Gonatocaris decora(Clarke, 1901) is an unusual, highly ornamented Silurian phyllocarid from the Pittsford Shale Member of the Vernon Formation, Salina Group of New York, that has been allied withEmmelezoein the past due to the possession of an 'optic tubercle.' The systematic positions ofGonatocarisandEmmelezoehave been difficult to assess due to the lack of complete remains, attributions based on spurious characters, and missing and unfigured specimens. Relatively recent collections ofGonatocaris decora, along with a relocation of the original type material ofEmmelezoe, have allowed a reexamination of all relevant genera and a more robust systematic placement forG. decora. Characters of generic importance forGonatocarisinclude a greatly elongated abdomen; an acute angle of the ventral carapace margin separating distinct anteroventral and posteroventral margins from each other; and distinctive, multiscale horizontal ridge-like ornament of the carapace valves. Growth was found to be isometric. Experimental work done using a model of the scale-like ornament and multiple grain sizes of substrate indicates that cuticle ornament may have served to increase friction between the animal and a fine sand substrate, although resistance to predation is the currently favored hypothesis. BecauseGonatocarisspecies are currently known only from the eastern margin of Laurentia and northern South China, it is likely that this genus was nektonic. Accumulations of similarly sized carapaces and other disarticulated sclerites in shallow-water settings may indicate spawning events following molting en masse.

Phyllocarida (Crustacea, Malacostraca) are among the most diversified and widespread Late Devonian arthropods. Although previous studies mention phyllocarid fossils from Late Devonian (Frasnian and Famennian) deposits of the Holy Cross Mountains of south‐central Poland, phyllocarids from the Kowala quarry have not been systematically described. Two new species are described from Kowala strata: Echinocaris bisulcata sp. nov. characterized by oval carapace valves with a short hinge line, cone‐like tubercules on the carapace anterior lobe, two pronounced lateral sulci (ventral and median) and two pairs of short spines on every abdominal segment; and Montecaris marynowskii sp. nov. characterized by two pairs of robust abdominal spines, a telson that is shorter than furcal rami, distal parts of which are parallel to the telson, and a body length approximately four times longer than the telson length. Additionally, an isolated furca identified as Dithyrocaris sp. is described herein. Damage observed in the holotype specimen of Montecaris marynowski sp. nov. is consistent with a healed injury, possibly caused by predatory fish. Notes concerning the global occurrences of montecaridids, echinocaridids and the genus Dithyrocaris in the Late Devonian are also provided.

Euthycarcinoid arthropods (Cambrian-Triassic) were likely the first animals to transition from oceanic to freshwater and emergent environments. Although their basic bauplan is well known, they have a poor fossil record because their non-sclerotized exoskeleton was rarely preserved. Euthycarcinoids' unusual morphology (varying numbers of body segments, seemingly dichotomous possession of either mandibles or a labrum, specialized or generalized limbs, and possession by some euthycarcinoid species of sternal poresstructures possibly analogous to coxal vesicles in myriapods) contribute to uncertainty regarding their relationship to other arthropod groups; while their poor fossil record masks the evolutionary transitions within and between the separate realms they inhabited (marine, freshwater, emergent). A new euthycarcinoid from a Permian polar proglacial lake is described herein that is morphologically unlike all other euthycarcinoids, and interpreted as being well adapted for a nekton-benthic lifestyle. Antarcticarcinus pagoda n. gen. n. sp. possesses a pair of large wing-like processes that project laterally from the preabdominal dorsal exoskeleton. A trace fossil from the overlying Mackellar Formation, cf. Orbiculichnus, which was previously interpreted as having been produced by insects taking off or landing on wet sediments, is reinterpreted herein as being produced by A. pagoda n. gen. n. sp. due to the high degree of morphological similarity between traces and body fossils. This occurrence indicates that euthycarcinoids were able to adapt to life in temperate freshwater environments, while possible subaerial adaptations hint at an ability to breathe air. Indeed, if euthycarcinoids could breathe air, Cambrian terrestrial forays and rapid transition (by the Ordovician) into freshwater environments might be explained.

Protichnites eremita from the Cambrian Elk Mound Group of Wisconsin is reinterpreted based on new material and trackway experiments. Two new forms of P. eremita suggest that the discrete medial imprints of these traces could be produced by the segmented postabdomen of euthycarcinoids from the same deposit. Form 1 could have been produced by a pair of euthycarcinoids traveling together, like in limulid amplexus, where both individuals made imprints with their postabdomens. In this scenario, if one individual held its postabdomen to the left side, it is possible to produce left-handed shingling in trackways and angled segmentation of each medial imprint. Form 2 could have been produced by a single animal traveling in arcing or tightly looping paths. Experimentally-produced medial imprints yield morphologies that are consistent with both trackway forms. Thus, it seems more likely that P. eremita was produced directly by the animal's body (alone or paired) rather than by employing hermit-like behavior.

Jurassic sandstones of the Hartford Basin are well known for their dinosaur trackways, but few studies have characterized their invertebrate ichnofaunas. A notable Portland Formation exposure in this area is the Hoover Quarry in East Longmeadow, Massachusetts, where vertebrate skeletal material (the type specimen of the crocodilian Stegomosuchus longipes) occurs in association with a diverse ichnofauna. Hoover Quarry ichnogenera include Eubrontes cf. gracilis, Planolites beverleyensis, Planolites montanus, probable Scoyenia burrows, and Skolithos isp. Also preserved at the site is Palaeophycus tortuosus, a sinusoidal burrow that had been previously synonymized with Palaeophycus tubularis. A probable Skolithos burrow termination with an unusual pattern of scratches also occurs, along with several problematic stellate structures. At this site, primary sedimentary structures on trace bearing surfaces are consistent with deposition in a shallow aquatic environment that was periodically emergent. Viewed in the context of nearby sections of the Portland Formation, Hoover Quarry exposures could have been deposited in fluvial, ephemeral lacustrine, or playa environments. Traces in the Hoover Quarry indicate Scoyenia-Skolithos-composite ichnofacies, elements of which are commonly produced in continental firmground environments. RÉSUMÉ Les grès du Jurassique dans le bassin de Hartford sont reconnus pour la présence d’empreintes de dinosaures. Mais peu d’études ont permis de caractériser l’ichnofaune invertébrée qu’on peut également y observer. Un affleurement notable de la Formation Portland dans la région est présent dans la carrière Hoover, à East Longmeadow, au Massachusetts, où des matériaux de squelettes de vertébrés (le spécimen type du crocodilien Stegomosuchus longipes) et une ichnofaune diversifiée sont présents. L’ichnofaune de la carrière Hoover comprend les espèces comme Eubrontes cf. gracilis, Planolites beverleyensis, Planolites montanus, vraisemblablement des terriers de Scoyenia, et Skolithos. Il y a également sur le site l’espèce Palaeophycus tortuosus, un terrier sinusoïdal qui a déjà été nommé Palaeophycus tubularis. L’extrémité d’un terrier de l’espèce probable Skolithos accompagnée d’une série inusitée de stries ou d’éraflures est en outre présente, tout comme plusieurs structures étoilées dont l’origine demeure mystérieuse. Sur le site, des structures primaires sur des surfaces marquées de traces correspondraient à une sédimentation dans un milieu aqua-tique peu profond qui a émergé à intervalles périodiques. Considéré dans le contexte des sections de la Formation Portland, situées à proximité, le dépôt des affleurements de la carrière Hoover pourrait être survenu dans un milieu fluvial, lacustre éphémère ou en présence d’un lac temporaire. Les traces relevées dans la carrière Hoover indiquent la présence d’un ichnofaciès composite de type Scoyenia-Skolithos, dont les éléments sont couramment produits dans un milieu de sol continental à cohésion moyenne. [Traduit par la redaction]

Exposures of the middle Cambrian Potsdam Group of northern New York, including the type section, represent a suite of interfingering eolian dune and aquatic deposits that record the activities of early land-going arthropods. Quartz arenites at these exposures are dominantly fine to medium grained, well sorted, and have hematite-coated well-rounded, high-sphericity quartz grains characterized by secondary optically continuous quartz cement overgrowths. Eolian beds are laminated and dominated by m- to dm-scale foresets characterized by large-scale, laterally extensive cross-beds that dip >similar to 15 degrees-34 degrees and contain reverse-graded lamination, en-echelon microfaulted slumps, adhesion structures, and very high ripple-index asymmetric ripples that lie on the foresets with crests that trend downdip. Lower parts of foresets are interpreted as toesets, and contain unusual Diplichnites and Protichnites trackways, which record the uphill, downhill, crest-parallel, and switchback-style movement of arthropods in dry, or damp sand. Trackways that ascend dune faces do not possess a medial tail drag, whereas trackways that descend do, and turns of trackways often have deep continuous medial impressions; these features suggest arthropods leaned into the slope when turning downhill in dry sand. More shallowly dipping (similar to 4 degrees-15 degrees) cross-beds are interpreted as bottomsets. Like nearby intertidal Potsdam deposits, these beds contain Protichnites trackways and Arenieolites burrows. Paleocurrent analyses imply a coastline in which offshore and mixed-direction winds moved dunes seaward. Considered together, these strata record migration of coastal dunes into aquatic environments and flooding and reworking of distal dune bottomsets. In this setting, the same suite of epifaunal arthropods inhabited dry, damp, and aquatic marine environments.

Two arthropod specimens assigned to Anabarochilina australis (Hinz-Schallreuter, 1993) from the late middle Cambrian (Guzhangian Stage, Lejopyge acantha Biozone) Karsha Formation, Zanskar Valley, northern India comprise the first record of the Bradoriida from the Himalaya. These Indian specimens cannot be distinguished statistically from other A. australis material based on valve length and height ratios, and differ only slightly in other characters. These observations justify the synonymy of a number of similar forms worldwide that previously have been only questionably attributed to A. australis. The occurrence of the species in Australia, India, Laurentia, and Kazakhstan encompassed an equatorial distribution from approximately 20° north to 20° south during late middle Cambrian time and indicates that A. australis had the ability to disperse across deep ocean basins. Such a distribution is consistent with a planktonic lifestyle. In contrast, other congeneric species of Anabarochilina apparently had more localized occurrence or, in the case of A. primordialis , were distributed across several paleocontinents and climatic zones.

Three new types of arthropod are described from Cambrian intertidal lithofacies of the Elk Mound Group and St. Lawrence Formation of Wisconsin and the Potsdam Group of Quebec. These arthropods are preserved ventrally in sandstone in life position and in three dimensions, allowing detailed characterization of limb morphologies, labrums, and other organs such as eyes. A taphonomic model is presented, illustrating this unusual, uncompressed, three-dimensional style of preservation. Arenosicaris inflata n. sp., from the Terreneuvian-Furongian Elk Mound Group and the Furongian St. Lawrence Formation, is the earliest unambiguous occurrence of a malacostracan phyllocarid. This 3 cm long arthropod had ovate valves, five pairs of biramous pleopods, and at least 3 pairs of thoracopods. Mosinieia macnaughtoni n. sp., a large (>10 cm long) euthycarcinoid of uncertain affinity with flattened or paddle-like appendages also occurs in Elk Mound strata. Mictomerus melochevillensis n. sp. represents a new euthycarcinoid family and is the first known non-trilobite arthropod from the middle Cambrian-Furongian Potsdam Group of Quebec. M. melochevillensis n. sp. is large (8–10+ cm long), with as many as eleven pairs of well-preserved homopodous, uniramous, non-paddle-like limbs. Both M. macnaughtoni and M. melochevillensis differ substantially from previously known euthycarcinoids in limb morphology and represent the oldest known representatives of the group. Additionally, both M. melochevillensis n. sp. and M. macnaughtoni n. sp. possess morphologies that are consistent with abundant subaerial and subaqueous Diplichnites and Protichnites trackways known from these units, suggesting that these may be the earliest land-going animals.

A phylogenetic analysis and review of Paleozoic phyllocarid systematics is presented using morphology-based characters from Cambrian to modern taxa. The resulting cladograms of the Phyllocarida suggest that the suborder Ceratiocaridina as traditionally defined (families Ceratiocarididae and Caryocarididae) is paraphyletic. Caryocarididae is subsequently elevated to subordinal rank with the erection of Caryocaridina n. suborder, resulting in two monophyletic suborders. Haplocaris n. gen. is erected to contain Caryocarididae taxa without triangular spine-like projections of the anterior telson margin. Emended diagnoses, quantified with morphometrics where appropriate, are integrated into this analysis, and result in synonymy of many Cambrian Silurian caryocaridids and ceratiocaridids with pre-existing taxa. Two representatives of the Leptostraca are included in this analysis. A visual key of well-established representatives of the Ceratiocaridina is presented and suggestions are offered that will help to improve the long-term stability of the Archaeostraca.

A rich assemblage (n = 223) of well-preserved phyllocarid crustacean remains is described from offshore calcareous shales of the Kopanina Formation (Silurian, Ludlow, early Ludfordian, Saetograptus linearis Biozone) exposed near the village of Vseradice, SE of Beroun. Specimens examined fall within the intraspecific variability of Ceratiocaris papilio Salter in Murchison, 1859, which is widely distributed in the Llandovery and Wenlock of Laurentia. Consequently, the Bohemian specimens represent the first occurrence of C. papilio outside of Laurentia. Additionally, the phyllocarid assemblage from Bohemia is younger than that of Laurentia. In Bohemia, Ceratiocaris papilio occurs in finely laminated calcareous shales. Its abundance varies distinctly from bed to bed, and phyllocarids are the dominant faunal component in only a few beds. Phyllocarids are associated with common graptolites and pelagic orthocerids while other benthic organisms are severely limited. Isolated or articulated furcae and telsons, and isolated mandibles are the most common components of this association, but articulated abdominal segments with caudal appendages (but without carapaces) also occur. An exceptional, slightly disarticulated specimen has articulated abdominal and partial thoracic segments, with mandibles preserved in situ. Additional possible occurrences of C. papilio and related species in Bohemia are also discussed.

The large euthycarcinoid arthropod Mictomerus melochevillensis from the middle Cambrian-Furongian Potsdam Group of Quebec occurs as three-dimensional casts at the end of Cruziana- and Didymaulichus-like trace fossils. This association provides a rare opportunity to test functional morphological hypotheses about these animals, it provides a framework for understanding how arthropods can be sand-cast in three dimensions, and it suggests that euthycarcinoids may have burrowed into mud as an antidesiccation strategy. In the coeval Elk Mound Group of Wisconsin, the phyllocarid arthropod Arenosicaris inflata occurs on the same beds as Cruziana-like and Rusophycus traces; together with morphologically similar ropelike traces, they are interpreted as having been produced by phyllocarids. These traces preserve the earliest known ethological evidence of phyllocarid crustaceans, and imply that Cambrian phyllocarids employed antidesiccation and possibly feeding strategies still used by modern intertidal leptostracan phyllocarids.

Two species of well-preserved phyllocarid crustaceans,Ceratiocaris macrouran. sp. andCeratiocaris papilioSalter, occur in the Eramosa Formation Lagerstätte of Ontario, Canada, represented by several dozen articulated fossils preserving limbs and thoracic segmentation.Ceratiocaris macrouran. sp. is distinguished by possession of an exceptionally elongate telson in relation to its body length.Ceratiocaris papiliopreserves fine detail of the abdominal scale-like ornamentation, allowing reinterpretation and enhanced characterization of this key feature.Ceratiocaris papiliohas a wide paleogeographic distribution across Laurentia but is restricted to shallow marine depositional settings within the middle Silurian.

Author(s): Collette, Joseph Henry | Advisor(s): Hughes, Nigel C. | Abstract: The family Saukiidae Ulrich and Resser, 1933 was one of the largest groups of late Cambrian trilobites, with representatives occurring on all major paleogeographic plates. However, inconsistent systematic practices that have been historically applied to this group have resulted in a muddled concept of the Saukiidae and an exaggerated species count. This has led to erouneous placement of many taxa due to a lack of distinct characters with which to diagnose some saukiid genera and species. To mitigate past systematic digressions and to re-elevate Saukiidae to a useful concept, a series of cladistic analyses were performed that incorporated all global occurrences of the Saukiidae for which there is a good fossil record. As a further test of the familial relationships of the Saukiidae, members of the Ptychaspididae and Pterocephaliidae were included to test what effect, if any, different outgroups would have on character polarity and the branching point with the Saukiidae. Results vary with outgroup choice, but suggest that some of the characters uniting Ptychaspididae and Saukiidae may be convergent. Because the 'upside-down' stratigraphic placement of taxa recovered with this outgroup is inconsistent with stratigraphic evidence, the Pterocephaliidae outgroup is preferred. The preferred phylogeny indicates that the Saukiidae is monophyletic, and is composed of two distinct groups of subfamilial rank: the Saukiinae, n. subfam., defined by the absence of a preglabellar field (Calvinella, Danzhaisaukia, Eosaukia, Linguisaukia, Lophosaukia, Mictosaukia, Saukia, Sinosaukia, and Tellerina); and the Prosaukiinae n. subfam., defined by possession of a preglabellar field (Anderssonella, Hoytaspis, Lichengia, Pacootasaukia, Prosaukia, and Saukiella). The ancestral geographic area(s) for each node on the preferred cladogram was then computed using Fitch optomization. The Fitch analysis revealed that toward the base of the tree, descendants that had originated from ancestors living in Laurentia likely moved westward towards Australia and North China, most likely as larvae. Further up the tree, a single dispersal event appears to have moved eastward toward South China; all taxa in a more derived position to this dispersal occur in Gondwana indicating a radiation across Gondwana from this event, and a likely Laurentian origin of the family Saukiidae.