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Abstract The Fezouata Shale Formation has dramatically impacted our understanding of Early Ordovician marine ecosystems before the great Ordovician biodiversification event (GOBE), thanks to the abundance and quality of exceptionally preserved animals within it. Systematic work has noted that the shelly fossil subassemblages of the Fezouata Shale biota are typical of open-marine deposits from the Lower Ordovician, but no studies have tested the quantitative validity of this statement. We extracted 491 occurrences of recalcitrant fossil genera from the Paleobiology Database to reconstruct 31 subassemblages to explore the paleoecology of the Fezouata Shale and other contemporary, high-latitude (66°S–90°S) deposits from the Lower Ordovician (485.4–470 Ma) and test the interpretation that the Fezouata Shale biota is typical for an Ordovician open-marine environment. Sørensen's dissimilarity metrics and Wilcoxon tests indicate that the subassemblages of the Tremadocian-aged lower Fezouata Shale are approximately 20% more heterogenous than the Floian-aged upper Fezouata Shale. Dissimilarity metrics and visualization suggest that while the lower Fezouata and upper Fezouata share faunal components, the two sections have distinct faunas. We find that the faunal composition of the lower Fezouata Shale is comparable with other Tremadocian-aged subassemblages from high latitudes, suggesting that it is typical for an Early Ordovician open-marine environment. We also find differences in faunal composition between Tremadocian- and Floian-aged deposits. Our results corroborate previous field-based and qualitative systematic studies that concluded that the shelly assemblages of the Fezouata Shale are comparable with those of other Lower Ordovician deposits from high latitudes. This establishes the first quantitative baseline for examining the composition and variability within the assemblages of the Fezouata Shale and will be key to future studies attempting to discern the degree to which it can inform our understanding of marine ecosystems just before the start of the GOBE. 

Abstract Evidence of interspecific interactions in the fossil record is rare but offers valuable insights into ancient ecologies. Exceptional fossiliferous sites can preserve complex ecological interactions involving non-biomineralized organisms, but most of these examples are restricted to Cambrian Lagerstätten. Here we report an exceptionally preserved cross-phylum interspecific interaction from the Tremadocian-aged Lower Fezouata Shale Formation of Morocco, which consists of the phragmocone of an orthocone cephalopod that has been extensively populated post-mortem by tubicolous epibionts. Well-preserved transverse bands in a zig-zag pattern and crenulations along the margin of the unbranched tubes indicate that they correspond to pterobranch hemichordates, with a close morphological similarity to rhabdopleurids based on the bush-like growth of the dense tubarium. The discovery of rhabdopleurid epibionts in the Fezouata Shale highlights the paucity of benthic graptolites, which also includes the rooted dendroidsDidymograptusandDictyonema, relative to the substantially more diverse and abundant planktic forms known from this biota. We propose that the rarity of Paleozoic rhabdopleurid epibionts is likely a consequence of their ecological requirement for hard substrates for initial settlement and growth. The Fezouata rhabdopleurid also reveals a 480-million-year-old association of pterobranchs as epibionts of molluscs that persist to the present day. 

Abstract Tunicates are an evolutionarily significant subphylum of marine chordates, with their phylogenetic position as the sister-group to Vertebrata making them key to unraveling our own deep time origin. Tunicates greatly vary with regards to morphology, ecology, and life cycle, but little is known about the early evolution of the group, e.g. whether their last common ancestor lived freely in the water column or attached to the seafloor. Additionally, tunicates have a poor fossil record, which includes only one taxon with preserved soft-tissues. Here we describeMegasiphon thylakosnov., a 500-million-year-old tunicate from the Marjum Formation of Utah, which features a barrel-shaped body with two long siphons and prominent longitudinal muscles. The ascidiacean-like body of this new species suggests two alternative hypotheses for early tunicate evolution. The most likely scenario positsM. thylakosbelongs to stem-group Tunicata, suggesting that a biphasic life cycle, with a planktonic larva and a sessile epibenthic adult, is ancestral for this entire subphylum. Alternatively, a position within the crown-group indicates that the divergence between appendicularians and all other tunicates occurred 50 million years earlier than currently estimated based on molecular clocks. Ultimately,M. thylakosdemonstrates that fundamental components of the modern tunicate body plan were already established shortly after the Cambrian Explosion. 

Abstract The Fezouata Biota (Morocco) is a unique Early Ordovician fossil assemblage. The discovery of this biota revolutionized our understanding of Earth’s early animal diversifications—the Cambrian Explosion and the Ordovician Radiation—by suggesting an evolutionary continuum between both events. Herein, we describe Taichoute, a new fossil locality from the Fezouata Shale. This locality extends the temporal distribution of fossil preservation from this formation into the upper Floian, while also expanding the range of depositional environments to more distal parts of the shelf. In Taichoute, most animals were transported by density flows, unlike thein-situpreservation of animals recovered in previously investigated Fezouata sites. Taichoute is dominated by three-dimensionally preserved, and heavily sclerotized fragments of large euarthropods—possibly representing nektobenthic/nektic bivalved taxa and/or hurdiid radiodonts. Resolving whether this dominance reflects a legitimate aspect of the original ecosystem or a preservational bias requires an in-depth assessment of the environmental conditions at this site. Nevertheless, Taichoute provides novel preservational and palaeontological insights during a key evolutionary transition in the history of life on Earth. 

Abstract There is a contemporary trend in many major research institutions to de‐emphasize the importance of natural history education in favor of theoretical, laboratory, or simulation‐based research programs. This may take the form of removing biodiversity and field courses from the curriculum and the sometimes subtle maligning of natural history research as a “lesser” branch of science. Additional threats include massive funding cuts to natural history museums and the maintenance of their collections, the extirpation of taxonomists across disciplines, and a critical under‐appreciation of the role that natural history data (and other forms of observational data, including Indigenous knowledge) play in the scientific process. In this paper, we demonstrate that natural history knowledge is integral to any competitive science program through a comprehensive review of the ways in which they continue to shape modern theory and the public perception of science. We do so by reviewing how natural history research has guided the disciplines of ecology, evolution, and conservation and how natural history data are crucial for effective education programs and public policy. We underscore these insights with contemporary case studies, including: how understanding the dynamics of evolutionary radiation relies on natural history data; methods for extracting novel data from museum specimens; insights provided by multi‐decade natural history programs; and how natural history is the most logical venue for creating an informed and scientifically literate society. We conclude with recommendations aimed at students, university faculty, and administrators for integrating and supporting natural history in their mandates. Fundamentally, we are all interested in understanding the natural world, but we can often fall into the habit of abstracting our research away from its natural contexts and complexities. Doing so risks losing sight of entire vistas of new questions and insights in favor of an over‐emphasis on simulated or overly controlled studies. 

ABSTRACT Deuterostomes are the major division of animal life which includes sea stars, acorn worms, and humans, among a wide variety of ecologically and morphologically disparate taxa. However, their early evolution is poorly understood, due in part to their disparity, which makes identifying commonalities difficult, as well as their relatively poor early fossil record. Here, we review the available morphological, palaeontological, developmental, and molecular data to establish a framework for exploring the origins of this important and enigmatic group. Recent fossil discoveries strongly support a vermiform ancestor to the group Hemichordata, and a fusiform active swimmer as ancestor to Chordata. The diverse and anatomically bewildering variety of forms among the early echinoderms show evidence of both bilateral and radial symmetry. We consider four characteristics most critical for understanding the form and function of the last common ancestor to Deuterostomia: Hox gene expression patterns, larval morphology, the capacity for biomineralization, and the morphology of the pharyngeal region. We posit a deuterostome last common ancestor with a similar antero‐posterior gene regulatory system to that found in modern acorn worms and cephalochordates, a simple planktonic larval form, which was later elaborated in the ambulacrarian lineage, the ability to secrete calcium minerals in a limited fashion, and a pharyngeal respiratory region composed of simple pores. This animal was likely to be motile in adult form, as opposed to the sessile origins that have been historically suggested. Recent debates regarding deuterostome monophyly as well as the wide array of deuterostome‐affiliated problematica further suggest the possibility that those features were not only present in the last common ancestor of Deuterostomia, but potentially in the ur‐bilaterian. The morphology and development of the early deuterostomes, therefore, underpin some of the most significant questions in the study of metazoan evolution. 

Scalidophoran worms represent common infaunal components of early and middle Cambrian Burgess Shale-type fossil biotas. Early scalidophorans resemble extant priapulids based on overall morphology, but the genusSelkirkiarepresents the earliest record of tube dwelling for the group. Despite its ubiquitous presence in exceptional marine deposits, whether the exclusively Cambrian occurrence ofSelkirkiareflects its entire evolutionary history or is affected by taphonomic biases remains unresolved. Here, we demonstrate the post-Cambrian survival ofSelkirkiabased on new material from the Lower Ordovician Fezouata Shale biota of Morocco. The discovery ofSelkirkiain the Fezouata Shale extends the biostratigraphic range of the genus by 25 million years and its palaeobiogeographic occurrence to the high latitudes of Gondwana, strengthens the evolutionary links between Cambrian and Ordovician Burgess Shale-type biotas and increases scalidophoran diversity for the Fezouata Shale biota otherwise consisting exclusively of the palaeoscolecidPalaeoscolex? tenensis. The tube ofSelkirkiaunderwent negligible external change for over 40 million years, indicating a high degree of morphological stasis during the Early Palaeozoic. A tubicolous mode of life is rare among extant priapulids and expressed only inMaccabeus, which forms a delicate tube from agglutinated plant debris, unlike the macroscopic secreted cuticular tube ofSelkirkia. 

The ability to enrol for protection is an effective defensive strategy that has convergently evolved multiple times in disparate animal groups ranging from euarthropods to mammals. Enrolment is a staple habit of trilobites, and their biomineralized dorsal exoskeleton offered a versatile substrate for the evolution of interlocking devices. However, it is unknown whether trilobites also featured ventral adaptations for enrolment. Here, we report ventral exoskeletal adaptations that facilitate enrolment in exceptionally preserved trilobites from the Middle Ordovician Walcott–Rust Quarry in New York State, USA. Walcott–Rust trilobites reveal the intricate three-dimensional organization of the non-biomineralized ventral anatomy preserved as calcite casts, including the spatial relationship between the articulated sternites (i.e. ventral exoskeletal plates) and the wedge-shaped protopodites. Enrolment in trilobites is achieved by ventrally dipping the anterior margin of the sternites during trunk flexure, facilitated by the presence of flexible membranes, and with the close coupling of the wedge-shaped protopodites. Comparisons with the ventral morphology of extant glomerid millipedes and terrestrial isopods reveal similar mechanisms used for enrolment. The wedge-shaped protopodites of trilobites closely resemble the gnathobasic coxa/protopodite of extant horseshoe crabs. We propose that the trilobites' wedge-shaped protopodite simultaneously facilitated tight enrolment and gnathobasic feeding with the trunk appendages.