scholarly journals Molecular clocks indicate turnover and diversification of modern coleoid cephalopods during the Mesozoic Marine Revolution

2017 ◽  
Vol 284 (1850) ◽  
pp. 20162818 ◽  
Author(s):  
Alastair R. Tanner ◽  
Dirk Fuchs ◽  
Inger E. Winkelmann ◽  
M. Thomas P. Gilbert ◽  
M. Sabrina Pankey ◽  
...  
Keyword(s):  
Molecular Clocks ◽  
Early Mesozoic ◽  
Bony Fishes ◽  
Unique Nature ◽  
Molecular Dataset ◽  
Divergence Estimates ◽  
Mesozoic Marine Revolution ◽  
Marine Vertebrates ◽  
Cephalopod Evolution ◽  
Coleoid Cephalopod

Coleoid cephalopod molluscs comprise squid, cuttlefish and octopuses, and represent nearly the entire diversity of modern cephalopods. Sophisticated adaptations such as the use of colour for camouflage and communication, jet propulsion and the ink sac highlight the unique nature of the group. Despite these striking adaptations, there are clear parallels in ecology between coleoids and bony fishes. The coleoid fossil record is limited, however, hindering confident analysis of the tempo and pattern of their evolution. Here we use a molecular dataset (180 genes, approx. 36 000 amino acids) of 26 cephalopod species to explore the phylogeny and timing of cephalopod evolution. We show that crown cephalopods diverged in the Silurian–Devonian, while crown coleoids had origins in the latest Palaeozoic. While the deep-sea vampire squid and dumbo octopuses have ancient origins extending to the Early Mesozoic Era, 242 ± 38 Ma, incirrate octopuses and the decabrachian coleoids (10-armed squid) diversified in the Jurassic Period. These divergence estimates highlight the modern diversity of coleoid cephalopods emerging in the Mesozoic Marine Revolution, a period that also witnessed the radiation of most ray-finned fish groups in addition to several other marine vertebrates. This suggests that that the origin of modern cephalopod biodiversity was contingent on ecological competition with marine vertebrates.

scholarly journals Anti-predator adaptations in a great scallop (Pecten maximus) – a palaeontological perspective

2015 ◽  
Vol 1 (1-2) ◽  
pp. 16-20 ◽  
Author(s):  
Krzysztof Roman Brom ◽  
Krzysztof Szopa ◽  
Tomasz Krzykawski ◽  
Tomasz Brachaniec ◽  
Mariusz Andrzej Salamon
Keyword(s):  
Mechanical Strength ◽  
Middle Part ◽  
Predation Pressure ◽  
Shell Morphology ◽  
Pecten Maximus ◽  
Shell Weight ◽  
Predator Attack ◽  
Early Mesozoic ◽  
Mesozoic Marine Revolution ◽  
Highly Porous

Abstract Shelly fauna was exposed to increased pressure exerted by shell-crushing durophagous predators during the so-called Mesozoic Marine Revolution that was initiated in the Triassic. As a result of evolutionary ‘arms race’, prey animals such as bivalves, developed many adaptations to reduce predation pressure (e.g. they changed lifestyle and shell morphology in order to increase their mechanical strength). For instance, it was suggested that Pectinidae had acquired the ability to actively swim to avoid predator attack during the early Mesozoic. However, pectinids are also know to have a specific shell microstructure that may effectively protect them against predators. For instance, we highlight that the shells of some recent pectinid species (e.g. Pecten maximus) that display cross-lamellar structures in the middle part playing a significant role in the energy dissipation, improve the mechanical strength. In contrast, the outer layers of these bivalves are highly porous, which allow them to swim more efficiently by reducing the shell weight. Pectinids are thus perfect examples of animals optimising their skeletons for several functions. We suggest that such an optimisation of their skeletons for multiple functions likely occurred as a results of increased predation pressure during the so-called Mesozoic Marine Revolution.

scholarly journals Biogeography of worm lizards (Amphisbaenia) driven by end-Cretaceous mass extinction

2015 ◽  
Vol 282 (1806) ◽  
pp. 20143034 ◽  
Author(s):  
Nicholas R. Longrich ◽  
Jakob Vinther ◽  
R. Alexander Pyron ◽  
Davide Pisani ◽  
Jacques A. Gauthier
Keyword(s):  
North America ◽  
Mass Extinction ◽  
Continental Drift ◽  
Molecular Clocks ◽  
Mass Extinctions ◽  
The North ◽  
Divergence Estimates ◽  
Dispersal Events

Worm lizards (Amphisbaenia) are burrowing squamates that live as subterranean predators. Their underground existence should limit dispersal, yet they are widespread throughout the Americas, Europe and Africa. This pattern was traditionally explained by continental drift, but molecular clocks suggest a Cenozoic diversification, long after the break-up of Pangaea, implying dispersal. Here, we describe primitive amphisbaenians from the North American Palaeocene, including the oldest known amphisbaenian, and provide new and older molecular divergence estimates for the clade, showing that worm lizards originated in North America, then radiated and dispersed in the Palaeogene following the Cretaceous-Palaeogene (K-Pg) extinction. This scenario implies at least three trans-oceanic dispersals: from North America to Europe, from North America to Africa and from Africa to South America. Amphisbaenians provide a striking case study in biogeography, suggesting that the role of continental drift in biogeography may be overstated. Instead, these patterns support Darwin and Wallace's hypothesis that the geographical ranges of modern clades result from dispersal, including oceanic rafting. Mass extinctions may facilitate dispersal events by eliminating competitors and predators that would otherwise hinder establishment of dispersing populations, removing biotic barriers to dispersal.

Terquemia (Dentiterquemia) eudesdeslongchampsinew subgenus and species, an interesting cementing bivalve from the Lower Jurassic of the western Carpathians (Slovakia)

2004 ◽  
Vol 78 (6) ◽  
pp. 1086-1090 ◽  
Author(s):  
M. Hautmann ◽  
M. Golej
Keyword(s):  
Mass Extinction ◽  
Type Species ◽  
Sensu Stricto ◽  
Lower Jurassic ◽  
Western Carpathians ◽  
Defense Strategy ◽  
Early Mesozoic ◽  
New Subgenus ◽  
Mesozoic Marine Revolution ◽  
Permian Mass Extinction

Based on well-preserved material from the Sinemurian of the western Carpathians, the new subgenusTerquemia (Dentiterquemia) is proposed, which is presently represented only by its type speciesT. (Dentiterquemia) eudesdeslongchampsin. sp.Dentiterquemiais separated fromTerquemiasensu stricto by a series of denticles along the hinge margin and corresponding, chevronlike ridges on the ligament area. The combination of hinge teeth with a cementing habit is interpreted as a defense strategy inhibiting torsion of the valves as well as manipulation of the animal as a whole. Whereas different kinds of articulating hinge structures evolved independently in several clades of early Mesozoic cementing bivalves, Paleozoic cementing bivalves generally lack such structures. It is proposed that this difference reflects an early Mesozoic proliferation of durophagous predators and therefore points to a beginning of the “Mesozoic marine revolution” soon after the end-Permian mass extinction.

Intrinsic versus extrinsic biases in the fossil record: contrasting the fossil record of echinoids in the Triassic and early Jurassic using sampling data, phylogenetic analysis, and molecular clocks

Paleobiology ◽  
2007 ◽  
Vol 33 (2) ◽  
pp. 310-323 ◽  
Author(s):  
Andrew B. Smith
Keyword(s):  
Fossil Record ◽  
Critical Time ◽  
Lower Jurassic ◽  
Time Interval ◽  
Molecular Clocks ◽  
The Past ◽  
Consistent Feature ◽  
Divergence Estimates ◽  
Lineage Analysis

Four independent lines of evidence, (1) the quality of specimen preservation, (2) taxonomic collection curves, (3) molecular divergence estimates, and (4) ghost lineage analysis of a genus-level cladogram, point to echinoids having a much poorer fossil record in the Triassic than in the Lower Jurassic. Furthermore, preservational differences between Triassic and Lower Jurassic echinoids have remained a consistent feature over 160 years of discovery. Differences exist in how effectively paleontologists have collected the fauna from available outcrops in the Triassic and Lower Jurassic. Collection curves suggest that rocks have been more efficiently searched for their fossils in Europe than elsewhere in the world, and that Lower Jurassic faunas are better sampled from available outcrop than Triassic faunas. The discovery of Triassic taxa has quickened in pace over the past 4 decades (though largely driven by a single Lagerstätte—the St. Cassian beds) while discoveries of new taxa from the Lower Jurassic have slowed. Molecular analysis of extant families and ghost lineage analysis of Triassic and Lower Jurassic genera both point to poorer sampling of Triassic faunas. This difference in the quality of the fossil record may be partially explained by differences in rock outcrop area, as marine sedimentary rocks are much less common in the Triassic than in the Lower Jurassic. However, improving biomechanical design of the echinoid test over this critical time interval was probably as important, and better explains observed preservational trends. Changes in the quality of the echinoid fossil record were thus driven as much by intrinsic biological factors as by sampling patterns.

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