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.

Recent discoveries of trackways and trails on ancient tidal flats at Blackberry Hill, Wisconsin, USA, have transformed our understanding of the initial invasion of land, 500 Ma. Huge slug‐like molluscs grazed on microbial mats. Euthycarcinoid (stem myriapod) death traces (mortichnia) suggest that they did not come onto land to feed or breed, but simply to survive; Moon was closer to Earth then, and massive tides stranded animals in tidal pools that gradually dried up.

Silurian (Llandovery–Ludlow) Encrinurinae from Wisconsin, Indiana, and Illinois include species ofBalizomaHolloway, 1980,CurriellaLamont, 1978,DistyraxLane, 1988,EncrinurusEmmrich, 1844,MackenziurusEdgecombe and Chatterton, 1990a, andNucleurusRamsköld, 1986.Mackenziurus lauriaen. sp. is described from Wenlock strata of the Racine and Sugar Run Dolomites; nine segments in the holaspid thorax are the fewest known for any encrinurid. A square rostral plate is diagnostic ofMackenziurus. New morphological data are provided by Illinois specimens ofBalizoma indianensis(Kindle and Breger, 1904) from the Wenlock–Ludlow Racine Dolomite, and ofCurriella tuberculifrons(Weller, 1907) from the Llandovery Elwood–Wilhelmi Formations.Nucleurusn. sp. is possibly from Llandovery strata in Wisconsin.Distyraxn. sp. occurs in the Brandon Bridge Member (late Llandovery–early Wenlock) of the Joliet Dolomite in Illinois. The type pygidia and possible topotype material ofEncrinurus nereusHall, 1867, confirm assignment to that genus as currently viewed; this reefal species is distinct from the closely related inter-reef speciesE. eganiMiller, 1880, and appears to be distinct from reefalE. reflexusRaymond, 1916. Lectotypes are selected for theseEncrinurusspecies.

The trilobite fauna of the Attawapiskat Formation of Ontario agrees with a late Llandoverian to early Wenlockian age assignment. This fauna is closely related to late Llandoverian and Wenlockian trilobite faunas from eastern Iowa and eastern Greenland. The numerically dominant trilobites of this fauna (illaenids, scutelluids, cheirurids) represent an association that is typical of Ordovician–Devonian carbonate buildups. These trilobites occur in localized accumulations formed by the entrapment of exuviae in depressions or other similar structures.Perryus severnensis gen. et sp. nov. from the Attawapiskat Formation is described. Its relationships with the Encrinuroides/Cromus lineage and possibly with Frammia are discussed.

Palmichnium gallowayi (Sharpe, 1932) new combination from the Middle Ordovician Martinsburg Formation (proximal deltaic facies) of Rondout, near Kingston, New York State, is redescribed. It consists of opposing series of five tracks, the outer two large and pear-shaped, the inner three smaller and elliptical, arranged in a chevron converging in the direction of travel, on either side of a wide medial impression. It is attributed to a medium-sized stylonurid eurypterid using a decapodous gait, crawling onto the shoreline, traversing the intertidal zone, a behavior interpreted as part of its reproductive life cycle. This provides the earliest ichnological evidence for the ‘mass-molt-mate’ hypothesis, which proposes that eurypterids migrated en masse into nearshore environments to molt and mate.