The Mesozoic marine revolution (MMR) refers to the increase in shell-crushing (durophagous) and boring predation in benthic organisms throughout the Mesozoic era (251 Mya to 66 Mya), along with bulldozing and sediment remodelling in marine habitats. [1] The term was first coined by Geerat J. Vermeij, [2] who based his work on that of Steven M. Stanley. [3] [4] [5] While the MMR was initially restricted to the Cretaceous (145 Mya to 66 Mya), more recent studies have suggested that the beginning of this ecological/evolutionary arms race extends as far back as the Triassic, [6] [7] [8] with the MMR now being considered to have started in the Anisian [9] or the Aalenian. [10] It is an important transition between the Palaeozoic evolutionary fauna and the Modern evolutionary fauna that occurred throughout the Mesozoic.
The Mesozoic marine revolution was not the first bout of increased predatory pressure; that occurred around the end of the Ordovician. [11] There is some evidence of adaptation to durophagy during the Palaeozoic, particularly in crinoids. [12]
The Mesozoic marine revolution was driven by the evolution of shell-crushing behaviour among Mesozoic marine predators, particularly marine reptiles, with the technique being perfected in the Late Cretaceous. This forced shelled marine invertebrates to develop defences against such predation or become extinct. The consequences of this can be seen in many invertebrates today. Such predators are thought to include: Triassic placodonts, Triassic ichthyosaurs, Triassic omphalosaurids, Triassic plesiosaurs, Jurassic pliosaurs, Late Cretaceous mosasaurs and Cretaceous ptychodontoid sharks. [2] Many gastropods also evolved to feed on prey with shells. [13] However, because most durophagous predators were generalists, their effect on anti-predator shell architecture has been viewed by some as diffuse and not as extensive as other authors have suggested. [14]
It is thought that the break-up of Pangaea and the formation of new oceans throughout the Mesozoic brought together previously isolated marine communities, forcing them to compete and adapt. The increased shelf space caused by sea-level rise and a hyper-greenhouse climate provided more iterations and chances to evolve, resulting in increasing biodiversity. [2]
The explosion of angiosperms in the Cretaceous also enhanced the hydrological cycling, speeding up rates of weathering and nutrient flow into the oceans, which has been cited as a possible driver of the MMR. [15]
Another proposal is the evolution of hermit crabs. These exploit the shells of dead gastropods, effectively doubling the life-span of the shell. This allows durophagous predators nearly twice the prey, making it a viable niche to exploit. [2]
The net result of the Mesozoic marine revolution was a change from the sedentary epifaunal lifestyle of the Palaeozoic evolutionary fauna to the infaunal/planktonic mode of life of the modern fauna. [5] Non-mobile types that failed to re-attach to their substrate (such as brachiopods) when removed were picked off as easy prey, whereas those that could hide from predation or be mobile enough to escape had an evolutionary advantage. [2] Per capita mean metabolic rates among marine gastropods living in shallow water increased by approximately 150% from the Late Triassic to the Late Cretaceous. [16]
Three major trends can be associated with this: [17]
Major casualties of the Mesozoic marine revolution include: sessile crinoids, gastropods, brachiopods and epifaunal bivalves.[ citation needed ]
The Mesozoic Marine Revolution heavily affected the crinoids, making the majority of their forms extinct. Their sessile nature made them easy prey for durophagous predators since the Triassic. [9] Survivors (such as the comatulids) could swim or crawl, behaved nocturnally or had autotomy (the ability to shed limbs in defence). [12]
The shift in the range of sessile stalked crinoids during the late Mesozoic from the shallow shelf to habitats further offshore suggests that they were forced by increased predation pressure in shallow water to migrate to a deep water refuge environment where predation pressure was lower and their mode of life more viable. [19] [20] This migration was not globally synchronous and delayed in the Southern Hemisphere; it did not occur until the Late Eocene in Australia and Antarctica, and until the Early Miocene in Zealandia. [21]
Echinoids do not suffer major predation (save for general infaunalisation) during the Mesozoic Marine Revolution but it is clear from bromalites (fossilised ‘vomit’) that cidaroids were consumed by predators. [22] Echinoids radiate into predatory niches and are thought to have perfected coral grazing in the Late Cretaceous. [2] Cidaroids too may have contributed to the downfall of the crinoids. [9] The increases in echinoid predation continued into the Cenozoic. [23]
Brachiopods, the dominant benthic organism of the Palaeozoic, suffered badly during the Mesozoic Marine Revolution. Their sessile foot-attached nature made them easy prey to durophagous predators. [2] The fact that they could not re-attach to a substrate if an attack failed meant their chances of survival were slim. Unlike bivalves, brachiopods never adapted to an infaunal habit (excluding lingulids) and so remained vulnerable throughout the Mesozoic Marine Revolution. As a result of increased predation pressure on top of heightened competition with bivalves, brachiopods became a minor component of most marine faunas by the Cenozoic despite their incredible diversity and abundance during the Palaeozoic and early Mesozoic. [24]
Bivalves adapted more readily than the brachiopods to this ecological transition. Many bivalves adopted an infaunal habit, using their siphons to gather nutrients from the sediment-water interface while remaining safe. [2] [5] Corbulids developed layers of conchiolin within their shells to better resist predation. [25] Others still, like Pecten, developed the ability to jump a short distance away from predators by contracting their valves.
Like brachiopods, epifaunal varieties of bivalves were preyed upon heavily. Among epifaunal types (such as mussels and oysters), the ability to fuse to the substrate made them more difficult to consume for smaller predators. Epifaunal bivalves were preyed on heavily before the Norian but extinction rates diminish after this. [17]
Benthic gastropods were heavily preyed upon throughout the Mesozoic Marine Revolution, the weaker shelled types being pushed out of the benthic zone into more isolated habitats. The Palaeozoic archaeogastropods were subsequently replaced by neritaceans, mesogastropods and neogastropods. [2] The former typically have symmetrical, umbilicate shells that are mechanically weaker than the latter. These lack an umbilicus and also developed the ability to modify the interior of their shells, allowing them to develop sculptures on their exterior to act as defence against predators. [2]
Another development among Muricidae was the ability to bore through shells and consume prey. These marks (while relatively rare) generally occur on sessile invertebrates, implying that they put pressure on Palaeozoic-type faunas during the Mesozoic Marine Revolution. [26]
Bryozoans exhibited no significant anti-predatory adaptations during the Jurassic, suggesting that they were during this period unaffected by the MMR. [27]
The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified.
Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are members of the largest crinoid order, Comatulida. Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. They live in both shallow water and in depths over 9,000 metres (30,000 ft).
Plesiosauroidea is an extinct clade of carnivorous marine reptiles. They have the snake-like longest neck to body ratio of any reptile. Plesiosauroids are known from the Jurassic and Cretaceous periods. After their discovery, some plesiosauroids were said to have resembled "a snake threaded through the shell of a turtle", although they had no shell.
Globidens is an extinct genus of mosasaurid oceanic lizard classified as part of the Globidensini tribe in the Mosasaurinae subfamily. Globidens belongs to the family Mosasauridae, which consists of several genera of predatory marine lizards of various sizes that were prevalent during the Late Cretaceous. Specimens of Globidens have been discovered in Angola, Brazil, Morocco, Syria and the United States. Among mosasaurs, Globidens is probably most well known for the highly rounded, globe-like teeth that give it its name.
Conulariida are an extinct group of medusozoan cnidarians known from fossils spanning from the latest Ediacaran up until the Late Triassic. They are almost exclusively known from their hard external structures, which were pyramidal in shape and made up of numerous lamellae.
Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and rays (Neoselachii) as part of the clade Euselachii. They are distinguished from other chondrichthyans by their distinctive fin spines and cephalic spines present on the heads of males. An ecologically diverse group, they were abundant in marine and freshwater environments during the late Paleozoic and early Mesozoic, but were rare in open marine environments by the end of the Jurassic, having been largely replaced by modern sharks, though they were still common in freshwater and marginal marine habitats. They survived until the end of the Cretaceous, before going extinct.
The origin of the brachiopods is uncertain; they either arose from reduction of a multi-plated tubular organism, or from the folding of a slug-like organism with a protective shell on either end. Since their Cambrian origin, the phylum rose to a Palaeozoic dominance, but dwindled during the Mesozoic.
Musculus somaliensis is an extinct species of small saltwater mussel, a fossil marine bivalve mollusc in the family Mytilidae, the mussels. The size, shape and sometimes color of these fossils are reminiscent of a pistachio nut.
Somalirhynchia africana is a species of extinct, medium-sized brachiopod, a marine rhynchonellate lampshell in the family Tetrarhynchiidae. It is roughly the size and shape of a 1-inch (25 mm) toy marble, and has about 29 ribs fanning out from the hinge.
The geological history of North America comprises the history of geological occurrences and emergence of life in North America during the interval of time spanning from the formation of the Earth through to the emergence of humanity and the start of prehistory. At the start of the Paleozoic Era, what is now "North" America was actually in the Southern Hemisphere. Marine life flourished in the country's many seas, although terrestrial life had not yet evolved. During the latter part of the Paleozoic, seas were largely replaced by swamps home to amphibians and early reptiles. When the continents had assembled into Pangaea, drier conditions prevailed. The evolutionary precursors to mammals dominated the country until a mass extinction event ended their reign.
The concept of the three great evolutionary faunas of marine animals from the Cambrian to the present was introduced by Jack Sepkoski in 1981 using factor analysis of the fossil record. An evolutionary fauna typically displays an increase in biodiversity following a logistic curve followed by extinctions.
The Agardhfjellet Formation is a geologic formation in Svalbard, Norway. It preserves fossils dating back to the Oxfordian to Berriasian stages, spanning the Late Jurassic-Early Cretaceous boundary. The formation contains the Slottsmøya Member, a highly fossiliferous unit (Lagerstätte) where many ichthyosaur and plesiosaur fossils have been found, as well as abundant and well preserved fossils of invertebrates.
This list, 2018 in paleomalacology, is a list of new taxa of ammonites and other fossil cephalopods, as well as fossil gastropods, bivalves and other molluscs that are scheduled to be described during the year 2018, as well as other significant discoveries and events related to molluscan paleontology that are scheduled to occur in the year 2018.
This list 2019 in paleomalacology is a list of new taxa of ammonites and other fossil cephalopods, as well as fossil gastropods, bivalves and other molluscs that are scheduled to be described during the year 2019, as well as other significant discoveries and events related to molluscan paleontology that are scheduled to occur in the year 2019.
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2018.
The Antalo Limestone, also known as the Antalo Sequence, is a geological formation in Ethiopia. It is between 300 and 800 metres thick and comprises fossiliferous limestones and marls that were deposited in a reef. Marine microfossils have shown an age between 165 and 150 million years.
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2019.
Elizabeth M. Harper (Liz) is an evolutionary biologist known for her work on molluscs. She is an honorary fellow of the British Antarctic Survey and was accorded the title of Honorary Professor by the University of Cambridge in 2019.
This list of fossil molluscs described in 2022 is a list of new taxa of fossil molluscs that were described during the year 2022, as well as other significant discoveries and events related to molluscan paleontology that occurred in 2022.
This list of fossil molluscs described in 2023 is a list of new taxa of fossil molluscs that were described during the year 2023, as well as other significant discoveries and events related to molluscan paleontology that occurred in 2023.