All intelligent organisms presumably originally have a number of inherited behavior patterns (IBP... more All intelligent organisms presumably originally have a number of inherited behavior patterns (IBPs) that are not fine-tuned for conditions prevailing in civilized communities. Indeed, some IBPs may be highly incompatible with such conditions and have high potential to induce self-destruction. These patterns may include responses of social organisms seeking power over conspecifics in relation to harvesting and consuming energy. It is possible that all emerging civilizations could face problems associated with incompatible IBPs, which may partially explain why civilizations are apparently rare (since we have not detected any others in our galaxy).
Rare Oichnus simplex drill holes occur in mature obolid shells from the Cambrian/Ordovician bound... more Rare Oichnus simplex drill holes occur in mature obolid shells from the Cambrian/Ordovician boundary beds of northern Estonia (Iru and Ülgase) and the uppermost Cambrian of NW Russia (Lava River). The drill holes are significantly more common in the central rather than the marginal regions of the obolid valves. Drilling predators attacked Ungula ingrica in the Kallavere Formation and Ungula convexa in the Ladoga Formation. Failed predatory attacks on obolids were relatively common in the latest Cambrian-earliest Tremadocian of Estonia. Presumably drilling predators at Lava River and Iru differed from those at the Ülgase as indicated by significant differences in drill hole sizes at these locations. Most likely some types of worms preyed on obolids in the latest Cambrian-earliest Tremadocian of Estonia and latest Cambrian of NW Russia. The predation rate (6% to 9%) of studied obolids indicates that they likely had an epibenthic life mode. In addition to Oichnus drill holes in the obolids, there are also common pseudoborings caused by mineral dissolution.
Oligochaetes, despite their important role in terrestrial ecosystems and a tremendous biomass, ar... more Oligochaetes, despite their important role in terrestrial ecosystems and a tremendous biomass, are extremely rare fossils. The palaeontological record of these worms is restricted to some cocoons, presumable trace fossils and a few body fossils the most convincing of which are discovered in Mesozoic and Cenozoic strata. The Olenekian (Lower Triassic) siliciclastic lacustrine Petropavlovka Lagerstätte of the southern Cis-Urals yields a number of extraordinary freshwater fossils including an annelid. The segmented body with a secondary annulation of this fossil, a subtriangular prostomium, a relatively thick layered body wall and, possibly, the presence of a genital region point to its oligochaete affinities. Other fossil worms which have been ascribed to clitellates are reviewed and, with a tentative exception of two Pennsylvanian finds, affinities of any pre-Mesozoic forms to clitellate annelids are rejected. The new fossil worm allows tracing of a persuasive oligochaete record to the lowermost Mesozoic and confirms a plausibility of the origin of this annelid group in freshwater conditions. See SOM at http://www.app.pan.pl/archive/published/SOM/app65-Shcherbakov_SOM.pdf
The Messinian diatomaceous deposits are widely exposed in the Lower Chelif Basin (NW-Algeria). Th... more The Messinian diatomaceous deposits are widely exposed in the Lower Chelif Basin (NW-Algeria). The upper part of the Diatomaceous Formation is intercalated by four diatomaceous beds rich in Zoophycos and Chondrites. Both these traces were produced by the members of endo-benthonic fauna adapted to nutrient exploitation within sediments. In the Diatomaceous Formation, larger dark-coloured Chondrites targionii cross-cuts smaller C. in-tricatus, which could indicate ecological succession perhaps due to conditions getting less oxygenated and causing the need for larger burrows. Size increase of Zoophycos upwards in the section may indicate that environment became less stressed, shallower and likely had a higher nutrient content or alternatively there was a change in the trace-maker biological affinity. The depositional environment shows some evidence of low-oxy-genated to dysoxic conditions, because abundant Chondrites occurs without any other trace fossils with the exception of Zoophycos. Chondrites trace-makers likely maintained a connection to oxygenated water but penetrate into anoxic sediments rich in sulfides or ammonium that are required for microbe-breeding and feeding. Most likely studied Zoophycos-Chondrites and pure Zoophycos associations of the Upper Member of the Diatomaceous Formation are of deeper shelf origin. The diatomaceous volcanic ash beds of the upper part of the formation are intensively bioturbated by a horizontal network of large-size Thalassinoides, which represents domichnial and fodinichnial structures, and suggesting an enough oxygenated environment with sufficient nutrients. Thalassinoides level likely represents shallower water conditions (shallow shelf) than the underlying levels characterised with Zoophycos-Chondrites and Zoophycos associations.
Ten distinct microstructures occur in fossil serpulids and serpulid tubes can contain several lay... more Ten distinct microstructures occur in fossil serpulids and serpulid tubes can contain several layers with different microstructures. Diversity and complexity of serpulid skeletal structures has greatly increased throughout their evolution. In general, Cenozoic serpulid skeletal structures are better preserved than Mesozoic ones. The first complex serpulid microstructures comparable to those of complex structures of molluscs appeared in the Eocene. The evolution of serpulid tube microstructures can be explained by the importance of calcareous tubes for serpulids as protection against predators and environmental disturbances. Both fossil cirratulids and sabellids are single layered and have only spherulitic prismatic tube microstructures. Microstructures of sabellids and cirratulids have not evolved since the appearance of calcareous species in the Jurassic and Oligocene, respectively. The lack of evolution in sabellids and cirratulids may result from the unimportance of biomineralization for these groups as only few species of sabellids and cirratulids have ever built calcareous tubes.
The trepostome bryozoans Diplotrypa abnormis, D. bicornis, D. petropolitana, Esthoniopora communi... more The trepostome bryozoans Diplotrypa abnormis, D. bicornis, D. petropolitana, Esthoniopora communis, E. subsphaerica, Mesotrypa excentrica, M. expressa, M. raritabulata, and Monotrypa jewensis have symbiotic associations with the conulariid Climacoconus bottnicus in the Upper Ordovician of Estonia. All bryoimmured conulariids are very small and oriented perpendicular (or nearly so) to the growth surface of the host trepostome colony. Muddy seafloors may have promoted this symbiosis between conulariids and bryozoans because the former required a hard substrate for attachment. It is possible that the numerous smaller specimens among endobiotic conulariids usually died as juveniles together with their bryozoan host, or alternatively, the smaller endobiotic conulariids may have been Lilliput forms of free-living conulariids that died at a mature age. Conulariid-trepostome associations were likely not a result of accidental intergrowth of two organisms. Additional protection against predators provided by the calcitic bryozoan skeleton may have been among the benefits for the conulariid symbionts. Usually trepostomes with conulariid symbionts do not contain other invertebrates, but in the Katian in some cases they also hosted Anoigmaichnus bioclaustrations. The exact type of symbiosis between trepostomes and conulariids remains unresolved, but most likely the associations were slightly parasitic or commensal. The available data suggest that bryozoans preferred cnidarians over the other invertebrates as symbionts.
A light grey nautiloid conch has a dark brown colony attached to its internal surface. This colon... more A light grey nautiloid conch has a dark brown colony attached to its internal surface. This colonial fossil resembles hederellids and bryozoans, but is in fact a crustoid graptolite (Hormograptus? sp.). The colony has been lithoimmured inside this nautiloid conch by early cementation. Crustoid graptolites were a part of the encrusting communities in the Middle Ordovician of Baltica, but their abundance among encrusters of biogenic substrates reached a peak in the middle Sandbian. The cryptic mode of life appeared very early in the evolution of the crustoids. The discovery of this crustoid graptolite in a nautiloid conch indicates that the Baltic Middle Ordovician cryptic communities were taxonomically more diverse than was known previously. The nautiloid conch studied is sparsely encrusted with an encrustation density that is similar to those of other Middle Ordovician cryptic surfaces described from Estonia.
Abstract: Lingulides from Lower Permian of Brazil (24% substrates) showed signs of bioerosion in ... more Abstract: Lingulides from Lower Permian of Brazil (24% substrates) showed signs of bioerosion in form of multiple small shallow pits that resemble incomplete Oichnus paraboloides borings. A single lingulide valve showed a centrally located large circular predatory Oichnus simplex boring. Several lin-gulide shells (c. 21%) show small Arachnostega traces in their interior. The diameter of Arachnostega burrows is relatively constant. These burrows are more similar to juvenile stages of Arachnostega gastrochaena and do not form well-developed meshwork of tunnels. This is the first record of Arachno-stega from the interior of lingulide shells and indicates that even very small lingulide shells were suitable substrates for cryptic organisms. Résumé : Ichnofossiles associés à des coquilles de lingulides du Permien inférieur du Bré-sil.-Les lingulides du Permien inférieur du Brésil (24% des substrats) portent des traces de bio-éro-sion sous forme de nombreux petits trous peu profonds qui ressemblent à des perforations incomplètes d'Oichnus paraboloides. Une seule coquille de lingulide montre une grande perforation prédatrice circu-laire d'Oichnus simplex localisée en son centre. Plusieurs coquilles de lingulides (environ 21%) présen-tent des traces d'Arachnostega à l'intérieur. Le diamètre des terriers d'Arachnostega est relativement constant. Ces terriers sont très semblables aux stades juvéniles d'Arachnostega gastrochaena et ne forment pas de réseaux de tunnels bien développés. C'est la première mention d'Arachnostega à l'inté-rieur de coquilles de lingulides et ce qui prouve que des coquilles de lingulides, même très petites, pouvaient constituer un substrat convenable pour des organismes cryptiques.
Warm-water Dasycladaceae algae Mastopora and Cyclocrinites were for the first time recorded from ... more Warm-water Dasycladaceae algae Mastopora and Cyclocrinites were for the first time recorded from the Takche Formation (Upper Ordovician-lower Silurian), Parahio Valley, Spiti, India. They are preserved as external and internal moulds of the non-globular or possibly bulb-like cortical skeleton showing flattened thalli with a high degree of compaction. The occurrence of abundant cyclocrinitid remains in the Takche Formation indicates that the Spiti region of the northwestern Himalaya must have been located at about 30° palaeolatitude during the Late Ordovician and early Silurian. The cyclocrinitids were warm-water algae and their extinction at the end of the Ordovician is related to cooling and glaciations. The cyclocrinitids in the Ordovician are known from several localities in central and southern Asia, including Kazakhstan and western China.
b bu ur rr ro ow ws s f fr ro om m c ca ar rb bo on na at te e r ro oc ck ks s o of f t th he e L... more b bu ur rr ro ow ws s f fr ro om m c ca ar rb bo on na at te e r ro oc ck ks s o of f t th he e L Lo ow we er r P Pa al le eo oz zo oi ic c o of f E Es st to on ni ia a Abstract: Teichichnus burrows occur in the Sandbian, Katian and Telychian of Estonia associated with carbonate rocks. It is possible that Teichichnus is more common in the Sandbian than in the Lower to Middle Ordovician and in the Silurian. Two ichnospecies, T. rectus and T. patens, have been identified from the Lower Paleozoic of Estonia. This is the first record of T. patens in the Ordovician of Baltica. Teichichnus in the Sandbian, Katian and Telychian of Estonia is restricted to the shallowest tier levels. The rarity of Teichichnus in the carbonate sequences of the Ordovician and Silurian of Estonia reflects little bathymetric variability and an extremely low sedimentation rate in the shallow epicontinental basin.
A new parasite trace fossil, Burrinjuckia clitambonitofilia ichnosp. nov., is described from the ... more A new parasite trace fossil, Burrinjuckia clitambonitofilia ichnosp. nov., is described from the ventral mantle cavity of the Sandbian (Late Ordovician) brachiopod Clitambonites squamatus. This is the earliest record of a parasite associated with a rhynchonelliform brachiopod. The parasite that produced Burrinjuckia clitambonitofilia caused damage to the ventral mantle of C. squamatus, used brachiopod resources for building its mineralized domicile, and likely stole food from the host's inhalant currents. Predation pressure and the need for easily exploited food resources (i.e., brachiopod-created nutrient flow) may have been the primary driving forces behind the evolution of brachiopod parasites.
Four cornulitid species occur in the Rakvere Regional Stage in NW Russia. The new species Conchic... more Four cornulitid species occur in the Rakvere Regional Stage in NW Russia. The new species Conchicolites rossicus is here described; it is the earliest known Conchicolites from the Ordovician of Baltica. The new species has very small tubes with sharp, strong and regular annulations. The diversity of cornulitids in the Rakvere Regional Stage at the Pechurki quarry is usual for the Upper Ordovician of Baltica. The cornulitids of Pechurki quarry encrusted hard organic substrates in a mud bottom (clay and carbonate clay) environment. Cornulites sterlingensis occurs both in the Upper Ordovician of North America and Baltica, which suggest a short distance between these two paleocontinents and/or similar environmental conditions.
The earliest cornulitid Cornulites sp. appears in the Darriwilian (Lasnamägi Regional Stage) of E... more The earliest cornulitid Cornulites sp. appears in the Darriwilian (Lasnamägi Regional Stage) of Estonia. Internal annulation is present in all Middle Ordovician cornulitids and could be a plesiomorphic character for the group. The encrusted trilobites are rare in the Ordovician of Estonia. Illaenid pygidia and cranidia were encrusted by cornulitids and trepostome bryozoans. The encrustation of both Middle Ordovician and Late Ordovician trilobites took place post mortem. The studied hard substrate communities of Middle Ordovician and Late Ordovician trilobite pygidia and cranidia are typical of the Ordovician.
Two relatively large specimens of the rugosan Lambelasma sp. are fully intergrown with the bryozo... more Two relatively large specimens of the rugosan Lambelasma sp. are fully intergrown with the bryozoan Stigmatella massalis colony. The intergrown specimen occurs in the Oandu Regional Stage (lower Katian) of Estonia and constitutes the earliest record of bryozoan-rugosan intergrowth from Baltica. Most likely this symbiotic association was accidental. Rugosans presumably benefitted from the bryozoan, which served as an anchor to stabilize them in hydrodynamically active waters. The lack of malformations and no decrease in the size of bryozoan zooids near the rugosans indicate a lack of negative effect of the rugosans on the bryozoan. Bryozoan-rugosan symbiosis is only known from the Ordovician of Baltica and Laurentia.
Skolithos burrows indicate high-energy nearshore environment. In this paper, abundant Scolithos b... more Skolithos burrows indicate high-energy nearshore environment. In this paper, abundant Scolithos burrows from two particular levels of the Cambrian–Ordovician boundary interval of the Central Anti-Atlas, Morocco, are described for the first time. The first level occurs at the boundary between the Azlag Formation and Jbel Lmgaysmat Formation (Furongian), where the burrows are 5–80 cm long and 3–7 mm wide, straight to slightly curved, with mostly circular, but sometimes also oval apertures. The second level occurs within the unconformity underlining the Tremadocian cycle (Fezouata Shale). The burrows of Skolithos linearis associated with that level are straight to slightly curved, 2–15 cm long and 2–4 mm wide. The absence of encrustation above the burrowed beds indicates that these traces were made in a soft sediment.
Organisms of unknown biological affinity are widespread in Paleozoic ecosystems and play key ecol... more Organisms of unknown biological affinity are widespread in Paleozoic ecosystems and play key ecological roles. Recognition of these roles relies on consistent identification and sound taxonomy, yet many microproblematica lack complex morphological features that could be the basis for qualitative taxonomic diagnoses. Allonema is an incertae sedis calcareous sclerobiont widespread in Paleozoic carbonates. At least seven species of Allonema have been proposed, but their diagnoses based on size ranges overlap. In this work, dimensions of 590 individuals from the Silurian of Estonia and Sweden have been measured. Regression analysis of the dimensions revealed two groups, overlapping in size ranges, but differing significantly in proportions. These groups could be matched with previously described A. botellus and A. moniliforme, but both showed a wider range of sizes than previously reported. Another previously described species , A. minimum, fell within the range of dimensions of A. moniliforme and is proposed to be its junior synonym. Differences in proportions revealed in the study do not seem to be dependent on sedimentary environment or local growth conditions such as competition for space, and thus may represent consistent interspecific variability. Although the affinity of Allonema remains unknown, this quantitative approach to its taxonomy reduces unnecessary species in the genus. The success of this approach may encourage its application to other microproblematica populating the fossil record. •
All intelligent organisms presumably originally have a number of inherited behavior patterns (IBP... more All intelligent organisms presumably originally have a number of inherited behavior patterns (IBPs) that are not fine-tuned for conditions prevailing in civilized communities. Indeed, some IBPs may be highly incompatible with such conditions and have high potential to induce self-destruction. These patterns may include responses of social organisms seeking power over conspecifics in relation to harvesting and consuming energy. It is possible that all emerging civilizations could face problems associated with incompatible IBPs, which may partially explain why civilizations are apparently rare (since we have not detected any others in our galaxy).
Rare Oichnus simplex drill holes occur in mature obolid shells from the Cambrian/Ordovician bound... more Rare Oichnus simplex drill holes occur in mature obolid shells from the Cambrian/Ordovician boundary beds of northern Estonia (Iru and Ülgase) and the uppermost Cambrian of NW Russia (Lava River). The drill holes are significantly more common in the central rather than the marginal regions of the obolid valves. Drilling predators attacked Ungula ingrica in the Kallavere Formation and Ungula convexa in the Ladoga Formation. Failed predatory attacks on obolids were relatively common in the latest Cambrian-earliest Tremadocian of Estonia. Presumably drilling predators at Lava River and Iru differed from those at the Ülgase as indicated by significant differences in drill hole sizes at these locations. Most likely some types of worms preyed on obolids in the latest Cambrian-earliest Tremadocian of Estonia and latest Cambrian of NW Russia. The predation rate (6% to 9%) of studied obolids indicates that they likely had an epibenthic life mode. In addition to Oichnus drill holes in the obolids, there are also common pseudoborings caused by mineral dissolution.
Oligochaetes, despite their important role in terrestrial ecosystems and a tremendous biomass, ar... more Oligochaetes, despite their important role in terrestrial ecosystems and a tremendous biomass, are extremely rare fossils. The palaeontological record of these worms is restricted to some cocoons, presumable trace fossils and a few body fossils the most convincing of which are discovered in Mesozoic and Cenozoic strata. The Olenekian (Lower Triassic) siliciclastic lacustrine Petropavlovka Lagerstätte of the southern Cis-Urals yields a number of extraordinary freshwater fossils including an annelid. The segmented body with a secondary annulation of this fossil, a subtriangular prostomium, a relatively thick layered body wall and, possibly, the presence of a genital region point to its oligochaete affinities. Other fossil worms which have been ascribed to clitellates are reviewed and, with a tentative exception of two Pennsylvanian finds, affinities of any pre-Mesozoic forms to clitellate annelids are rejected. The new fossil worm allows tracing of a persuasive oligochaete record to the lowermost Mesozoic and confirms a plausibility of the origin of this annelid group in freshwater conditions. See SOM at http://www.app.pan.pl/archive/published/SOM/app65-Shcherbakov_SOM.pdf
The Messinian diatomaceous deposits are widely exposed in the Lower Chelif Basin (NW-Algeria). Th... more The Messinian diatomaceous deposits are widely exposed in the Lower Chelif Basin (NW-Algeria). The upper part of the Diatomaceous Formation is intercalated by four diatomaceous beds rich in Zoophycos and Chondrites. Both these traces were produced by the members of endo-benthonic fauna adapted to nutrient exploitation within sediments. In the Diatomaceous Formation, larger dark-coloured Chondrites targionii cross-cuts smaller C. in-tricatus, which could indicate ecological succession perhaps due to conditions getting less oxygenated and causing the need for larger burrows. Size increase of Zoophycos upwards in the section may indicate that environment became less stressed, shallower and likely had a higher nutrient content or alternatively there was a change in the trace-maker biological affinity. The depositional environment shows some evidence of low-oxy-genated to dysoxic conditions, because abundant Chondrites occurs without any other trace fossils with the exception of Zoophycos. Chondrites trace-makers likely maintained a connection to oxygenated water but penetrate into anoxic sediments rich in sulfides or ammonium that are required for microbe-breeding and feeding. Most likely studied Zoophycos-Chondrites and pure Zoophycos associations of the Upper Member of the Diatomaceous Formation are of deeper shelf origin. The diatomaceous volcanic ash beds of the upper part of the formation are intensively bioturbated by a horizontal network of large-size Thalassinoides, which represents domichnial and fodinichnial structures, and suggesting an enough oxygenated environment with sufficient nutrients. Thalassinoides level likely represents shallower water conditions (shallow shelf) than the underlying levels characterised with Zoophycos-Chondrites and Zoophycos associations.
Ten distinct microstructures occur in fossil serpulids and serpulid tubes can contain several lay... more Ten distinct microstructures occur in fossil serpulids and serpulid tubes can contain several layers with different microstructures. Diversity and complexity of serpulid skeletal structures has greatly increased throughout their evolution. In general, Cenozoic serpulid skeletal structures are better preserved than Mesozoic ones. The first complex serpulid microstructures comparable to those of complex structures of molluscs appeared in the Eocene. The evolution of serpulid tube microstructures can be explained by the importance of calcareous tubes for serpulids as protection against predators and environmental disturbances. Both fossil cirratulids and sabellids are single layered and have only spherulitic prismatic tube microstructures. Microstructures of sabellids and cirratulids have not evolved since the appearance of calcareous species in the Jurassic and Oligocene, respectively. The lack of evolution in sabellids and cirratulids may result from the unimportance of biomineralization for these groups as only few species of sabellids and cirratulids have ever built calcareous tubes.
The trepostome bryozoans Diplotrypa abnormis, D. bicornis, D. petropolitana, Esthoniopora communi... more The trepostome bryozoans Diplotrypa abnormis, D. bicornis, D. petropolitana, Esthoniopora communis, E. subsphaerica, Mesotrypa excentrica, M. expressa, M. raritabulata, and Monotrypa jewensis have symbiotic associations with the conulariid Climacoconus bottnicus in the Upper Ordovician of Estonia. All bryoimmured conulariids are very small and oriented perpendicular (or nearly so) to the growth surface of the host trepostome colony. Muddy seafloors may have promoted this symbiosis between conulariids and bryozoans because the former required a hard substrate for attachment. It is possible that the numerous smaller specimens among endobiotic conulariids usually died as juveniles together with their bryozoan host, or alternatively, the smaller endobiotic conulariids may have been Lilliput forms of free-living conulariids that died at a mature age. Conulariid-trepostome associations were likely not a result of accidental intergrowth of two organisms. Additional protection against predators provided by the calcitic bryozoan skeleton may have been among the benefits for the conulariid symbionts. Usually trepostomes with conulariid symbionts do not contain other invertebrates, but in the Katian in some cases they also hosted Anoigmaichnus bioclaustrations. The exact type of symbiosis between trepostomes and conulariids remains unresolved, but most likely the associations were slightly parasitic or commensal. The available data suggest that bryozoans preferred cnidarians over the other invertebrates as symbionts.
A light grey nautiloid conch has a dark brown colony attached to its internal surface. This colon... more A light grey nautiloid conch has a dark brown colony attached to its internal surface. This colonial fossil resembles hederellids and bryozoans, but is in fact a crustoid graptolite (Hormograptus? sp.). The colony has been lithoimmured inside this nautiloid conch by early cementation. Crustoid graptolites were a part of the encrusting communities in the Middle Ordovician of Baltica, but their abundance among encrusters of biogenic substrates reached a peak in the middle Sandbian. The cryptic mode of life appeared very early in the evolution of the crustoids. The discovery of this crustoid graptolite in a nautiloid conch indicates that the Baltic Middle Ordovician cryptic communities were taxonomically more diverse than was known previously. The nautiloid conch studied is sparsely encrusted with an encrustation density that is similar to those of other Middle Ordovician cryptic surfaces described from Estonia.
Abstract: Lingulides from Lower Permian of Brazil (24% substrates) showed signs of bioerosion in ... more Abstract: Lingulides from Lower Permian of Brazil (24% substrates) showed signs of bioerosion in form of multiple small shallow pits that resemble incomplete Oichnus paraboloides borings. A single lingulide valve showed a centrally located large circular predatory Oichnus simplex boring. Several lin-gulide shells (c. 21%) show small Arachnostega traces in their interior. The diameter of Arachnostega burrows is relatively constant. These burrows are more similar to juvenile stages of Arachnostega gastrochaena and do not form well-developed meshwork of tunnels. This is the first record of Arachno-stega from the interior of lingulide shells and indicates that even very small lingulide shells were suitable substrates for cryptic organisms. Résumé : Ichnofossiles associés à des coquilles de lingulides du Permien inférieur du Bré-sil.-Les lingulides du Permien inférieur du Brésil (24% des substrats) portent des traces de bio-éro-sion sous forme de nombreux petits trous peu profonds qui ressemblent à des perforations incomplètes d'Oichnus paraboloides. Une seule coquille de lingulide montre une grande perforation prédatrice circu-laire d'Oichnus simplex localisée en son centre. Plusieurs coquilles de lingulides (environ 21%) présen-tent des traces d'Arachnostega à l'intérieur. Le diamètre des terriers d'Arachnostega est relativement constant. Ces terriers sont très semblables aux stades juvéniles d'Arachnostega gastrochaena et ne forment pas de réseaux de tunnels bien développés. C'est la première mention d'Arachnostega à l'inté-rieur de coquilles de lingulides et ce qui prouve que des coquilles de lingulides, même très petites, pouvaient constituer un substrat convenable pour des organismes cryptiques.
Warm-water Dasycladaceae algae Mastopora and Cyclocrinites were for the first time recorded from ... more Warm-water Dasycladaceae algae Mastopora and Cyclocrinites were for the first time recorded from the Takche Formation (Upper Ordovician-lower Silurian), Parahio Valley, Spiti, India. They are preserved as external and internal moulds of the non-globular or possibly bulb-like cortical skeleton showing flattened thalli with a high degree of compaction. The occurrence of abundant cyclocrinitid remains in the Takche Formation indicates that the Spiti region of the northwestern Himalaya must have been located at about 30° palaeolatitude during the Late Ordovician and early Silurian. The cyclocrinitids were warm-water algae and their extinction at the end of the Ordovician is related to cooling and glaciations. The cyclocrinitids in the Ordovician are known from several localities in central and southern Asia, including Kazakhstan and western China.
b bu ur rr ro ow ws s f fr ro om m c ca ar rb bo on na at te e r ro oc ck ks s o of f t th he e L... more b bu ur rr ro ow ws s f fr ro om m c ca ar rb bo on na at te e r ro oc ck ks s o of f t th he e L Lo ow we er r P Pa al le eo oz zo oi ic c o of f E Es st to on ni ia a Abstract: Teichichnus burrows occur in the Sandbian, Katian and Telychian of Estonia associated with carbonate rocks. It is possible that Teichichnus is more common in the Sandbian than in the Lower to Middle Ordovician and in the Silurian. Two ichnospecies, T. rectus and T. patens, have been identified from the Lower Paleozoic of Estonia. This is the first record of T. patens in the Ordovician of Baltica. Teichichnus in the Sandbian, Katian and Telychian of Estonia is restricted to the shallowest tier levels. The rarity of Teichichnus in the carbonate sequences of the Ordovician and Silurian of Estonia reflects little bathymetric variability and an extremely low sedimentation rate in the shallow epicontinental basin.
A new parasite trace fossil, Burrinjuckia clitambonitofilia ichnosp. nov., is described from the ... more A new parasite trace fossil, Burrinjuckia clitambonitofilia ichnosp. nov., is described from the ventral mantle cavity of the Sandbian (Late Ordovician) brachiopod Clitambonites squamatus. This is the earliest record of a parasite associated with a rhynchonelliform brachiopod. The parasite that produced Burrinjuckia clitambonitofilia caused damage to the ventral mantle of C. squamatus, used brachiopod resources for building its mineralized domicile, and likely stole food from the host's inhalant currents. Predation pressure and the need for easily exploited food resources (i.e., brachiopod-created nutrient flow) may have been the primary driving forces behind the evolution of brachiopod parasites.
Four cornulitid species occur in the Rakvere Regional Stage in NW Russia. The new species Conchic... more Four cornulitid species occur in the Rakvere Regional Stage in NW Russia. The new species Conchicolites rossicus is here described; it is the earliest known Conchicolites from the Ordovician of Baltica. The new species has very small tubes with sharp, strong and regular annulations. The diversity of cornulitids in the Rakvere Regional Stage at the Pechurki quarry is usual for the Upper Ordovician of Baltica. The cornulitids of Pechurki quarry encrusted hard organic substrates in a mud bottom (clay and carbonate clay) environment. Cornulites sterlingensis occurs both in the Upper Ordovician of North America and Baltica, which suggest a short distance between these two paleocontinents and/or similar environmental conditions.
The earliest cornulitid Cornulites sp. appears in the Darriwilian (Lasnamägi Regional Stage) of E... more The earliest cornulitid Cornulites sp. appears in the Darriwilian (Lasnamägi Regional Stage) of Estonia. Internal annulation is present in all Middle Ordovician cornulitids and could be a plesiomorphic character for the group. The encrusted trilobites are rare in the Ordovician of Estonia. Illaenid pygidia and cranidia were encrusted by cornulitids and trepostome bryozoans. The encrustation of both Middle Ordovician and Late Ordovician trilobites took place post mortem. The studied hard substrate communities of Middle Ordovician and Late Ordovician trilobite pygidia and cranidia are typical of the Ordovician.
Two relatively large specimens of the rugosan Lambelasma sp. are fully intergrown with the bryozo... more Two relatively large specimens of the rugosan Lambelasma sp. are fully intergrown with the bryozoan Stigmatella massalis colony. The intergrown specimen occurs in the Oandu Regional Stage (lower Katian) of Estonia and constitutes the earliest record of bryozoan-rugosan intergrowth from Baltica. Most likely this symbiotic association was accidental. Rugosans presumably benefitted from the bryozoan, which served as an anchor to stabilize them in hydrodynamically active waters. The lack of malformations and no decrease in the size of bryozoan zooids near the rugosans indicate a lack of negative effect of the rugosans on the bryozoan. Bryozoan-rugosan symbiosis is only known from the Ordovician of Baltica and Laurentia.
Skolithos burrows indicate high-energy nearshore environment. In this paper, abundant Scolithos b... more Skolithos burrows indicate high-energy nearshore environment. In this paper, abundant Scolithos burrows from two particular levels of the Cambrian–Ordovician boundary interval of the Central Anti-Atlas, Morocco, are described for the first time. The first level occurs at the boundary between the Azlag Formation and Jbel Lmgaysmat Formation (Furongian), where the burrows are 5–80 cm long and 3–7 mm wide, straight to slightly curved, with mostly circular, but sometimes also oval apertures. The second level occurs within the unconformity underlining the Tremadocian cycle (Fezouata Shale). The burrows of Skolithos linearis associated with that level are straight to slightly curved, 2–15 cm long and 2–4 mm wide. The absence of encrustation above the burrowed beds indicates that these traces were made in a soft sediment.
Organisms of unknown biological affinity are widespread in Paleozoic ecosystems and play key ecol... more Organisms of unknown biological affinity are widespread in Paleozoic ecosystems and play key ecological roles. Recognition of these roles relies on consistent identification and sound taxonomy, yet many microproblematica lack complex morphological features that could be the basis for qualitative taxonomic diagnoses. Allonema is an incertae sedis calcareous sclerobiont widespread in Paleozoic carbonates. At least seven species of Allonema have been proposed, but their diagnoses based on size ranges overlap. In this work, dimensions of 590 individuals from the Silurian of Estonia and Sweden have been measured. Regression analysis of the dimensions revealed two groups, overlapping in size ranges, but differing significantly in proportions. These groups could be matched with previously described A. botellus and A. moniliforme, but both showed a wider range of sizes than previously reported. Another previously described species , A. minimum, fell within the range of dimensions of A. moniliforme and is proposed to be its junior synonym. Differences in proportions revealed in the study do not seem to be dependent on sedimentary environment or local growth conditions such as competition for space, and thus may represent consistent interspecific variability. Although the affinity of Allonema remains unknown, this quantitative approach to its taxonomy reduces unnecessary species in the genus. The success of this approach may encourage its application to other microproblematica populating the fossil record. •
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Papers by Olev Vinn
See SOM at
http://www.app.pan.pl/archive/published/SOM/app65-Shcherbakov_SOM.pdf
See SOM at
http://www.app.pan.pl/archive/published/SOM/app65-Shcherbakov_SOM.pdf