Russell Bicknell

American Museum of Natural History

Caryocaridids exhibited a wide geographical distribution and high diversity during the Great Ordovician Biodiversification Event. The global geographical distribution, limited taxonomic examination and lack of insight into preservational conditions have collectively contributed to an inadequate systematic assessment of Ordovician caryocaridids. To...

Triarthrus novoaustralis, a new species of olenid trilobite, is described from the Malachis Hill Formation (mid-Katian, Late Ordovician) near Keenans Bridge and Canobolas State Forest, west of Orange, New South Wales, Australia. This is the second named (and youngest) olenid occurrence from the entire Ordovician of eastern Gondwana. Additionally, i...

Xiphosurans, commonly known as horseshoe crabs, are predominantly marine chelicerates famous for their apparent morphological stasis and limited diversity. However, some fossil representatives of this group have radically diverged in form from the classic horseshoe crab morphology emphasized by the Recent Limulus, challenging this traditional view...

Pyritization of soft tissues of invertebrates is rare in the fossil record. In New York State, it occurs in black shales of the Lorraine Group (Late Ordovician), the best-known example of which is Beecher's Trilobite Bed. Exceptional preservation at the quarry where this bed is exposed allowed detailed examination of trilobite and ostracod soft-tis...

Pedipalps – chelate ‘pincers’ as the second pair of prosomal appendages – are a striking feature of scorpions and are employed in varied biological functions. Despite the distinctive morphology and ecological importance of these appendages, their anatomy remains underexplored. To rectify this, we examined the pedipalps of the Australian black rock...

Documentation of cryptic trilobite behavior has presented important insights into the paleoecology of this fully extinct arthropod group. One such example is the preservation of trilobites inside the remains of larger animals. To date, evidence for trilobites within cephalopods, gastropods, hyoliths, and other trilobites has been presented. Importa...

Malformed horseshoe crabs have been documented for over a century. However, most of these records are anecdotal observations of often striking morphologies recorded in isolation. There is therefore little understanding of how malformations are manifested and how they can develop in the group. Here we consider the moult sequences of three extant Lim...

The Bear Gulch Limestone houses a diverse, exceptionally preserved marine fauna from the early Carboniferous. A wealth of vertebrate and invertebrate forms has previously been recorded from this deposit, including fish, annelids, and several arthropods. To expand the record of Bear Gulch marine arthropods, a new enigmatic, possibly blind euchelicer...

Biomineralised remains of trilobites provide important insight into the evolutionary history of a diverse, extinct group of arthropods. Their exoskeletons are also ideal for recording malformations, including evidence of post-injury repair. Re-examination of historic collections and the study of new specimens is important for enhancing knowledge on...

Trace fossils can illustrate important palaeobiological interactions within a fossil assemblage that body fossils do not record. A group of these trace fossils that showcase feeding ecology, and evidence of predation, are coprolites. Shelly coprolites are useful for documenting records of durophagous predators or scavengers within a substrate. To e...

Injured trilobites present insight into how a completely extinct group of arthropodsresponded to traumatic experiences, such as failed predation and moulting complica-tions. These specimens are therefore important for more thoroughly understandingthe Paleozoic predator-prey systems that involved trilobites. To expand the record ofinjured trilobites...

Insight into how extinct animals responded to injuries developmental malfunctions and pathologies can be derived by examining malformed specimens. Trilobites are an ideal group for understanding how a completely extinct group of arthropods responded to and recovered from these conditions, as their biomineralised exoskeletons preserves malformations...

The stem-group euarthropod Anomalocaris canadensis is one of the largest Cambrian animals and is often considered the quintessential apex predator of its time. This radiodont is commonly interpreted as a demersal hunter, responsible for inflicting injuries seen in benthic trilobites. However, controversy surrounds the ability of A. canadensis to us...

Armoured jawed fishes known as placoderms are a well-documented group with a fossil record spanning the Silurian to end-Devonian. They have a global distribution and a marked diversity within Devonian deposits of Australia. Despite their notable Gondwanan fossil record, new material is occasionally identified and can present important stratigraphic i...

Evidence of successful predation or scavenging in the fossil record represents important palaeobiological data to more thoroughly understanding extinct ecosystems. Shelly coprolites are particularly useful indications of durophagous predation in deposits, as they can have a higher preservational potential than their producers. Here we present a new...

Malformed trilobite specimens present important insight into understanding how this extinct arthropod group recovered from developmental or moulting malfunctions, pathologies, and injuries. Previously documented examples of malformed trilobite specimens are often considered in isolation, with few studies reporting on multiple malformations in the s...

Eurypterids (sea scorpions) are extinct aquatic chelicerates. Within this group, members of Pterygotidae represent some of the largest known marine arthropods. Representatives of this family all have hypertrophied, anteriorly-directed chelicerae and are commonly considered Silurian and Devonian apex predators. Despite a long history of research int...

Abnormal trilobites present insight into how arthropods with fully biomineralised exoskeletons recovered from injuries, genetic malfunctions, and pathologies. Records of abnormal Silurian trilobites in particular show an abundance of specimens with teratologies and a limited record of injuries. Here we expand the record of abnormal Silurian trilobi...

Durophagous predation in the Cambrian is typically recorded as malformed shells and trilobites, with rarer evidence in the form of coprolites and shelly gut contents. Reporting novel evidence for shell-crushing further expands the understanding of where and when in the Cambrian durophagy was present. To expand the current documentation and present...

The endostoma of eurypterids is a small ventral structure previously known from only 11 specimens and in detail from only a single species, Eurypterus tetraganophthalmus. Four previously undescribed eurypterid specimens from the Samuel J. Ciurca Jr. Collection, Yale Peabody Museum of Natural History, likely belonging to Eurypterus, and a previously...

Xiphosurids are marine chelicerates that have been subject to extensive biological and palaeontological scrutiny over the past two centuries. This research effort is fuelled by the unique anatomical and physiological characteristics of the group, a long fossil record with conserved morphology, and use as modern analogues for understanding extinct a...

Horseshoe crabs are extant chelicerates with a fossil record extending back to the Ordovician. Despite the documentation of their long evolutionary history, xiphosurids are rarely preserved within fossil assemblages due to their unmineralized cuticular exoskeleton. However, in exceptional circumstances, an abundance of fossil xiphosurid specimens h...

Constraining the timing of morphological innovations within xiphosurid evolution is central for understanding when and how such a long-lived group exploited vacant ecological niches over the majority of the Phanerozoic. To expand the knowledge on the evolution of select xiphosurid forms, we reconsider the four Australian taxa: Austrolimulus fletche...

Records of abnormal fossil arthropods present important insight into how extinct forms responded to traumatic damage and developmental complications. Trilobites, bearing biomineralized dorsal exoskeletons, have arguably the most well-documented record of abnormalities spanning the Cambrian through the end-Permian. As such, new records of malformed,...

Australian dinosaur research has undergone a renaissance in the last 10 years, with growing knowledge of mid-Cretaceous assemblages revealing an endemic high-paleolatitude Gondwanan fauna. One of its most conspicuous members is ankylosaurs, which are rare but nonetheless occur in most Australian dinosaur-bearing formations spanning the uppermost Ba...

The Cambrian explosion represents the rapid emergence of complex marine ecosystems on Earth. The propagation of predator-prey interactions within these systems was almost certainly one of the major drivers of this evolutionary event, sparking an arms race that promoted the proliferation of biomineralised exoskeletons and shells, and the evolution o...

Palaeozoic fossil-bearing deposits in Russia record important and rare insights into pre-Mesozoic palaeoecological systems. Among the known formations, the Late Devonian (Famennian) deposits exposed in the central part of Russian platform have been under-documented. To expand the record of these formations, some of which show evidence of soft-bodie...

The Cambrian explosion represents the rapid emergence of complex marine ecosystems on Earth. The propagation of predator-prey interactions within these systems was almost certainly one of the major drivers of this evolutionary event, sparking an arms race that promoted the proliferation of biomineralised exoskeletons and shells, and the evolution o...

Records of evolutionary stasis over time are central to uncovering large-scale evolutionary modes, whether by long-term gradual change or via enduring stability punctuated by rapid shifts. The key to this discussion is to identify and examine groups with long fossil records that, ideally, extend to the present day. One group often regarded as the q...

Xiphosura are a group of marine euchelicerates with a fossil record spanning the majority of the Phanerozoic. Despite this longevity, horseshoe crab fossils are uncommon. This rarity is a result of their cuticular exoskeleton that limits the preservational potential of xiphosurid specimens. Nonetheless, a xiphosurid evolutionary radiation is record...

Studies considering local knowledge of Indian xiphosurans—Tachypleus gigas and Carcinoscorpius rotundicauda—are rare. Further, data concerning the West Bengal coast is even more limited. We therefore conducted interviews among the West Bengal coastal community to identify possible threats to horseshoe crabs, while also expanding knowledge regarding...

Megalograptidae and Mixopteridae with elongate, spinose prosomal appendages are unique early Palaeozoic sea scorpions (Eurypterida). These features were presumably used for hunting, an untested hypothesis. Here, we present 3D model-based kinematic range of motion (ROM) analyses of Megalograptus ohioensis and Mixopterus kiaeri and compare these to m...

Sea scorpions (Euchelicerata: Eurypterida) explored extreme limits of the aquatic euchelicerate body plan, such that the group contains the largest known marine euarthropods. Inferences on eurypterid life modes, in particular walking and eating, are commonly made by comparing the group with horseshoe crabs (Euchelicerata: Xiphosura). However, no mo...

The fossil record of scorpions in Australia is effectively non-existent. This lack of data is striking as there is evidence for other euchelicerates including eurypterids, spiders, and xiphosurids. Here, we describe a euarthropod from the Middle Triassic Hawkesbury Sandstone of Sydney, New South Wales, and attribute it to the Order Scorpiones. Due...

Documentation of malformed trilobites has presented invaluable insight into the palaeobiology of a wholly extinct euarthro-pod group. Although the northern hemisphere record is relatively well documented, examples of abnormal trilobites from Australia are limited. Furthermore, most recorded specimens are from Cambrian-aged rocks. To extend this lim...

Paleolimulids represent a group of fossil horseshoe crabs that are morphologically comparable to the extant limulids. Recent work has highlighted that, contrary to traditional opinions, Paleolimulidae has a limited taxonomic and morphological diversity at the species and generic level. In the light of this new perspective, it is imperative that mat...

An exceptionally preserved specimen of the horseshoe crab Euproops danae (Xiphosurida, Belinurina) in a siderite concretion from the Carboniferous (Upper Pennsylvanian, Virgilian) Lawrence Formation, Kansas, shows anatomical details of the prosomal musculature. The extrinsic appendicular muscles are comparable to those of Limulus polyphemus (the mo...

Eurypterids (sea scorpions) are a group of extinct, marine euchelicerates that have an extensive Palaeozoic record. Despite lacking a biomineralised exoskeleton, eurypterids are abundantly preserved within select deposits. These collections make statistical analyses comparing the morphology of different genera possible. However, eurypterid shape ha...

Amblypygi are tropical and subtropical ambush predators that use elongated, raptorial pedipalps for different activities. Although pedipalps use for predation and courtship has been explored in videography in-vivo analyses, kinematic ex-vivo examination of these appendages has not been conducted yet. Here, we rectify this lack of data by using micr...

Records of extinct organisms interacting with each other are limited primarily to evidence of predation and records of parasitism. However, in rare cases, records of organisms living within another one (inquilinism) have been identified. To expand the rather limited record of documented euarthropod inquilinism, we present a new example of three art...

The central nervous system (CNS) presents unique insight into the behaviors and ecology of extant and extinct animal groups. However, neurological tissues are delicate and prone to rapid decay, and thus their occurrence as fossils is mostly confined to Cambrian Burgess Shale-type deposits and Cenozoic amber inclusions. We describe an exceptionally...

Horseshoe crabs are extant marine euchelicerates that have a fossil record extending well into the Palaeozoic. Extreme xiphosurid morphologies arose during this evolutionary history. These forms often reflected the occupation of freshwater or marginal conditions. This is particularly the case for Austrolimulidae—a xiphosurid family that has recentl...

Trilobite malformations are often ascribed to failed predation and represent key evidence for Paleozoic arthropod predator–prey systems. A large number of malformed trilobites are known to Cambrian-aged deposits and have recently been discussed at length. Conversely, most post-Cambrian records are noted as anecdotal points within larger taxonomic w...

Xiphosurida are iconic group of marine chelicerates that have been subject to more than 200 years of neonatological and palaeontological scrutiny. However, recent studies have identified that there is very little data concerning abnormal specimens, and even less data on wild populations. The present study aims to rectify this dearth of information...

Xiphosurida are iconic group of marine chelicerates that have been subject to more than 200 years of neonatological and palaeontological scrutiny. However, recent studies have identified that there is very little data concerning abnormal specimens, and even less data on wild populations. The present study aims to rectify this dearth of information...

Xiphosurida is an ingroup of marine Euchelicerata often referred to as “living fossils”. However, this oxymoronic term is inapplicable for Paleozoic and early Mesozoic forms, as during these periods the group experienced notable evolutionary radiations; particularly the diverse late Palaeozoic clade Belinurina. Despite the iconic nature of the grou...

Horseshoe crabs are archetypal marine chelicer-ates with an exceptionally long fossil record. Due to the historical nature of the genus Limulus, which extends back to Linnaeus' descriptions, many horseshoe crab fossils were traditionally placed in Limulus and the family Limulidae. Despite continued research into the accurate placement of species wi...

Horseshoe crabs within Austrolimulidae represent the extreme limits to which the xiphosurid Bauplan could be modified. Recent interest in this group has uncovered an unprecedented diversity of these odd-ball xiphosurids and led to suggestions that Austrolimulidae arose during the Permian Period and had become extinct by the end of the Triassic Peri...

Durophagy arose in the Cambrian and greatly influenced the diversification of biomineralized defensive structures throughout the Phanerozoic. Spinose gnathobases on protopodites of Cambrian euarthropod limbs are considered key innovations for shell-crushing, yet few studies have demonstrated their effectiveness with biomechanical models. Here we pr...

Sea scorpions (Euchelicerata: Eurypterida) explored extreme limits of the aquatic euchelicerate body plan, such that the group contains the largest known marine euarthropods. Inferences on eurypterid life modes, in particular walking and eating, are commonly made by comparing the group with horseshoe crabs (Euchelicerata: Xiphosura). However, no mo...

The fossil record of phyllocarids in Australia is decidedly limited, with only a few specimens known from Ordovician to Devonian deposits. Therefore, the identification of examples from older deposits would uncover more facets of Gondwanan crustacean evolution. Here, a supposed phyllocarid reported by Chapman (1925 Chapman, F. , 1925. The Wade Coll...

Xiphosura are extant marine chelicerates that have displayed apparent morphological conservatism and remarkable survivorship across their ~ 480 Ma fossil record. The easily recognisable features that are known to even the earliest xiphosurans—a crescentic prosoma and often trapezoidal thoracetron (opisthosoma)—have generated debate surrounding thei...

Xiphosura, the so-called horseshoe crabs, are a group of extant marine chelicerates that have a fossil record extending back to the Lower Ordovician. Their temporal range, coupled with a possible record of bradytelic evolution has made them a focus of palaeontological consideration for over two centuries. As such, there are an array of taxa erected...

Horseshoe crabs are an iconic group of extant chelicerates, with a stunning fossil record that extends to at least the Lower Ordovician (~480 million years ago). As such, the group has retained significant biological and palaeontological interest. The sporadic nature of descriptive and systematic research into fossil horseshoe crabs over the last t...

Eurypterids, the so-called sea scorpions, are a group of extinct chelicerates with a diversity of over 250 species. Although the group has a distribution across most of the globe, the majority of taxa are known from the northern Hemisphere. Despite the general palaeontological interest in sea scorpions, Gondwanan—specifically Australian—taxa have r...

Biomineralised trilobite exoskeletons provide a 250 million year record of abnormalities in one of the most diverse arthropod groups in history. One type of abnormality-repaired injuries-have allowed palaeobiologists to document records of Paleozoic predation, accidental damage, and complications in moulting experienced by the group. Although Cambr...

Biomineralised exoskeletons of trilobites are ideal for recording abnormalities, documenting injuries from failed attacks, and understanding predation in the fossil record. The illustration of new injured Cambrian-aged trilobites is particularly important for elucidating aspects of early Paleozoic predator-prey systems and identifying groups that w...