Early Cretaceous succession of the Oued Fodda Formation in the Ouarsenis Mountains(northwestern Algeria) is mainly composed of marl—limestone alternations, which are subdivided into four informal units(Units 1 to 4),...Early Cretaceous succession of the Oued Fodda Formation in the Ouarsenis Mountains(northwestern Algeria) is mainly composed of marl—limestone alternations, which are subdivided into four informal units(Units 1 to 4), based on distinct lithological, stratonomical, and ichnological features. The ichnological analysis reveals a low diversity of the trace-fossil assemblage, which is exclusively reported from Units 2 and 3.The ichnoassemblage contains six ichnotaxa(Chondrites intricatus, Ophiomorpha isp., Planolites isp., Thalassinoides isp., Zoophycos brianteus, and Zoophycos cauda-galli), among which Zoophycos and Chondrites are the most common elements of the assemblage and occur in distinct mud-rich substrates showing different bioturbation intensities. The development of Zoophycos in the middle part of Unit 2 shows a high degree of bioturbation(bioturbation index(BI) = 4). Zoophycos specimens are of large size, between 45 cm and 75 cm in width, which were interpreted to have formed in a lower offshore environment where the oxygenation amount was optimal, the sedimentation rate was low, and the benthic food was abundant on the seafloor. Toward the upper part of Unit 2, Zoophycos-bearing levels exhibit a less intense degree of bioturbation(BI between 1 and2) in contrast to Planolites-and Chondrites-bearing levels which have a bioturbation index(BI) between 3 and4. At these levels, Zoophycos displays relatively small, coiled to U-shaped spreiten, probably in response to stressful and dysoxic conditions prevailing in the water bottom. With improved oxygenation in a quiet lower offshore to shelf margin environment in Unit 3, the benthic organisms recovered, as represented by medium to large size Zoophycos in association with Ophiomorpha and scarce Chondrites burrows, even if the overall bioturbation intensity is very low. The combination of trace-fossil assemblage and lithofacies of the Oued Fodda Formation indicates relatively stable outer shelf environments below the storm wave base, which corresponds classically to the lower offshore to shelf edge environments, and the prevailing palaeoecological conditions are optimal and stressful for the benthic organisms.展开更多
The thiolliericrinids(Thiolliericrinidae) are comatulids(Comatulida),which retained their stalks as adults.Here,we report a centrodorsal from the Bajocian strata(Middle Jurassic) of the Djebel Kérdacha area,north...The thiolliericrinids(Thiolliericrinidae) are comatulids(Comatulida),which retained their stalks as adults.Here,we report a centrodorsal from the Bajocian strata(Middle Jurassic) of the Djebel Kérdacha area,northwestern Algeria(Africa).It is the first thiolliericrinid report from outside of Europe and also the oldest representative of the Thiolliericrinidae whose first occurrence is from the Oxfordian.The crinoid is assigned to Copernicrinus zamorae gen.et sp.nov.The reported new taxon shows strong similarities with the stemless ‘true’comatulids,Solanocrinites;the only difference is the presence of a facet to the stem in Copernicrinus.The closest comparable thiolliericrinid to Copernicrinus is the Oxfordian Thiolliericrinus,interpreted as a descendant of the latter.The origin and overview of all thiolliericrinid representatives are also discussed herein.展开更多
Sheltered preservation,in which organisms are trapped within shells of cephalopods,is a wellknown phenomenon.This preservational style constitutes an important source of paleontological data.Here,we report the first c...Sheltered preservation,in which organisms are trapped within shells of cephalopods,is a wellknown phenomenon.This preservational style constitutes an important source of paleontological data.Here,we report the first crinoid preserved inside the early Albian ammonite Cleoniceras besairiei Collignon from Madagascar.This crinoid is assigned to the aspidocrinid phyllocrinid(Apsidocrinus,Phyllocrinidae),and constitutes the first phyllocrinid from the African continent,the second from the southern margin of the Tethys(after New Zealand),and also from the southern hemisphere.This specimen represents the youngest occurrence of a phyllocrinid in the world as well,and constitutes one of the youngest occurrences of cyrtocrinids from shallow sea environments,before predation-induced migration of the stalked crinoids to the deep sea refugia due to the so-called Mesozoic Marine Revolution.This finding highlights that ammonite shells may also be a convenient material for studying echinoderms.展开更多
The marl and limestone alternations of the Lower Jurassic Ain Ouarka and Ain Rhezala formations(Pliensbachian-Toarcian)in the western Saharan Atlas,Northwest Algeria,yield a diverse micro-and mac-rofauna,including mod...The marl and limestone alternations of the Lower Jurassic Ain Ouarka and Ain Rhezala formations(Pliensbachian-Toarcian)in the western Saharan Atlas,Northwest Algeria,yield a diverse micro-and mac-rofauna,including moderately numerous crinoids,which are represented by remains of isocrinids,i.e.,Bal-anocrinus ticinensis Hess and columnals of the genus Percevalicrinus.So far,the latter genus has been observed from the Upper Jurassic-Lower Cretaceous strata of Eurasia,North America,and the African continent.Thus,the present find is the oldest record of this crinoid genus,and the second one from the southern Tethyan margin.In this paper,it is shown that Percevalicrinus,which is traditionally regarded as a representative of the subfamily Balanocrininae,displays several features of the subfamily Isocrininae.The crinoid assemblage and associated facies and invertebrate fauna are typical of a low-energy deep outer shelf/ramp(below the storm wave-base)setting.展开更多
基金supported by the General Directorate of Scientific Research and Technological Development“DGRSDT”(Algeria) to Imad Bouchemla and Madani Benyoucefthe Fundamental Research Funds for the Universities of Henan Province (NSFRF200340)+1 种基金the Program for Innovative Research Team (in Science and Technology) of Henan Polytechnic University(T2022-5) to Li-Jun Zhang“Male Projekty 2022”(Faculty of Natural Sciences, University of Silesia in Katowice) to Mariusz A. Salamon。
文摘Early Cretaceous succession of the Oued Fodda Formation in the Ouarsenis Mountains(northwestern Algeria) is mainly composed of marl—limestone alternations, which are subdivided into four informal units(Units 1 to 4), based on distinct lithological, stratonomical, and ichnological features. The ichnological analysis reveals a low diversity of the trace-fossil assemblage, which is exclusively reported from Units 2 and 3.The ichnoassemblage contains six ichnotaxa(Chondrites intricatus, Ophiomorpha isp., Planolites isp., Thalassinoides isp., Zoophycos brianteus, and Zoophycos cauda-galli), among which Zoophycos and Chondrites are the most common elements of the assemblage and occur in distinct mud-rich substrates showing different bioturbation intensities. The development of Zoophycos in the middle part of Unit 2 shows a high degree of bioturbation(bioturbation index(BI) = 4). Zoophycos specimens are of large size, between 45 cm and 75 cm in width, which were interpreted to have formed in a lower offshore environment where the oxygenation amount was optimal, the sedimentation rate was low, and the benthic food was abundant on the seafloor. Toward the upper part of Unit 2, Zoophycos-bearing levels exhibit a less intense degree of bioturbation(BI between 1 and2) in contrast to Planolites-and Chondrites-bearing levels which have a bioturbation index(BI) between 3 and4. At these levels, Zoophycos displays relatively small, coiled to U-shaped spreiten, probably in response to stressful and dysoxic conditions prevailing in the water bottom. With improved oxygenation in a quiet lower offshore to shelf margin environment in Unit 3, the benthic organisms recovered, as represented by medium to large size Zoophycos in association with Ophiomorpha and scarce Chondrites burrows, even if the overall bioturbation intensity is very low. The combination of trace-fossil assemblage and lithofacies of the Oued Fodda Formation indicates relatively stable outer shelf environments below the storm wave base, which corresponds classically to the lower offshore to shelf edge environments, and the prevailing palaeoecological conditions are optimal and stressful for the benthic organisms.
基金supported by the ‘Male Projekty Badawcze 2022’(Faculty of Natural Sciences,University of Silesia in Katowice) to Mariusz A. Salamonfinancially supported by the statutory activities of the Institute of Botany,Faculty of Biology,Jagiellonian University in Krakow(N18/DBS/000002) to Bartosz J. PlachnoAGH-UST Grant No. 16.16.140.315 to Marcin Krajewski。
文摘The thiolliericrinids(Thiolliericrinidae) are comatulids(Comatulida),which retained their stalks as adults.Here,we report a centrodorsal from the Bajocian strata(Middle Jurassic) of the Djebel Kérdacha area,northwestern Algeria(Africa).It is the first thiolliericrinid report from outside of Europe and also the oldest representative of the Thiolliericrinidae whose first occurrence is from the Oxfordian.The crinoid is assigned to Copernicrinus zamorae gen.et sp.nov.The reported new taxon shows strong similarities with the stemless ‘true’comatulids,Solanocrinites;the only difference is the presence of a facet to the stem in Copernicrinus.The closest comparable thiolliericrinid to Copernicrinus is the Oxfordian Thiolliericrinus,interpreted as a descendant of the latter.The origin and overview of all thiolliericrinid representatives are also discussed herein.
基金supported by the National Science CentrePoland (www.ncn.gov.pl)-Grant No.2020/39/B/ST10/00006。
文摘Sheltered preservation,in which organisms are trapped within shells of cephalopods,is a wellknown phenomenon.This preservational style constitutes an important source of paleontological data.Here,we report the first crinoid preserved inside the early Albian ammonite Cleoniceras besairiei Collignon from Madagascar.This crinoid is assigned to the aspidocrinid phyllocrinid(Apsidocrinus,Phyllocrinidae),and constitutes the first phyllocrinid from the African continent,the second from the southern margin of the Tethys(after New Zealand),and also from the southern hemisphere.This specimen represents the youngest occurrence of a phyllocrinid in the world as well,and constitutes one of the youngest occurrences of cyrtocrinids from shallow sea environments,before predation-induced migration of the stalked crinoids to the deep sea refugia due to the so-called Mesozoic Marine Revolution.This finding highlights that ammonite shells may also be a convenient material for studying echinoderms.
基金supported by the National Science Centre,Poland(www.ncn.gov.pl)-Grant No.2020/39/B/ST10/00006.
文摘The marl and limestone alternations of the Lower Jurassic Ain Ouarka and Ain Rhezala formations(Pliensbachian-Toarcian)in the western Saharan Atlas,Northwest Algeria,yield a diverse micro-and mac-rofauna,including moderately numerous crinoids,which are represented by remains of isocrinids,i.e.,Bal-anocrinus ticinensis Hess and columnals of the genus Percevalicrinus.So far,the latter genus has been observed from the Upper Jurassic-Lower Cretaceous strata of Eurasia,North America,and the African continent.Thus,the present find is the oldest record of this crinoid genus,and the second one from the southern Tethyan margin.In this paper,it is shown that Percevalicrinus,which is traditionally regarded as a representative of the subfamily Balanocrininae,displays several features of the subfamily Isocrininae.The crinoid assemblage and associated facies and invertebrate fauna are typical of a low-energy deep outer shelf/ramp(below the storm wave-base)setting.
