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The oldest representative of a modern deep-sea ophiacanthid brittle-star clade from Jurassic shallow-water coral reef sediments

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Thuy B., Schulz H.

Acta Palaeontologica Polonica

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2013

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tom 58

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nr 3

Ophiurites crinitus is a fossil brittle−star species which passed largely unnoticed since its original description. In this paper, we redescribe the type material of O. crinitus with the aim to put it into the context of modern ophiuroid systematics, and propose the new genus name Ophiosternle to replace the invalid Ophiurites. The re−assessed species is shown to be a member of the extant deep−sea family Ophiacanthidae, articulated fossils of which are extremely rare. It presents greatest affinities with members of the Ophioplinthaca–Ophiocamax–Ophiomitra clade, of which it most probably represents the oldest known fossil species. The depositional environment of the strata, which yielded the described specimens is interpreted as shallow, storm−influenced marine setting in the immediate vicinity of coral reefs. This contrasts with the distribution pattern of extant species of the Ophioplinthaca–Ophiocamax–Ophiomitra clade, which almost exclusively occur at depths exceeding the shelf break.

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A new brittle star from the early Carboniferous of Poland and its implications on Paleozoic modern-type ophiuroid systematics

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Thuy B., Kutscher M., Plachno B. J.

Acta Palaeontologica Polonica

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2015

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tom 60

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nr 4

The fossil record of Paleozoic ophiuroids includes a number of forms which share striking similarities with modern relatives in terms of skeletal morphology. These so called modern-type Paleozoic ophiuroids yield an enormous potential for a better understanding of ophiuroid evolution, yet the scarcity of accurate and sufficiently detailed morphological descriptions available to date precludes any further-reaching assessments. Here, we describe an articulated ophiuroid specimen from the Late Tournaisian (early Carboniferous) of Czatkowice quarry, southern Poland, as a new species Aganaster jagiellonicus sp. nov. The good preservation of the specimen allowed for a morphological analysis at a level comparable to recent ophiuroid descriptions. It shows remarkable morphological similarities with extant former ophio-lepidids Ophiomusium and Ophiosphalma. The new find thus contributes to a solid basis for future investigations on the position of the modern-type Paleozoic ophiuroid in the phylogeny of the class.

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Pyritized tube feet in a protasterid ophiuroid from the Upper Ordovician of Kentucky, U.S.A.

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Glass A.

Acta Palaeontologica Polonica

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2006

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tom 51

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nr 1

A single specimen of the protasterid ophiuroid Protasterina flexuosa from the Kope Formation (Cincinnatian, Upper Ordovician) of Kentucky exhibits three−dimensionally pyritized tube feet. This represents the first report of soft−tissue preservation in an echinoderm from the type−Cincinnatian series. The tube feet are solid and lack all internal structure. They consist of aggregated masses of small euhedral to subhedral pyrite crystals suggesting that pyritization, although decay−induced and mediated, did not necessarily replicate soft−tissues but might instead have formed inside the void−spaces left behind during the decay process. The discovery of pyritized soft−tissue as delicate as ophiuroid tube feet suggests that similar forms of soft−tissue preservation might be found in other taxa in the Kope Formation. Perhaps much more importantly, this unexpected occurrence demonstrates the incompleteness of our knowledge of permissible conditions for the preservation of soft−tissues and it thereby indicates promise for discovery of other such occurrences in diverse organisms in unexpected settings. Systematics of Paleozoic ophiuroids remains problematic in spite of many years of study by capable paleontologists. The incomplete but well−preserved specimens treated here include the types of Protasterina flexuosa and Protasterina fimbriata as well as previously undescribed specimens. Together they permit a revised diagnosis and detailed description of the genus Protasterina. Protasterina fimbriata is the type species of the genus but is a subjective junior synonym of Protaster flexuosus (= Protasterina flexuosa). The genus is clearly differentiated from the only other known protasterid ophiuroid from the Cincinnatian series, Taeniaster spinosus, and from all other protasterid genera.

Ograniczanie wyników

3 Acta Palaeontologica Polonica

2 Thuy B.

1 Glass A.

1 Kutscher M.

1 Plachno B. J.

1 Schulz H.

1 2015

1 2013

1 2006

The oldest representative of a modern deep-sea ophiacanthid brittle-star clade from Jurassic shallow-water coral reef sediments

A new brittle star from the early Carboniferous of Poland and its implications on Paleozoic modern-type ophiuroid systematics

Pyritized tube feet in a protasterid ophiuroid from the Upper Ordovician of Kentucky, U.S.A.