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A new species of Pseudhimalayites (Ammonitina, Aspidoceratoidea) from the Lower Tithonian of the Betic Range, Southern Spain

Parent Horacio, Ramos-Agustino Enrique, Scherzinger Armin, Schweigert Günter

Volumina Jurassica

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2023

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Vol. 21

19--26

EN

The Late Jurassic aspidoceratoid genus Pseudhimalayites Spath is scarcely recorded but widely distributed in the Andean basins, the Caribbean region, and in the European Tethys. From Ponti Zone (Lower Tithonian) rocks of the Betic Range in Carchelejo we describe here the new species Pseudhimalayites carchelejensis, based on a macroconch (female) holotype. The corresponding microconch (male), described from the same ammonite assemblage, would belong to the morphogenus Simocosmoceras Spath which groups the microconchs of Pseudhimalayites. P. carchelejensis n. sp. differs from the coeval Pseudhimalayites steinmanni (Haupt) by lacking ventral tubercles in the phragmocone and by bearing umbilical tubercles only from the adult whorl of the phragmocone. These differences illustrate a significant morphologic divergence between the Andean and the Tethyan lineages.

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New records of Tmaegoceras lacordarii (Michelin, 1835) from the Lower Jurassic Arietenkalk Formation of SW Germany and its systematic relationships

Schweigert Günter, Scherzinger Armin, Gräbenstein Stefan

Volumina Jurassica

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2021

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Vol. 19, no. 1

95--108

EN

New material of the enigmatic cosmopolitan ammonite genus Tmaegoceras Hyatt, 1889 is reported from the upper Lower Sinemurian (Bucklandi Zone, ‛cf. pinguisʼ Biohorizon) of SW Germany. It is better preserved than previously described material. All specimens are assigned to Tmaegoceras lacordarii (Michelin, 1835), an almost forgotten subjective senior synonym of Tmaegoceras crassiceps Pompeckj, 1901. The presence of an extreme rursiradiate ribbing style in some specimens allows a better understanding of this genus and provides a hint for its systematic affiliation. This diagnostic ribbing style is shared with some extremely rare Alpine taxa such as Ammonites salinarius Hauer, 1846 and “Arietites” subsalinarius Wähner, 1891. Tmaegoceras is included here in Pseudotropitinae Donovan, 1973. Pseudotropitinae are possibly an early offshoot of Arietitidae indigenous of the Panthalassa Realm that occasionally spread into the Tethys and its adjacent shelves. A phyletic relationship with Late Triassic Tropitidae Mojsisovics, 1875, however, cannot be excluded either.

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Arietites solarium (Quenstedt, 1883) – a diagnostic ammonite species in the Lower Jurassic (Early Sinemurian, Bucklandi Zone) of SW Germany

Scherzinger Armin, Gräbenstein Stefan, Schweigert Günter

Volumina Jurassica

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2020

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Vol. 18, no. 1

37--46

EN

The coarse-ribbed and big-sized Arietites solarium (Quenstedt, 1883) is one of the largest-grown and most iconic ammonite taxa in the entire Swabian Lower Jurassic; however, despite previous revisions including the designation of a lectotype, there has been some confusion concerning its correct identification, and its type horizon within the Lower Sinemurian Arietenkalk Formation was not exactly known. Arietites solarium characterises the herein introduced solarium Biohorizon of the upper Bucklandi Zone of the Sinemurian. For nomenclatorial stability, we designate a neotype based on the only surviving specimen of Quenstedtʼs original type series. In addition, we provide a preliminary succession of recognized biohorizons in the Lower Sinemurian of Swabia, which will make correlations with other areas more reliable.

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A review of the classification of Jurassic aspidoceratid ammonites – the Superfamily Aspidoceratoidea

Parent Horacio, Schweigert Günter, Scherzinger Armin

Volumina Jurassica

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2020

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Vol. 18, no. 1

47--52

EN

The aspidoceratid ammonites have been traditionally included in the superfamily Perisphinctoidea. However, the basis of this is unclear for they bear unique combinations of characters unknown in typical perisphinctoids: (1) the distinct laevaptychus, (2) stout shells with high growth rate of the whorl section area, (3) prominent ornamentation with tubercles, spines and strong growth lines running in parallel over strong ribs, (4) lack of constrictions, (5) short to very short bodychamber, and (6) sexual dimorphism characterized by miniaturized microconchs and small-sized macroconchs besides the larger ones, including changes of sex during ontogeny in many cases. Considering the uniqueness of these characters we propose herein to raise the family Aspidoceratidae to the rank of a superfamily Aspidoceratoidea, ranging from the earliest Late Callovian to the Early Berriasian Jacobi Zone. The new superfamily includes two families, Aspidoceratidae (Aspidoceratinae, Euaspidoceratinae, Epipeltoceratinae and Hybonoticeratinae), and Peltoceratidae (Peltoceratinae and Gregoryceratinae nov. subfam.). The highly differentiated features of the aspidoceratoids indicate that their life-histories were very different from those of the perisphinctoids; these ammonites show great promise for studies of developmental and evolutionary patterns and processes, and can be used for biostratigraphic-chronostratigraphic purposes and interprovincial correlations.