Rafał Lach

Roveacrinids (Crinoidea, Echinodermata) survived the Cretaceous-Paleogene (K-Pg) extinction event

Although crinoids appear not to have been involved in the great change in diversity at the Cretaceous-Paleogene (K-Pg) boundary extinction event, it has been assumed that representatives of order Roveacrinida became extinct during this time. Well-preserved fossils from the Danian (early Paleocene) of Poland demonstrate that these crinoids survived into the earliest Cenozoic. This find merits the qualification of this order as a “dead clade walking.”

Microlens arrays in the complex visual system of Cretaceous echinoderms

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-related adaptation to increased predation pressure during the so-called Mesozoic Marine Revolution.

Ophiuroids discovered in the middle triassic hypersaline environment.

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.

Late Cretaceous crinoids (Echinodermata) from the southwestern margin of the Holy Cross Mts. (southern Poland) and phylogenetic relationships among bourgueticrinids

A systematic account of crinoids from the Upper Coniacian–Lower Campanian of the southwestern margin of the Holy Cross Mountains in southern Poland is presented. Seven crinoid taxa [Marsupites testudinarius (von Schlotheim), Bourgueticrinus ellipticus (Miller), Bourgueticrinus sp., I.? granosus Valette, Isocrinus? sp., Nielsenicrinus carinatus Roemer and Austinocrinus bicoronatus (von Hagenow)] are described and illustrated. The new material from Poland extends down the stratigraphic range of Austinocrinus bicoronatus to the Lower Campanian. Morphometric data support that Bourgueticrinus ellipicus and B.? suedicus are conspecific. Taphonomy and paleoecology of recorded crinoid assemblages are discussed. Phylogeny of Cretaceous bourgueticrinids is also revisited.KurzfassungEs wird ein systematischer Überblick zu den oberkretazischen (Ober-Coniacium bis Unter-Campanium) Crinoiden vom SW-Rand des Heiligkreuzgebirges (Südpolen) vorgestellt. Insgesamt werden 7 Seelilientaxa, Marsupites testudinarius (von Schlotheim), B. ellipticus (Miller), Bourgueticrinus sp., I.? granosus Valette, Isocrinus? sp., Nielsenicrinus carinatus Roemer und Austinocrinus bicoronatus (von Hagenow), beschrieben und abgebildet. Die neuen Funde aus Polen erweitern die stratigraphische Reichweite von Austinocrinus bicoronatus bis in das frühe Campanium. Desweiteren implizieren die vorliegenden morphometrischen Daten, dass Bourgueticrinus ellipicus und B.? suedicus konspezifisch sind. Taphonomie und Paläoökologie der Crinoiden-Vergesellschaftung werden diskutiert, wie auch die Phylogenie der kreidezeitlichen Bourgueticriniden revidiert wird.

Echinoid Bite Traces on Late Cretaceous (Early Maastrichtian) Sea Lilies from Southern Poland

Abstract. Echinoid bite traces on Late Cretaceous (early Maastrichtian) bourgueticrinids and isocrinids of southern Poland (Miechów Trough) were documented. The bitten sea lilies co-occurred with Goniopygus, a regular echinoid possessing an Aristotles lantern. This is the first record of Goniopygus in the lower Maastrichtian of Poland. Considering former studies, as well as direct in situ observations of extant sea lilies and sea urchin behavior, the traces at hand could be most likely linked with predatory actions of the Goniopygus echinoid. Such studies on predatory phenomena are crucial and could provide baseline data concerning the evolutionary trends among organisms engaged in the “arms race”.

Life and Death: An Intriguing History of a Jurassic Crinoid

Abstract. A stalk fragment of the millericrinid crinoid Pomatocrinus sp. from the lower Kimmeridgian of Małogoszcz 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.