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| 2. |
- Butler, Aodhán D., 1986-
(författare)
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Decoding the fossil record of early lophophorates : Systematics and phylogeny of problematic Cambrian Lophotrochozoa
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The evolutionary origins of animal phyla are intimately linked with the Cambrian explosion, a period of radical ecological and evolutionary innovation that begins approximately 540 Mya and continues for some 20 million years, during which most major animal groups appear. Lophotrochozoa, a major group of protostome animals that includes molluscs, annelids and brachiopods, represent a significant component of the oldest known fossil records of biomineralised animals, as disclosed by the enigmatic ‘small shelly fossil’ faunas of the early Cambrian. Determining the affinities of these scleritome taxa is highly informative for examining Cambrian evolutionary patterns, since many are supposed stem-group Lophotrochozoa. The main focus of this thesis pertained to the stem-group of the Brachiopoda, a highly diverse and important clade of suspension feeding animals in the Palaeozoic era, which are still extant but with only with a fraction of past diversity. Major findings include adding support for tommotiid affinity as stem-group lophophorates. Determining morphological character homologies vital to reconstructing the brachiopod stem-group was achieved by comparing Cambrian Lagerstätten with the widespread biomineralised record of Cambrian stem-brachiopods and small shelly fossils. Polarising character changes associated with the putative transition from scleritome organisms to crown-group brachiopods was furthered by the description of an enigmatic agglutinated tubular lophophorate Yuganotheca elegans from the Chengjiang Lagerstätte, China, which possesses an unusual combination of phoronid, brachiopod and tommotiid characters. These efforts were furthered by the use of X-ray tomographic techniques that revealed novel anatomical features, including exceptionally preserved setae in the tommotiid Micrina. The evidence for a common origin of columnar brachiopod shell structures in the tommotiids is suggested and critically examined. Enigmatic and problematic early and middle Cambrian lophotrochozoans are newly described or re-described in light of new evidence, namely: the stem-brachiopod Mickwitzia occidens Walcott from the Indian Springs Lagerstätte, Nevada; a putative stem-group entoproct Cotyledion tylodes Luo and Hu from Chengjiang, China; a new enigmatic family of rhynchonelliform brachiopods exemplified by the newly described Tomteluva perturbata from the Stephen Formation, Canada; and the tommotiid Micrina etheridgei (Tate) from the Flinders Ranges, South Australia. Cladistic analyses of fossil morphological data supports a monophyletic Brachiopoda.
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| 3. |
- Butler, Aodhán D., 1986-
(författare)
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Exceptionally Preserved Cambrian Lophotrochozoa : Taxonomy, Systematics and Taphonomy of Chengjiang and Indian Springs Lophophorates
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The origin and evolution of Lophotrochozoa can be traced to the plethora of lower Cambrian scleritome taxa. We aim to determine the character suites linking these stem-Lophotrochozoa to their extant crown relatives, in particular the small shelly tommotiids and the stem-group brachiopods. Tracing the origin of morphological characters from these fossils informs the evolution and construction of lophotrochozoan body plans associated with the Cambrian Explosion. This is achieved by comparing records of exceptional preservation, most conspicuously Burgess Shale type Lagerstätten with more widespread Cambrian stem-brachiopods and small shelly fossils with their purported extant relatives, for example. Determining morphological character homologies is crucial to reconstructing the brachiopod stem-group and in polarising character changes associated with the putative transition from scleritome organisms to crown-group brachiopods. In this thesis arguments for a common origin of specific shell structures and exceptionally preserved soft-tissues are investigated. New records of enigmatic stem-group lophotrochozoans are described from two localities, the Indian Springs and Chengjiang Lagerstätte. Comprising the stem-brachiopod Mickwitzia cf. occidens, a putative stem-group entoproct Cotyledion tylodes and an enigmatic agglutinated tubular lophophorate possessing an unusual combination of phoronid, brachiopod and tommotiid characters, Yuganotheca elegans gen. et sp. nov. The interplay of bauplan, microbial activity and environmental factors resulting in such incidences of exceptional soft tissue preservation is also examined critically. Consequently, the evolution of through-gut bearing bilaterians is suggested as the reason for why the Cambrian hosts such a plethora of Lagerstätten. The closure of this taphonomic window is then associated with increased bioturbation following the Cambrian substrate revolution.
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| 4. |
- Butler, Aodhán D., 1986-, et al.
(författare)
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Exceptionally-preserved Mickwitzia from the Indian Springs Lagerstätte.
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Ingår i: Journal of Paleontology. - 0022-3360 .- 1937-2337.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A new assemblage of the early Cambrian stem group brachiopod Mickwitzia is described from the Indian Springs Lagerstätte possessing exceptionally preserved mantle setae. Critical analysis of shell structure and mantle setae from these specimens with those from additional sites with variable diagenetic history reveals the extent of taphonomic alteration and further sheds light on the phylogenetic position of the mickwitziids. A morphometric approach to shell outline and growth landmarks within these specimens reveals a clear species level discriminant signal of Nevada Mickwitzia in comparison to M. monlifera from Sweden. Detailed electron micrographs allow revision of the genus diagnosis for Mickwitzia based on presence of inward pointing phosphatic cones and tangential setae bearing tubes. We also conclude the inward pointing cone structures are not consistent with setal bearing structures as previously thought, but rather represent an endopunctae-like structure. A tommotiid-like shell architecture and presence of acrotretid columns in the dorsal juvenile shell of M. cf. occidens further strengthens the proposed close relationship between stem-group brachiopods and tommotiids.
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| 5. |
- Butler, Aodhán D., et al.
(författare)
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Exceptionally preserved Mickwitzia from the Indian Springs Lagerstätte (Cambrian Stage 3), Nevada
- 2015
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Ingår i: Journal of Paleontology. - : Cambridge University Press (CUP). - 0022-3360 .- 1937-2337. ; 89:6, s. 933-955
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT Exceptionally preserved specimens of the Cambrian stem-group brachiopod Mickwitzia occidens Walcott, 1908 are described in detail from the Indian Springs LagerstÀtte in Nevada, USA. Shell structure and preserved mantle setae from these specimens reveal a variable diagenetic (taphonomic) history and provide insight into the phylogenetic position of mickwitziids. Morphologic and morphometric comparison to M. monilifera (Linnarsson, 1869) from Sweden and M. muralensis Walcott, 1913 from British Columbia, Canada reveals clear species-level distinctions. Scanning electron microscopic analysis allows revision of the generic diagnosis. The Mickwitzia shell is characterized by the presence of inwardly pointing phosphatic cones and tangential setae-bearing tubes. The inwardly pointing cone structures are not consistent with setal bearing structures as previously thought, but rather represent endopunctae-like structures. Acrotretid-like shell structures and shell-penetrating setae in M. occidens strengthen the previously proposed close relationship between stem-group brachiopods and tommotiids, a group of small shelly fossils.
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| 6. |
- Butler, Aodhán D., et al.
(författare)
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Experimental taphonomy of Artemia reveals the role of endogenous microbes in mediating decay and fossilization
- 2015
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 282, s. 20150476-
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Tidskriftsartikel (refereegranskat)abstract
- Exceptionally preserved fossils provide major insights into the evolutionaryhistory of life. Microbial activity is thought to play a pivotal role in both thedecay of organisms and the preservation of soft tissue in the fossil record,though this has been the subject of very little experimental investigation.To remedy this, we undertook an experimental study of the decay of thebrine shrimp Artemia, examining the roles of autolysis, microbial activity,oxygen diffusion and reducing conditions. Our findings indicate thatendogenous gut bacteria are the main factor controlling decay. Followinggut wall rupture, but prior to cuticle failure, gut-derived microbes spreadinto the body cavity, consuming tissues and forming biofilms capable ofmediating authigenic mineralization, that pseudomorph tissues and structuressuch as limbs and the haemocoel. These observations explain patternsobserved in exceptionally preserved fossil arthropods. For example, gutsare preserved relatively frequently, while preservation of other internal anatomyis rare. They also suggest that gut-derived microbes play a key role in thepreservation of internal anatomy and that differential preservation betweenexceptional deposits might be because of factors that control autolysis andmicrobial activity. The findings also suggest that the evolution of a throughgut and its bacterial microflora increased the potential for exceptional fossilpreservation in bilaterians, providing one explanation for the extreme rarityof internal preservation in those animals that lack a through gut.
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| 7. |
- Butler, Aodhán D., 1986-, et al.
(författare)
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The role of microbes in decay and preservation: a Cambrian Explosion of animals and Lagerstätten.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The abrupt appearance of animals in the early Cambrian has been interpreted either as an explosive biological diversification or, alternatively, as an artefact resulting from a sudden increase in the probability of animal remains becoming fossilised. We attempt to reconcile these competing interpretations in exceptionally-preserved biota, which provide a vital part of our knowledge of the disparity and diversity of the Cambrian fauna. We assess the factors influencing the potential for exceptional fossil preservation using the brine shrimp Artemia salina as our experimental model. Following gut wall rupture, but prior to cuticle failure, internal, gut-derived microbes spread into the body cavity and formed pseudomorphs of tissues. Gut-derived microbes were shown to be the main factor mediating both decay and biofilm replacement and tissue stabilisation. This pattern of preservation is consistent with results from other experimental studies and with the nature of Burgess Shale type fossil remains. Thus, the evolution of a through-gut may have not only underpinned the ecological revolution that bilaterian diversification represents, but also catalysed the exceptional preservation of early bilaterian fossils.
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| 10. |
- Butler, Aodhan, et al.
(författare)
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Recent palaeobiological and stratigraphical advances from the Cambrian of Estonia
- 2011
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Ingår i: The 2nd Wiman Meeting. - Uppsala. ; , s. 5-5
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Konferensbidrag (refereegranskat)abstract
- The unique Cambrian sediments of Estonia represent an important and understudied component of the Baltic system. Here we present an overview of recent field studies conducted by Uppsala University in association with colleagues from the Baltic Geotourism project, that have revealed a number of exciting discoveries in terms of Cambrian palaeontology and stratigraphy of Estonia. These include new purported stem lophotrochozoans with bizarre shell structure. Current efforts to describe and systematically appraise this material are outlined. The presence of unusual shell structure and whether this is the result of taphonomic alteration or indeed represents a novel shell structure type is examined. We propose herein affinities to the inarticulate stem-brachiopod Mickwitzia based upon the presence of an umbo and the overall gross morphology. Possible new records of Estoniadiscus discinoides (Schmidt 1888), an extremely rare enigmatic organism with postulated affinities to eldonioids or other stem-group lophophorates are also described from the type section at Kakumägi, within the Kakumägi member Member of the lower Cambrian Tiskre formationFormation. The discovery of Dictyonema Rhabdinopora sp. graptolites, which have until now demarcated the Cambrian-Ordovician boundary, in-situ approximately 3 m below the previous reported occurrence from the Pakri cape section of the Kallavere formation Formation is also significant. Our findings highlight the need for both a stratigraphical and palaeobiological reapprasal of these important sequences, and their correlative implications for the Swedish and broader Baltoscandian regions.
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| 11. |
- Butler, Aodhan, 1986-
(författare)
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Resolving the position of problematic lower to middle Cambrian Lophotrochozoa: a critical appraisal of tommotiid and stem-brachiopod character homologies.
- 2012
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Ingår i: 23.1 Martin Glaessner Symposium: The Ediacaran and the Cambrian Explosion.
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Konferensbidrag (refereegranskat)abstract
- The origin and early evolution of Brachiopoda can be traced back to the plethora of scleritomes and brachiopod-like taxa in the lower Cambrian. Most conspicuous are members of Lagerstätten such as the Burgess Shale and Chengjiang faunas. By combining records of exceptionally-preserved faunas with more widespread records of lower Cambrian stem-brachiopods and small shelly faunas, we aim to determine the characters suites associated with the evolution of these organisms. This determination is crucial to reconstructing the brachiopod stem-group and to polarising character changes associated with a transition from scleritome organisms to crown-group brachiopods. Critical comparison of the shell structure and setae of extant lophotrochozoans with those from fossil specimens from Sweden, Estonia and Nevada reveals the extent of taphonomic alteration, further informing previous taxonomic efforts.Characters previously proposed as systematically important are re-evaluated, based on critical examination of two distinct character suites: firstly examination of the homology of striated tubes which are associated with the secretion of setae, which are exceptionally preserved in many cases; and secondly, the occurrence of phosphatised columnar shell structures previously referred to as 'punctae'. Overall we provide further support for homologous character suites shared between tommotiids such as Micrina, Sunnaginia and Eccentrotheca, and stem-brachiopods including Mickwitzia and Setatella. These suggested homologies are of phylogenetic significance, and shed further light on the early evolution of the lophotrochozoan body plan in the early Cambrian.
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| 13. |
- Lagebro, Linda, 1980-, et al.
(författare)
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The oldest notostracan (Upper Devonian Strud locality, Belgium)
- 2015
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Ingår i: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 58:3, s. 497-509
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Tidskriftsartikel (refereegranskat)abstract
- A new notostracan crustacean, Strudops goldenbergi gen. et sp. nov., is described from the well-preserved terrestrial arthropod fauna of the Upper Devonian of Strud, Belgium. The fossil notostracan bears a close resemblance to modern notostracans in possessing a large, simple head shield covering almost half of the whole body, a set of phyllopodous thoracic appendages and a legless posterior abdomen with a telson bearing a caudal furca. The differentiation and relative size of mouthparts and limbs suggest that these specimens are all adults. The notostracans described herein are the earliest clear members of the total group Notostraca.
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| 14. |
- Streng, Michael, et al.
(författare)
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A new family of Cambrian rhynchonelliformean brachiopods (Order Naukatida) with an aberrant coral-like morphology
- 2016
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Ingår i: Palaeontology. - : Wiley. - 0031-0239 .- 1475-4983. ; 59:2, s. 269-293
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Tidskriftsartikel (refereegranskat)abstract
- Tomteluva perturbata gen. et sp. nov. and Nasakia thulensis gen. et sp. nov., two new rhynchonelliformean brachiopod taxa, are described from carbonate beds from the lower middle Cambrian (Series 3, Stage 5) basinal Stephen Formation, Canada, and the upper lower Cambrian (Series 2, Stage 4) Henson Gletscher Formation, North Greenland, respectively. The two taxa are characterized by an unusual coral-like morphology typified by a high conical ventral valve with an anteriorly curved umbo and a tube-like structure inside the ventral valve, interpreted as pedicle tube. Both resemble the problematic late middle Cambrian (Drumian) species Anomalocalyx cawoodi Brock from Australia, whose systematic affiliation is controversial. Together, the three genera are interpreted as representatives of a new family of rhynchonelliformean brachiopods, the Tomteluvidae fam. nov., which is interpreted as an aberrant or derived taxon within the Order Naukatida. Convergence between the Tomteluvidae and the coralla of small solitary Cambrian coralimorphs, as well as the late Palaeozoic reef-building richthofenioid brachiopods, might indicate adaptation to a similar life habits and environments. However, their small size (length 4 mm), well-developed pedicle and perfect morphological symmetry make it more likely that tomteluvids lived attached to frondose algae or sponges, above the seafloor, in a similar fashion to the acrotretoid brachiopods with which they show a high degree of morphological convergence. Morphological features of the pedicle tube of N. thulensis suggest that the tomteluvid pedicle is homologous to that in modern rhynchonelliformean brachiopods. This is the first evidence of the pedicle type within the Naukatida and represents the oldest confirmation of a rhynchonellate pedicle.
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| 15. |
- Van Houte, Emma, et al.
(författare)
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A new genus and species of ?parthenogenic anostracan (Pancrustacea, Branchiopoda, ?Thamnocephalidae) from the Lower Cretaceous Koonwarra Fossil Bed in Australia
- 2022
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Ingår i: Alcheringa. - : Informa UK Limited. - 0311-5518 .- 1752-0754. ; 46:2, s. 180-187
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Tidskriftsartikel (refereegranskat)abstract
- The fossil record of fairy shrimp, or anostracan crustaceans, is poor with only six species formally described to date. The group stratigraphically ranges from the Devonian to recent. The Lower Cretaceous (middle-upper Aptian) Koonwarra Fossil Bed in Australia contains a new species of anostracan, which we describe here. The Koonwarra Fossil Bed is famous for its rich fossil assemblage of avian-line dinosaur feathers, bony fish, insects and aquatic invertebrates that were preserved in the fine bottom sediments of a restricted montane waterbody. Previously, the Koonwarra Fossil Bed anostracans were classified as taxonomically indeterminate; however, we show that they are potentially attributable to Thamnocephalidae based on the egg shape found in gravid female individuals. Notably, all of the recovered Koonwarra Fossil Bed anostracans (similar to 40 individuals) are either females or juveniles. This suggests that the species might have undergone parthenogenic reproduction. Furthermore, the preservation of the fossils resembles experimentally decayed modern anostracans, evidencing decay-induced fabrics that retained remnants of the cuticle, digestive tract and internal anatomy to varying degrees.
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| 16. |
- Zhang, Zhifei, et al.
(författare)
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A sclerite-bearing stem group entoproct from the early Cambrian and its implications
- 2013
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Ingår i: Scientific Reports. - London : Nature Publishing Group. - 2045-2322. ; 3, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- The Lophotrochozoa includes disparate tentacle-bearing sessile protostome animals, which apparently appeared in the Cambrian explosion, but lack an uncontested fossil record. Here we describe abundant well preserved material of Cotyledion tylodes Luo et Hu, 1999, from the Cambrian (Series 2) Chengjiang deposits, reinterpreted here as a stem-group entoproct. The entoproct affinity is supported by the sessile body plan and interior soft anatomy. The body consists of an upper calyx and a lower elongate stalk with a distal holdfast. The soft anatomy includes a U-shaped gut with a mouth and aboral anus ringed by retractable marginal tentacles. Cotyledion differs from extant entoprocts in being larger, and having the calyx and the stalk covered by numerous loosely-spaced external sclerites. The description of entoprocts from the Chengjiang biota traces the ancestry of yet another lophotrochozoan phylum back to the Cambrian radiation, and has important implications for the earliest evolution of lophotrochozoans.
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| 17. |
- Zhang, Zhifei, et al.
(författare)
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An early Cambrian agglutinated tubular lophophorate with brachiopod characters
- 2014
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4:4682, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- The morphological disparity of lophotrochozoan phyla makes it difficult to predict the morphology of the last common ancestor. Only fossils of stem groups can help discover the morphological transitions that occurred along the roots of these phyla. Here, we describe a tubular fossil Yuganotheca elegans gen. et sp. nov. from the Cambrian (Stage 3) Chengjiang Lagersta¨tte (Yunnan, China) that exhibits an unusual combination of phoronid, brachiopod and tommotiid (Cambrian problematica) characters, notably a pair of agglutinated valves, enclosing a horseshoe-shaped lophophore, supported by a lower bipartite tubular attachment structure with a long pedicle with coelomic space. The terminal bulb of the pedicle provided anchorage in soft sediment. The discovery has important implications for the early evolution of lophotrochozoans, suggesting rooting of brachiopods into the sessile lophotrochozoans and the origination of their bivalved bauplan preceding the biomineralization of shell valves in crown brachiopods.
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