Browsing by Author "Plotnick, Roy E."
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Item Ex vivo three-dimensional reconstruction of Acutiramus : a giant pterygotid sea scorpion (American Museum novitates, no. 4004)(American Museum of Natural History., 2023-11-20) Bicknell, Russell D. C.; Kenny, Katrina; Plotnick, Roy E.Pterygotid eurypterids include some of the largest aquatic arthropods in the fossil record and are known from middle Silurian to Middle Devonian deposits across the globe. These forms primarily preserve as mostly two-dimensional impressions, a situation that has impacted the accurate reconstruction of pterygotid ventral structures and organization. By documenting specimens displaying important dorsal and ventral structures from both Acutiramus—a larger, well-documented pterygotid genus—and other pterygotids, we reconstruct Acutiramus in three-dimensions (3D) to more thoroughly understand the functional morphology and limb arrangement of these large eurypterids. With this comprehensive 3D reconstruction, we demonstrate a much more anterior insertion of appendages II–V, a near-horizontal orientation of appendages II–VI coxae, the presence of reduced appendage II, and a labrum and epistomel region. The labrum and epistomel sections are identified as the locality for cheliceral articulation. This model also uncovers the streamlined nature and low-profile morphology of Acutiramus. We use our model to explore the morphofunctionality of pterygotid eurypterids, including their feeding strategies, addressing a conundrum inherent in previous pterygotid reconstructions.Item Revision of the pseudoniscine merostome genus Cyamocephalus Currie. American Museum novitates ; no. 2557(New York, N.Y. : American Museum of Natural History, 1974) Eldredge, Niles.; Plotnick, Roy E."We present an emended diagnosis for the monotypic genus Cyamocephalus Currie, 1927, based on examination of the holotype of Cyamocephalus loganensis and study of a second, very well-preserved specimen we attribute to Cyamocephalus cf. C. loganensis. Both specimens, which were collected from Upper Silurian rocks of Great Britain, are described in detail. The holotype specimen is remarkable in that a pair of dark stains, the possible remains of a portion of the dorsal longitudinal muscle system, are preserved within the cardiac lobe of the prosoma and the axial lobe of the opisthosoma. The prosomal morphology of Cyamocephalus is similar to that of other pseudoniscids; as in other Pseudoniscidae, cardiophthalmic morphology is obscure but similar in general plan to that of other Limulina. There are 10 opisthosomal segments; the first (anterior) segment is greatly reduced with very short pleura. Segments 2-10 have well-developed pleura, and segments 6 and 7 are fused into a solid tergite on which is developed a complex pattern of ridges and furrows. All other segments are freely articulated. The axial furrow system of segments 2-5 on the second specimen is also complex. The telson is styliform. Although clearly pseudoniscine in character, the large overall size, the proportionally large size and rounded posterior outline of the opisthosoma, and the complexities of the furrows of the axis and on segments 6 and 7, readily differentiate this genus from Pseudoniscus and other related genera. Recently regarded as incertae sedis within the Merostomata (Eldredge, 1974), we now consider Cyamocephalus a valid genus, in some respects the most specialized (derived) member of the family Pseudoniscidae (sensu Eldredge, 1974)"--P. 3.Item Supplemental material for 'Ex vivo three-dimensional reconstruction of Acutiramus : a giant pterygotid sea scorpion (American Museum novitates, no. 4004)'(American Museum of Natural History., 2023-11) Bicknell, Russell D. C.; Kenny, Katrina; Plotnick, Roy E.Supplemental material for 'Ex vivo three-dimensional reconstruction of Acutiramus : a giant pterygotid sea scorpion (American Museum novitates, no. 4004)' - https://hdl.handle.net/2246/7335