Palaios最新文献

{"title":"BONE MODIFICATION FEATURES RESULTING FROM BARNACLE ATTACHMENT ON THE BONES OF LOGGERHEAD SEA TURTLES (Caretta caretta), CUMBERLAND ISLAND, GEORGIA, USA: IMPLICATIONS FOR THE PALEOECOLOGICAL, AND TAPHONOMIC ANALYSES OF FOSSIL SEA TURTLES","authors":"J. Zonneveld, Z.E.E. Zonneveld, W. Bartels, M. Gingras, J. Head","doi":"10.2110/palo.2022.021","DOIUrl":"https://doi.org/10.2110/palo.2022.021","url":null,"abstract":"Abstract: Sea turtles are characterized by a wide variety of invertebrate ectoparasites. Few of these ectoparasites leave a permanent indication of their presence on the skeletal remains of their host taxa and thus represent ecological information doomed to be lost in the paleontological record. Some barnacle taxa provide an exception to this, in that they cause the formation of small, subcircular to circular divots, pits, and holes on the skull, mandible, carapace or plastron of sea turtles. Loggerhead Sea Turtle (Caretta caretta) skeletons from Cumberland Island, Georgia, USA were examined to assess the presence, frequency, and loci of occurrence of barnacle pits, and to establish which taxa are involved in pit development. Six types of divot and pit attributed to barnacles are identified in this study. Type I traces are shallow, oval/semicircular in outline, with smooth, gently sloped bases. Type II traces are deep, hemispherical pits with smooth bases. Type III traces are deep, circular to subcircular pits with flat bases. Type IV traces are deep, circular to subcircular pits with multiple (4–6) small sub-pits on their bases. Type V traces are cylindrical, penetrative holes. Type VI traces comprise shallow ring-shaped grooves on the surface of the bone. Type I through III traces are identical to the ichnotaxon Karethraichnus lakkos. Type IV traces have not, as yet, been described in the rock record. Type V traces are identical to K. fiale. Type VI traces are identical to Thatchtelithichnus holmani. Barnacle taxa identified as emplacing non-penetrative divots and pits on C. caretta skulls, mandibles, and shell bones include Chelonibia caretta (Type I), Platylepas hexastylos (Types I–IV), Calyptolepas bjorndalae (Types I and II), and Stomatolepas elegans (Types I and II). Type V traces were most likely emplaced by either Stephanolepas muricata or Chelolepas cheloniae. Type VI traces reflect the former attachment of balanid or lepadid barnacles. Embedded barnacles were observed in epidermal material associated with Types I through IV traces but not for Type V and VI traces and thus the relationship is inferred for these latter traces. Barnacle-related pits, divots, and holes are believed to result from barnacle mediated chemical corrosion into the outer surface of sea turtle bone. The occurrence of these traces provides one of the few preservable lines of evidence of barnacle interactions with sea turtle hosts. Identification of definitive barnacle borings in fossil material will provide evidence of the evolution of platylepadid barnacles and the development of their commensal relationship with chelonid turtles.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"650 - 670"},"PeriodicalIF":1.6,"publicationDate":"2022-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42858973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ASSESSMENT OF A REEF COMMUNITY FROM LOWER JURASSIC (PLIENSBACHIAN) STRATA IN THE CENTRAL HIGH ATLAS MOUNTAINS OF MOROCCO","authors":"T. Stone, R. Martindale, T. Fonville, B. Lathuilière, S. Boivin, Raphäel Vasseur, M. Septfontaine","doi":"10.2110/palo.2022.010","DOIUrl":"https://doi.org/10.2110/palo.2022.010","url":null,"abstract":"Abstract: During the Early Jurassic, reefs in the shallow seas of the Atlas Rift experienced substantial changes as they recovered from the end-Triassic mass extinction. Excellent Lower Jurassic reef deposits documenting this change occur in the Central High Atlas region of Morocco, and herein we describe Owl Olistolith, a micro-olistolith found in lower Pliensbachian-aged (∼ 188.7 million years ago) Moroccan strata. The olistolith records the composition of a reef that grew within the Atlas rift zone and represents a snapshot of reef recovery ∼ 10 million years after the end-Triassic mass extinction. Owl Olistolith is derived from a reef that was originally situated on an outer platform within fair weather wave base; it broke loose and was transported to deeper water and deposited amongst marls. Corals and microbialites formed the primary framework of the reef; microproblematica, foraminifera, and other minor components were also present. The reef can be divided into two dominant facies: a microbialite facies that contains no corals (54%–94% microbialites), and a coral-microbialite facies with substantial proportions of both microbialite (23%–50%) and corals (14%–72%). The micro-olistolith contains at least 15 distinct coral types. In this study, seven coral genera were identified, three of which represent taxa that span the Triassic/Jurassic boundary, including Coryphyllia, Stylophyllopsis, and Margarosmilia. These results indicate that, although surviving taxa played a significant role, newly evolved corals were the most important taxa in the reestablishment of reef ecosystems in the Early Jurassic of Morocco.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"633 - 649"},"PeriodicalIF":1.6,"publicationDate":"2022-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48528653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"INTEGRATING EXPERIMENTS WITH SUBTIDAL DEATH ASSEMBLAGES TO UNVEIL THE PREDATORY HABITS OF MURICID GASTROPODS FROM THE SOUTHEASTERN PACIFIC","authors":"J. Martinelli, C. S. Ruz, A. Pérez‐Matus, M. Rivadeneira","doi":"10.2110/palo.2021.061","DOIUrl":"https://doi.org/10.2110/palo.2021.061","url":null,"abstract":"Abstract: As quantitative tools, drill holes have been used to calculate predation frequencies in time and space. These traces can also inform predator preference and some strategies predators use to drill on prey (e.g., edge drilling, site stereotypy, or alternative modes of predation when there is no drill hole). In this study, our goal was to leverage the informative power of drill holes to characterize the predatory habits of muricid gastropods from the central coast of Chile. We integrated information from experiments and death assemblages (DAs) to unveil the predatory strategy of Ancathina monodon, Crassilabrum crasilabrum, and Concholepas concholepas on the mobile gastropod Tegula tridentata and the sessile bivalve Perumytilus purpuratus. Experiments supported previous findings for predatory strategies (basal spine for Ancathina and alternative modes of predation for Concholepas), and showed the stereotypic predation of Crassilabrum on Tegula—a herbivore that is devastating subtidal kelp forests. Based on drill holes from DAs, at least 11 molluscan families are consumed by muricids in these communities. DAs also helped validate the stereotypic predation of Crassilabrum on Tegula, as drill holes were found in the same position both in experiments and DAs. Despite their thinner shells, mytilids were well represented in DAs and were found with drill holes in the five locations sampled. We describe for the first time the predatory strategy of Crassilabrum in Chile and confirm that muricids other than Concholepas are active predators on subtidal rocky habitats from the southeastern Pacific Ocean, a region that is still understudied.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"574 - 584"},"PeriodicalIF":1.6,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43566298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NEOICHNOLOGY OF AMPHIBIOUS ARTHROPODS: EFFECTS OF SUBAQUEOUS AND SUBAERIAL SUBSTRATE CONDITIONS ON TRACE MORPHOLOGY","authors":"L. Devine, N. Minter","doi":"10.2110/palo.2021.062","DOIUrl":"https://doi.org/10.2110/palo.2021.062","url":null,"abstract":"Abstract: Neoichnology, the study of the traces of extant organisms, provides a vital tool for better understanding trace fossils. We conducted neoichnological experiments to test hypotheses regarding producers and the effects of substrate conditions on trace fossils produced by aquatic to amphibious arthropods. Our experiments comprised two protocols: subaerial and subaqueous substrates; and we utilized five arthropods: fully aquatic ostracods (Ostracoda indet.), to amphibious horseshoe crabs (Limulus polyphemus), shore crabs (Carcinus maenas), and scarlet hermit crabs (Paguristes cadenati), and the largely terrestrial sea slaters (Ligia oceanica). The different arthropods were observed performing locomotory, resting/stationary, and feeding behaviors, which all resulted in different traces influenced by the substrate conditions and their preference for living in and out of water. In general, trace depth increased with arthropod mass and, for each individual arthropod except the scarlet hermit crab, trace depth was also greater in subaerial compared to subaqueous substrates. In the majority of cases, comparisons with selected trace fossils supported previous hypotheses as to their producers. The traces of horseshoe crabs, shore crabs, sea slaters, and ostracods resembled the ichnotaxa Kouphichnium, Laterigradus, Pterichnus, and Mermia, respectively. Other experimental work has shown hermit crabs produce traces similar to Coenobichnus and our results further increase the range of trace morphologies that can be attributed to hermit crabs. The results of this research have bearing on debates in ichnology where the interpretation of producers and substrate conditions at the time of trace formation are critical, such as the trace fossil evidence for the colonization of land.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"585 - 605"},"PeriodicalIF":1.6,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47228521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"APPLICATIONS OF PHOTOGRAMMETRY TO NEOICHNOLOGICAL STUDIES: THE SIGNIFICANCE OF SHOREBIRD TRACKWAY DISTRIBUTIONS AT THE BAY OF FUNDY","authors":"S. Melnyk, A. Cowper, J. Zonneveld, M. Gingras","doi":"10.2110/palo.2021.055","DOIUrl":"https://doi.org/10.2110/palo.2021.055","url":null,"abstract":"Abstract: Low-level drone photogrammetry is a technique that allows for the construction of surface orthomosaics and elevation models. Despite being used for a wide range of geological applications, these types of datasets have not yet been explored from a neoichnological perspective. This study uses three examples of tidal flats from the Bay of Fundy to demonstrate the usefulness of 3D photogrammetry in the collection of high-resolution neoichnological datasets. The first site is a bar top along the Petitcodiac River that is situated between a salt marsh and tidal channel margin. The second site, which is located along the Shepody River, represents a laterally accreting channel margin and thus has a relatively high relief. In contrast, the final site comprises a gently sloping tidal flat that is far from the influence of a major tidal channel. Spatial analysis of the shorebird tracks at each site was used to assess the relationship between shorebird track distributions (e.g., track density, stride orientation, stride length) and various environmental and ecological factors (e.g., topography, tidal current direction, invertebrate prey distributions). Additionally, morphological analysis of the tracks was used to assess variations in substrate cohesiveness, which is the environmental factor that exhibited the most variability at the study locations. The track record at each site represents a shorebird flock that traversed the tidal flats in such a way as to optimize foraging success. As a result, the abundance and availability of macrobenthic invertebrate prey was the primary factor contributing to shorebird track density. This paper aims to assess local-scale variations in tidal flat substrate cohesiveness and provide context for the interpretation of fossilized shorebird trackways.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"606 - 621"},"PeriodicalIF":1.6,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49400303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"STRONTIUM ISOTOPE STRATIGRAPHY REVEALS 100 KY-SCALE CONDENSATION, BEVELING, AND INTERNAL SHINGLING OF TRANSGRESSIVE SHELL BEDS IN THE MARYLAND MIOCENE","authors":"J. Zimmt, S. Kidwell, R. Lockwood, M. Thirlwall","doi":"10.2110/palo.2022.004","DOIUrl":"https://doi.org/10.2110/palo.2022.004","url":null,"abstract":"Abstract: Condensed transgressive shell beds, rich in paleobiological information, are common in the Phanerozoic stratigraphic record, but their interpretation is complicated by the uncertain amount of time that each deposit represents. Miocene strata exposed in the Calvert Cliffs (Maryland, USA) are known for a series of regionally extensive, densely packed, meters-thick shell beds that serve as global exemplars of shallow-water condensation during marine transgression and onlap. Applying Sr isotope stratigraphy to calcitic scallops from the base and top of the oldest of these beds (Shattuck Zone 10), we demonstrate that its most densely fossiliferous part accumulated over the interval of 16.60–15.95 Ma, reflecting approximately 0.65 ±0.20 Myr of skeletal accumulation within the Miocene Climatic Optimum, with a likely 0.15 Myr-scale of time averaging per each firmground-bounded subunit. Both of these estimates are an order of magnitude longer than previous best estimates based on radiocarbon-dated Holocene analogs. Sr isotopes confirm subtle low-angle erosional beveling of the main body of Zone 10, truncating 0.3-Myr of record in updip sections, and demonstrate that a down-dip wedge of less shelly sand is an entirely younger (by ∼ 0.5 Myr) interleaved body. This condensation, beveling, and inter-shingling within Zone 10 quantified here sets a precedent for the magnitude of lateral and vertical temporal variability within condensed transgressive deposits, relevant to paleobiologic and other geohistorical analysis, and justifies the interpretation of comparably complex temporal fabrics based upon similar physical stratigraphic features found elsewhere in this and other very thin stratigraphic records.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"553 - 573"},"PeriodicalIF":1.6,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43533329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LEAVES IN IRON OXIDE: REMARKABLE PRESERVATION OF A NEOGENE FLORA FROM NEW CALEDONIA","authors":"Emma R. Locatelli, D. Briggs, A. Leslie, J. Munzinger, P. Grandcolas, P. Lowry, D. Cantrill, P. Maurizot, Dominique Cluzel, N. Folcher, R. Garrouste, A. Nel","doi":"10.2110/palo.2022.019","DOIUrl":"https://doi.org/10.2110/palo.2022.019","url":null,"abstract":"Abstract: A Neogene hematite-goethite concretionary ‘ironstone’ horizon in laterized fluvial sediments in the Massif du Sud of New Caledonia yields abundant fossil dicotyledonous angiosperm leaves. The leaves are preserved in iron oxide, mainly goethite, which replicates the morphology and anatomy of the leaf tissues and comprises 73% of the matrix. Organic remains are minimal and associated with aluminosilicate clay. Leaf tissues are preserved three-dimensionally in multiple ways including casts/molds, permineralization/petrifaction, and replacement. Although the mesophyll is less well preserved, reflecting its greater susceptibility to decay, cellular details of vascular and epidermal tissues are commonly evident. Analyses of leaves from an analogous modern setting reveal the early encrustation and impregnation of tissues by amorphous iron-oxides and clays in association with a microbial biofilm. We propose a taphonomic model in which the fossil leaves, like their modern counterparts, were permeated by iron oxides due to the high availability of iron derived from weathering of ultramafic basement. In contrast to the iron-rich aluminosilicate coatings that form in relatively iron-poor settings, the unusually high concentration of dissolved iron oxides permitted rapid anatomical preservation.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"622 - 632"},"PeriodicalIF":1.6,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47791230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"INSIGHTS FROM A MONOSPECIFIC LINGULID BRACHIOPOD BED IN THE LATE DEVONIAN OF SOUTH AFRICA","authors":"C. Harris, R. Gess","doi":"10.2110/palo.2021.046","DOIUrl":"https://doi.org/10.2110/palo.2021.046","url":null,"abstract":"Abstract: A formerly unknown fossil-bearing locality in the lower part of the Witpoort Formation (Witteberg Group, Cape Supergroup) is described from the Eastern Cape (South Africa). Uniquely for these strata, it provides evidence for a back-barrier lagoon hosting a monospecific lingulid brachiopod fauna. This represents the youngest record of marine invertebrates within the Cape Supergroup. The occurrence extends the age range of the genus Dignomia Hall into the Famennian Stage, contrary to previous estimates of an Ordovician to mid-Devonian range. Abundant lingulid brachiopod valves are associated with plant and fish remains within a laterally extensive, up to nine-meter-thick mudstone. Shell compressions are concentrated in patches within the upper portion of the horizon and are preserved parallel to bedding as well as perpendicular and oblique to bedding (apparently in situ). Plant fossils exhibit a greater degree of transport than in other studied Witpoort Formation mudrock layers (Coombs Hill and Waterloo Farm). The monospecifity of the shelly invertebrate fauna derives from environmental stress and lingulid brachiopods' unusual ability to tolerate fluctuating environmental conditions, including salinity, oxygen levels, and temperature. Ichnofauna within the deposit include, among others, Nereites and ‘Spirophyton’, suggesting opportunistic colonization of the substrate by deposit feeding invertebrates in a marine-dominated backshore setting. The Late Devonian was a time of global environmental disequilibrium, characterized by periodic flooding of continental margins and massive biotic overturn. Ongoing research into eustatic and environmental changes recorded within the Witpoort Formation uniquely provide insights into high latitude conditions during the Famennian.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"471 - 485"},"PeriodicalIF":1.6,"publicationDate":"2022-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47709325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NEW BIOCLAUSTRATION OF A SYMBIONT IN THE MANTLE CAVITY OF CLITAMBONITES SCHMIDTI (BRACHIOPODA) FROM THE SANDBIAN (UPPER ORDOVICIAN) OF ESTONIA","authors":"O. Vinn, Mark A. Wilson, M. Isakar, U. Toom","doi":"10.2110/palo.2021.067","DOIUrl":"https://doi.org/10.2110/palo.2021.067","url":null,"abstract":"Abstract: A new bioclaustration of a symbiont is here described from the mantle cavity of the strophomenatan brachiopod Clitambonites schmidti. It is the second bioclaustration in brachiopods known from the Kukruse Regional Stage (Sandbian) of Estonia. It shares affinities with the bioclaustrations Burrinjuckia and Haplorygma. The outgrowth in the ventral valve interior was secreted by the brachiopod around a symbiont. Most likely the symbiont was a suspension feeder that collected food particles from the brachiopod's mantle cavity. The symbiont was either a kleptoparasite or fed on the brachiopod's feces (coprophagy). The majority of symbiosis cases in brachiopods in the Ordovician of Baltica involve clitambonitids as the hosts. Thus, clitambonitid brachiopods were more likely hosts for symbiosis than other brachiopods in the Ordovician of Baltica.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"520 - 524"},"PeriodicalIF":1.6,"publicationDate":"2022-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44534615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THE OCCURRENCE OF BONE MODIFICATION FEATURES IN THE CARAPACE AND PLASTRON OF THE EXTANT RED-EARED SLIDER TRACHEMYS SCRIPTA ELEGANS (WIED-NEUWIED, 1839): IMPLICATIONS FOR PALEOECOLOGICAL ANALYSES OF FOSSIL TURTLE ASSEMBLAGES","authors":"J. Zonneveld, W. Bartels","doi":"10.2110/palo.2022.018","DOIUrl":"https://doi.org/10.2110/palo.2022.018","url":null,"abstract":"Abstract: The carapace and plastron bones of fossil turtles are often characterized by bone modification features such as pits, grooves, and holes. The significance, origin, and frequency of these features remains unclear because they have not been described from the bones of modern turtles. Taxon-specific description and analyses of defleshed turtle shell is essential for assessing the paleoecological significance of bone modification features. This study focuses on bone modification features on carapace and plastron bones of the emydid turtle Trachemys scripta elegans. Four subadult and 14 adult turtle shells were examined for non-ontogenetic features such as pits, grooves, holes, wounds, abrasions, and pathological growth structures. Bone modification features were lacking on subadult specimens but observed on each adult. Shallow, circular to subcircular pits (similar to the ichnotaxon Karethraichnus lakkos), and to a lesser extent pit clusters, are the most common feature noted on T. scripta elegans shells. Although they occur on both the plastron and the carapace, they proved far more common on the lower shell. Sparsely distributed ring-shaped grooves similar to the ichnotaxon Thatchtelithichnus holmani were present on approximately half of the turtle plastra studied. Amorphous surface etching was observed on several turtles, most commonly near the plastron midline (posterior portion of the hyoplastron/anterior portion of the hypoplastron). Pathological responses to these marks are lacking, but were noted on two turtles in response to sustained injuries. The occurrence of circular and subcircular pits, pit clusters, and ring traces on the external surface of every adult turtle analyzed in this study (regardless of sex or geographical occurrence), their discrete size and shape, and the lack of evidence of a systemic pathological response by the host suggests parasites, possibly leeches, as the etiological agent responsible for these features.","PeriodicalId":54647,"journal":{"name":"Palaios","volume":"37 1","pages":"499 - 519"},"PeriodicalIF":1.6,"publicationDate":"2022-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49555597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}