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 endPermian extinction.macroecology | macroevolution | predation | escalation | cidaroids P redator-prey interactions may represent a significant driving force of evolutionary change (1-4), but predation and its consequences are often difficult to assess in Recent communities and even more so in the fossil record. Data on fossil and extant crinoids, commonly known as sea lilies and feather stars (Echinodermata), indicate that they suffer from predation by fishes, and numerous evolutionary trends have been ascribed to such interactions (5-15). Among these are (i) crawling and swimming abilities in comatulids (6), (ii) choice of semicryptic habits and nocturnal-diurnal behavior among comatulids (6), (iii) increasing plate thickness and spinosity among Paleozoic crinoids (9), (iv) offshore displacement of late Mesozoic/Cenozoic stalked crinoids (11), and (v) origin of autotomy (shedding) planes in the stalk and arms (13). Some of these trends have served as examples of dramatic change in marine ecosystems, such as the Mesozoic marine revolution (MMR) (2, 16) and the middle-Paleozoic marine revolution (9).Although predation by fish has received the most attention, crinoids may be the prey of other organisms, most notably benthic invertebrates. Until recently, few data hinted at the importance of benthic predators to crinoids, including a swimming response in a comatulid when perturbed by the predatory sea star Pycnopodia helianthoides (17), the presence of crinoid pinnulars in the gut of the goniasterid Plinthaster dentatus (18), and a crinoid arm observed in the claw of the crab Oregonia gracilis (17). Recently, submersible studies of stalked crinoids belonging to the Isocrinidae have revealed that they are prey to cidaroids, or pencil urchins. Evidence for this interaction includes (i) in situ observations of cidaroids among large aggregations of motile isocrinid sea lilies (Neocrinus decorus and Endoxocrinus parrae), (ii) proximi...

No abstract

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.echinoderms | escalation | macroecology I t has long been hypothesized that predator-prey interactions represent a significant driving force of evolutionary change in the history of life (1-4). However, not only is predation itself hard to detect in the fossil record, which makes it difficult to ascertain its intensity over geologic time, but macroevolutionary predictions of the hypothesis are far from simple (5-13). Recent sea urchins (Echinoidea), are known to play a key role in shallow sea ecosystems as grazers and benthic predators that can modify the distribution, abundance, and species composition of coral and algal reef communities (14-16); however, only few data have hinted at the importance of sea urchins to crinoids (17)(18)(19).Crinoids (Crinoidea), commonly known as sea lilies or feather stars, were one of the dominant components of many shallow-sea environments through much of geologic history and a key contributor to the sedimentary record (20). Although predation by fish on crinoids and its evolutionary consequences have received the most attention (21-27), sparse data indicated that crinoids may be the prey of benthic invertebrates (28), most notably sea urchins (17-19, 29, 30). Recently it has been shown that during the Triassic, the radiation of cidaroid sea urchins capable of handling the crinoid skeleton coincided with high frequency of bite marks on crinoids likely produced by the jaw apparatus of these sea urchins (18). Because it was also during the Triassic that various modes of active and passive motility appeared among crinoids, a group that throughout its rich pre-Triassic history was almost exclusively sessile, it was argued that crinoid motility, an effective escape strategy against benthic predation, was an evolutionary response to echinoid predation (18).The hypothesized evolutionary response of crinoids to benthic pr...

A rich assemblage of various types of bromalites from the lower Carnian “Konservat-Lagerstätte” from the Reingraben Shales in Polzberg (Northern Calcareous Alps, Lower Austria) is described for the first time in detail. They comprise large regurgitalites consisting of numerous entire shells of ammonoid Austrotrachyceras or their fragments and rare teuthid arm hooks, and buccal cartilage of Phragmoteuthis. Small coprolites composed mainly of fish remains were also found. The size, shape and co-occurrence with vertebrate skeletal remains imply that regurgitalites were likely produced by large durophagous fish (most likely by cartilaginous fish Acrodus). Coprolites, in turn, were likely produced by medium-sized piscivorous actinopterygians. Our findings are consistent with other lines of evidence suggesting that durophagous predation has been intense during the Triassic and that the so-called Mesozoic marine revolution has already started in the early Mesozoic.

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.