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Blom, Henning
Publications (10 of 74) Show all publications
Zaton, M., Niedzwiedzki, G., Rakocinski, M., Blom, H. & Kear, B. P. (2018). Earliest Triassic metazoan bioconstructions from East Greenland reveal a pioneering benthic community in the immediate aftermath of the end-Permian mass extinction. Global and Planetary Change, 167, 87-98
Open this publication in new window or tab >>Earliest Triassic metazoan bioconstructions from East Greenland reveal a pioneering benthic community in the immediate aftermath of the end-Permian mass extinction
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2018 (English)In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 167, p. 87-98Article in journal (Refereed) Published
Abstract [en]

Marine benthic ecosystems collapsed during the catastrophic end-Permian mass extinction, and subsequently endured a protracted phase of biotic recovery under harsh environmental conditions. In particular, metazoan reef communities almost totally disappeared and were replaced by microbe-dominated mounds during the latest Permian-earliest Triassic. Here we report the stratigraphically oldest exclusively metazoan bioconstructions from earliest Triassic (mid-Induan) strata in East Greenland - these formed within the first ca 300 ka after the Permian-Triassic boundary. Unlike the multitaxic sponge-microbe and bivalve-based buildups recorded from the Early Triassic peri-paleoequatorial Panthalassan and Tethyan margins, the East Greenland bioaccumulations developed within a restricted Boreal mid-paleolatitude seaway, and comprised a monospecific primary framework of microconchid 'lophophorate tubes with shell fragments and phosphatic debris cemented by biogenic calcite. Prostrate growth of the microconchids likely facilitated their accretion into successive sheet-like biostromes and small bioherms. These are associated with a regional paleoenvironmental shift towards well-oxygenated bottom waters, and locally punctuated sedimentation that created a favorable habitat. Although microconchids were both abundant and geographically widespread throughout the earliest Triassic, such buildups formed solely by these metazoans have not been reported from that time frame outside the Boreal Realm. These apparently flourished in the absence of more stable complex communities, and suggest that a locally variable, rather than ubiquitously sequential revival of metazoan bioconstruction activity took place in the immediate aftermath of the end-Permian extinction. However, these may also suggest that ecological recovery of benthic marine ecosystems following the end-Permian mass extinction might have started earlier in higher paleolatitudes.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Microconchids, Boreal Realm, Reefs, Build-ups, Paleoecology, Biotic crisis
National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-361676 (URN)10.1016/j.gloplacha.2018.05.009 (DOI)000438322900007 ()
Funder
Swedish Polar Research SecretariatWallenberg Foundations
Available from: 2018-10-08 Created: 2018-10-08 Last updated: 2018-10-08Bibliographically approved
Bazzi, M., Kear, B. P., Blom, H., Ahlberg, P. & Campione, N. E. (2018). Static Dental Disparity and Morphological Turnover in Sharks across the End-Cretaceous Mass Extinction. Current Biology, 28(16), 2607-2615
Open this publication in new window or tab >>Static Dental Disparity and Morphological Turnover in Sharks across the End-Cretaceous Mass Extinction
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2018 (English)In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 28, no 16, p. 2607-2615Article in journal (Refereed) Published
Abstract [en]

The Cretaceous-Palaeogene (K-Pg) mass extinction profoundly altered vertebrate ecosystems and prompted the radiation of many extant clades [1, 2]. Sharks (Selachimorpha) were one of the few larger-bodied marine predators that survived the K-Pg event and are represented by an almost-continuous dental fossil record. However, the precise dynamics of their transition through this interval remain uncertain [3]. Here, we apply 2D geometric morphometrics to reconstruct global and regional dental morphospace variation among Lamniformes (Mackerel sharks) and Carch-arhiniformes (Ground sharks). These clades are prevalent predators in today's oceans, and were geographically widespread during the late Cretaceous-early Palaeogene. Our results reveal a decoupling of morphological disparity and taxonomic richness. Indeed, shark disparity was nearly static across the K-Pg extinction, in contrast to abrupt declines among other higher-trophic-level marine predators [4, 5]. Nevertheless, specific patterns indicate that an asymmetric extinction occurred among lamniforms possessing lowcrowned/triangular teeth and that a subsequent proliferation of carcharhiniforms with similar tooth morphologies took place during the early Paleocene. This compositional shift in post-Mesozoic shark lineages hints at a profound and persistent K-Pg signature evident in the heterogeneity of modern shark communities. Moreover, such wholesale lineage turnover coincided with the loss of many cephalopod [6] and pelagic amniote [5] groups, as well as the explosive radiation of middle trophic-level teleost fishes [1]. We hypothesize that a combination of prey availability and post-extinction trophic cascades favored extant shark antecedents and laid the foundation for their extensive diversification later in the Cenozoic [7-10].

Place, publisher, year, edition, pages
CELL PRESS, 2018
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-363937 (URN)10.1016/j.cub.2018.05.093 (DOI)000442111300030 ()30078565 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationThe Royal Swedish Academy of Sciences, GS2017-0018
Available from: 2018-10-23 Created: 2018-10-23 Last updated: 2018-10-23Bibliographically approved
Bremer, O., Niedzwiedzki, G., Blom, H., Dec, M. & Kozłowski, W. (2018). Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland. Geological Magazine, 155(7), 1523-1541
Open this publication in new window or tab >>Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland
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2018 (English)In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 155, no 7, p. 1523-1541Article in journal (Refereed) Published
Abstract [en]

Vertebrate microremains from the upper Silurian Winnica Formation in the Holy Cross Mountains, Poland are described from the Winnica and Rzepin sections. Both sites record the uppermost part of the Supianka Member, but represent different depositional environments. The Winnica samples come from a low-energy environment, while the Rzepin sample was taken from a high-energy, oolitic facies. Both sites contain thelodonts Thelodus parvidens, Thelodus trilobatus, an anaspid cf. Liivilepis and a number of acanthodian scales of 'nostolepid', poracanthodid and 'gomphonchid' types. Notable differences between the sites are the addition of the osteostracan Tahulaspis cf. ordinata, the thelodont Paralogania ludlowiensis and acanthodian scales identified as Nostolepis gracilis in the Rzepin section. Placing the vertebrate faunas within the vertebrate biozonation established for the Silurian proved difficult. The suggested late Ludlow age for the Supianka Member based on sequence stratigraphical and chemostratigraphical correlations cannot be definitely confirmed or refuted, but a late Ludfordian age seems the most plausible based on invertebrate and vertebrate faunas. The much lower abundance of poracanthodid acanthodians in the Rzepin sample supports the notion of Poracanthodes porosus Zone as a deep-water equivalent to a number of vertebrate biozones. The presence of P. ludlowiensis only in the oolitic sample confirms a long temporal range, but restricted environmental distribution for this taxon.

National Category
Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-281657 (URN)10.1017/S0016756817000681 (DOI)000443814900008 ()
Available from: 2016-03-29 Created: 2016-03-29 Last updated: 2018-11-06Bibliographically approved
Chen, D. L., Blom, H., Sanchez, S., Tafforeau, P., Märss, T. & Ahlberg, P. E. (2017). Development of cyclic shedding teeth from semi-shedding teeth: the inner dental arcade of the stem osteichthyan Lophosteus . Royal Society Open Science, 4(5), Article ID 161084.
Open this publication in new window or tab >>Development of cyclic shedding teeth from semi-shedding teeth: the inner dental arcade of the stem osteichthyan Lophosteus 
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2017 (English)In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 4, no 5, article id 161084Article in journal (Refereed) Published
Abstract [en]

The numerous cushion-shaped tooth-bearing plates attributed to the stem-group osteichthyan Lophosteus superbus, which are argued here to represent the ancient form of inner dental arcade, display a unique and presumably primitive way of tooth shedding by basal hard tissue resorption. They carry regularly spaced, recumbent, gently recurved teeth arranged in transverse tooth files that diverge towards the lingual margin of the cushion. Three-dimensional (3D) reconstruction from propagation phase contrast synchrotron microtomography (PPC-SRμCT) reveals remnants of the first-generation teeth embedded in the basal plate that have never been discerned in any taxa. These teeth were shed by semi-basal resorption with the periphery of their bases retained as dentine rings. The rings are highly overlapped, which evidences tooth shedding prior to adding the next first-generation tooth. Later teeth at the same sites underwent cyclical replacing and shedding through basal resorption, producing stacks of buried resorption surfaces separated by bone of attachment. The number and spatial arrangement of resorption surfaces elucidates that basal resorption of replacement teeth had taken place at the older tooth sites before the addition of the youngest first-generation teeth at the lingual margin. Thus the replacement tooth buds cannot have been generated by a single permanent dental lamina, but must have arisen either from successional dental laminae associated with the predecessor teeth, or directly from the dental epithelium of these teeth. The virtual histological dissection of these Late Silurian microfossils broadens our understanding of the development of the gnathostome dental systems and the acquisition of the osteichthyan-type of tooth replacement. 

Place, publisher, year, edition, pages
ROYAL SOC, 2017
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-315882 (URN)10.1098/rsos.161084 (DOI)000402541800020 ()28573003 (PubMedID)
Available from: 2017-02-22 Created: 2017-02-22 Last updated: 2017-08-02Bibliographically approved
Qu, Q., Sanchez, S., Zhu, M., Blom, H. & Ahlberg, P. E. (2017). The origin of novel features by changes in developmental mechanisms: ontogeny and three-dimensional microanatomy of polyodontode scales of two early osteichthyans. Biological Reviews, 92(2), 1189-1212
Open this publication in new window or tab >>The origin of novel features by changes in developmental mechanisms: ontogeny and three-dimensional microanatomy of polyodontode scales of two early osteichthyans
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2017 (English)In: Biological Reviews, ISSN 1464-7931, E-ISSN 1469-185X, Vol. 92, no 2, p. 1189-1212Article in journal (Refereed) Published
Abstract [en]

Recent advances in synchrotron imaging allow us to study the three-dimensional (3D) histology of vertebrate fossils, including microfossils (e.g. teeth and scales) of early jawed vertebrates. These microfossils can often be scanned at submicron resolution (<1 µm) because of their small size. The resulting voxel (3D pixel) stacks can be processed into virtual thin sections revealing almost every internal detail of the samples, comparable to traditional thin sections. In addition, 3D models of the internal microanatomical structures, such as embedded odontodes and vasculature, can be assembled and examined in situ. Scales of two early osteichthyans, Psarolepis romeri from the Early Devonian of China and Andreolepis hedei from the Late Silurian of Sweden, were scanned using propagation phase-contrast synchrotron X-ray microtomography (PPC-SRµCT), and 3D models of internal canal systems and buried odontodes were created from the scans. Based on these new data, we review the evolutionary origin of cosmine and its associated pore-canal system, which has been long recognized as a synapomorphy of sarcopterygians. The first odontode that appeared during growth shows almost identical morphology in the two scales, but the second odontode of the Psarolepis scale shows a distinctive morphology with several pores on the surface. It is suggested that a shift from ridge-like odontode to pore-bearing odontode was the key step in the origin of cosmine, which was then elaborated further in more-derived sarcopterygians. We perform a detailed comparison between the two scales and propose a primary homology framework to generate microanatomical characters, which can be used in the phylogenetic analysis of early osteichthyans when more 3D data become available. Our results highlight the importance of 3D data for the study of histology and ontogeny of the dermal skeleton of early jawed vertebrates, especially scales of the polyodontode type. The traditional microvertebrate collection is not only useful for biostratigraphic studies, but also preserves invaluable biological information about the growth of vertebrate hard tissues. Today, we are only beginning to understand the biological meaning of the new 3D data. The increasing availability of such data will enable, and indeed require, a complete revision of traditional palaeohistological studies on early vertebrates.

National Category
Evolutionary Biology Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-298047 (URN)10.1111/brv.12277 (DOI)000398567200032 ()27194072 (PubMedID)
Funder
EU, European Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2016-06-29 Created: 2016-06-29 Last updated: 2017-05-04Bibliographically approved
Bremer, O., Niedźwiedzki, G., Blom, H., Dec, M. & Kozłowski, W. (2017). Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland. In: : . Paper presented at 14th International Symposium on Early and Lower Vertebrates in the Holy Cross Mountains, Poland, July 3-8 2017.
Open this publication in new window or tab >>Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland
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2017 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-328147 (URN)
Conference
14th International Symposium on Early and Lower Vertebrates in the Holy Cross Mountains, Poland, July 3-8 2017
Available from: 2017-08-18 Created: 2017-08-18 Last updated: 2017-11-27Bibliographically approved
Zaton, M., Niedzwiedzki, G., Blom, H. & Kear, B. P. (2016). Boreal earliest Triassic biotas elucidate globally depauperate hard substrate communities after the end-Permian mass extinction. Scientific Reports, 6, Article ID 36345.
Open this publication in new window or tab >>Boreal earliest Triassic biotas elucidate globally depauperate hard substrate communities after the end-Permian mass extinction
2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 36345Article in journal (Refereed) Published
Abstract [en]

The end-Permian mass extinction constituted the most devastating biotic crisis of the Phanerozoic. Its aftermath was characterized by harsh marine conditions incorporating volcanically induced oceanic warming, widespread anoxia and acidification. Bio-productivity accordingly experienced marked fluctuations. In particular, low palaeolatitude hard substrate communities from shallow seas fringing Western Pangaea and the Tethyan Realm were extremely impoverished, being dominated by monogeneric colonies of filter-feeding microconchid tubeworms. Here we present the first equivalent field data for Boreal hard substrate assemblages from the earliest Triassic (Induan) of East Greenland. This region bordered a discrete bio-realm situated at mid-high palaeolatitude (> 30 degrees N). Nevertheless, hard substrate biotas were compositionally identical to those from elsewhere, with microconchids encrusting Claraia bivalves and algal buildups on the sea floor. Biostratigraphical correlation further shows that Boreal microconchids underwent progressive tube modification and unique taxic diversification concordant with changing habitats over time. We interpret this as a post-extinction recovery and adaptive radiation sequence that mirrored coeval subequatorial faunas, and thus confirms hard substrate ecosystem depletion as a hallmark of the earliest Triassic interval globally.

National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-309809 (URN)10.1038/srep36345 (DOI)000387314500001 ()27821855 (PubMedID)
Funder
Swedish Polar Research Secretariat
Available from: 2016-12-14 Created: 2016-12-07 Last updated: 2017-11-29Bibliographically approved
Hairapetian, V., Blom, H. & Turner, S. (2016). Early Frasnian thelodont scales from central Iran and their implications for turiniid taxonomy, systematics and distribution. Journal of Vertebrate Paleontology, 36(3), Article ID e1100632.
Open this publication in new window or tab >>Early Frasnian thelodont scales from central Iran and their implications for turiniid taxonomy, systematics and distribution
2016 (English)In: Journal of Vertebrate Paleontology, ISSN 0272-4634, E-ISSN 1937-2809, Vol. 36, no 3, article id e1100632Article in journal (Refereed) Published
Abstract [en]

We describe isolated shark teeth collected in levels of the Calafate Formation (Maastrichtian, Late Cretaceous) on the southeast coast of Argentino Lake, Calafate City, Santa Cruz Province, Argentina. The teeth belong to the hexanchiform Notidanodon dentatus, a new species of the squaliform Protosqualus, and an indeterminate species of the echinorhiniform genus Echinorhinus. The record of Notidanodon constitutes the first in South America. The report of Notidanodon associated with plesiosaur remains is in accordance with previous records from around the world. Protosqualus argentinensis, nov. sp., which is the first record of the genus in South America, is characterized by having teeth with a apicobasally tall root and serrated cutting edges, among other features.Echinorhinus sp. constitutes one of the oldest records of this genus on the continent and one of the few Mesozoic records worldwide. This shark association is clearly distinct from coeval selachian faunas from northern Patagonia, which exhibit clear Tethyan influences. Instead, it shows some similarities to other high-latitude selachian faunas, including Australia, New Zealand, and Antarctica. It is possible that the Cretaceous selachian assemblages of Patagonia may be separated into two different associations: northern Patagonian faunas are related to more temperate associations of lower paleolatitudes, whereas those of southern Patagonia are closer to other southern localities.

National Category
Natural Sciences Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-282430 (URN)10.1080/02724634.2016.1100632 (DOI)000374557800011 ()
Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2017-11-30Bibliographically approved
Wretman, L., Blom, H. & Kear, B. P. (2016). Resolution of the Early Jurassic actinopterygian fish Pachycormus and a dispersal hypothesis for Pachycormiformes. Journal of Vertebrate Paleontology, 36(5), Article ID e1206022.
Open this publication in new window or tab >>Resolution of the Early Jurassic actinopterygian fish Pachycormus and a dispersal hypothesis for Pachycormiformes
2016 (English)In: Journal of Vertebrate Paleontology, ISSN 0272-4634, E-ISSN 1937-2809, Vol. 36, no 5, article id e1206022Article in journal (Refereed) Published
Abstract [en]

The Early Jurassic (Toarcian) actinopterygian Pachycormus is a basal taxon within Pachycormiformes, a Mesozoic marine neopterygian radiation that evolved an extreme ecomorph divergence between hyperspecialized billfish-like' macrocarnivores and gigantic suspension feeders, including the largest fish of all time. Current phylogenies place Pachycormus as an early member of the suspension-feeding lineage; however, species disparity renders character states uncertain and potential exists for considerable intraspecific variability. Given its importance for resolution of pachycormiform phylogenetic topology, we comprehensively reassessed Pachycormus fossils housed in collections across Europe and found that the proportional traits traditionally used to discriminate between species are actually consistent with an ontogenetic size morphocline. Our cladistic analyses further show that the monotypic senior synonym, Pachycormus macropterus, is a wildcard that manifests a mosaic of transitional states. This has significant implications for hypothesized Toarcian marine vertebrate provincialism because P. macropterus had a ubiquitous Boreal Tethyan distribution. Moreover, our tree-based palaeobiogeographical optimizations infer that the western Tethyan region was a pachycormiform dissemination center, with global dispersals occurring through transoceanic migration and invasion of epeiric basins.Citation for this article: Wretman, L., H. Blom, and B. P. Kear. 2016. Resolution of the Early Jurassic actinopterygian fish Pachycormus and a dispersal hypothesis for Pachycormiformes. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1206022.

National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:uu:diva-305928 (URN)10.1080/02724634.2016.1206022 (DOI)000384029300020 ()
Available from: 2016-11-14 Created: 2016-10-24 Last updated: 2017-11-29Bibliographically approved
Chen, D., Blom, H., Sanchez, S., Tafforeau, P. & Ahlberg, P. (2016). The stem osteichthyan Andreolepis and the origin of tooth replacement. Nature, 539(7628), 237-+
Open this publication in new window or tab >>The stem osteichthyan Andreolepis and the origin of tooth replacement
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2016 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 539, no 7628, p. 237-+Article in journal (Refereed) Published
Abstract [en]

The teeth of gnathostomes (jawed vertebrates) show rigidly patterned, unidirectional replacement that may or may not be associated with a shedding mechanism. These mechanisms, which are critical for the maintenance of the dentition, are incongruently distributed among extant gnathostomes. Although a permanent tooth-generating dental lamina is present in all chondrichthyans, many tetrapods and some teleosts, it is absent in the non-teleost actinopterygians. Tooth-shedding by basal hard tissue resorption occurs in most osteichthyans (including tetrapods) but not in chondrichthyans. Here we report a three-dimensional virtual dissection of the dentition of a 424-million-year-old stem osteichthyan, Andreolepis hedei, using propagation phase-contrast synchrotron microtomography, with a reconstruction of its growth history. Andreolepis, close to the common ancestor of all extant osteichthyans, shed its teeth by basal resorption but probably lacked a permanent dental lamina. This is the earliest documented instance of resorptive tooth shedding and may represent the primitive osteichthyan mode of tooth replacement.

National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-310754 (URN)10.1038/nature19812 (DOI)000387318500034 ()27750278 (PubMedID)
Funder
EU, European Research Council, 233111Knut and Alice Wallenberg Foundation
Available from: 2016-12-20 Created: 2016-12-19 Last updated: 2017-11-29Bibliographically approved
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