Mariusz A. Salamon

Post-Paleozoic crinoid radiation in response to benthic predation preceded the Mesozoic marine revolution

It has been argued that increases in predation over geological time should result in increases in defensive adaptations in prey taxa. Recent in situ and laboratory observations indicate that cidaroid sea urchins feed on live stalked crinoids, leaving distinct bite marks on their skeletal elements. Similar bite marks on fossil crinoids from Poland strongly suggest that these animals have been subject to echinoid predation since the Triassic. Following their near-demise during the end-Permian extinction, crinoids underwent a major evolutionary radiation during the Middle–Late Triassic that produced distinct morphological and behavioral novelties, particularly motile taxa that contrasted strongly with the predominantly sessile Paleozoic crinoid faunas. We suggest that the appearance and subsequent evolutionary success of motile crinoids were related to benthic predation by post-Paleozoic echinoids with their stronger and more active feeding apparatus and that, in the case of crinoids, the predation-driven Mesozoic marine revolution started earlier than in other groups, perhaps soon after the end-Permian extinction.

Predator-induced macroevolutionary trends in Mesozoic crinoids

Sea urchins are a major component of recent marine communities where they exert a key role as grazers and benthic predators. However, their impact on past marine organisms, such as crinoids, is hard to infer in the fossil record. Analysis of bite mark frequencies on crinoid columnals and comprehensive genus-level diversity data provide unique insights into the importance of sea urchin predation through geologic time. These data show that over the Mesozoic, predation intensity on crinoids, as measured by bite mark frequencies on columnals, changed in step with diversity of sea urchins. Moreover, Mesozoic diversity changes in the predatory sea urchins show a positive correlation with diversity of motile crinoids and a negative correlation with diversity of sessile crinoids, consistent with a crinoid motility representing an effective escape strategy. We contend that the Mesozoic diversity history of crinoids likely represents a macroevolutionary response to changes in sea urchin predation pressure and that it may have set the stage for the recent pattern of crinoid diversity in which motile forms greatly predominate and sessile forms are restricted to deep-water refugia.

Trends in shell fragmentation as evidence of mid-Paleozoic changes in marine predation

Abstract Recent observations indicate that shell fragmentation can be a useful tool in assessing crushing predation in marine communities. However, criteria for recognizing shell breakage caused by durophagous predators versus physical factors are still not well established. Here, we provide data from tumbling and aquarium experiments to argue that physical and biotic processes lead to different patterns of shell damage, specifically that angular shell fragments are good indicators of durophagous predation. Using such angular shell fragments as a predation proxy, we analyze data from 57 European Paleozoic localities spanning the Ordovician through the Mississippian. Our results reveal a significant increase in angular shell fragments (either occurring as isolated valves or present in regurgitalites) in the Mississippian. The timing of this increase is coincident with the increased diversity of crushing predators as well as marked anti-predatory changes in the architecture and mode of life of invertebrate prey observed after the end-Devonian Hangenberg extinction (359 Ma). More specifically, the observed trend in shell fragmentation constitutes strong and independent confirmation of a recently suggested end-Devonian changeover in the primary method of fish predation from shearing to crushing. These results also highlight the important effect of extinction events, not only on taxonomic diversity, but also on the nature of predator-prey interactions.

Signs of benthic predation on Late Jurassic stalked crinoids, preliminary data

Abstract Although most investigations of crinoid-predator interactions have focused on nektonic vertebrates (fishes and sharks), slow-moving benthic animals such as cidaroid echinoids may also interact antagonistically with stalked crinoids. This was recently supported by observations of extant isocrinids in modern deep-sea environments near the west end of Grand Bahama Island. In this paper, we report on stalks of crinoids from the Late Jurassic of south-central Poland, which co-occur with remains of cidaroids and show characteristic holes, bite marks, and signs of breakage. By analogy with the modern example, we interpret this as evidence of predation by cidaroids on crinoids. These Late Jurassic data may indicate that benthic predation was intense during the mid-Mesozoic. Importantly, this discovery also strengthens the hypothesis that benthic predators may have exerted considerable influence on the evolution of stalked crinoids.

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.

Drill holes and predation traces versus abrasion-induced artifacts revealed by tumbling experiments.

Drill holes made by predators in prey shells are widely considered to be the most unambiguous bodies of evidence of predator-prey interactions in the fossil record. However, recognition of traces of predatory origin from those formed by abiotic factors still waits for a rigorous evaluation as a prerequisite to ascertain predation intensity through geologic time and to test macroevolutionary patterns. New experimental data from tumbling various extant shells demonstrate that abrasion may leave holes strongly resembling the traces produced by drilling predators. They typically represent singular, circular to oval penetrations perpendicular to the shell surface. These data provide an alternative explanation to the drilling predation hypothesis for the origin of holes recorded in fossil shells. Although various non-morphological criteria (evaluation of holes for non-random distribution) and morphometric studies (quantification of the drill hole shape) have been employed to separate biological from abiotic traces, these are probably insufficient to exclude abrasion artifacts, consequently leading to overestimate predation intensity. As a result, from now on, we must adopt more rigorous criteria to appropriately distinguish abrasion artifacts from drill holes, such as microstructural identification of micro-rasping traces.

The callovian (Middle Jurassic) crinoids from northern Lithuania

Callovian strata in northern Lithuania (Papilė area) have yielded some crinoid taxa[Chariocrinus andreae (Desor),Balanocrinus berchteniHess —Pugin,B. subteres (Münster inGoldfuss) andIsocrinus nicoleti (Desor)], which have not been described from this area. The only form known previously wasBalanocrinus pentagonalis (Goldfuss).Palaeocomaster jaegeri n. sp. is the first free-living crinoid recorded from the Callovian of eastern Europe. It is characterized by possessing a very low, strongly flattened and narrow radial cavity. A very similar crinoid assemblage is known from the Callovian glacially-derived clays exposed in the Łuków region (eastern Poland), which were originally located near the Baltic Sea during the Middle Jurassic. It is considered that the allochthonous Callovian deposits from Poland are facies equivalents of the deposits known from Lithuania. The sole significant exception is the domination of free-moving comatulids (Comatulida) in the sediments known from the Papilė region, which may suggest that the Lithuanian sea basin was a little shallower than that located farther west in the Baltic area.ZusammenfassungAblagerungen des Calloviums in Nord-Litauen (Gebiet von Popilani) lieferten einige Crinoiden-Taxa, die von dort noch nicht bekannt waren [Chariocrinus andreae (Desor),Balanocrinus berchteniHess —Pugin,B. subteres (Münster inGoldfuss) undIsocrinus nicoleti (Desor)]. Die einzige Form, die bisher aus Litauen bekannt war, istBalanocrinus pentagonalis (Goldfuss).Palaeocomaster jaegeri n. sp. ist die erste frei bewegliche Crinoide aus dem Callovium Osteuropas. Sie wird durch den Besitz einer sehr niedrigen, stark abgeplatteten und schmalen radialen Leibeshöhle charakterisiert. Eine sehr ähnliche Crinoiden-Vergesellschaftung ist aus den glazial entwurzelten callovischen Tonsteinen der Region von Łuków (Ostpolen) bekannt, die ursprünglich aus dem Gebiet der Ostsee stammt. Es wird angenommen, dass die allochthonen Ablagerungen Polens aus dem Callovium fazielle Äquivalente der Ablagerungen in Litauen darstellen. Die einzige signifikante Ausnahme ist die Dominanz frei beweglicher Comatuliden (Comatulida) in den Ablagerungen der Popilani-Region, was ausdrücken könnte, dass das litauische Meeresbecken etwas flacher war als das mehr westlich gelegene im Baltikum.

Reassessing the improbability of a muscular crinoid stem

Muscular articulations in modern stalked crinoids are only present in the arms. Although it has been suggested that certain coiled-stemmed fossil taxa may have been functionally adapted to utilize muscles, evidence supporting this interpretation is lacking. Here, we use cathodoluminescence and SEM to reveal the skeletal microstructure of the enigmatic coiled-stemmed taxon Ammonicrinus (Flexibilia). Based on the well-established link between skeletal microstructure and the nature of infilling soft tissues in modern echinoderms, we reconstructed the palaeoanatomy of the Middle Devonian ammonicrinids. We show that their median columnals with elongated lateral columnal enclosure extensions (LCEE) have stereom microstructure unexpectedly resembling that in the crinoid muscular arm plates. In particular, large ligamentary facets, that are present on each side of a transverse ridge, are mainly comprised of fine galleried stereom that is indicative of the mutable collagenous tissues. In contrast, fine labyrinthic stereom, commonly associated with muscles, is situated in the periphery on each side of the surface of elongated LCEE. Our findings thus strongly suggest that the muscles may have also been present in the stem of ammonicrinids. These results reassess the previous hypotheses about evolution of muscles in crinoids and provide new insights into the mode of life of Ammonicrinus.

The Lilliput effect in crinoids at the end of the Oceanic Anoxic Event 2: a Case study from Poland

Abstract. The Cretaceous Period (145–66 Ma) consisted of several oceanic anoxic events (120–80 Ma), stimulated by global greenhouse effects. The Oceanic Anoxic Event 2 (OAE2) occurred worldwide from the late Cenomanian to the early-middle Turonian, causing a significant faunal turnover, mostly in marine biota, pushing some species to the brink of extinction. Some organisms also underwent morphological changes, including reduction in size. This anoxic event drove other changes—e.g., in habitats or strategy of life. We show that stalkless crinoids (comatulids) from the Turonian of Poland adapted to unfavorable environmental conditions by reducing their body size. Furthermore, at the moment when environmental factors became favorable again, these crinoids regained their regular (pre-event) size. This phenomenon likely illustrates the so-called dwarfing mode of the Lilliput effect.