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Decoding the fossil record of early lophophorates: Systematics and phylogeny of problematic Cambrian Lophotrochozoa
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. (Brachiopod group)ORCID iD: 0000-0002-1906-0009
2015 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
De tidigaste fossila lofoforaterna : Problematiska kambriska lofotrochozoers systematik och fylogeni (Swedish)
Abstract [en]

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.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 65 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1284
Keyword [en]
Brachiopoda, Chengjiang, Lagerstätte, Cambrian Explosion, palaeobiology, stem-group, entoproct, phoronid, tommotiid, exceptional preservation
National Category
Other Earth and Related Environmental Sciences Natural Sciences
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
URN: urn:nbn:se:uu:diva-261907ISBN: 978-91-554-9327-1 (print)OAI: oai:DiVA.org:uu-261907DiVA: diva2:851505
Public defence
2015-10-23, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 13:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2008-3768, 621-2011-4961Swedish Research Council, 2009-4395, 2012-1658
Available from: 2015-09-29 Created: 2015-09-05 Last updated: 2017-01-20
List of papers
1. Exceptionally-preserved Mickwitzia from the Indian Springs Lagerstätte.
Open this publication in new window or tab >>Exceptionally-preserved Mickwitzia from the Indian Springs Lagerstätte.
(English)In: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337Article in journal (Other academic) Accepted
Abstract [en]

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.

Keyword
Brachiopoda, Mickwitzia, shell penetrating setae, lower Cambrian, Indian Springs
National Category
Other Earth and Related Environmental Sciences Geology Evolutionary Biology
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
urn:nbn:se:uu:diva-216149 (URN)
Funder
Swedish Research Council, 2009-4395, 2012-1658
Available from: 2014-01-21 Created: 2014-01-19 Last updated: 2017-12-06
2. X-ray microtomography of the tommotiid Micrina reveals cellular and ultrastructural preservation, confirming a tommotiid stem-linguliform affinity
Open this publication in new window or tab >>X-ray microtomography of the tommotiid Micrina reveals cellular and ultrastructural preservation, confirming a tommotiid stem-linguliform affinity
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Evolutionary Biology Other Earth and Related Environmental Sciences
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
urn:nbn:se:uu:diva-261903 (URN)
Available from: 2015-09-05 Created: 2015-09-05 Last updated: 2017-01-20
3. A new family of Cambrian rhynchonelliformean brachiopods (Order Naukatida) with an aberrant coral-like morphology
Open this publication in new window or tab >>A new family of Cambrian rhynchonelliformean brachiopods (Order Naukatida) with an aberrant coral-like morphology
Show others...
2016 (English)In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 59, no 2, 269-293 p.Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-261904 (URN)10.1111/pala.12226 (DOI)000370607400007 ()
Funder
Swedish Research Council, 621-2011-4961
Available from: 2015-09-05 Created: 2015-09-05 Last updated: 2017-12-04Bibliographically approved
4. An early Cambrian agglutinated tubular lophophorate with brachiopod characters
Open this publication in new window or tab >>An early Cambrian agglutinated tubular lophophorate with brachiopod characters
2014 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, 4682- p.Article in journal (Refereed) Published
Abstract [en]

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 Lagerstätte (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 coelomic pedicle providing anchorage. 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.

National Category
Geology Other Earth and Related Environmental Sciences Evolutionary Biology
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
urn:nbn:se:uu:diva-216152 (URN)10.1038/srep04682 (DOI)000335885800001 ()
Funder
Swedish Research Council, 2009-4395, 2012-1658
Available from: 2014-01-21 Created: 2014-01-19 Last updated: 2017-12-06Bibliographically approved
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