Browsing by Author "Hopkins, Melanie J."
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- ItemModularity in the trilobite head consistent with hypothesized segmental origin of the eyes(2022) Vargas-Parra, Ernesto E.; Hopkins, Melanie J.Landmark data, R-script, and associated files for modularity analyses of Calyptaulax annulata and Cloacaspis senilis.
- ItemThe Ordovician succession adjacent to Hinlopenstretet, Ny Friesland, Spitsbergen. (American Museum novitates, no. 3882)(American Museum of Natural History., 2017-09-05) Kröger, Björn.; Finnegan, Seth.; Franeck, Franziska.; Hopkins, Melanie J.The Ordovician sections along the western shore of the Hinlopen Strait, Ny Friesland, Spitsbergen were discovered in the late 1960s and since then prompted numerous paleontological publications; several of these publications are now considered classical in the literature of paleontology of Ordovician trilobites and of Ordovician paleogeography and stratigraphy. Our 2016 expedition aimed at a major recollection and reappraisal of these classical sites. Here we provide a first high-resolution lithological description of the Kirtonryggen and Valhallfonna formations (Tremadocian-Darriwilian), which together comprise a thickness of 843 m, a revised bio- and lithostratigraphy, and an interpretation of the depositional sequences. We find that the sedimentary succession is very similar to successions of eastern Laurentia; its Tremadocian and early Floian part is composed of predominantly peritidal dolostones and limestones characterized by ribbon carbonates, intraclastic conglomerates, microbial laminites, and stromatolites, and its late Floian to Darriwilian part is composed of fossil-rich, bioturbated, cherty mud-wackestone, skeletal grainstone and shale, with local siltstone and glauconitic horizons. The succession can be subdivided into five third-order depositional sequences, which are interpreted as representing the Sauk IIIB Supersequence known from elsewhere on the Laurentian platform.
- ItemPhylogenetic analysis and revision of the trilobite subfamily Balnibarbiinae (Olenidae). (American Museum novitates, no. 3928)(American Museum of Natural History., 2019-05-07) Hopkins, Melanie J.The Balnibarbiinae is one of eight subfamilies of the Olenidae, a diverse family of late Cambrian to Ordovician trilobites. Balnibarbiine species occur in a relatively continuous section of deeper-water sediments exposed along the northeastern coastline of Spitsbergen, Svalbard, as well as scattered deeper-water beds in central Nevada. Results of phylogenetic analyses of the subfamily using both parsimony and Bayesian methods are consistent with a previous hypothesis based on phyletic similarity and stratigraphic range. Cloacaspis Fortey, 1974, is supported as monophyletic, but the support for Balnibarbi Fortey, 1974, is weak, and the genus may be paraphyletic to Cloacaspis even with the reassignment of Balnibarbi ceryx Fortey, 1974, to Cloacaspis. New field collections and discovery of previously undescribed material in museum and survey collections provides the basis for emended descriptions of the genus Cloacaspis, as well as Cloacaspis tesselata Fortey and Droser, 1999, Cloacaspis ekphymosa Fortey, 1974, and Balnibarbi erugata Fortey, 1974, and expands the geographic range of the subfamily to Alaska.
- ItemSupplemental Material for "Gill function in an early arthropod and the widespread adoption of the countercurrent exchange mechanism"(2023-07-24) Hou, Jin-bo; Hughes, Nigel C.; Hopkins, Melanie J.; Shu, DeganSupplemental Material for: Jin-bo Hou, et. al. (2023) Gill function in an early arthropod and the widespread adoption of the countercurrent exchange mechanism. Royal Society Open Science, 10: 230341. doi: http://doi.org/10.1098/rsos.230341.
- ItemSupplemental Material for "Permian trilobites and the applicability of the "living fossils" concept to extinct clades"(2023-03-27) Hopkins, Melanie J.; Wagner, Peter; Jordan, KatherineSupplemental Material for: Hopkins, Melanie J., Peter Wagner, and Katherine Jordan. (2023) Permian trilobites and the applicability of the" living fossils" concept to extinct clades. Frontiers in Ecology and Evolution, 11. DOI: 10.3389/fevo.2023.1166126
- ItemA trilobite cluster from the Silurian Rochester Shale of New York : predation patterns and possible defensive behavior. (American Museum novitates, no. 3937)(American Museum of Natural History., 2019-09-09) Bicknell, Russell D. C.; Paterson, John R.; Hopkins, Melanie J.Evidence of predator-prey interactions in the fossil record offers important insights into extinct ecosystems. As direct predator-prey relationships are rarely preserved, records of failed predation upon prey species are often considered. The biomineralized exoskeleton of trilobites is exemplary for recording injuries that have resulted from predation. Despite the extensive documentation of trilobite injuries, abnormal specimens are often documented in isolation, with examples of injuries among clustered individuals being poorly known. Here we document a well-preserved body cluster of 18 individuals of the large lichid trilobite Arctinurus boltoni from the mid-Silurian (Wenlock) Rochester Shale of New York, with eight specimens showing injuries. Landmark geometric morphometrics of the specimens is used to explore possible patterns between injured and noninjured specimens. Results of the morphometric analysis indicate that injured and noninjured specimens do not show any systematic difference in overall shape of the exoskeleton, but many of the larger specimens have injuries. The majority of injuries are posteriorly located and right-side dominant, highlighting the possibility of predator or prey lateralization. Biostratinomic evidence suggests that the cluster represents a biological aggregation that was rapidly buried in situ. Potential reasons for this gregarious behavior are discussed, including the possibility that individuals of A. boltoni grouped together to provide "safety in numbers" against predatory attack.