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Late Visean pelagic chondrichthyans from northern Europe

100%

Ginter M., Duffin C. J., Dean M. T., Korn D.

Acta Palaeontologica Polonica

2015

tom 60

nr 4

The relatively rich assemblages of shark teeth from pelagic limestone (Mississippian, late Viséan, late Asbian-middle Brigantian) of three northern European regions: the Rhenish Mountains (Westenfeld Quarry, Germany), the Holy Cross Mountains (Todowa Grząba at the edge of Ostrówka Quarry, Poland), and Derbyshire (Cawdor Quarry, Matlock, England, UK) display certain similarities, with the absolute predominance of the teeth of Falcatidae (small Symmoriiformes) and the constant presence of Thrinacodus spp. The largest and most diverse assemblage from Todowa Grząba contains at least three species of a falcatid Denaea, a xenacanthimorph Bransonella nebraskensis, a newly described phoebodontid Thrinacodus dziki sp. nov., a few ctenacanthiform and euselachian teeth, and two abraded euchondrocephalan dental elements. Anachronistidae, common in the most of late Viséan pelagic faunas, are absent from Todowa Grząba and Westenfeld. The material under study differs from the shallow-water chondrichthyan fauna, hitherto described from the Mississippian carbonate platform facies, by its taxonomic content (particularly almost total absence of Euchondro-cephali), generally lower diversity, and higher frequency of small teeth.

Exploring the limits of morphospace: ontogeny and ecology of Late Visean ammonoids from the Tafilalt, Morocco

84%

Klug C., De Baets K., Korn D.

Acta Palaeontologica Polonica

2016

tom 61

nr 1

Early late Viséan ammonoid assemblages in Morocco are composed of diverse and well-preserved specimens. The material was found in a plain in the Tafilalt (eastern Anti-Atlas). Here, we describe mass-occurrences of juvenile specimens, in which subadult and adult specimens occur in low numbers. The juveniles of some species display a conch morphology that differs fundamentally from the adult stages. Accordingly, we emend the species diagnoses of Goniatites lazarus as well as Calygirtyoceras darkaouaense, introduce the species Entogonites bucheri sp. nov., and discuss possible ecological implications of the morphologic changes throughout ontogeny. In particular, we compare the changes in conch morphology through ontogeny in the light of Pareto Optimiality according to which the morphology of organisms would fill a polygon or polyhedron in morphospace. Data points in one of the vorteces of the polyhedron indicate optimisation for the corresponding task. Although shape is not a proof of function, it appears plausible that juvenile conchs were selected rather for compactness while adult conchs were positively selected for conchs with improved hydrodynamic properties. This appears plausible because at small conch diameters, swimming movements will not suffice for effective translocation and a planktonic mode of life is likely.

Ograniczanie wyników

2 Acta Palaeontologica Polonica

2 Korn D.

1 De Baets K.

1 Dean M. T.

1 Duffin C. J.

1 Ginter M.

1 Klug C.

1 2016

1 2015

Wyniki wyszukiwania

Late Visean pelagic chondrichthyans from northern Europe

Exploring the limits of morphospace: ontogeny and ecology of Late Visean ammonoids from the Tafilalt, Morocco