Usuario:LaraPoasting/Taller
Distribución, Hábitat y Taxonomía[editar]
This jellyfish is best known from the North Atlantic region, ranging from 4th parallel north (just north of Equator) to the North Sea and Atlantic Canada, including the Mediterranean and Gulf of Mexico.[2][3]
There are reports from most other tropical or warm temperate seas around the world, including both the Pacific and Indian Oceans, with its apparent southern limit being 42nd parallel south.[4][5] Some of the locations are California (rare),[6] Hawaii (rare),[5] and all around Australia (common).[7] However, it is suspected that Pelagia noctiluca—as currently defined—is a species complex with records outside the North Atlantic region involving other closely related species that presently are unrecognized or undescribed.[1] Even North Atlantic and South Atlantic populations show significant genetic differences.[8] A comprehensive taxonomic review is necessary to resolve the situation.[9] In 2014, a second species in the genus Pelagia was described from the Mediterranean, but two years later it was moved to its own genus as Mawia benovici.[10]
The swimming ability of Pelagia noctiluca is limited and as a result large swarms (also known as blooms) of this oceanic species are occasionally carried by the wind or current to inshore areas, sometimes ending up stranded on beaches.[4][2] This also means that the species sometimes appears in waters outside its normal temperature preference, with records as far north as the Shetland Islands and the Norwegian deep.[4] It generally occurs at water temperatures between 10 grados Celsius (50,0 °F) and 27 grados Celsius (80,6 °F), but below 11 grados Celsius (51,8 °F) it stops pulsating.[5] It mostly ranges from the surface to a depth of 150 metros (164 yd), but has been recorded to 1400 metros (1531,1 yd).[4] Pelagia noctiluca partakes in the diel vertical migration, occurring near the surface at night and deeper during the day.[11]
Local populations fluctuate greatly and the species may go virtually unrecorded in a region for years, only to suddenly reappear in huge swarms.[2][12][13] On occasion, a swarm may cover tens of square kilometers,[14] include millions of Pelagia noctiluca,[15] and reach densities of more than 500 individuals per m3 (14 per ft3).[11]
Comportamiento[editar]
Ciclo Vital y Reproducción[editar]
Pelagia noctiluca está adaptada a una vida pelágica, vive en el mar abierto. Mientras que otras especies, incluyendo miembros de su familia Pelagiidae, tienen fases vitales tanto nadadoras (plánula, éfira y medusa) como un pólipo que habita el fondo marino, P. noctiluca se ha adaptado de tal modo que la fáse de pólipo está ausente (cae entre la éfira y la medusa).[16] P. noctiluca se reproduce sexualmente, machos y hembras expulsan su esperma y huevos directamente al mar durante horas de luz. Al pasar 3 días, los huevos fertilizados se convierten en plánulas, esta fase se mueve exclusívamente mediante cilios, tras una semana, se convierten en pequeñas éfiras y al pasar un mes éstas se convierten directamente en medusas adultas.[5] Si las aguas rondan los 10ºC las éfiras apenas crecen,[12] no son capaces de sobrevivir a menos de 8ºC.[17] En su principio, la campana de P. noctiluca solo míde 1cm de diámetro, algunas pueden alcanzar la madurez sexual al alcanzar los 3.5cm de diámetro
only has a bell diameter of about 1 centímetro (0,4 plg). Some already reach maturity at 3,5 centímetros (1,4 plg) in bell diameter and at 6 centímetros (2,4 plg) all are mature.[12] In the Mediterranean Sea, P. noctiluca appear to mostly spawn between the late summer and early winter, but also at lower levels in the spring to early summer.[2][12] P. noctiluca rely on favorable trophic conditions to spawn, so when their criteria is not met, the medusae will stop reproducing immediately and lose weight when presented with an inadequate amount of food.[18] Large swarms of adults at the ocean surface in certain times of the year possibly are spawning aggregations.[2] This jellyfish typically lives for about 9 months.[12]
Feeding[editar]
Pelagia noctiluca are opportunistic and have been recorded feeding on a wide range of small organisms like planktonic crustaceans (cladocerans, copepods, ostracods and crustacean larvae), mollusk larvae, larvaceans, hydromedusae, siphonophorans, arrow worms, fish eggs and fish larvae,[5][2][11] as well as detritus suspended in the open water and microscopic phytoplankton.[19] The phytoplankton can be consumed either directly or indirectly by eating herbivorous crustaceans with stomachs filled with it. The ability to eat phytoplankton is—as far as known—highly unusual among cnidarians.[19] P. noctiluca will eat small warty comb jellies (Mnemiopsis leidyi), potentially helping to control this invasive species.[20] Cannibalism where adults consume young of their own species is also common in P. noctiluca.[11] The stomach contents of P. noctiluca also vary throughout the seasons. Copepods tend to be their largest food source all year round, but fish eggs and pteropods are a close second. During the spring months, P. noctiluca mainly prey on copepods and fish eggs, while pteropods are preyed on more during December and May. The variability in this species' diet suggests that they are generalists, and do not have strong prey selectivity.[21]
Feeding reactions were studied by Bozler (1926), where a piece of food was given to the marginal tentacle, the tentacle contracted quickly. There was a slow contraction of the coronal muscle which brought the tentacle nearer to the mouth. The food was grasped by the lip of one of the oral arm and transported slowly along until it reached the stomach. They were found to feed on the salp Thalia democratica; however, they are found mainly to feed by taking food particle by the amoeboid process of the endoderm cells, thus being suspension feeders.[cita requerida]
Picadura[editar]
Pelagia noctiluca is considered the most important stinging jellyfish in the Mediterranean Sea.[22][23] Both its tentacles and—unusual among jellyfish—the bell are covered in cnidocytes (stinging cells), and even recently dead, stranded individuals can sting.[22] P. noctiluca contains four different types of nematocysts, but two are important for stinging, O-isorhiza and eurytele.[24] The sting causes pain that typically lasts 1–2 weeks, local redness, swelling and a rash, but it is generally not dangerous and there are no known fatalities.[22][25] On occasion, symptoms may be more general and include dizziness, vomiting and diarrhea. Sudden recurrent skin eruptions may occur years later. Rarely, the sting can cause a serious allergic reaction and leave scars or hyperpigmented marks on the skin that can remain for years after the encounter.[22] If stung by P. noctiluca there can be cross-reactivity (an allergic reaction) if later stung by Portuguese man o' war (Physalia physalis) or sea nettles (Chrysaora).[22][25] There is one known case where a sting by P. noctiluca caused Guillain–Barré syndrome, but all symptoms disappeared within 6 months.[26] Peculiarly, there is a record of a seven-arm octopus "borrowing" the stinging capability of a P. noctiluca. The open-sea octopus grabbed and positioned the jellyfish in such a way that it provided a defense.[27] The sting of P. noctiluca can possibly be relieved with the use of Hydroxyacetophenone and Symsitive® since they are nematocyst inhibitor compounds, meaning they inhibit the discharge of cnidocysts.[24]
Descripción[editar]
The skull of Mekosuchus was brachycephalic or altirostral, meaning that it was notably short and raised rather than elonagted and flattened as seen in most extant crocodilian species. In this regard Mekosuchus has been compared to Trilophosuchus and the modern, only distantly related genus Osteolaemus, which includes the extant dwarf crocodiles.[28] Other researchers have also drawn comparisons between this genus and various other terrestrial crocodylomorphs including notosuchians.[29] Two reconstructions of the skull of Mekosuchus have been published, differing greatly from one another. Following the discovery of additional remains, Holt and colleagues reconstructed Mekosuchus inexpectatus in 2007 with a skull similar to that of modern dwarf crocodiles.[30] In 2014 on the other hand, Scanlon produced a composite skeletal for the skull of M. whitehunterensis, reconstructing it with a much more gently sloping rostrum that differed greatly from the previous depiction of the genus.[31]
The best known species is Mekosuchus inexpectatus, which was described as displaying a unique mix of basal and derived features of the skull. The palatine bones, which form part of the roof of the mouth, narrow towards the back. The choanae, which connect the nasal passages with the throat, are located further forward (near the palatine-pterygoid suture) than in modern crocodiles and resemble what is seen in some Late Cretaceous crocodiles like Albertochampsa and Thoracosaurus. The wings of the pterygoid bone are well developed towards the back of the skull and the quadratojugal lacks a spine, which is a feature shared by alligatoroids but not by crocodylids. The position of the postorbital bar also differs from modern crocodilians, as it isn't displaced inward or only to a very small degree. The external nares open towards the sides and front of the skull (anterolaterally) rather than facing upwards (dorsally) and the opening is not contacted by the nasal bone. The eye sockets were well-developed and large and, unique among crocodilians, are in part formed by the maxilla, preventing the jugal and lacrimal bone from contacting each other. This unique contribution of the maxilla to the orbital rim is among the diagnostic features of this genus.[31][29][32][33][34][35][30]
As in many crocodilians, the tooth row of Mekosuchus is placed in a distinct, wave-like manner also referred to as festooning. Festooning is usually the least pronounced in longirostrine forms like gharials, which have rather straight toothrows and much more prominent in short-snouted species. The maxilla displays some festooning in M. whitehunterensis[36] and a much more extreme wave-form in M. kalpokasi. While festooning may be exaggerated in younger individuals, an analysis conducted on the material of M. kalpokasi has confirmed it to be an adult.[37]
Other cranial features that can be used to differentiate the four species includes the extent of the palatal fenestrae. In M. sanderi and M. inexpectatus the front edge of the fenestrae extends until the 6th tooth of the maxilla,[38] while in M. kalpokasi and M. whitehunterensis it extends only until the 7th.[37] M. whitehunterensis further differs from all other species by possessing a longitudinal furrow beneath the eyes,[33] while M. sanderi possesses a crest atop the squamosal bone.[38][30] The extent of the shallow mandibular symphysis, the fused section at the front of the lower jaw, also differs between species. In M. inexpectatus the symphysis extends until the position of the 7th dentary tooth, while in M. whitehunterensis it ends at the 6th dentary tooth. This prevents the splenial from contributing to the symphysis, as it only extends forward to the level of the 7th dentary tooth across all species of the genus. The mandibular fenestra is strongly reduced, being almost closed in M. whitehunterensis, and the angular and surangular bones possess out-turned flanges, both of these are diagnostic for Mekosuchus.[38][30]
Some postcranial remains are also known, primarily from M. inexpectatus and M. whitehunterensis. Between the two, the vertebrae of M. whitehunterensis are described in greater detail. They are procoelous[32] and the neck (cervical) vertebrae specifically were noted to be shorter than those of the extant freshwater crocodile, even when accounting for the small size of Mekosuchus. This may indicate that at least M. inexpectatus had a shortened neck. The axis vertebra displays the typical sloping neural spine of crocodilians, but bears closer resemblance to alligatorids than to crocodylids. The following neural spines follow the overall pattern expected from a crocodile, though comparably taller than in other similarily sized animals. At the same time, the neural spines are not as inclined as in today's crocodiles, especially towards the front of the neck. This has been taken as evidence that, in spite of being small, Mekosuchus had well developed and strong epaxial neck musculature. It is possible that the neck anatomy of M. whitehunterensis represents a compromise between needed mobility and enlarged musculature.[36] Similar neck vertebrae have been described for both Mekosuchus inexpectatus as well as the genera Trilophosuchus and Volia, indicating that this anatomy may have been more widespread among derived mekosuchines.[36][32]
According to Willis, the humerus was similar in form to that of modern monitor lizards[29] and Balouet & Buffetaut make mention of well developed insertions for the musculature.[32][33] In a 2013 abstract it is mentioned that the tuber of the calcaneus, the heel, is robust and unusually short.[39]
Various parts of the osteoderms, the bony armor, are known from across the different species and were specifically mentioned for M. inexpectatus and the Oligocene mainland species. The dorsal and tail osteoderms of the continental species are described as being highly modified, which may be related to biomechanics or simply a defensive adaptation.[39]
Dentition[editar]
The dentition of the four known Mekosuchus species varies between the taxa both in shape, number and occlusion. For instance, the lower jaw of M. inexpectatus contained 13 teeth, whereas that of M. whitehunterensis contained 16.[32][33] Upper jaws on the other hand can be compared between M. kalpokensis and M. sanderi, with the former possessing 12 maxillary teeth and the latter 13.[38][37]
However, the differences in shape are more noticable. The oldest species, M. whitehunterensis, was described as having smooth maxillary teeth that would display flattened sides towards the back of the jaw, making them blade-like.[33] A similar condition can be observed in the younger mainland species, M. sanderi, in which the teeth become laterally compressed following the 5th tooth of the maxilla.[38][37] The Holocene species meanwhile lack these blade-like teeth. Although only the tooth sockets are known from M. kalpokasi, these suggest that the teeth were circular to ovate in crosssection, with no signs of the lateral compression seen in older forms. The teeth of M. inexpectatus are better known, but likewise fail to display the same condition as seen in the continental species. Rather than being blade-like, the posterior teeth of M. inexpectatus were bulbous molariforms, better suited for crushing than for slicing.[35] Similar tribodont teeth are seen in many unrelated types of eusuchians, including Allognathosuchus, Bernissartia and modern dwarf crocodiles.[32][37][30]
Similarily, the way the maxillary teeth occlude with one another also varies between these forms. This can be determined either by the form of the toothrow itself or through the presence of occlusal pits that the teeth could slide into when the jaw was closed. Generally, two states are known. Interfingering teeth as seen in modern members of Crocodylus and an overbite as seen in Alligator, however, some species of Mekosuchus also display an intermediate pattern, combining an overbite with some degree of interfingering. M. inexpectatus displays a full overbite in the maxillary toothrow[32][30] and the same is the case for M. whitehunterensis.[33] In case of the later, most maxillary teeth were simply too closely spaced to allow for interlocking dentition and towards the back of the skull, occlusal pits confirm that certain dentary teeth were positioned further inside (medially) relative to those of the upper jaw. M. sanderi and M. kalpokasi on the other hand feature a mix. In both of these species, the teeth towards the tip of the jaw and towards the back were arranged in an overbite, however, M. sanderi had an interlocking dentary tooth between the 7th and 8th teeth of the maxilla,[38] while in M. kalpokasi the dentition interlocked between the 6th and 7th as well as the 7th and 8th maxillary teeth.[37][30]
Size[editar]
Mekosuchus is among the smallest mekosuchines and is often referred to as a dwarf species in the same fashion as Trilophosuchus.[31] While growth is a consistent feature in crocodilians throughout their lives, the rate at which they grow each year decreases as an individual approaches maturity. Subsequently, in dwarf species like Mekosuchus this growth rate begins to decrease early on, resulting in their small body size relative to other crocodilians. The fact that Mekosuchus specimens are mature or at least almost mature can be found in the anatomy of the vertebrae. According to Christopher Brochu, maturity in crocodilians can be determined by the fusion between the neural centra and the neural spine, which progresses from the last tail vertebra to the first neck vertebra. Based on this, the vertebrae of the mailand M. whitehunterensis could clearly be identified as having belonged to an almost mature individual, despite its small size. The most complete skull of this species measures only 100 mm (3,9 plg), which may result in a total body length of only 60 cm (23,6 plg). This puts M. whitehunterensis within the lower size range of today's dwarf crocodilians, Osteolaemus and Paleosuchus, both of which typically reach lengths of over 1 m (1,1 yd) when fully grown.[36][31][29] Estimates for other members of the genus are generally less precise, but fall into the same overall size range. M. inexpectatus for instance has been estimated to have reached a length of approximately 2 m (2,2 yd) by Balouet,[35] while Holt and colleagues estimate members of Mekosuchus to be around 1 m (1,1 yd) in length.[30]
Phylogeny[editar]
When first describing Mekosuchus, Balouet and Buffetaut struggled to determine the relationship between it and modern crocodilians, noting how the taxon displayed a variety of basal and derived traits that did not allign perfectly with any of the modern groups. They ultimately determined that Mekosuchus was a Eusuchian based on the choanae and the procoelous vertebrae, and placed it in the monotypic family Mekosuchidae, which they believed to have been the sister group to all three modern crocodilian families.[35][32][29] Since then, research on Australasian crocodiles has placed a wide range of other taxa in the family, which is now referred to by the name Mekosuchinae. Although mekosuchines are still a poorly understood group who's internal and external relationships commonly shift, Mekosuchus is traditionally allied with other altirostral forms such as Trilophosuchus and Quinkana. Willis (1997) suggests a close link between Mekosuchus and Trilophosuchus, with Quinkana as their sister taxon,[29] while Mead et al. (2002) place Mekosuchus, Quinkana and a then unnamed Volia in a large polytomy as sisters to Trilophosuchus within the clade Mekosuchini.[37] A 2018 tip dating study by Lee & Yates using a combination of morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data recovered broadly similar results, although the precise relations within Mekosuchini do differ. Here, Trilophosuchus was recovered as the closest relative of Quinkana, with Mekosuchus being the sister taxon to their grouping and Volia as the basalmost mekosuchinin.[40]
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The most recent analysis was performed by Ristevski et al. in 2023 and put a broader focus on not just Mekosuchines but Australasian crocodylifroms in general, which includes the extant crocodylids of Australia, Australian gavialoids as well as more basal taxa like those placed in Susisuchidae. Six out of eight analyses recovered Mekosuchinae as a monophyletic group similar to the results of Lee and Yates. These analyses recovered most mekosuchines within Mekosuchini, which in turn was split into two clades. On the one hand large, continental forms and on the other small and/or insular taxa. The latter clade somewhat resembles the previous relationships suggested for Mekosuchus, as it also contains Volia and Trilophosuchus. Notably however, "Baru" huberi was recovered as the basalmost member of this group, while Quinkana was placed in the large-bodied, continental clade. The remaining two trees deviated greatly from the traditional composition of Mekosuchinae, with Kambara and Australosuchus being recovered elsewhere in Crocodylia and Mekosuchinae also including the clade Orientalosuchina, small-bodied Cretaceous to Paleogene crocodilians from Asia. However, support for these trees is low as indicated by both phylogenetic results and morphological similarities, with many uniting characters being widespread among crocodilians. Regardless of the relationship between Mekosuchinae and Orientalosuchina, the closest relatives to Mekosuchus remain the same across the analyses, generally recovering the same small-bodied clade composed of "Baru" huberi, Volia, Trilophosuchus and Mekosuchus.[34]
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Paleobiogeography[editar]
While fossil evidence shows that Mekosuchus originated on mainland Australia, little is known about how it dispersed throughout the South Pacific. Currently, three mekosuchines are known from the region, M. inexpectatus, M. kalpokasi and Volia. M. inexpectatus may have had the largest range in time among them, with estimates suggesting that it may have first appeared nearly 4,000 years ago. This species is known exclusively from New Caledonia, which makes it the closest geographically to mainland Australia. There is some overlap between the fauna of New Caledonia and that of Vanuatu, with the two islands sharing 12% of their native lizards. One factor possibly important to the similarities and differences among the islands of the region is the geology of the Inner and Outer Melanesian Arc. The former split from Australia during the Cretaceous, while the latter only formed during the Paleogene and Neogene. As mekosuchines first appeared during the Eocene, Mead and colleagues argue that continental drift and break up could not have played a part in their appearance in the South Pacific. Instead, it is considered more likely that the ancestors of the insular mekosuchines traveled short distances across the ocean to arrive on the islands of the Inner Melanesian Arc, before dispersing between the islands of the South Pacific from there. Although it is not known whether or not mekosuchines were tolerant to saltwater or had the same adaptations for marine dispersal as modern crocodiles (such as salt glands), it is possible that they could have actively swam between landmasses or drifted with the use of natural rafts. This process would have greatly profited from the lower sea levels present during the late Cenozoic, decreasing the distance between now isolated islands and in some instances uniting whole island chains. The presence of these significant landmasses could have served as stops or even supported populations during the dispersal of these animals. For this reason, it is believed that Mekosuchus only dispersed into the South Pacific relatively recently. Mead and colleagues name the Oligocene as the earliest possible date, though an even more recent Quarternary dispersal is deemed more likely.[37][29]
Paleobiology[editar]
Mekosuchus, like some of its closest relatives, is believed to have been a terrestrial animal. Evidence for this may be found in several parts of its anatomy.[39][38] The skull is altirostral, similar to extinct terrestrial forms like Notosuchians and members of the Planocraniidae, while semi-aquatic crocodilians typically have flattened platyrostral skulls, adapted to reduce drag and allow raising the eyes and nose out of the water without drawing the attention of potential prey items. In Mekosuchus, both the eyes and nares are not built for an aquatic mode of life. Rather than opening towards the top of the skull, which would allow the animal to breathe while remaining largely submerged, the nares open towards the front of the skull, and the eyes are similarily directed towards the sides, not the top.[34] Balouet and Buffetaut further point to the well developed muscular insertions and the absence of freshwater in the deposition area, while pointing out that karstic environments are often associated with terrestrial crocodylomorphs.[32] In 1995 Australian paleontologist Paul Willis informally suggested that animals like Mekosuchines may have filled a niche equivalent to modern monitor lizards, even going as far as to suggest arboreal (climbing) habits.[29] However, this idea has been dismissed by more recent research, as monitor lizards had been present in Australia for longer than assumed by Willis, while analysis of mekosuchine toe bones showed no significant differences to those of other crocodilians and thus not supporting the notion that they were exceptional climbers.[31][41]
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The strong neck musculature inferred for Mekosuchus whitehunterensis has been interpreted as being an adaptation for ripping chunks of flesh from carcasses. In modern crocodilians this is achieved either through shaking the head side to side or by employing the death roll maneuver. It is noted that the small size of Mekosuchus would render the death roll maneuver less effective than in species with a body length between 3-4 m (3,3-4,4 yd) long, whereas headshaking is favored by small animals like juveniles. Furthermore Stein, Archer and Hand argue that the well-developed epaxial musculature would primarily increase the force generated by headshaking whereas a death roll would bear a greater risk of the animal harming itself and damaging its limbs trying to perform it on land. Finally, M. whitehunterensis could have also used its neck musculature to strip flesh by pulling and lifting its head against a constrainted or weighed down carcass, behavior that has also been inferred for more ancient archosaurs. Whether or not this mode of feeding was used to rip apart much larger prey items or utilized for scavenging is unclear, though Stein, Archer and Hand suggest that it may have been especially advantageous for the latter, allowing for even relatively small animals to consume an excess of food.[39][36]
These mainland species are known from localities that have also preserved the fossilised remains of multiple other mekosuchines, which they may have coexisted with. The White Hunter Site that yielded M. whitehunterensis also preserved the broad-snouted generalist Baru wickeni and the narrower-snouted Baru huberi as well as the terrestrial ziphodont Quinkana meboldi. The younger Ringtail Site of the Riversleigh on the other hand preserves another species of Baru, Mekosuchus sanderi and Trilophosuchus.[38] The longirostrine Ultrastenos may have also been present.[42] How so many crocodilians could have coexisted with one another may have multiple explanations. On the one hand, the differing skull shapes between them, especially in regards to the White Hunter Site, may be enough for all taxa to fill different niches and thus not come into competition with one another. It is also possible that these assemblages were the result of thanatocoenosis and that in life, all these animals could have had different habitat preferences. However, Willis observed that the mammalian fauna of the Riversleigh WHA indicates a complex but clearly defined pattern of different ecomorphs that filled different niches. For this reason, he suggests that the Riversleigh crocodiles were truly sympatric.[33] Willis does take particular note of Trilophosuchus, which was a box-headed terrestrial form similar to Mekosuchus and thus may have inhabited a similar niche as opposed to the much larger, semi-aquatic crocodiles of the site. It is however possible that they were morphologically and ecologically much more different than currently thought and that the similarities may simply be exacerbated by the lack of better material.[29][38]
Unlike the bladed teeth of the mainland species, Mekosuchus inexpectatus had specialized back teeth more suited for cracking hard-shelled invertebrates such as molluscs, crustaceans and insects.[35] Balouet and Buffetaut suggest that it may have fed on molluscs of the genus Placostylus, which was common on New Caledonia.[32] Based on newer material and the previously noted similarities between Mekosuchus and modern dwarf crocodiles, Holt and colleagues suggest that M. inexpectatus could have possibly lived a similar lifestyle to the modern dwarf crocodiles (Osteolaemus spp.) or dwarf caimans (Paleosuchus spp.). According to their hypothesis, M. inexpectatus may have inhabited small, slow moving streams in the rainforests of New Caledonia and foraged at night near the waters edge and on land.[30][34]
Extinction[editar]
The extinction of Mekosuchus in the South Pacific has historically been linked to the arrival of human settlers, in particular the Lapita people. Supporters of this hypothesis point at the fact that the range of Mekosuchus overlaps with human settlement of Vanuatu and the direct association between the bones of Mekosuchus kalpokasi with human artifacts at the Arapus archaeological site on the island of Efate. If the extinction of this taxon was linked to the arrival of humans, there may have been multiple factors contributing to their disappearance. These include the introduction of invasives like pigs and rats, habitat destruction and being used as a food source.[37] However, this idea is not universally accepted and has been disputed by other researchers. Anderson and colleagues for instance note that in the case of Mekosuchus inexpectatus, most remains were deposited prior to human settlement of New Caledonia, with only a single mandible overlapping with human presence. They further highlight that no evidence exists of humans contributing to the crocodile's extinction.[43][34]
La Formación Wolfville contiene un conjunto diverso de tetrápodos del Triásico que incluye anfibios temnospóndilos, reptiles procolofónidos y cinodontes traversodontes . Basado en la presencia del temnospóndilo Koskinonodon (un fósil índice común del Triásico), el conjunto está fechado en la etapa carniana del Triásico tardío. [44]
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| Megalodón | ||
|---|---|---|
| Rango temporal: 23 Ma - 2,6 Ma Aquitaniense (Mioceno) - Piacenziense (Plioceno) | ||
 Modelo de las mandíbulas del megalodón en el Museo Americano de Historia Natural. | ||
| Taxonomía | ||
| Reino: | Animalia | |
| Filo: | Chordata | |
| Subfilo: | Vertebrata | |
| Clase: | Chondrichthyes | |
| Subclase: | Elasmobranchii | |
| Superorden: | Selachimorpha | |
| Orden: | Lamniformes | |
| Familia: | †Otodontidae | |
| Género: | †Otodus | |
| Especie: |
Otodus megalodon (Agassiz, 1843)[45] | |
| Sinonimia | ||
Lista de sinónimos Género Carcharias
Género Carcharocles
Género Carcharodon
Género Megaselachus
Género Procarcharodon
Género Selache
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Otodus megalodon, mejor conocido por su nombre común Megalodón, "diente grande", es una especie extinta de tiburón lamniformeque vivió aproximadamente entre hace 23 y 2.6 millones de años, del Mioceno temprano al Plioceno. Originalmente se pesnó que era miembro de la familia Lamnidae, además pariente cercano del tiburón blanco (Carcharodon carcharias). Actualmente entendemos que pertenecía a la familia extinta Otodontidae, divergente con el linaje del tiburón blanco en el Cretácico temprano.
Pese a ser considerado uno de los depredadores más grandes y poderos que jamás vivió, como es típico de los tiburones fósiles megalodón solo es conocido en base a restos fragmentarios, dejando su tamaño y forma exactas inciertas. Se disputa si su cuerpo se parecía a una versión más robusta del tiburón blanco, tiburón ballena, tiburón peregrino o del tiburón toro. Las estimaciones de su tamaño más recientes, y con un menor rango de error, sugieren una longitud máxima de 20 metros, aunque sugieren una moda de 10,5. Basándose en una comparación de los centros vertebrales con el tiburón blanco se obtienen una longitudes de 16 metros y 48 toneladas de peso, 17 metros y 59 toneladas y un máximo de 20,3 metros y 103 toneladas. Extrapolando de una columna vertebral y recoinstruyendo un modelo 3D basados en lámnidos sugieren que aquel individuo de 16m fue mucho más pesado que las estimaciones previas, pesando alrededor de 61.5 toneladas; un individuo de tal tamaño debería consumir 98,175 kcal por día. Sus dientes eran gruesos y robustos, especializados para agarrar presas y partir huesos, apoyado por una fuerza de mordida de 08,500 to 182,200 newtons.
Referencias[editar]
- ↑ a b Larkins, Damien; Bern Young (25 August 2016). «Mysterious red jellyfish found on Gold Coast beach». ABC News. Consultado el 30 June 2019.
- ↑ a b c d e f Canepa, Antonio; Verónica Fuentes; Ana Sabatés; Stefano Piraino; Ferdinando Boero; Josep-María Gili (2014). «Pelagia noctiluca in the Mediterranean Sea». En Kylie A. Pitt; Cathy H. Lucas, eds. Jellyfish Blooms. Springer. pp. 237-266. ISBN 978-94-007-7014-0.
- ↑ Pepin, P.; G. Maillet; S. Fraser; G. Doyle; A. Robar; T. Shears; G. Redmond (2017). «Optical, chemical, and biological oceanographic conditions on the Newfoundland and Labrador Shelf during 2014-2015». Canadian Science Advisory Secretariat (CSAS). Consultado el 3 July 2019.
- ↑ a b c d Mariottini, Gian Luigi; Elisabetta Giacco; Luigi Pane (2008). «The Mauve Stinger Pelagia noctiluca (Forsskål, 1775). Distribution, Ecology, Toxicity and Epidemiology of Stings, A Review». Mar. Drugs 6 (3): 496-513. PMC 2579739. PMID 19005582. doi:10.3390/md20080025. Parámetro desconocido
|doi-access=ignorado (ayuda) - ↑ a b c d e Houghton, J. (4 August 2008). «Pelagia noctiluca (mauve stinger)». Invasive Species Compendium. Consultado el 30 June 2019.
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- ↑ «Beach Safety: Sting. Stab. Strike. Marine Stingers». Surf Life Saving Queensland. 2018. Consultado el 30 June 2019.
- ↑ Miller, B.J.; S. von der Heyden; M.J. Gibbons (2012). «Significant population genetic structuring of the holoplanktic scyphozoan Pelagia noctiluca in the Atlantic Ocean». African Journal of Marine Science 34 (3): 425-430. S2CID 84738937. doi:10.2989/1814232X.2012.726646.
- ↑ Gul, S.; A.C. Morandini (2013). «New records of scyphomedusae from Pakistan coast: Catostylus perezi and Pelagia cf. noctiluca (Cnidaria: Scyphozoa)». Marine Biodiversity Records 6: e86. doi:10.1017/S1755267213000602.
- ↑ Collins, Allen G. (2017). «Mawia benovici». WoRMS. Registro Mundial de Especies Marinas. Consultado el 30 June 2019.
- ↑ a b c d Tilves, U.; J.E. Purcell; V.L. Fuentes; A. Torrents; M. Pascual; V. Raya; J.-M. Gili; A. Sabatés (2016). «Natural diet and predation impacts of Pelagia noctiluca on fish eggs and larvae in the NW Mediterranean». Journal of Plankton Research 38 (5): 1243-1254. doi:10.1093/plankt/fbw059. Parámetro desconocido
|doi-access=ignorado (ayuda) - ↑ a b c d e Malej, A.; M. Malej (1992). «Population dynamics of the jellyfish Pelagia noctiluca (Forsskal, 1775)». En Colombo, G.; I. Ferrari; V.U. Ceccherelli et al., eds. Marine Eutrophication and Population Dynamics: 25th European Marine Biology Symposium, Ferrara (Italy), 10-15 September 1990. Olsen & Olsen: Fredensborg. pp. 215-219. ISBN 87-85215-19-8.
- ↑ Raines, Ben (30 July 2011). «Slimy purple people stingers: Glow-in-the-dark mauve stinger jellyfish invade Gulf Coast beaches». al.com. Consultado el 30 June 2019.
- ↑ Vince, Garcia (5 April 2012). «Jellyfish blooms creating oceans of slime». BBC. Consultado el 30 June 2019.
- ↑ Piraino, Stefano (2015). «Genetic connectivity of Pelagia noctiluca populations reveal spatial and temporal reproductive subunits». marine-vectors.eu. Consultado el 30 June 2019.
- ↑ Helm, Rebecca R.; Stefano Tiozzo; Martin K.S. Lilley; Fabien Lombard; Casey W. Dunn (2015). «Comparative muscle development of scyphozoan jellyfish with simple and complex life cycles». EvoDevo 6 (11): 11. PMC 4415277. PMID 25932322. doi:10.1186/s13227-015-0005-7. Parámetro desconocido
|doi-access=ignorado (ayuda) - ↑ Brotz, L.; D. Pauly; Martin K.S. Lilley; Fabien Lombard; Casey W. Dunn (2012). «Jellyfish populations in the Mediterranean Sea». Acta Adriat. 53 (2): 213-232.
- ↑ Larson, R. J. (October 1, 2013). «A Note on the Feeding, Growth, and Reproduction of the Epipelagic Scyphomedusa Pelagia noctiluca». Taylor&FrancisOnline. doi:10.1080/01965581.1987.10749501 (inactivo 1 August 2023). Consultado el December 1, 2022. Parámetro desconocido
|doi-broken-date=ignorado (ayuda) - ↑ a b Milisenda, G.; S. Rossi; S. Vizzini; V.L. Fuentes; J.E. Purcell; U. Tilves; S. Piraino (2018). «Seasonal variability of diet and trophic level of the gelatinous predator Pelagia noctiluca (Scyphozoa)». Scientific Reports 8 (1): 12140. Bibcode:2018NatSR...812140M. PMC 6092325. PMID 30108231. doi:10.1038/s41598-018-30474-x. Parámetro desconocido
|doi-access=ignorado (ayuda) - ↑ Tilves, Uxue; Jennifer E. Purcell; Macarena Marambio; Antonio Canepa; Alejandro Olariaga; Verónica Fuentes (2013). «Predation by the scyphozoan Pelagia noctiluca on Mnemiopsis leidyi ctenophores in the NW Mediterranean Sea». Journal of Plankton Research 35 (1): 218-224. doi:10.1093/plankt/fbs082. Parámetro desconocido
|doi-access=ignorado (ayuda) - ↑ Milisenda, Giacomo; Rossi, Sergio; Vizzini, Salvatrice; Fuentes, Veronica L.; Purcell, Jennifer E.; Tilves, Uxue; Piraino, Stefano (December 2018). «Seasonal variability of diet and trophic level of the gelatinous predator Pelagia noctiluca (Scyphozoa)». Scientific Reports (en inglés) 8 (1): 12140. Bibcode:2018NatSR...812140M. ISSN 2045-2322. PMC 6092325. PMID 30108231. doi:10.1038/s41598-018-30474-x.
- ↑ a b c d e Mariottini, Gian Luigi; Elisabetta Giacco; Luigi Pane (2008). «The Mauve Stinger Pelagia noctiluca (Forsskål, 1775). Distribution, Ecology, Toxicity and Epidemiology of Stings, A Review». Mar. Drugs 6 (3): 496-513. PMC 2579739. PMID 19005582. doi:10.3390/md20080025. Parámetro desconocido
|doi-access=ignorado (ayuda) - ↑ Canepa, Antonio; Verónica Fuentes; Ana Sabatés; Stefano Piraino; Ferdinando Boero; Josep-María Gili (2014). «Pelagia noctiluca in the Mediterranean Sea». En Kylie A. Pitt; Cathy H. Lucas, eds. Jellyfish Blooms. Springer. pp. 237-266. ISBN 978-94-007-7014-0.
- ↑ a b Ballesteros, Ainara; Trullas, Carles; Jourdan, Eric; Gili, Josep-Maria (September 8, 2022). «Inhibition of Nematocyst Discharge from Pelagia noctiluca (Cnidaria: Scyphozoa)—Prevention Measures against Jellyfish Stings». Marine Drugs (en inglés) 20 (9): 571. ISSN 1660-3397. PMC 9501295. PMID 36135760. doi:10.3390/md20090571. Parámetro desconocido
|doi-access=ignorado (ayuda) - ↑ a b Tibballs, J.; A.A. Yanagihara; H.C. Turner; K. Winkel (2011). «Immunological and Toxinological Responses to Jellyfish Stings». Inflamm Allergy Drug Targets 10 (5): 438-446. PMC 3773479. PMID 21824077. doi:10.2174/187152811797200650.
- ↑ Schwartz, M.S.; K.A. Pang (1993). «Guillain–Barré syndrome following jellyfish stings (Pelagia noctiluca)». Journal of Neurology, Neurosurgery, and Psychiatry 56 (10): 1133. PMC 1015247. PMID 8410016. doi:10.1136/jnnp.56.10.1133.
- ↑ Rosa, R.; J.T. Kelly; V.M. Lopes; J.R. Paula; J. Gonçalves; R. Calado; M.D. Norman; J.P. Barreiros (2019). «Deep-sea seven-arm octopus hijacks jellyfish in shallow waters». Marine Biodiversity 49 (1): 495-499. S2CID 41348775. doi:10.1007/s12526-017-0767-3.
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- ↑ a b c d e f g h i Holt, T.R.; Salisbury, S.W.; Worthy, T.; Sand, C.; Anderson, A. (2007). New material of Mekosuchus inexpectatus (Crocodylia: Mekosuchinae) from the Quaternary of New Caledonia. 11th Conference on Australian Vertebrate Evolution, Palaeontology and Systematics. Melbourne, Australia.
- ↑ a b c d e Scanlon, J.D. (2014). «Giant terrestrial reptilian carnivores of Cenozoic Australia.». Carnivores of Australia: past, present and future. CSIRO Publishing. ISBN 0643103171.
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- ↑ a b c d e f g Willis, P.M.A. (1997). «New crocodilians from the late Oligocene White Hunter Site, Riversleigh, northwestern Queensland». Memoirs of The Queensland Museum 41: 423-438. ISSN 0079-8835.
- ↑ a b c d e Ristevski, J.; Willis, P.M.A.; Yates, A.M.; White, M.A.; Hart, L.J.; Stein, M.D.; Price, G.J.; Salisbury, S.W. (2023). «Migrations, diversifications and extinctions: the evolutionary history of crocodyliforms in Australasia». Alcheringa: An Australasian Journal of Palaeontology. doi:10.1080/03115518.2023.2201319.
- ↑ a b c d e Balouet, J.C. (1991). «The fossil vertebrate record of New Caledonia». En Vickers-Rich, P.; Monaghan, J.M.; Baird, R.F. et al., eds. Vertebrate Palaeontology of Australasia. Monash University Publications Committee, Melbourne, Australia. pp. 1381-1409.
- ↑ a b c d e Stein, M.; Archer, M.; Hand, S.J. (2016). «Dwarfism and feeding behaviours in Oligo-Miocene crocodiles from Riversleigh, northwestern Queensland, Australia». Acta Palaeontologica Polonica 61 (1): 135-142. doi:10.4202/app.00134.2014.
- ↑ a b c d e f g h i Mead, Jim I; Steadman, David W; Bedford, Stuart H; Bell, Christopher J; Spriggs, Matthew (2002). «New Extinct Mekosuchine Crocodile from Vanuatu, South Pacific». Copeia 2 (3): 632. doi:10.1643/0045-8511(2002)002[0632:NEMCFV]2.0.CO;2.
- ↑ a b c d e f g h i Willis, P. M. A. (2001). «New crocodilian material from the Miocene of Riversleigh (northwestern Queensland, Australia)». Crocodilian biology and evolution. Surrey Beatty & Sons.
- ↑ a b c d Stein, M.; Yates, A.M.; Scanlon, J.D.; Archer, M.; Willis, P.M.A.; Salisbury, S.; Hand, S.J. (2013). New materials of Oligo–Miocene Mekosuchus from the Riversleigh World Heritage Area indicate unusual development and palaeoecology. Proceedings of the 14th Conference on Australasian Vertebrate Evolution, Palaeontology & Systematics 79.
- ↑ Michael S. Y. Lee; Adam M. Yates (27 June 2018). «Tip-dating and homoplasy: reconciling the shallow molecular divergences of modern gharials with their long fossil». Proceedings of the Royal Society B 285 (1881). PMC 6030529. PMID 30051855. doi:10.1098/rspb.2018.1071. Parámetro desconocido
|doi-access=ignorado (ayuda) - ↑ Darren Naish, "Tetrapod Zoology": "The small, recently extinct, island-dwelling crocodilians of the south Pacific", 2006
- ↑ Stein, M.D.; Hand, S.J.; Archer, M.; Wroe, S.; Wilson, L.A.B. (2020). «Quantitatively assessing mekosuchine crocodile locomotion by geometric morphometric and finite element analysis of the forelimb». PeerJ. doi:10.7717/peerj.9349.
- ↑ Anderson, Atholl; Sand, C; Petchey, F; Worthy, T. H (2010). «Faunal extinction and human habitation in New Caledonia: Initial results and implications of new research at the Pindai Caves». Journal of Pacific Archaeology 1 (1). Consultado el 23 February 2021.
- ↑ Sues, H.-D. (2003). «An unusual new archosauromorph reptile from the Upper Triassic Wolfville Formation of Nova Scotia». Canadian Journal of Earth Sciences 40 (4): 635-649. Bibcode:2003CaJES..40..635S. doi:10.1139/e02-048.
- ↑ Agassiz, Louis (1843). Recherches sur les poissons fossiles [Research on the fossil fishes] (en francés). Neuchatel: Petitpierre. p. 41.