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- Bazzi, Mohamad, et al.
(författare)
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Static Dental Disparity and Morphological Turnover in Sharks across the End-Cretaceous Mass Extinction
- 2018
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Ingår i: Current Biology. - : CELL PRESS. - 0960-9822 .- 1879-0445. ; 28:16, s. 2607-2615
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Tidskriftsartikel (refereegranskat)abstract
- 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].
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| 2. |
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| 3. |
- Bazzi, Mohamad, et al.
(författare)
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Tooth morphology elucidates shark evolution across the end-Cretaceous mass extinction
- 2021
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Ingår i: PLoS biology. - : Public Library of Science (PLoS). - 1544-9173 .- 1545-7885. ; 19:8
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Tidskriftsartikel (refereegranskat)abstract
- Sharks (Selachimorpha) are iconic marine predators that have survived multiple mass extinctions over geologic time. Their prolific fossil record is represented mainly by isolated shed teeth, which provide the basis for reconstructing deep time diversity changes affecting different selachimorph clades. By contrast, corresponding shifts in shark ecology, as measured through morphological disparity, have received comparatively limited analytical attention. Here, we use a geometric morphometric approach to comprehensively examine tooth morphologies in multiple shark lineages traversing the catastrophic end-Cretaceous mass extinction-this event terminated the Mesozoic Era 66 million years ago. Our results show that selachimorphs maintained virtually static levels of dental disparity in most of their constituent clades across the Cretaceous-Paleogene interval. Nevertheless, selective extinctions did impact apex predator species characterized by triangular blade-like teeth. This is particularly evident among lamniforms, which included the dominant Cretaceous anacoracids. Conversely, other groups, such as carcharhiniforms and orectolobiforms, experienced disparity modifications, while heterodontiforms, hexanchiforms, squaliforms, squatiniforms, and dagger synechodontiforms were not overtly affected. Finally, while some lamniform lineages disappeared, others underwent postextinction disparity increases, especially odontaspidids, which are typified by narrow-cusped teeth adapted for feeding on fishes. Notably, this increase coincides with the early Paleogene radiation of teleosts as a possible prey source, and the geographic relocation of disparity sampling "hotspots," perhaps indicating a regionally disjunct extinction recovery. Ultimately, our study reveals a complex morphological response to the end-Cretaceous mass extinction and highlights an event that influenced the evolution of modern sharks.
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| 4. |
- Blom, Henning, 1969-
(författare)
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A new anaspid fish from the middle Silurian Cowie Harbour fish bed of Stonehaven, Scotland
- 2008
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Ingår i: Journal of Vertebrate Paleontology. - 0272-4634 .- 1937-2809. ; 28:3, s. 594-600
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Tidskriftsartikel (refereegranskat)abstract
- A new birkeniid anaspid, Cowielepis ritchiei gen. et sp. nov., from the mid Silurian Cowie Harbour fish bed in Scotland is described on the basis of three specimens. Although sharing characters with various well-known anaspids, it possesses a unique combination of features that justifies the establishment of a new genus. Cowielepis is characterized by a single row of dorsolateral scales and a distinctive skull roof pattern with a large pineal plate and elongated posterior plates. The presence of paired ventrolateral fins in C. ritchiei supports previous suggestions that all anaspids possess such fins, but leaves open the question of homology with the gnathostome pectoral fin.
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| 7. |
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| 8. |
- Blom, Henning, Dr, 1969-, et al.
(författare)
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Thelodont scales from the Lower Devonian of Novaya Zemlya Archipelago, Arctic Russia.
- 2022
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Ingår i: Spanish Journal of Palaeontology. - : Universitat de Valencia. - 2255-0550 .- 2660-9568.
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Tidskriftsartikel (refereegranskat)abstract
- Scales of a new thelodont species, Amaltheolepis terranovi sp. nov., are described from the upper Emsian, Lower Devonian Shevchenkinskaya Formation of Novaya Zemlya, Arctic Russia. The new species shows strong resemblance with the Emsian “Verdalen assemblage” from Spitsbergen, supporting an Emsian age for the upper part of the Shevchenkinskaya Formation. This conclusion in the context of the various Amaltheolepisassemblages from Spitsbergen allows for a more accurate comparison and correlation between assemblages from different regions in the Northern Hemisphere, suggesting that the type species, Amaltheolepis winsnesifrom Spitsbergen, is Eifelian in age
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| 9. |
- Bremer, Oskar, 1985-, et al.
(författare)
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Biostratigraphy of early vertebrates on Gotland
- 2014
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Ingår i: 4th Annual Meeting of IGCP 591, Estonia, 10 - 19 June 2014.. - Tartu : University of Tartu. - 9789985408223 ; , s. 21-21
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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