Palaeontologia Electronica最新文献

{"title":"Non-traditional applications of fire in fossil preparation","authors":"M. Brown, C. Holliday","doi":"10.26879/1149","DOIUrl":"https://doi.org/10.26879/1149","url":null,"abstract":"Fossils have been collected from the field in plaster and burlap field jackets for more than a century. These jackets support and protect the contained fossils until they can be exposed under controlled conditions in the laboratory. The challenging nature of field work and complications caused by limited time, adverse weather, or supply shortages often produce suboptimal jackets that are less protective or difficult to remove. Often, the growth of vegetation through rock and fossils or poorly consolidated sediments compromises the stability of the jacket contents. In such cases, traditional methods of field jacket removal and fossil preparation can cause damage or destruction of the fossils within. We experimented with controlled application of flame to burn away organic materials from field jackets to facilitate safer extraction of sauropod fossils from the Late Cretaceous of Madagascar. To remove the field jacket, acetone was applied to burlap as an accelerant and then ignited with a propane torch. Combined with scoring from a utility knife, this caused the jacket to slowly weaken to the point of pliability and allow safe removal. Direct flame was also applied to plant roots infiltrating the jacket to remove them without causing vibration and mechanical damage within the specimen. Experimentation showed that with monitoring, temperatures did not reach levels that would damage the specimens through thermal shock or discoloration. Subsequent applications of these techniques demonstrate that they can be applied safely when specimens would be destroyed using more conservative methods. Matthew A. Brown. Texas Vertebrate Paleontology Collections, The University of Texas at Austin, Austin, TX, USA., matthewbrown@utexas.edu Casey M. Holliday. Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO, USA and Texas Vertebrate Paleontology Collections, The University of Texas at Austin, Austin, TX, USA. hollidayca@health.missouri.edu MAB ORCID: https://orcid.org/0000-0002-2713-1161 CMH ORCID: https://orcid.org/0000-0001-8210-8434","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-11"},"PeriodicalIF":2.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43213891","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":"A large, pathological skeleton of Smilosuchus gregorii (Archosauriformes: Phytosauria) from the Upper Triassic of Arizona, U.S.A., with discussion of the paleobiological implications of paleopathology in fossil archosauromorphs","authors":"A. Heckert, T. Viner, M. Carrano","doi":"10.26879/1123","DOIUrl":"https://doi.org/10.26879/1123","url":null,"abstract":"Phytosaurs were a widespread clade of Triassic predatory archosauriforms whose skull anatomy is well known, but whose paleobiology is underexplored. Here we report on a well-preserved specimen from Adamanian (early–mid-Norian) strata in Arizona that includes not only the skull and lower jaws but much of the postcranial skeleton, which exhibits extensive evidence of pathologies. This specimen has a complex taxonomic history, and we verify its referral to Smilosuchus gregorii based on multiple cranial characters. The shafts of eight limb bones preserve extensive exostoses—more paleopathological elements than in any other Triassic archosauromorph. These exostoses are often centered on cavitations reminiscent of draining tracts. Extensive, irregular, proliferative lesions have completely engulfed the left deltopectoral crest and thoroughly altered the architecture of both femora. The animal’s presumed low metabolic rate would have allowed several months of lesion progression before it died of either nutritional deficiency or systemic infection. This is the fourth, and by far the most extensive, report of pathology in a phytosaur, and only the eighth in a non-dinosaurian Triassic archosauromorph. The character and location of the lesions evokes aspects of both osteomyelitis and hypertrophic osteopathy—though neither is fully consistent with the changes present, nor are these conditions well-explored in extant reptiles. The most likely cause of the pathologies exhibited here is osteomyelitis; indeed, this specimen bears more osteomyelitis-like paleopathological elements than any other fossil archosaur. Andrew B. Heckert. Department of Geological and Environmental Sciences, Appalachian State University, ASU Box 32067, Boone, North Carolina 28608-2067 USA. heckertab@appstate.edu Tabitha C. Viner. USFWS National Fish and Wildlife Forensic Laboratory, 1490 E. Main St. Ashland, Oregon 97520, USA. tabitha_viner@fws.gov Matthew T. Carrano. Department of Paleobiology, P.O. Box 37012, MRC 121, Smithsonian Institution, Washington, DC 20013-7012, USA. carranom@si.edu HECKERT, VINER, & CARRANO: PATHOLOGICAL PHYTOSAUR 2","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-36"},"PeriodicalIF":2.0,"publicationDate":"2021-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47676167","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":"Palaeoecology and sea level changes: Decline of mammal species richness during late Quaternary island formation in the Montebello Islands, north-western Australia","authors":"C. Piper, P. Veth","doi":"10.26879/1050","DOIUrl":"https://doi.org/10.26879/1050","url":null,"abstract":"Changes in sea level and the formation of islands impact the distributions and abundances of local flora and fauna, with palaeo-environmental investigations providing a context for biological conservation. The palaeo-environmental knowledge of the north-west of Australia during the late Quaternary is sparse, particularly the impact of island formation on local faunas. In 1991 and 1993 Peter Veth and colleagues conducted archaeological surveys of the Montebello Islands, an archipelago situated 70 – 90 km from the present-day coastline of north-west Australia. A group of three caves were found during this survey on the eastern side of Campbell Island. Two of the caves, Noala and Hayne’s Caves, were analysed by Veth and colleagues in the early 1990s; the last cave, Morgan’s Cave, remained unanalysed because it contained negligible archaeological material. It provides an opportunity to refine the interpretation of palaeo-environmental conditions, further information on the original pre-European fauna of the north-west shelf, the formation of the islands due to sea level rise, and the impact of sea level rise on local faunas. The fossil fauna assemblage of Morgan’s Cave was sorted, identified to the lowest taxonomic level possible, and counted for analysis on relative abundance for paleoenvironmental interpretation. There are marked patterns of species loss and changing relative abundances in certain species, consistent with island formation due to sea level rise. This palaeoecological interpretation can be used in conservation efforts on nearby Barrow Island, a Class A ecological reserve, and management of faunas in conservation reserves and on islands. Cassia J. Piper. Department of Earth and Planetary Sciences, Western Australian Museum, 49 Kew Street, Welshpool, 6101. cassia.piper@gmail.com Peter M. Veth. Indian Oceans Institute, University of Western Australia, Perth, WA 6009. Peter.Veth@uwa.edu.au PIPER & VETH: PALAEOECOLOGY AND RISING SEAS 2","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-21"},"PeriodicalIF":2.0,"publicationDate":"2021-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47768158","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":"A megatoothed shark (Carcharocles angustidens) nursery in the Oligocene Charleston Embayment, South Carolina, USA","authors":"A. Miller, M. Gibson, R. Boessenecker","doi":"10.26879/1148","DOIUrl":"https://doi.org/10.26879/1148","url":null,"abstract":"Many extant sharks are cosmopolitan as adults but inhabit nursery areas as youngsters often shallow, dynamic ecosystems with abundant prey for neonates and juveniles. Megatoothed sharks (Otodontidae) were the largest sharks of all time, and nursery areas have been demonstrated for Carcharocles megalodon in the Miocene of Panama, Spain, Florida, and Maryland. An earlier study hypothesized a nursery area for Carcharocles angustidens in the upper Oligocene (23-25 Ma) Chandler Bridge Formation of Charleston, South Carolina. We tested this by reporting and analyzing two collections (n=127) dominated by small teeth of C. angustidens from the Chandler Bridge Formation and some teeth from the underlying lower Oligocene (29-26.57 Ma) Ashley Formation (n=9). Correcting for tooth position, published body length estimation equations yielded body length estimates of 1.5-6.5 m for most individuals. Size-based assignment to age classes (neonates, juveniles, adults) is modified from the larger C. megalodon and scaled based on the largest available specimens of C. angustidens, reported herein. These assemblages are dominated by small individuals (juveniles and neonates) and include few adults. The Oligocene Charleston embayment therefore represents the first documented paleo-nursery area for C. angustidens. Addison Miller. Department of Geology and Environmental Geosciences, College of Charleston, Charleston, South Carolina 29424, USA. addisonemiller12@gmail.com Matthew Gibson. Charleston Museum, Charleston, South Carolina 29403, USA. mgibson@charlestonmuseum.org Robert Boessenecker, Mace Brown Museum of Natural History and Department of Geology and Environmental Geosciences, College of Charleston, Charleston, South Carolina 29424, USA. Corresponding Author. boesseneckerrw@cofc.edu","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-19"},"PeriodicalIF":2.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49280489","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":"Modern vegetation proxies reflect Palaeogene and Neogene vegetation evolution and climate change in Europe, Turkey, and Armenia","authors":"J. Kovar-Eder, P. Mazouch, V. Teodoridis, A. Roth-Nebelsick, C. Traiser, Janina Wypich","doi":"10.26879/1131","DOIUrl":"https://doi.org/10.26879/1131","url":null,"abstract":"Recently two tools, Drudge 1 and 2, were introduced to more easily assess modern vegetation proxies for the fossil record. They are based on three similarities: the Integrated Plant Record (IPR) Similarity assessing the similarity between fossil assemblages and modern vegetation based on the proportion of major zonal angiosperm components; the Taxonomic Similarity (TS) reflecting the similarity based on the coincidence of genera among the fossil record and modern vegetation; and the combination of both similarities (Results Mix). In this paper, we apply Drudge 1 and 2 to 54 fossil plant assemblages from Europe, Turkey, and Armenia covering the time span from the early Eocene to the Pleistocene. For every fossil plant assemblage, a set of 25 proxies (modern vegetation units) is derived by the Drudges, reflecting its physiognomy and floristic composition. The results for all fossil plant assemblages feature the overall vegetation evolution and climate change in Europe, Turkey, and Armenia providing deeper insight into the relationships of the fossil record to the modern Asian and European vegetation. This study strives to provide an improved understanding of the Palaeogene/Neogene vegetation evolution in Europe and Asia beyond the community of specialists. Our results can help model future scenarios. They also improve our understanding of how climate change may affect vegetation and more broadly ecosystems as a whole. Johanna Kovar-Eder. State Museum of Natural History Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany. johanna.eder@smns-bw.de Petr Mazouch. Faculty of Informatics and Statistics, University of Economics, Prague, Czech Republic. mazouchp@vse.cz Vasilis Teodoridis. Department of Biology and Environmental Studies, Faculty of Education, Charles University, Prague, Czech Republic. vasilis.teodoridis@pedf.cuni.cz Anita Roth-Nebelsick. State Museum of Natural History Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany. anita.rothnebelsick@smns-bw.de KOVAR-EDER ET AL.: VEGETATION EVOLUTION AND CLIMATE CHANGE 2 Christopher Traiser. University Tübingen, Departement of Geoscience, Schnarrenbergstr. 94-96, 72076 Tübingen, Germany. christopher.traiser@uni-tuebingen.de Janina Wypich. State Museum of Natural History Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany. janina.wypich@smns-bw.de","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-45"},"PeriodicalIF":2.0,"publicationDate":"2021-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43830121","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":"Paleoclimate and paleoecology of the Upper Oligocene Tehuacán Formation, Puebla State, Mexico, as determined from wood anatomical characters","authors":"Marco A. Rubalcava-Knoth, S. Cevallos-Ferriz","doi":"10.26879/1136","DOIUrl":"https://doi.org/10.26879/1136","url":null,"abstract":"Climatic conditions that prevailed during the deposition time of the Tehuacán Formation, Mexico (upper Oligocene) are proposed based on a previous model using wood anatomical characters. Different paleoclimatic variables were calculated, and the anatomical characteristics of the Tehuacán Formation paleoflora were compared with the characteristics of other extant and fossil plant communities to infer water conductive capacities of the Tehuacán Fm. plants. The paleoclimatic inference suggests that the environmental conditions under which the fossilized plants of the Tehuacán Fm. grew were seasonally warm and humid. Statistical analysis and the presence of growth rings in some woods suggest that the paleoflora of the Tehuacán Fm. were similar to extant tropical communities such as tropical semi-deciduous forests and the tropical deciduous forests, most probably representing a transitional community: containing plants that were efficient in transporting water like those in the tropical wet forests, but with phenological adaptations typical of drier tropical forests. Marco A. Rubalcava-Knoth. Posgrado en Ciencias Biológicas, Instituto de Geología, UNAM; Ciudad Universitaria, Circuito de la Investigación Científica, Copilco El Alto, Coyoacán; 04510 Mexico D.F., Mexico. paleoplantas@gmail.com Sergio R.S. Cevallos-Ferriz. Departamento de Paleontología, Instituto de Geología, UNAM; Ciudad Universitaria, Circuito de la Investigación Científica, Copilco El Alto, Coyoacán; 04510 Mexico D.F., Mexico. scrscfpb@unam.mx","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-22"},"PeriodicalIF":2.0,"publicationDate":"2021-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42255232","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":"Termite nests in eolian backshore settings: An unusual record throughout the Quaternary in the Neotropical realm","authors":"Karen Yahaira Solano Ramos, R. Netto, Daniel Sedorko","doi":"10.26879/1146","DOIUrl":"https://doi.org/10.26879/1146","url":null,"abstract":"In this paper, we report the unusual presence of extant termite nests in frontal beach eolian sandy substrates in the Rio Grande do Sul Coastal Plain (southernmost Brazil) and describe the nest architectures, aiming to compare them with termite fossil nests preserved in Pleistocene backshore deposits of this same coastal plain. Four sites were analyzed along the modern beach, and the architecture of the termite nests was described. The nests are composed of a rounded convex epigeal portion and a hypogeal portion with variable dimensions formed by interconnecting spherical to semispherical chambers. Considering that termites are assumed to colonize more mature, vegetated soils due to the need for abundant cellulosic material, the occurrence of termite nests in backshore dunes close to the shoreline opens a discussion about the distribution and habit of termites and the applicability of their trace fossils for paleoenvironmental reconstitutions. Kimberly Silva Ramos. ICHNOS Research Group, Geology Graduate Program, Unisinos University, Av. Unisinos, 950, 93022-000, São Leopoldo, RS, Brazil. kimberlyr@edu.unisinos.br Renata Guimarães Netto. ICHNOS Research Group, Geology Graduate Program, Unisinos University, Av. Unisinos, 950, 93022-000, São Leopoldo, RS, Brazil. nettorg@unisinos.br Daniel Sedorko. ICHNOS Research Group, Geology Graduate Program, Unisinos University, Av. Unisinos, 950, 93022-000, São Leopoldo, RS, Brazil and Universidade Federal de Uberlândia, Laboratório de Paleontologia Aplicada, Campus Monte Carmelo. Av. XV de Novembro, 501, Boa Vista, Monte Carmelo – MG. 38500-000, Brazil. sedorko@ufu.br","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-17"},"PeriodicalIF":2.0,"publicationDate":"2021-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45521429","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 findings of Stephanorhinus kirchbergensis in Siberia","authors":"Y. V. Lobachev, А.V. Shpansky, A. A. Bondarev, A. Lobachev, S. Vasiliev, A. M. Klementev, I. Grebnev, V. Silaev","doi":"10.26879/734","DOIUrl":"https://doi.org/10.26879/734","url":null,"abstract":"New findings of Stephanorhinus kirchbergensis (Jäger, 1839) remains, obtained from the Asian part of Russia, are described. The material includes 39 specimens from 13 localities in West Siberia and East Siberia. It considerably expands the geographic distribution of this species of rhinoceros. A series of 11 mandibles from Siberia, including one juvenile individual with deciduous teeth, is described for the first time. We also present a large set of data on well-preserved postcranial remains. The morphology and sizes of mandibles, teeth, and postcranial remains of adult individuals of S. kirchbergensis from Siberia are similar to individuals of this species described from European localities. A series of upper teeth was subjected to mesowear analysis to assess the diet of S. kirchbergensis from West Siberia. The chemical composition (including stable isotopes) of the Siberian Stephanorhinus teeth is analyzed for the first time. Comparisons of Siberian S. kirchbergensis with European S. kirchbergensis and West Siberian Coelodonta antiquitatis broaden our understanding of the ecology, variability, and evolution of S. kirchbergensis under climatic changes in continental settings from the Middle to the Late Pleistocene. Despite small samples, we can suppose that S. kirchbergensis was widely distributed in Siberia. Y.V. Lobachev. PAO Novosibirsk Institute of Software Systems, Novosibirsk, Russia. yvlobachev@gmail.com А.V. Shpansky. Tomsk State University, Russia. shpansky@ggf.tsu.ru A.A. Bondarev. Omsk Regional Branch of the Russian Geographical Society, Omsk 644007, Russia. gilgamesh-lugal@mail.ru A.Y. Lobachev. PAO Sberbank, Novosibirsk, Russia. inobges@gmail.com S.K. Vasiliev. Institute of Archaeology and Ethnography of SB RAS, Russia. Svasiliev@archaeology.nsc.ru A.M. Klementev. Institute of the Earth’s Crust SB RAS, Russia. klem-al@bk.ru I.E. Grebnev. Paleopark Altai Republic, Russia. mnh66@mail.ru V.I. Silaev. Institute of Geology of Komi SC UB RAS, Syktyvkar, Russia, silaev@geo.komisc.ru","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-42"},"PeriodicalIF":2.0,"publicationDate":"2021-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41978551","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":"Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles","authors":"Asher Lichtig, S. Lucas","doi":"10.26879/886","DOIUrl":"https://doi.org/10.26879/886","url":null,"abstract":"Chinlechelys tenertesta is a turtle from the Upper Triassic Bull Canyon Formation of the Chinle Group of eastern New Mexico, USA, which has largely been ignored in recent studies of the phylogenetic position of turtles (Testudinata) within the Tetrapoda. Here, we present the first comprehensive description of the morphology of Chinlechelys tenertesta and reaffirm its unequivocal support for the composite model of costal bone formation in turtles. We also document the presence in Chinlechelys tenertesta of separate ribs reminiscent of those of Odontochelys semitestacea, a Late Triassic prototurtle from China, and costal plates, as would be expected under the composite model. This indicates that the two-phase embryological model of costal and plastral bone formation approximately corresponds to the formation of the endochondal rib and plastral primary ossifications and then the later dermal formation of the plastral and costal plates, as is suggested by the composite model. We challenge the identification of Permian Eunotosaurus africanus as a stem turtle and instead suggest that it is a caseid synapsid. We do not consider Pappochelys rosinae to be a close relative of turtles. It more closely resembles the basal placodont sauropterygians, particularly Palatodonta bleekeri. Indeed, phylogenetic analysis based on correctly coded character states places Pappochelys rosinae in the Sauropterygia as the sister taxon of placodonts. The morphology of Chinlechelys tenertesta supports the placement of Testudines outside of crown Sauria, as a taxon derived from pareiasaurs based on the morphology of the dorsal osteoderms and skull roof. Asher J. Lichtig. New Mexico Museum of Natural History & Science, 1801 Mountain Road N. W., Albuquerque, New Mexico 87104, USA. ajlichtig@gmail.com Spencer G. Lucas. New Mexico Museum of Natural History & Science, 1801 Mountain Road N. W., Albuquerque, New Mexico 87104, USA. spencer.lucas@state.nm.us","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-49"},"PeriodicalIF":2.0,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42509640","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 genera that never were: The impact of Janeia and Janacekia on phyletic and taxonomic relations within the Solemyidae (Bivalvia: Protobranchia)","authors":"J. Bailey","doi":"10.26879/945","DOIUrl":"https://doi.org/10.26879/945","url":null,"abstract":"Proposed taxonomies of the Solemyoidea remain conflicted, particularly regarding the familiar genera, Solemya and Acharax, whose close phyletic kinship has been obscured by: 1) imperfect understanding of the chronological morphogenesis of diagnostically important ligament support structures, and 2) misconceptions triggered by two problematic Paleozoic genera, Janeia and Janacekia, including the prevalent mischaracterization that the primary ligament in Janeia was located in an internal chondrophore. Whereas Janacekia and certain Janeia are synonyms of Acharax, other alleged Janeia are shown to be clinopisthins such as Dystactella and Clinopistha. Morphological analysis supports DNA studies suggesting Acharax and Solemya are monophyletic, thereby challenging recent taxonomies placing them in separate families or superfamilies. The primary ligaments of Acharax and Solemya are basically similar (opisthodetic, parivincular, attached at nymphae), the main differences being placement: external in Acharax but slightly internal (submarginal) in Solemya. Character analyses suggest the external nymphae of Acharax are plesiomorphic, arising by the Early Devonian, whereas the submarginal placement of the nymphae in Solemya is shown to be a Mesozoic apomorphy involving depression and secondary enclosure of the ligament and nymphae by a shelly outer layer. Nymphal enclosure has had two concomitant effects: 1) dorsal occlusion of the posterior adductor muscle; 2) fusion of the nymphae to internal buttresses that plesiomorphically functioned as simple reinforcement for the anterior margin of the posterior adductor muscles whereas, by exaptation, they become apomorphically modified to serve as supporting braces for the submarginal nymphae by dorsally uniting with them. Jack Bowman Bailey. Department of Earth, Atmospheric and Geographic Information Sciences Western Illinois University, 1 University Circle, Macomb, IL 61455 USA. jb-bailey@wiu.edu","PeriodicalId":56100,"journal":{"name":"Palaeontologia Electronica","volume":"24 1","pages":"1-47"},"PeriodicalIF":2.0,"publicationDate":"2021-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49368976","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}