| 1. |
- Helander, Björn, et al.
(författare)
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Undersökning av skalförändringar hos havsörn
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Abnorm uttorkning av äggen var ett problem av mycket stor omfattning hos havsörnar vid Östersjökusten under 1960 -70- och -80talet. Problemet har kopplats till påverkan från miljögifter och starkast samband har visats för DDE. Förekomsten av uttorkade ägg minskade under 1980-talet och försvann i stort sett under 1990-talet i beståndet. Detta har tolkats som ett resultat av att de gamla honor som uppvisade dessa problem med äggen successivt ersattes med yngre fåglar som inte hade utsatts för samma belastningsnivåer av miljögifter under sin levnad. Efter att ha varit helt borta under nära 20 års tid har kraftigt uttorkade ägg åter påträffats under den senaste femårsperioden (2009-2013) . Samtliga fall hittills kommer från Bottenhavskusten (Gävleborgs och Västernorrlands län).Onormal uttorkning av äggen kopplar till förändringar i skalstrukturen som medför en ökad permeabilitet genom skalet. Något samband med den skalförtunning - som sedan länge varit känd som en effekt av DDE hos flera (men inte alla) fågelgrupper - har inte visat sig finnas. Fenomenet med uttorkning av äggen har inte heller uppmärksammats tidigare hos vildlevande fåglar. Hos våra havsörnar vid Östersjökusten är uttorkning av äggen den parameter som visat starkast koppling till den starkt nedsatta fortplantningen under 40 års tid. De strukturella förändringar i skalen som gett upphov till detta har dock inte studerats tidigare i havsörnsäggen.Syftet med studien som redovisas i denna rapport är att belysa skillnader i skalstrukturer som kan förklara uttorkning hos vissa ägg jämfört med normala ägg.
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| 2. |
- Kouchinsky, Artem, et al.
(författare)
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A Middle Cambrian fauna of skeletal fossils from the Kuonamka Formation, northern Siberia.
- 2011
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Ingår i: Alcheringa. - : Informa UK Limited. - 0311-5518 .- 1752-0754. ; 35:1, s. 123-189
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Tidskriftsartikel (refereegranskat)abstract
- An assemblage of mineralized skeletal fossils containing molluscs, hyoliths, chancelloriids, protoconodonts, lobopods, paleoscolecids, bradoriids, echinoderms and hexactinellid sponges is described from the middle Cambrian part of the Kuonamka Formation, exposed along the Malaya Kuonamka and Bol’shaya Kuonamka rivers, northern Siberian Platform. The sampled succession is attributed to the Kuonamkites and lower Tomagnostus fissus–Paradoxides sacheri biozones of the Amgan Stage of Siberia, correlated with Series 3, Stage 5—lower Drumian Stage of the IUGS chronostratigraphical scheme for the Cambrian. This work complements descriptions of molluscs from the same samples published by Gubanov et al. (2004) with additional material. It contains forms in common with coeval faunas from Australia, China, Western Gondwana, Avalonia, Laurentia and Baltica, increasing potential for global biostratigraphic correlation and understanding of palaeogeographic connections.
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| 3. |
- Kouchinsky, Artem, et al.
(författare)
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An early Cambrian fauna of skeletal fossils from the Emyaksin Formation, northern Siberia.
- 2015
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Ingår i: Acta Palaeontologica Polonica. - : Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). - 0567-7920 .- 1732-2421. ; 60:2, s. 421-512
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Tidskriftsartikel (refereegranskat)abstract
- An assemblage of mineralised skeletal fossils containing molluscs, hyoliths, halkieriids, chancelloriids, tommotiids, lobopodians, paleoscolecids, bradoriids, echinoderms, anabaritids, hyolithelminths, hexactinnelid, and heteractinid sponges is described from the early Cambrian Emyaksin Formation exposed along the Malaya Kuonamka and Bol’shaya Kuonamka rivers, eastern flanks of the Anabar Uplift, northern Siberian Platform. The sampled succession is attributed to the Tommotian–Botoman Stages of Siberia and correlated with Stage 2 of Series 1–Stage 4 of Series 2 of the IUGS chronostratigraphical scheme for the Cambrian. Carbon isotope chemostratigraphy is applied herein for regional correlation. The fauna contains the earliest Siberian and probably global first appearances of lobopodians, paleoscolecids, and echinoderms, and includes elements in common with coeval faunas from Gondwana, Laurentia, and Baltica. For the first time from Siberia, the latest occurrence of anabaritids is documented herein from the Atdabanian Stage. Problematic calcium phosphatic sclerites of Fengzuella zhejiangensis have not been previously known from outside China. The sellate sclerites, Camenella garbowskae and mitral sclerites, C. kozlowskii are unified within one species, C. garbowskae. In addition to more common slender sclerites, Rhombocorniculum insolutum include broad calcium phosphatic sclerites. A number of fossils described herein demonstrate excellent preservation of fine details of skeletal microstructures. Based on new microstructural data, sclerites of Rhombocorniculum are interpreted as chaetae of the type occurring in annelids. A new mollusc Enigmaconus? pyramidalis Kouchinsky and Vendrasco sp. nov. and a hyolith Triplicatella papilio Kouchinsky sp. nov. are described.
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| 4. |
- Kouchinsky, Artem, et al.
(författare)
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Carbon isotope stratigraphy of the Precambrian-Cambrian Sukharikha River section, northwestern Siberian platform
- 2007
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Ingår i: Geological Magazine. - 0016-7568 .- 1469-5081. ; 144:4, s. 609-618
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Tidskriftsartikel (refereegranskat)abstract
- A high-resolution carbon isotope profile through the uppermost Neoproterozoic-Lower Cambrian part of the Sukharikha section at the northwestern margin of the Siberian platform shows prominent secular oscillations of delta C-13 with peak-to-peak range of 6-10 parts per thousand. There are six minima, In-6n, and seven maxima 1p-7p, in the Sukharikha Formation and a rising trend of VC from the minimum In of - 8.6 parts per thousand to maximum 6p of + 6.4 parts per thousand. The trough In probably coincides with the isotopic minimum at the Precambrian-Cambrian boundary worldwide. Highly positive delta C-13 values of peaks 5p and 6p are typical of the upper portion of the Precambrian-Cambrian transitional beds just beneath the Tommotian Stage in Siberia. A second rising trend of VC is observed through the Kxasnoporog and lower Shumny formations. It consists of four excursions with four major maxima that can be correlated with Tommotian-Botomian peaks II, IV, V, and VII of the reference profile from the southeastern Siberian platform. According to the chemostratigraphic correlation, the first appearances of the index forms of archaeocyaths are earlier in the Sukharikha section than in the Lena-Aldan reuion.
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| 5. |
- Kouchinsky, Artem, et al.
(författare)
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Chronology of early Cambrian biomineralization.
- 2012
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Ingår i: Geological Magazine. - 0016-7568. ; 149:2, s. 221-251
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Tidskriftsartikel (refereegranskat)abstract
- Data on the first appearances of major animal groups with mineralized skeletons on the Siberian Platform and worldwide are revised and summarized herein with references to an improved carbon isotope stratigraphy and radiometric dating in order to reconstruct the Cambrian radiation (popularly known as the ‘Cambrian explosion’) with a higher precision and provide a basis for the definition of Cambrian Stages 2 to 4. The Lophotrochozoa and, probably, Chaetognatha were first among protostomians to achieve biomineralization during the Terreneuvian Epoch, mainly the Fortunian Age. Fast evolutionary radiation within the Lophotrochozoa was followed by radiation of the sclerotized and biomineralized Ecdysozoa during Stage 3. The first mineralized skeletons of the Deuterostomia, represented by echinoderms, appeared in the middle of Cambrian Stage 3. The fossil record of sponges and cnidarians suggests that they acquired biomineralized skeletons in the late Neoproterozoic, but diversification of both definite sponges and cnidarians was in parallel to that of bilaterians. The distribution of calcium carbonate skeletal mineralogies from the upper Ediacaran to lower Cambrian reflects fluctuations in the global ocean chemistry and shows that the Cambrian radiation occurred mainly during a time of aragonite and high-magnesium calcite seas.
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| 6. |
- Kouchinsky, Artem, et al.
(författare)
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Early-middle Cambrian stratigraphy and faunas from northern Siberia
- 2022
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Ingår i: Acta Palaeontologica Polonica. - : Institute of Paleobiology, Polish Academy of Sciences. - 0567-7920 .- 1732-2421. ; 67:2, s. 341-464
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Tidskriftsartikel (refereegranskat)abstract
- New assemblages of skeletal fossils chemically extracted from carbonates of the Cambrian Stage 2-Drumian Stage are reported from the lower reaches of the Lena River as well as from the Khorbusuonka, Malaya Kuonamka, and Bol'shaya Kuonamka rivers in northern part of the Siberian Platform. The fauna studied with scanning electron microscopy includes brachiopods, molluscs, hyoliths, halkieriids, chancelloriids, tommotiids, lobopodians, palaeoscolecidans, bradoriids, echinoderms, anabaritids, hyolithelminths, and sponges showing similarity to previously described fossil assemblages from Siberia, Laurentia, and Gondwana. The material includes emended descriptions of Halkieria proboscidea, Hadimopanella knappologica, Archaeopetasus typicus, and first descriptions of Hadimopanella foveata Kouchinsky sp. nov. and Archaeopetasus pachybasalis Kouchinsky sp. nov. Affinity of Archaeopetasus to chancelloriids is suggested. Finding of an in-place operculum in a planispiral shell of Michniakia minuta enables reinterpretation of this form as a hyolith, not a mollusc. The cambroclavids Cambroclavus sp. and Zhijinites clavus and the earliest echinoderms belonging to the Rhombifera and Ctenocystoidea are reported respectively from the lower Botoman stage and Botoman-Toyonian transitional beds, correlated with Cambrian Stage 4. Carbon isotopes are analysed from sections of the Chuskuna (upper Kessyusa Group), Erkeket, Kuonamka, Olenyok, Yunkyulyabit-Yuryakh, Tyuser and Sekten formations. A major part of the delta C-13 record is obtained from the Cambrian Stage 4-Drumian Stage strata which remain incompletely characterised by chemostratigraphy. The Lower Anomocarioides limbataeformis Carbon isotope Excursion (LACE) from the Drumian Stage of the Khorbusuonka River is introduced herein. New chemostratigraphic data are used for regional and global correlation and facilitate study of the evolutionary development of animals and faunas through the "Cambrian explosion".
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| 7. |
- Kouchinsky, Artem, et al.
(författare)
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Lower–Middle Cambrian faunas and stratigraphy from northern Siberia
- 2022
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Ingår i: Acta Palaeontologica Polonica. - Warsaw : Polish Academy of Sciences. - 0567-7920 .- 1732-2421. ; 67, s. 341-464
-
Tidskriftsartikel (refereegranskat)abstract
- New assemblages of skeletal fossils chemically extracted from carbonates of the Cambrian Stage 2–Drumian Stage are reported from the lower reaches of the Lena River as well as from the Khorbusuonka, Malaya Kuonamka, and Bol’shaya Kuonamka rivers in northern part of the Siberian Platform. The fauna studied with scanning electron microscopy includes brachiopods, molluscs, hyoliths, halkieriids, chancelloriids, tommotiids, lobopodians, palaeoscolecidans, bradoriids, echinoderms, anabaritids, hyolithelminths, and sponges showing similarity to previously described fossil assemblages from Siberia, Laurentia, and Gondwana. The material includes emended descriptions of Halkieria proboscidea, Hadimopanella knappologica, Archaeopetasus typicus, and first descriptions of Hadimopanella foveata Kouchinsky sp. nov. and Archaeopetasus pachybasalis Kouchinsky sp. nov. Affinity of Archaeopetasus to chancelloriids is suggested. Finding of an in-place operculum in a planispiral shell of Michniakia minuta enables reinterpretation of this form as a hyolith, not a mollusc. The cambroclavids Cambroclavus sp. and Zhijinites clavus and the earliest echinoderms belonging to the Rhombifera and Ctenocystoidea are reported respectively from the lower Botoman stage and Botoman–Toyonian transitional beds, correlated with Cambrian Stage 4. Carbon isotopes are analysed from sections of the Chuskuna (upper Kessyusa Group), Erkeket, Kuonamka, Olenyok, Yunkyulyabit-Yuryakh, Tyuser and Sekten formations. A major part ofthe δ13C record is obtained from the Cambrian Stage 4–Drumian Stage strata which remain incompletely characterised by chemostratigraphy. The Lower Anomocarioides limbataeformis Carbon isotope Excursion (LACE) from the Drumian Stage of the Khorbusuonka River is introduced herein. New chemostratigraphic data are used for regional and global correlation and facilitate study of the evolutionary development of animals and faunas through the “Cambrian explosion”.
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| 8. |
- Kouchinsky, Artem
(författare)
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Palaeobiology and Chemostratigraphy of the Precambrian - Cambrian Transitional Beds on the Siberian Platform
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biological innovations during the Precambrian-Cambrian transition opened evolutionary gates towards the modem biosphere. Two interrelated aspects of this process are investigated. The first one is the ecological radiation and beginning of calcareous biomineralization in mollusc-like organisms (shelled molluscs, coeloscleritophorans, and hyoliths). The second one is the carbon isotopic record as a long-scale environmental archive and stratigraphical tool. The early Cambrian diversification of mollusc-like forms was a result of their adaptations to various habitats. This ecological radiation led to the appearance of major trophic groups: deposit-feeders, scrapers and grazers, suspension feeders, predators and scavengers. General size increase of molluscan shells during the Cambrian was related to the invasion of shallow-water high-energy environments and seems to have accompanied changes in life cycles and the appearance of planktonic veliger larva. Shells of the Early Cambrian mollusc-like organisms grew by marginal accretion of new growth lamellae or sclerites. The former type of shells had an outer layer of possibly mineralized prism-like units and an inner layer of lamellar units consisting of aragonitic fibres. Nacreous and crossed-lamellar aragonitic microstructures probably evolved in the Cambrian from such lamellar aragonitic microstructures in different groups of molluscs. Shells composed of sclerites belong to the coeloscleritophorans, a group confined to the Cambrian. The juvenile part of some composite shells was assembled from needle-like sclerites; these were substituted by hollow broader sclerites at later stages of development. Palaeozoic group of hyoliths has been regarded as a separate phylum close to molluscs and sipunculans or been ascribed to one of these. Their exoskeleton, penetrated by numerous pores, consisted of organic filaments mineralized by aragonite and assembled as bundles forming a characteristic orthogonal network. Their alleged crossed-lamellar microstructure of mollusc type is, therefore, reinterpreted. Extremely well preserved fossils give an unexpected insight into early metazoan diversification. Phosphatised minute globules from the Precabmrian-Cambrian transitional strata of Siberia are interpreted as fossilized tetrameric embryos with features of modem cnidarian larva-actinula. Found in association with anabaritids (problematic early Cambrian organisms, characterized by triradially symmetrical tubular skeletons) they may represent their early developmental stages. However, until more material and new evidence is gathered, this connection is speculative. Carbon isotopic oscillations enable a novel angle of view on Vendian-Cambrian stratigraphy, evolutionary rates at the Precambrian-Cambrian boundary, and biogeochemical events accompanying this transition. New data from northern Siberia elucidate the correlation of the Lower Cambrian and Vendian-Cambrian transitional beds across the Siberian Platform. Several pronounced isotopic oscillations have been revealed in the lower beds of the Emyaksin Formation. They are absent at the base of the Tommotian Stage in its type section, owing to a depositional hiatus, and can be accommodated between the pre-Tommotian excursion I and Tommotian excursion II of the Siberian isotopic reference scale. These facts provide additional chemostratigraphical support for a pre-Tommotian Cambrian Stage in Siberia, the biostratigraphical framework for which has been elaborated earlier, and support suggestions of a gradual, rather than abrupt history of first appearances of the earliest skeletal groups.
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| 9. |
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| 10. |
- Kouchinsky, Artem, et al.
(författare)
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The new stem-group brachiopod Oymurania from the lower Cambrian of Siberia
- 2015
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Ingår i: Acta Palaeontologica Polonica. - : Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). - 0567-7920 .- 1732-2421. ; 60:4, s. 963-980
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Tidskriftsartikel (refereegranskat)abstract
- A stem-group brachiopod, Oymurania gravestocki Ushatinskaya gen. et sp. nov. is described herein from the middle Atdabanian-lower Botoman Stages (similar to Cambrian Stage 3) of the Siberian Platform. The fossils were extracted from limestone beds of the Emyaksin, Perekhod, and Pestrotsvet formations as assemblages of disarticulated orthoconic to cyrtoconic porous shells in apatite preservation. The originally organophosphatic shells of Oymurania are externally similar to mitral sclerites (ventral valves) of the stem-group brachiopod Micrina, although no sellate-like sclerites, nor differentiated subapical area with apophyses were recognised in our material. The range of Oymurania shells with subcentral to posteromarginal apex is similar to that of ventral valves of Mickwitzia. Oymurania is also characterised by the system of radial and orthogonal canals open in pairs or triplets in small depressions or indentations of growth lamellae in the outer shell surface. The orthogonal (Micrina-Setatella type) and radial (horizontal setigerous tubes) canals are widespread among the early Cambrian stem-group brachiopods, such as Micrina, Mickwitzia, and Setatella. In addition to these canals, Oymurania exhibits a well-developed acrotretoid columnar microstructure, also known from Setatella. A broad subapical platform in cyrtoconic shells (presumably ventral valves) of Oymurania is interpreted homologous to the deltoid area in mitrals of Micrina and pseudointerarea/interarea in ventral valves of Setatella/paterinid brachiopods. Except with probable cell imprints and openings of orthogonal canals, no morphological differentiation was, however, reflected by the shell interior of Oymurania gravestocki. Being closely related to tannuolinids and mickwitziids, Oymurania complements the picture of diversification of the early Cambrian stem-group brachiopods that occurred in parallel with radiation of paterinids and other crow-group brachiopods on the Siberian Platform and worldwide.
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| 11. |
- Peel, John Stuart, et al.
(författare)
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Middle Cambrian (Miaolingian Series, Wuliuan Stage) molluscs and mollusc-like microfossils from North Greenland (Laurentia)
- 2022
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Ingår i: Bulletin of the Geological Society of Denmark. - : Geological Society of Denmark. - 0011-6297 .- 2245-7070. ; 70, s. 69-104
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Tidskriftsartikel (refereegranskat)abstract
- Diverse assemblages of helcionelloid molluscs and mollusc-like microfossils are described from the upper Henson Gletscher Formation (Cambrian, Miaolingian Se-ries, Wuliuan Stage) of Lauge Koch Land and western Peary Land, North Greenland (Laurentia). The fauna compares closely to an assemblage of similar age from the Coonigan Formation of Australia, although the latter is preserved as silica replicas while the North Greenland fossils are dominantly preserved as phosphatized internal moulds. These internal moulds often retain a detailed impression of the inner surface of the shell, with a fine pitted texture typically present. Prominent deep grooves on the sub-apical surface in the erect helcionellids Dorispira and Erugoconus, correspond-ing to ridges on the shell interior, seem to be associated with control of water flow through the mantle cavity. Well-developed shell pores, preserved as tubercles on the internal mould, are common in species of the laterally compressed Mellopegma. New taxa: Dorispira avannga sp. nov., Dorispira septentrionalis sp. nov., Dorispira tavsenensis sp. nov., Dorispira tippik sp. nov., Erugoconus acuminatus gen. et sp. nov., Scenella? siku sp. nov., Sermeqiconus gen. nov., Tavseniconus erectus gen. et sp. nov., Vendrascospira troelseni gen. et sp. nov., Vendrascospira frykmani gen. et sp. nov.
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| 12. |
- Peel, John, S., et al.
(författare)
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Ovatoryctocara granulata assemblage (Cambrian Series 2–Series 3 boundary) of Løndal, North Greenland
- 2016
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Ingår i: Australasian Palaeontological Memoirs. ; 49, s. 241-282
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Tidskriftsartikel (refereegranskat)abstract
- Ovatoryctocara granulata Chernysheva 1962, a key trilobite in discussions concerning intercontinental correlation and the placement of the Cambrian Series 2–Series 3 boundary, occurs together with more than 60 other species in a fossil assemblage from the Henson Gletscher Formation of Løndal, Peary Land, North Greenland. Most taxa are described from acid residues in which diverse protoconodonts, helcionellid molluscs and hyoliths occur together with linguliformean brachiopods, bradoriids and other fossils. Recognition of an earlier First Appearance Datum for O. granulata in Løndal consolidates the biostratigraphic relationship between the assemblage and other partly co-occurring trilobites valuable for correlation within Laurentia and beyond. The assemblage can be correlated with the Ovatoryctocara Biozone, the basal biozone of the Molodian Stage in the Republic of Sakha (Yakutia, north-eastern Siberia), proposed as the earliest stage of Cambrian Series 3. New taxa are Tulenicornus? frykmani sp. nov., Conotheca hensoni sp. nov., Capitoconus borealis sp. nov., ‘Hipponicharion’ pearylandica sp. nov. and Liangshanella? nivalis sp. nov.
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| 13. |
- Skovsted, Christian B., et al.
(författare)
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The problematic early Cambrian fossil Tumulduria incomperta represents the detached ventral interarea of a paterinid brachiopod.
- 2014
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Ingår i: Acta Palaeontologica Polonica. - : Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). - 0567-7920 .- 1732-2421. ; 59:2, s. 359-365
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Tidskriftsartikel (refereegranskat)abstract
- The organophosphatic early Cambrian (Terreneuvian, Cambrian Stage 2) fossil Tumulduria incomperta has been problematic ever since its original description in 1969. Comparison of abundant specimens from the Lower Cambrian of Siberia with co-occurring brachiopod valves show that T. incomperta represents the central portion of the ventral interarea of a paterinid brachiopod similar to Cryptotreta neguertchenensis, and that the domed central portion of typical Tumulduria specimens represents the ridge-like pseudodeltidium of the interarea.
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| 14. |
- Skovsted, Christian, 1974-, et al.
(författare)
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Taxonomy, morphology, shell structure and early ontogeny of Pelmanotreta nom. nov. from the lower Cambrian of Siberia
- 2015
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 137:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- The new generic name Pelmanotreta is proposed under the provisions of the International Code of Zoological Nomenclature (ICZN) to replace Cryptotreta Pelman, 1977 (Brachiopoda), a junior homonym of Cryptotreta Blanc & Foote, 1961 (Arthropoda). This poorly known brachiopod genus and its type and only species, Pelmanotreta neguertchenensis (Pelman, 1977), from the early Cambrian of Siberia is redescribed. The family-level taxonomy of Pelmanotreta and other “cryptotretid” brachiopods is uncertain. In Pelmanotreta, dorsal valves vastly outnumber ventral valves in all collections but new specimens of the poorly known ventral valve reveal a possibly septate and poorly mineralized apical region. A prismatic hexagonal shell structure comparable to that of Salanygolina is described. P. neguertchenensis preserves the earliest known record of a larval shell in brachiopods.
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| 15. |
- Wotte, Thomas, et al.
(författare)
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Isotopic evidence for temperate oceans during the Cambrian Explosion
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The Cambrian Explosion was a key event in the evolution of life on Earth. This event took place at a time when sea surface temperatures have been proposed to reach about 60 °C. Such high temperatures are clearly above the upper thermal limit of 38 °C for modern marine invertebrates and preclude a major biological revolution. To address this dichotomy, we performed in situ δ18O analyses of Cambrian phosphatic brachiopods via secondary ion mass spectrometry (SIMS). The δ18Ophosphate data, which are considered to represent the most primary δ18Oseawater signature, were identified by evaluating the diagenetic alteration of the analyzed shells. Assuming ice-free conditions for the Cambrian ocean and no change in δ18Oseawater (-1.4‰ to -1‰; V-SMOW) through time, our temperatures vary between 35 °C ± 12 °C and 41 °C ± 12 °C. They are thus clearly above (1) recent subequatorial sea surface temperatures of 27 °C–35 °C and (2) the upper lethal limit of 38 °C of marine organisms. Our new data can therefore be used to infer a minimal depletion in early Cambrian δ18Oseawater relative to today of about -3‰. With this presumption, our most pristine δ18Ophosphate values translate into sea surface temperatures of about 30 °C indicating habitable temperatures for subequatorial oceans during the Cambrian Explosion.
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