| 1. |
- Dupret, Vincent, et al.
(författare)
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New cranial material of the acanthothoracid placoderm Palaeacanthaspis vasta from the Lower Devonian of Podolia-phylogenetic and taxonomic significance
- 2021
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Ingår i: Acta Palaeontologica Polonica. - : INST PALEOBIOLOGII PAN. - 0567-7920 .- 1732-2421. ; 66:2, s. 337-347
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Tidskriftsartikel (refereegranskat)abstract
- The Early Devonian vertebrates of Podolia in Ukraine are well known thanks to the material of the basal arthrodire placodenn genus Kujdanowiaspis, originally mentioned by Brotzen in 1934. The anatomical fame of Kujdanowiaspis brought by Erik Stensio almost eclipsed the presence of the acanthothoracid placoderm Palaeacanthapsis vasta in the underlying beds, with the original material of P. vasta being less well preserved and abundant than that of Kujdanowiaspis. Here we describe a newly discovered specimen of the acanthothoracid P. vasta from the Lochkovian of Podolia (Ukraine). The specimen, although incomplete, is very well preserved in three dimensions and allows a thorough description of its external morphology, which is compared to that of Romundina stellina and other well-known Acanthothoraci. A phylogenetic analysis is performed and the acanthothoracid nature of Palaeacanthaspis is confirmed. However, the position of Palaeacanthaspis within the Acanthothoraci remains uncertain, and its resemblance with Romundina could be due to either synapomorphies or symplesiomorphies. Similarities and differences between the two forms are exposed, and lead to the lack of synonymy at the specific level. Generic synonymy is also questioned for the first time but remains equivocal.
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| 2. |
- Dupret, Vincent, et al.
(författare)
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Non-tetrapod sarcopterygians from the Valentia Slate Formation (Givetian, Devonian) of the Iveragh Peninsula, south-western Ireland: systematic reappraisal and palaeobiogeographic implications
- 2023
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Ingår i: Spanish Journal of Palaeontology. - 2255-0550 .- 2660-9568. ; 38:1, s. 37-45
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Tidskriftsartikel (refereegranskat)abstract
- The Middle Devonian (Givetian) Valentia Slate Formation in the Iveragh Peninsula, southwest Ireland, is more renowned for the second oldest record of tetrapod trackways in the world than for its heavily metamorphosed bone remains. The present study focuses on new discoveries of non-tetrapod sarcopterygian fish fossils from the Valentia Slate Formation. Micro-CT scanning technology allows a re-interpretation of a previously published acanthodian fin spine as a fanged coronoid of a probable Rhizodontida and the identification of a Dipnoi tooth plate and bone. In addition, a scale of Holoptychius is described. The presence of rhizodontids suggests Gondwanan ties, and a first northward dispersal wave of these vertebrates into Euramerica as early as middle Givetian. This hypothesis is supported by the common occurrence of the placoderm Bothriolepis in the Valentia Slate Formation.
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| 3. |
- Dupret, Vincent, et al.
(författare)
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The Bothriolepis (Placodermi, Antiarcha) material from the Valentia Slate Formation of the Iveragh Peninsula (middle Givetian, Ireland) : Morphology, evolutionary and systematic considerations, phylogenetic and palaeogeographic implications
- 2023
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 18:2
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Tidskriftsartikel (refereegranskat)abstract
- Material of the antiarch placoderm Bothriolepis from the middle Givetian of the Valentia Slate Formation in Iveragh Peninsula, Ireland, is described and attributed to a new species, B. dairbhrensis sp. nov. A revision of the genus Bothriolepis is proposed, and its taxonomic content and previous phylogenetic analyses are reviewed, as well as the validity of morphologic characteristics considered important for the establishment of the genus, such as the shape of the preorbital recess of the neurocranium. A series of computerised phylogenetic analyses was performed, which reveals that our new species is the sister taxon to the Frasnian Scottish form B. gigantea. New phylogenetic and biogeographic analyses of the genus Bothriolepis together with comparisons between faunal assemblages reveal a first northward dispersal wave from Gondwana to Euramerica at the latest in the mid Givetian. Other Euramerican species of Bothriolepis seem to belong to later dispersal waves from Gondwana, non-excluding southward waves from Euramerica. Questions remain open such as the taxonomic validity and stratigraphic constraints for the most ancient forms of Bothriolepis in China, and around the highly speciose nature of the genus.
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| 4. |
- 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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| 5. |
- 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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| 6. |
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