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The myth of the Triassic lytoceratid ammonite Trachyphyllites Arthaber, 1927, in reality an Early Jurassic Analytoceras hermanni Gumbel, 1861

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Hoffmann R. , Keupp H.

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tom Vol. 60, no. 2

219-229

EN

The ammonoid "Trachyphyllites costatum" Arthaber (1927), based on a single specimen from an erratic boulder of presumed Late Triassic (Norian age) from Timor, (Indonesia), was originally described as a phylloceratid but later recognized as a true lytoceratid by Basse (1952) and Schindewolf (1961), and used by Wiedmann (1966a, 1966b, 1970) to support his idea of a polyphyletic origin of the post-Triassic ammonoids and of the Late Triassic roots of the lytoceratids. New collections of additional specimens and associated taxa from other erratic boulders in the type locality have confirmed observations (Tozer 1971; Krystyn 1978) that the age of the original boulder was misinterpreted, and have shown that "Trachyphyllites" is actually of Early Jurassic (Hettangian) age. An unpublished generic revision of the entire superfamily Lytoceratoidea by Hoffmann (2009) has shown that "Trachyphyllites costatum Arthaber" is a junior synonym of Analytoceras hermanni (Gumbel, 1861), a taxon thought by Wahner (1894) to be a subjective synonym of Analytoceras articulatum (J. Sowerby, 1831) We reestablish the species Analytoceras hermanni (Gumbel, 1861) for Analytoceras articulatum "Type B" (Wahner 1894), which is characterized by a wide umbilicus and a small whorl expansion rate. The morphologically distinct "Type A" (Wahner 1894) corresponds to the type species of Analytoceras, A. articulatum (J. Sowerby, 1831). A revised phylogeny of the Early Jurassic lytoceratids is presented.

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Conellae, enigmatic structures on cephalopod shells - shapes, distribution, and formation

80%

Hoffmann R. , Mironenko A. , Keupp H.

Acta Palaeontologica Polonica

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2019

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tom 64

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nr 4

EN

Conellae, enigmatic cone-shaped structures which can be found on the surface of internal moulds of cephalopod shells (predominantly of ammonoids), are regarded herein as the product of remote (biologically induced) biomineralization formed in closed-off cavities during lifetime and might be primarily composed of vaterite, aragonite, or calcite. To date conellae have been interpreted in many different ways: (i) as organisms (gastropods, cirriped crustaceans, or disciniscid brachiopods), (ii) pre-diagenetic syn vivo features, i.e., biologically controlled or induced, the product of remote biomineralization, (iii) and diagenetic, i.e., abiogenic origin and post-mortem. The proposed processes of conellae formation seem insufficient to explain conellae related phenomena. Further, their assumed primary aragonitic or calcitic mineralogy are reviewed and based on new material critically assessed. The stratigraphic range of conellae extends from the Middle Ordovician and probably to modern Nautilus. Predominantly, conellae can be found on internal moulds along the keel, ribs or nodes, umbilical shoulder, at the transition between phragmocone and body chamber, and can be associated with repaired scars. However, conellae are also common on the smooth body chambers of large macroconchs of Jurassic ammonites. Conellae, which are located on ammonite body chambers, are filled with the same material found in the body chamber and can contain small burrows, sand grains, or coprolites. Some of these conellae are partially covered with nacreous shell material. Limonitic conellae were also found on the limonitic internal moulds of orthocone nautiloids. Moreover, disciniscid brachiopods found on inoceramid bivalves were re-identified herein as conellae. A short guide for conellae identification has been provided herein.

3

Taphonomy of the earliest Cambrian linguliform brachiopods

70%

Forchielli A. , Steiner M. , Hu S. , Luter C. , Keupp H.

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nr 1

EN

The Early Cambrian Burgess Shale−type fossil Lagerstätten of Yunnan Province (Chengjiang; Guanshan) are crucial in understanding the Cambrian bioradiation. Brachiopods are applied here as a critical model phylum to analyze the taphonomy of Yunnan fossil Lagerstätten, because shell and tissue composition of modern brachiopods can be compared with exceptionally preserved Cambrian remains. Systematic elemental mapping and energy−dispersive X−ray analyses have been carried out to study fossil brachiopods and their matrix from Cambrian Stages 3–4 and modern linguliform brachiopods from several geographical regions in order to evaluate the detailed structure of the shells and the biological and environmental influences on shell composition. Analyses of earliest Cambrian fossils encompassing the complete spectrum of weathering stages show a primary organo−phosphatic brachiopod shell, visible in unweathered specimens, and a successive dissolution and replacement of the shell during weathering, observable in specimens that underwent dif− ferent stages of weathering. Therefore, our study reveals that earliest Cambrian linguliform brachiopods from the Chengjiang and Guanshan Biotas developed organo−phosphatic shells as their Recent counterparts. Early carbon and apa− tite preservation together with rapid deposition in claystone, instead of early iron adsorption, appears crucial for the pres− ervation of highly delicate tissue. Primary calcium, phosphorus, organic carbon, and a multilayered shell are present, by inference between Cambrian fossils and Recent specimens, through the whole Phanerozoic. Elements such as silicon, sul− phur, calcium, phosphorus, and iron were detected, impregnated with organic compounds in some organs of modern Lingula, and related to the potential of fossilization of Cambrian linguliform brachiopods. Ferromanganese precipitates traced in the shell of in vivo specimens of modern Lingula may enhance the potential for fossilization too.