wright and Kennedy (2015), the FO of S. lymensis is in the Middle Cenomanian terminal Acanthoceas jukesbrownei Zone and acme in the Upper Cenomanian Calycoceras guerangeri Zone. The LO is reported from the Praeactinocamax plenus Zone within the Metoicoceas geslinianum Zone. The occurence in the BCB falls into the Calycoceras guerangeri through the Metoicoceras geslinianum Zones.

This species is known from England (Dorset, Lyme Regis, Shapwick Grange, Bincombe, Eastbourne), France (Seine-Maritime, Rouen, Craie, Les Lattes, Alpes-de- Haute), Germany (Münster Basin), Poland (Holy Cross Mts), Romania (Haţeg) ( Wright and Kennedy 2015), and the BCB – this paper ( Text-fig. 3 ).

Figures

Text-fig. 2. a–g. Schloenbachia lymensis SPATH, 1926. a–d. S. lymensis from the Plaňany quarry. a. Lateral view. b. Ventral view. c. Whorl section (improved from Soukup 1971). d. Suture line (adopted from Soukup 1971; improved). E – external lobe, A – adventive lobe, U1 and U2 – umbilical lobes. e–g. S. lymensis from the locality Slaný. e, g. Ventro-lateral view showing larger clavi modified into spines closely to the aperture. f. Ventral view. Scale bars equal 10 mm.

Text-fig. 3. Palaeogeographic distribution of Schloenbachia lymensis (red dots) in the Upper Cenomanian Calycoceras guerangeri through the Metoicoceras geslinianum Zones. Light blue – shallow epicontinental sea, dark blue – deep marine settings, yellow – land. * asterisk – occurrence in the BCB (modified after Wilmsen 2012).