| 1. |
- Chris, Mays, 1983-, et al.
(författare)
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Pushing the limits of neutron tomography in palaeontology: Three-dimensional modelling of in situ resin within fossil plants
- 2017
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Ingår i: Palaeontologia Electronica. - California : Coquina Press. - 1935-3952 .- 1094-8074. ; 20:3, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Computed tomography is an increasingly popular technique for the non-destructivestudy of fossils. Whilst the science of X-ray computed tomography (CT) has greatlymatured since its first fossil applications in the early 1980s, the applications and limitationsof neutron tomography (NT) remain relatively unexplored in palaeontology. Thesehighest resolution neutron tomographic scans in palaeontology to date were conductedon a specimen of Austrosequoia novae-zeelandiae (Ettingshausen) Mays and Cantrillrecovered from mid-Cretaceous (Cenomanian; ~100–94 Ma) strata of the ChathamIslands, eastern Zealandia. Previously, the species has been identified with in situ fossilresin (amber); the new neutron tomographic analyses demonstrated an anomalouslyhigh neutron attenuation signal for fossil resin. The resulting data provided astrong contrast between, and distinct three-dimensional representations of the: 1) fossilresin; 2) coalified plant matter; and 3) sedimentary matrix. These data facilitated ananatomical model of endogenous resin bodies within the cone axis and bract-scalecomplexes. The types and distributions of resin bodies support a close alliance withSequoia Endlicher (Cupressaceae), a group of conifers whose extant members areonly found in the Northern Hemisphere. This study demonstrates the feasibility of NTas a means to differentiate chemically distinct organic compounds within fossils.Herein, we make specific recommendations regarding: 1) the suitability of fossil preservationstyles for NT; 2) the conservation of organic specimens with hydrogenous consolidantsand adhesives; and 3) the application of emerging methods (e.g., neutronphase contrast) for further improvements when imaging fine-detailed anatomical structures.These findings demonstrate that we are still far from reaching the conceptuallimits of NT as a means of virtually extracting fossils, or imaging their internal anatomyeven when embedded within a rock matrix.
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| 2. |
- Frauenfelder, Timothy G., et al.
(författare)
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New Ankylosaurian Cranial Remains From the Lower Cretaceous (Upper Albian) Toolebuc Formation of Queensland, Australia
- 2022
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Ingår i: Frontiers in Earth Science. - : Frontiers Media S.A.. - 2296-6463. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Australian dinosaur research has undergone a renaissance in the last 10 years, with growing knowledge of mid-Cretaceous assemblages revealing an endemic high-paleolatitude Gondwanan fauna. One of its most conspicuous members is ankylosaurs, which are rare but nonetheless occur in most Australian dinosaur-bearing formations spanning the uppermost Barremian to lower Cenomanian. Here we describe a partial ankylosaur skull from the marine Toolebuc Formation exposed near Boulia in western Queensland, Australia. This skull represents the oldest ankylosaurian material from Queensland, predating the holotype of Kunbarrasaurus ieversi, which was found in the overlying Allaru Mudstone. The ankylosaur skull is encased in a limestone concretion with the maxillary tooth rows preserved only as impressions. Synchrotron radiation X-ray tomography was used to non-destructively image and reconstruct the specimen in 3D and facilitate virtual preparation of the separate cranial bones. The reconstruction of the skull revealed the vomer, palatines, sections of the ectopterygoids and maxillae, and multiple teeth. The palate has posteriorly positioned choanae that differs from the more anterior placement seen in most other ankylosaurians, but which is shared with K. ieversi, Akainacephalus johnsoni, Cedarpelta bilbeyhallorum, Gobisaurus domoculus, and Panoplosaurus mirus. Phylogenetic analyses place the new cranial material within the recently named basal ankylosaurian clade Parankylosauria together with K. ieversi. This result, together with the anatomical similarities to the holotype of K. ieversi, permits its referral to cf. Kunbarrasaurus sp. This specimen elucidates the palatal anatomy of Australian ankylosaurs and highlights one of the most ubiquitous components of Australian mid-Cretaceous dinosaur faunas.
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| 3. |
- Herrera, Fabiany, et al.
(författare)
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Reconstructing Krassilovia mongolica supports recognition of a new and unusual group of Mesozoic conifers
- 2020
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Ingår i: PLOS ONE. - : PLoS. - 1932-6203. ; 15:1, s. 1-21
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Tidskriftsartikel (refereegranskat)abstract
- Previously unrecognized anatomical features of the cone scales of the enigmatic Early Cretaceous conifer Krassilovia mongolica include the presence of transversely oriented paracytic stomata, which is unusual for all other extinct and extant conifers. Identical stomata arepresent on co-occurring broad, linear, multiveined leaves assigned to Podozamites harrisii, providing evidence that K. mongolica and P. harrisii are the seed cones and leaves of the same extinct plant. Phylogenetic analyses of the relationships of the reconstructed Krassilovia plant place it in an informal clade that we name the Krassilovia Clade, which also includes Swedenborgia cryptomerioides–Podozamites schenkii, and Cycadocarpidium erdmanni–Podozamites schenkii. All three of these plants have linear leaves that are relatively broad compared to most living conifers, and that are also multiveined with transversely oriented paracytic stomata. We propose that these may be general features of the Krassilovia Clade. Paracytic stomata, and other features of this new group, recall features of extant and fossil Gnetales, raising questions about the phylogenetic homogeneity of the conifer clade similar to those raised by phylogenetic analyses of molecular data.
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| 4. |
- Mays, Chris, 1983-, et al.
(författare)
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Polar wildfires and conifer serotiny during the Cretaceous globalhothouse
- 2017
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Ingår i: Geology. - Boulder : Geological Society of America. - 0091-7613 .- 1943-2682. ; 45:12, s. 1119-1122
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Tidskriftsartikel (refereegranskat)abstract
- Several highly effective fire-adaptive traits first evolved among modern plants duringthe mid-Cretaceous, in response to the widespread wildfires promoted by anomalously highatmospheric oxygen (O2) and extreme temperatures. Serotiny, or long-term canopy seedstorage, is a fire-adaptive strategy common among plants living in fire-prone areas today,but evidence of this strategy has been lacking from the fossil record. Deposits of abundantfossil charcoal from sedimentary successions of the Chatham Islands, New Zealand, recordwildfires in the south polar regions (75°–80°S) during the mid-Cretaceous (ca. 99–90 Ma).Newly discovered fossil conifer reproductive structures were consistently associated withthese charcoal-rich deposits. The morphology and internal anatomy as revealed by neutrontomography exhibit a range of serotiny-associated characters. Numerous related fossils fromsimilar, contemporaneous deposits of the Northern Hemisphere suggest that serotiny was akey adaptive strategy during the high-fire world of the Cretaceous.
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| 5. |
- Trinajstic, Kate, et al.
(författare)
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Exceptional preservation of organs in Devonian placoderms from the Gogo lagerstätte
- 2022
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 377:6612, s. 1311-1314
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Tidskriftsartikel (refereegranskat)abstract
- The origin and early diversification of jawed vertebrates involved major changes to skeletal and soft anatomy. Skeletal transformations can be examined directly by studying fossil stem gnathostomes; however, preservation of soft anatomy is rare. We describe the only known example of a three-dimensionally mineralized heart, thick-walled stomach, and bilobed liver from arthrodire placoderms, stem gnathostomes from the Late Devonian Gogo Formation in Western Australia. The application of synchrotron and neutron microtomography to this material shows evidence of a flat S-shaped heart, which is well separated from the liver and other abdominal organs, and the absence of lungs. Arthrodires thus show the earliest phylogenetic evidence for repositioning of the gnathostome heart associated with the evolution of the complex neck region in jawed vertebrates.
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| 6. |
- Trinajstic, Kate, et al.
(författare)
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Response to comment on "Exceptional preservation of organs in Devonian placoderms from the Gogo largerstätte"
- 2023
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 380:6645
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Jensen et al. (1) question evidence presented of a chambered heart within placoderms, citing its small size and apparently ventral atrium. However, they fail to note the belly-up orientation of the placoderm within one nodule, and the variability of heart morphology within extant taxa. Thus, we remain confident in our interpretation of the mineralized organ as the heart.
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