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1

Upper Bathonian and lower Callovian ammonites from Chacay Melehue [Argentina]

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Parent H.

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nr 1

69-130

EN

The upper Bathonian-lower Callovian ammonite fauna of Chacay Melehué was sampled through new exposures under close stratigraphic control. Two new faunal horizons are described: the Iniskinites gulisanoi horizon and the Iniskinites crassus horizon, lying in the lower and middle parts, respectively, of the Steinmanni Zone. The ammonite fauna contains some species not previously described: Choffatia aff. neumayri (Siemiradzki, 1899) [M&m], Iniskinites evolutus sp. n. [M], Iniskinites sp. A [M], Eurycephalites aff. gottschei (Tornquist, 1898) [M], Xenocephulites aff. neuquensis (Stehn, 1923) [m], and Xenocephalites sp. A [m]. Oxycerites tenuistriatus (de Grossouvre, 1888) is new for the Andean region. Several species are represented by large samples that allow descriptions and analyses to be made of the entire ontogeny and the characterization of the principal morphs within each species. It is then possible to propose sexual dimorphic correspondence between some nominal morphospecies. The successive species Lilloettia steinmanni (Spath, 1928), Eurycephalites gottschei (Tornquist, 1898), E. rotundus (Tornquist, 1898), and E. extremus (Tornquist, 1898) form a phyletic morphocline here interpreted as a mosaic heterochronocline.

PL

W pracy opisano amonity górnego batonu i dolnego keloweju zebrane warstwa po warstwie z nowych odsłonięć w rejonie Chacay Melehué w Argentynie. Wyróżniono dwa nowe horyzonty: Iniskinites gulisanoi oraz Iniskinites crassus, pierwszy z dolnej, a drugi ze środkowej części poziomu Steinmanni. Zebrana fauna amonitowa zawiera nie opisane dotąd gatunki: Choflatia aff. neumayri (Siemiradzki, 1899) [M&m], Iniskinites evolutus sp. n. [M], Iniskinites sp. A [M], Eurycephalites aff. gottschei (Tornquist, 1898) [M], Xenocephalites aff. neuquensis (Stehn, 1923) [m] i Xenocephalites sp. A [m]. Gatunek Oxycerites tenuistriatus (de Grossouvre, 1888) jest nowy dla regionu andyjskiego. Wiele gatunków jest reprezentowanych przez duże próbki okazów o różnym stopniu rozwoju ontogenetycznego, co zezwala na dokładne prześledzenie ontogenezy, podanie charakterystyki głównych morfotypów w obrębie każdego gatunku oraz zaproponowanie relacji dymorficznych między niektórymi nominalnymi morfogatunkami. Nastepujące po sobie gatunki Lilloettia steinmanni (Spath, 1928), Eurycephalites gottschei (Tornquist, 1898), E. rotundus (Tornquist, 1898) i E. extremus (Tornquist, 1898) tworzą filetyczną morfoklinę, zinterpretowaną przez autora jako mozaikowa heterochronoklina.

2

Relationships between dimensionless models of ammonoid shell morphology

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Parent H. , Bejas M. , Greco A. , Hammer O.

Acta Palaeontologica Polonica

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2012

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tom 57

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nr 2

EN

In morphological studies the shape may be conveniently quantified by relative dimensions or dimensionless quantities. The analyses of shell morphology and morphospace occupation have been historically approached mainly by means of statistical analysis on classical dimensions (distance measurements: diameter, umbilical width, whorl width, whorl height and apertural whorl height), the Raup’s coiling and expansion rate parameters and, more recently, by means of the ADA−model which conjugates the classical variables in a single simple equation. Relationships between these studies should be possible based on mathematical equivalences between classical dimensions and those of coiling and expansion rates. These equivalences, which are presented in this paper, have been obtained on the basis of the ADA−model and a new general method for deriving dimensionless models of morphology based on exponential trajectories as a function of a rotational angle.

3

Additional Tithonian and Berriasian ammonites from the Vaca Muerta Formation in Pampa Tril, Neuquén Basin, Argentina

51%

Parent H. , Schweigert G. , Scherzinger A. , Garrido A. C.

Volumina Jurassica

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2017

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tom Vol. 15, no 1

139--154

EN

The ammonite fauna of the Tithonian–Berriasian of the Vaca Muerta Formation in Pampa Tril has been recently described in detail. New important specimens and additional information are presented in this paper. The phyletic evolution of Choicensisphinctes, passing from C. platyconus to C. erinoides is confirmed, as well as the sexual dimorphic correspondence of this latter with C. mendozanus. A microconch of the genus Krantziceras is described for the first time. New specimens of Substeueroceras koeneni identical to the paralec¬totype, along with material already described from the koeneni Hz. (Koeneni Zone), point to the fixation of this horizon as the type horizon of the species. New specimens of Subthurmannia boissieri from the Damesi Zone match clearly the range of variation of this species in Spain, thus providing an element for time-correlation with the Tethyan standard scale. Additional material from the internispinosum alpha Hz. confirms the origin of W. internispinosum from C. proximus by the inception of an evolutionary innovation in the juvenile ontogeny.

4

Towards a consistent Oxfordian/Kimmeridgian global boundary: current state of knowledge

26%

Wierzbowski A. , Atrops F. , Grabowski J. , Hounslow M. , Matyja B. A. , Olóriz F. , Page K. , Parent H. , Rogov M. A. , Schweigert G. , Villaseñor A. B. , Wierzbowski H. , Wright J. K.

Volumina Jurassica

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2016

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tom Vol. 14, no. 1

15--49

EN

New data are presented in relation to the worldwide definition of the Oxfordian/Kimmeridgian boundary, i.e. the base of the Kimmeridgian Stage. This data, mostly acquired in the past decade, supports the 2006 proposal to make the uniform boundary of the stages in the Flodigarry section at Staffin Bay on the Isle of Skye, northern Scotland. This boundary is based on the Subboreal-Boreal ammonite successions, and it is distinguished by the Pictonia flodigarriensis horizon at the base of the Subboreal Baylei Zone, and which corresponds precisely to the base of the Boreal Bauhini Zone. The boundary lies in the 0.16 m interval (1.24–1.08 m) below bed 36 in sections F6 at Flodigarry and it is thus proposed as the GSSP for the Oxfordian/ Kimmeridgian boundary. This boundary is recognized also by other stratigraphical data – palaeontological, geochemical and palaeomagnetic (including its well documented position close to the boundary between magnetozones F3n, and F3r which is placed in the 0.20 m interval – 1.28 m to 1.48 m below bed 36 – the latter corresponding to marine magnetic anomaly M26r). The boundary is clearly recognizable also in other sections of the Subboreal and Boreal areas discussed in the study, including southern England, Pomerania and the Peri-Baltic Syneclise, Russian Platform, Northern Central Siberia, Franz-Josef Land, Barents Sea and Norwegian Sea. It can be recognized also in the Submediterranean-Mediterranean areas of Europe and Asia where it correlates with the boundary between the Hypselum and the Bimmamatum ammonite zones. The changes in ammonite faunas at the boundary of these ammonite zones – mostly of ammonites of the families Aspidoceratidae and Oppeliidae – also enables the recognition of the boundary in the Tethyan and Indo-Pacific areas – such as the central part of the Americas (Cuba, Mexico), southern America, and southern parts of Asia. The climatic and environmental changes near to the Oxfordian/Kimmeridgian boundary discussed in the study relate mostly to the European areas. They show that very unstable environments at the end of the Oxfordian were subsequently replaced by more stable conditions representing a generally warming trend during the earliest Kimmeridgian. The definition of the boundary between the Oxfordian and Kimmeridgian as given in this study results in its wide correlation potential and means that it can be recognized in the different marine successions of the World.