Dissociated, specifically indeterminate columnals of representatives of the suborder Bourgueticri... more Dissociated, specifically indeterminate columnals of representatives of the suborder Bourgueticrinina have recently been recorded for the first time from Cenomanian strata in southern Poland. Here we add a proximale and a cup/proximale from the same stratigraphic level, both in open nomenclature. The theca bears a certain resemblance to Bourgueticrinus brydoneiRasmussen, 1961, originally described from the upper Campanian and lower Maastrichtian
It has long been assumed that photosensitivity in echinoderms is mainly related to diffuse photor... more It has long been assumed that photosensitivity in echinoderms is mainly related to diffuse photoreception mediated by photosensitive regions embedded within the dermis. Recent studies, however, have shown that some extant echinoderms may also display modified ossicles with microlenses acting as sophisticated photosensory organs. Thanks to their remarkable properties, these calcitic microlenses serve as an inspiration for scientists across various disciplines among which bio-inspired engineering. However, the evolutionary origins of these microlenses remain obscure. Here we provide microstructural evidence showing that analogous spherical calcitic lenses had been acquired in some brittle stars and starfish of Poland by the Late Cretaceous (Campanian, ~79 Ma). Specimens from Poland described here had a highly developed visual system similar to that of modern forms. We suggest that such an optimization of echinoderm skeletons for both mechanical and optical purposes reflects escalation...
Echinoderms have long been considered to be one of the animal phyla that is strictly marine. Howe... more Echinoderms have long been considered to be one of the animal phyla that is strictly marine. However, there is growing evidence that some recent species may live in either brackish or hypersaline environments. Surprisingly, discoveries of fossil echinoderms in non-(open)marine paleoenvironments are lacking. In Wojkowice Quarry (Southern Poland), sediments of lowermost part of the Middle Triassic are exposed. In limestone layer with cellular structures and pseudomorphs after gypsum, two dense accumulations of articulated ophiuroids (Aspiduriella similis (Eck)) were documented. The sediments with ophiuroids were formed in environment of increased salinity waters as suggested by paleontological, sedimentological, petrographical and geochemical data. Discovery of Triassic hypersaline ophiuroids invalidates the paleontological assumption that fossil echinoderms are indicators of fully marine conditions. Thus caution needs to be taken when using fossil echinoderms in paleoenvironmental reconstructions.
A stalk fragment of the millericrinid crinoid Pomatocrinus sp. from the lower Kimmeridgian of Ma ... more A stalk fragment of the millericrinid crinoid Pomatocrinus sp. from the lower Kimmeridgian of Ma ogoszcz Quarry (Central Poland) consists of a partly preserved holdfast and a distal stalk fragment, which yields numerous epibionts and echinoid grazing traces. Importantly, the described stalk shows evidence of narrowing of the proximal part. Such a pathological structure of the apical part of the column likely represents a nonregenerative overgrowth of the stalk following the loss of the proximal column and crown due to nektonic predation as inferred from associated bite marks. Analogous pathological structures in fossil crinoids, although rare, are known from as far back as the Ordovician.
Dissociated, specifically indeterminate columnals of representatives of the suborder Bourgueticri... more Dissociated, specifically indeterminate columnals of representatives of the suborder Bourgueticrinina have recently been recorded for the first time from Cenomanian strata in southern Poland. Here we add a proximale and a cup/proximale from the same stratigraphic level, both in open nomenclature. The theca bears a certain resemblance to Bourgueticrinus brydoneiRasmussen, 1961, originally described from the upper Campanian and lower Maastrichtian
It has long been assumed that photosensitivity in echinoderms is mainly related to diffuse photor... more It has long been assumed that photosensitivity in echinoderms is mainly related to diffuse photoreception mediated by photosensitive regions embedded within the dermis. Recent studies, however, have shown that some extant echinoderms may also display modified ossicles with microlenses acting as sophisticated photosensory organs. Thanks to their remarkable properties, these calcitic microlenses serve as an inspiration for scientists across various disciplines among which bio-inspired engineering. However, the evolutionary origins of these microlenses remain obscure. Here we provide microstructural evidence showing that analogous spherical calcitic lenses had been acquired in some brittle stars and starfish of Poland by the Late Cretaceous (Campanian, ~79 Ma). Specimens from Poland described here had a highly developed visual system similar to that of modern forms. We suggest that such an optimization of echinoderm skeletons for both mechanical and optical purposes reflects escalation...
Echinoderms have long been considered to be one of the animal phyla that is strictly marine. Howe... more Echinoderms have long been considered to be one of the animal phyla that is strictly marine. However, there is growing evidence that some recent species may live in either brackish or hypersaline environments. Surprisingly, discoveries of fossil echinoderms in non-(open)marine paleoenvironments are lacking. In Wojkowice Quarry (Southern Poland), sediments of lowermost part of the Middle Triassic are exposed. In limestone layer with cellular structures and pseudomorphs after gypsum, two dense accumulations of articulated ophiuroids (Aspiduriella similis (Eck)) were documented. The sediments with ophiuroids were formed in environment of increased salinity waters as suggested by paleontological, sedimentological, petrographical and geochemical data. Discovery of Triassic hypersaline ophiuroids invalidates the paleontological assumption that fossil echinoderms are indicators of fully marine conditions. Thus caution needs to be taken when using fossil echinoderms in paleoenvironmental reconstructions.
A stalk fragment of the millericrinid crinoid Pomatocrinus sp. from the lower Kimmeridgian of Ma ... more A stalk fragment of the millericrinid crinoid Pomatocrinus sp. from the lower Kimmeridgian of Ma ogoszcz Quarry (Central Poland) consists of a partly preserved holdfast and a distal stalk fragment, which yields numerous epibionts and echinoid grazing traces. Importantly, the described stalk shows evidence of narrowing of the proximal part. Such a pathological structure of the apical part of the column likely represents a nonregenerative overgrowth of the stalk following the loss of the proximal column and crown due to nektonic predation as inferred from associated bite marks. Analogous pathological structures in fossil crinoids, although rare, are known from as far back as the Ordovician.
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Papers by Rafał Lach