Tag Archives: extinct

Land snails on islands: fascinating diversity, worrying vulnerability

by Piter Kehoma Boll

The class Gastropoda, which includes snails and slugs, is only beaten by the insects in number of species worldwide, having currently about 80 thousand described species. Among those, about 24 thousand live on land, where they are a very successful group, especially on oceanic islands.

The Hawaiian Islands alone, for example, have more than 750 snail species and there are more than 100 endemic species in the small island of Rapa in the South Pacific. This diversity is much higher than that in any continental place, but the reason for that is not completely understood.

Mandarina

A land snail of the genus Mandarina, endemic to the Ogasawara Islands, Japan. Photo by flickr user kmkmks (Kumiko).*

One of the most likely explanations for this huge diversity on islands is related to the lack of predators. The most common predators of snails include birds, mammals, snakes, beetles, flatworms and other snails. Most of those are not present in small and isolated islands, which allows an increase in land snail populations in such places. Without too much dangers to worry about, the community of land snails n islands can explore a greater range of niches, eventually leading to speciation.

Unfortunately, as always, the lack of danger leads to recklessness. Without predators to worry about, insular land snails tend to lay fewer eggs than their mainland relatives. If there is no danger of having most of your children eaten, why would you have that many? It is better to lay larger eggs, putting more resources on fewer babies, and so assure that they will be strong enough to fight against other snail species. Afterall, the large number of species in such a small place as an island likely leads to an increased amount of competition between species.

But why is this recklessness? Well, because you never known when a predator will arrive. And they already arrived… due to our fault.

The diversity of insular land nails was certainly affected by habitat loss promoted by humans, but also by predators that we carried with us to the islands, whether intentionally or not. These predators include rats, the predatory snail Euglandina rosea and the land flatworm Platydemus manokwari, the latter being most likely the worst of all.

800px-platydemus_manokwari

The flatworm Platydemus manokwari in the Ogasawara Islands. Photo by Shinji Sugiura.

This flatworm arrived at the Chichijima Island, part of the Ogasawara Islands in the Pacific Ocean, in the early 1990s and in about two decades it led most land snail species on the island to extinction and many more are about to face the same fate on this island and on others. Not being prepared for predators, these poor snails cannot reproduce fast enough to replace all individuals eaten by the flatworm.

We have to act quickly if we want to save those that are still left.

See also: The New Guinea flatworm visits France – a menace.

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ResearchBlogging.orgReferences and further reading:

Chiba, S., & Cowie, R. (2016). Evolution and Extinction of Land Snails on Oceanic Islands. Annual Review of Ecology, Evolution, and Systematics, 47 (1), 123-141 DOI: 10.1146/annurev-ecolsys-112414-054331

Sugiura, S., Okochi, I., & Tamada, H. (2006). High Predation Pressure by an Introduced Flatworm on Land Snails on the Oceanic Ogasawara Islands. Biotropica, 38 (5), 700-703 DOI: 10.1111/j.1744-7429.2006.00196.x

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Biological fight: kites, mites, quite bright plights

ResearchBlogging.orgby Piter Kehoma Boll

A recently described fossil from the Silurian Herefordshire Lagerstätte in the United Kingdom has called much attention.

A photo of the fossil itself. Image by Briggs et al., extracted from news.nationalgeographic.com

A photo of the fossil itself. Image by Briggs et al., extracted from news.nationalgeographic.com

The appearance of the creature was build by scanning the rock and creating a 3D reconstruction of the fossil. It revealed that the animal, obviously and arthropod, had several smaller creatures attached by long threads, like kites. The species was named Aquilonifer spinosus, meaning “spiny kite-bearer”.

A 3D reconstruction of what Aquilonifer and its kites would have looked like. Image by Briggs et al. extracted from sci-news.com

A 3D reconstruction of what Aquilonifer and its kites would have looked like. Image by Briggs et al. extracted from sci-news.com

The authors (Briggs et al., 2016) thought about three possibilities to explain the unusual “kites”. They could be parasites, phoronts (i.e., hitchhikers), or babies. The idea of parasites was discarded because such long threads separating them from the host would have made it difficult to feed properly. They also considered it unlikely to be a case of phoronts, i.e., a species that uses the host as a mean to move from one site to another, because there were too many of them and the host most likely would have removed them by using the long antennae.

Artistic impression of Aquilonifer spinosus by Andrey Atuchin.

Artistic impression of Aquilonifer spinosus by Andrey Atuchin.

The remaining option is that the kites were offspring. The mother (or father) would have attached them to itself in order do carry them around in a unique mode of brood care. The authors compare it to several other arthropod groups in which some species carry their babies around during their first days. They also consider that the animal could have delayed its molting process to avoid discarding the babies with the exoskeleton.

But can we be sure that this is the case? The entomologist Ross Piper thinks differently. He compares the kites to uropodine mites, in which the juveniles (deutonymphs) attatch themselves to beetles by long stalks in order to be transported from one food source to another. As there are marine mites, that could be the case. He also points out that the kites are scattered through the body, which would make them unlikely to be offspring, as such a distribution would only hinder the parent’s mobility.

Briggs at al. responded to Piper’s critique arguing that marine mites have only recently evolved and that Aquilonifer is very different from a terrestrial beetle. It was most likely a bentonic species, crawling on the ocean’s floor, and not a swimmer, so that it would not be a very good dispersal agent.

What do you think of it? I find it difficult to choose one side. Piper’s comparison with mites is interesting, but only as a way to suggest a convergent evolution. I cannot see how the kites would have been really mites or even arachnids. Now the argument on the kites’ position on the body is a good point. No other group of animals carries their young attached to long stalks spread all over the body. Furthermore, how would the parent properly place the juveniles there? I can only see it as a plausible way if the host were the father and the mother crawled over him to stick the eggs in place. Additionally, couldn’t they be true phoronts  that were benefitial to the host? The little fellows could benefit by moving around on the big pal and reaching new food sources while giving protection or other advantage in return. And regarding the delay in molting, I cannot see any evidence that there was any delay. We don’t know how long the kites remained there and perhaps after molting they could simply leave their little houses and build new ones on the host’s new skeleton.

We may never know the truth, but we can keep exchanging ideas.

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References:

Briggs, D., Siveter, D., Siveter, D., Sutton, M., & Legg, D. (2016). Tiny individuals attached to a new Silurian arthropod suggest a unique mode of brood care Proceedings of the National Academy of Sciences, 113 (16), 4410-4415 DOI: 10.1073/pnas.1600489113

Briggs, D., Siveter, D., Siveter, D., Sutton, M., & Legg, D. (2016). Reply to Piper: Aquilonifer’s kites are not mitesProceedings of the National Academy of Sciences, 113 (24) DOI: 10.1073/pnas.1606265113

Piper, R. (2016). Offspring or phoronts? An alternative interpretation of the “kite-runner” fossil Proceedings of the National Academy of Sciences, 113 (24) DOI: 10.1073/pnas.1605909113

Switek, B. 2016. This bizarre creature flew its babies like kites. National Geographic News. Available at < http://news.nationalgeographic.com/2016/04/160404-bizarre-creature-flew-babies-kites-arthropod-fossils-science/ >. Access on July 07, 2016.

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Does Retallack suffer from Williamson’s syndrome? The land-dwelling Ediacara controversy

by Piter Kehoma Boll

ResearchBlogging.orgAs you may have heard, or read, a paper published this month in Nature claims that the famous Ediacaran biota, a set of fossils from the Ediacaran Period (ca. 635-542 Mya) of the Neoproterozoic Era, is not composed by marine creatures, but rather land lichens. Who made this claim? Gregory Retallack, a geologist at the University of Oregon.

Retallack works on this hypothesis since the 1990s and the main evidences presented by him are related to geological features, like the red color of the rock, which according to him would have a terrestrial origin. Another claim is that if those creatures were soft-bodied animals, they wouldn’t have been so well preserved without compaction, as some fossils have tridimensional features.

Well, I am not a geologist and have no knowledge enough to argue about the geological point of view, neither am I an expert in the Ediacaran biota, but as a biologist I think I can share some thoughts.

First, as it seems, Retallack’s ideas are not accepted by most paleontologists. At the beginning, the innovative view of Ediacaran biota as land-dwelling was interesting, but the arguments to support it are not enough and there are still simpler and more possible explanations for the unusual features of the Ediacaran rocks. This didn’t stop Retallack to pursue in his idea, however, and other paleontologists are getting tired to go on reviewing his papers.

Does such a behavior look familiar? It kind of reminds me of Williamson, whom I talked about some time ago, as you can read here.

Just as Williamson insists in his hybridogenesis idea despite all facts pointing to other directions, so Retallack insists in his land-dwelling lichens hypothesis.

Dickinsonia would have been a land-dwelling lichen, according to Retallack. Photo by Wikipedia user Verisimilus. Extracted from en.wikipedia.org

Dickinsonia would have been a land-dwelling lichen, according to Retallack. Photo by Wikipedia user Verisimilus. Extracted from en.wikipedia.org

Retallack claims that fossils like Dickinsonia and Charnia, despite their bilaterally symmetrical body plan, were lichens. Does anybody know so well symmetrical lichens? And to support this hypothesis, he simply throws any kind of “fungian” explanation for all the fossils, considering the more radially symmetrical ones as bacterial colonies and the more animal-like as simply fungal fruiting bodies. And to explain things like the trace fossils, he talks about land slugs (land slugs during the Proterozoic? Really?) or slime moulds.

But then one might think: does he have any reference to support his ideas? And the answer is: of course, his OWN previous works. There are no other paleontologists claiming the same but himself. It looks just like a case of what I call Williamson’s syndrome.

I’m sure we will find some people supporting his idea, most probably laymen, and they will most certainly use the classical argument “all great scientific discoveries started by being rejected by most of the scientific community”. And I will say that again: Yes, many theories were initially rejected and later proven right, but you cannot forget that many more theories were rejected and later proven wrong. And once you prove that something is wrong or at least highly, highly unlikely, you must think of another possible and more likely explanations and not move on insisting on a fairytale.

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References:

Cobb, M. 2012. The enigmatic Ediacaran biota just got more enigmatic. Or did it? Why Evolution Is True. Available online at <http://whyevolutionistrue.wordpress.com/2012/12/20/the-enigmatic-ediacaran-biota-just-got-more-enigmatic-or-did-it/ >

Retallack, G. 2012. Ediacaran life on land. Nature. DOI: 10.1038/nature11777

Retallack, G. 2007. Growth, decay and burial compaction of Dickinsonia, an iconic Ediacaran fossil. Alcheringa: An Australasian Journal of Palaeontology, 31 (3), 215-240 DOI: 10.1080/03115510701484705

Switek, B. 2012. Controversial claim puts life on land 65 million years early. Nature. DOI: 10.1038/nature.2012.12017

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If you like flowers, you should love insects

by Piter Kehoma Boll

ResearchBlogging.orgEverybody likes flowers, right? They are so colorful and beautiful and usually have a wonderful scent. People love to have them in their gardens and women love to receive a nice flower bouquet from their boyfriends.

Some flowering plants, from left to right: Rosa ‘Hybrid Tea’, Pachystachys lutea and Zinnia elegans. All photos by Piter K. Boll (i.e. myself!)*

But why are flowers so beautiful? Of course the flowers seen above are derived from varieties artificially selected by humans to increase their beauty, but flowers in nature are wonderful too!

Naturally occuring flowers. From left to right: Oxalis sp., Ipomoea fimbriosepala and Zephyranthes robusta. All photos again by myself (Piter K. Boll)*

Surely that beauty is not intended to please people or whatever. That’s totally nonsense and just some religious people could have such a wrong idea. If plants have nice flowers, it must give them some advantage.

As everybody knows (at least I hope so), plants usually cannot move like animals, so they are condemned to stay still on their spot. That can mean a lot of trouble when you are looking for resources like water, light or basic elements like nitrogen. So evolution leads to the rising of amazing structures to make plants survive, like getting a hard stem to become taller or developing smaller or larger leaves, thorns, tendrils or even becoming carnivorous. But plants also need to reproduce and for that they need a mate, but since they are attached to the substrate, they have to find alternative ways to join their gametes.

Most primitive plants manage to do that through water or wind, just letting their reproductive structures go and hoping that they will reach their destination. As you can see, this method is not the best one, since fertilization occurs totally by chance. Besides that, these ways are limited regarding to the places where they are successful. A plant fertilized through water needs to be inside water or live close to the ground on places where it eventually get submersed; the same way, a plant which relies on the winds needs, of course, to be where the wind blows.

Moss (left) relies on water to reproduce, while conifers (right) need wind. Once more, photos by Piter K. Boll. *

Those methods, though limited, worked well enough for millions of years until sometime in the Cretaceous period, when a group of animals started to diverse astonishingly: the insects.

Insects are small and prolific. They have a hard outer skeleton of chitin, which prevents dehydration and injuries, and many of them learned to fly, so being able to cross large distances and colonize new habitats.

Insects existed, of course, at least since the Carboniferous. The most famous of them is the giant dragonfly Meganeura. But during the Cretaceous those groups that today are the most diverse started to appear in fossils: ants, bees, termites, butterflies, moths, aphids and grasshoppers. Beetles, the most diverse group of insects today (containing more species than all other arthropods together) are found in fossils since the Carboniferous, but almost went extinct during the Permian-Triassic boundary that marks the most terrible mass extinction on Earth. After this tragic event, they stayed more discrete until a boom in diversification in Cretaceous together with the already mentioned insects.

Well, all those insects needed to eat like anything else and started to feed on plants, including their pollen. That could have been a serious trouble, but plants managed to deal with it by modifying themselves in a way that the insects now became something useful to them. If insects were attracted to their pollen, why couldn’t they carry it to other plants, so assuring a more secure fertilization?
That’s exactly what plants made, but in order to attract insects even more to their reproductive organs, those started to increase in size and get nice colors. It all happened through natural selection of random mutations, of course. No one is assuming that plants or insects actually chose to change, that’s nonsense. What I’m trying to say (through a simpler way) is that those plants that were able to attach some of their pollen grains to insects, so that it reached other plants that the insect visited, were more successful to reproduce. The same way, those plants with more beautiful flowers attracted more insects and were also more successful to reproduce.

Anyway, that’s why we should thank insects for existing, since without them we wouldn’t have so nice flowers to decorate our lives. And if you like flowers but hate insects, well, you are being extremely unfair to nature.

I know that some may say “but I like butterflies. They are beautiful and cool and cute and they pollinate everything, so I just need to like these insects and not all those disgusting things.”
Oh, really? So you like butterflies? I’m sure you like this one:

Caterpillar of Agraulis vanillae. Photo by Bill Frank extracted from jaxshells.org

Most people like butterflies and hate caterpillars, but they are exactly the same thing. And actually these insects spend most of their life as a larva. Now just to satiate your curiosity, this is what that caterpillar looks like as an adult:

An adult of Agraulis vanillae on a head of Zinnia elegans. Photo by Piter K. Boll.*

But butterflies are not the only pollinators and not even the most common ones. Bees, as you know, are also very important and the main pollinators of many economically important plants, especially fructiferous ones. Wasps, flies, mosquitos, scorpionflies and moths are also important, but we cannot forget beetles.

Most basal and primitive angiosperms are pollinated by beetles, so that its more likely that these were the guys behind the appearance and diversification of flowering plants. There are many evidences for that, like an increasing diversity of angiosperms in fossil records being contemporaneous to an increase of beetle species.

Recently, some fossil flowers from the Turonian age (about 90 million years old) were found in Sayreville, New Jersey. Those were called Microvictoria svitkoana due to their astonishing similarity to the giant Amazon water lily, Victoria amazonica, even though much smaller in size.

Flower of Victoria amazonica, one of the most primitive angiosperms. It’s easy to notice that it still resembles somewhat a conifer cone. Photo by Frank Wouters, extracted from commons.wikimedia.org.

Despite primitive, it’s certainly a very beautiful flower, and it can only exist thanks to beetles of the genus Cyclocephala, like this one.

Cyclocephala hardyi, a beetle that pollinates Victoria amazonica. Photo extracted from ssaft.com/Blog/dotclear/

What do you think about it? It’s actually a cool pal, isn’t it? If you look closer, you may see that every insect is amazing in it own way, even cockroaches!

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References:

Béthoux, O. 2009. The Earliest Beetle Identified. Journal of Paleontology, 83 (6), 931-937 DOI: 10.1666/08-158.1

Crepet, W. L. 1996. Timing in the evolution of derived floral characters: Upper Cretaceous (Turonian) taxa with tricolpate and tricolpate-derived pollen. Review of Palaeobotany and Palynology, 90, 339-359 DOI: 10.1016/0034-6667(95)00091-7

Gandolfo, M. A., Nixon, K. C. and Crepet, W. L. 2004. Cretaceous flowers of Nymphaeaceae and implications for complex insect entrapment pollination mechanisms in early Angiosperms. PNAS, 101 (21), 8056-8060 DOI: 10.1073/pnas.0402473101

Seymour, R. S. and Matthews, P. G. D. 2006. The Role of Thermogenesis in the Pollination Biology of the Amazon Waterlily Victoria amazonicaAnnals of Botany, 98 (6), 1129-1135 DOI: 10.1093/aob/mcl201

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The Macaw of Dominica

by Rafael Silva do Nascimento

ResearchBlogging.orgTalking and exuberant-colored birds always exerted a strong fascination over human beings, and with me it couldn’t be different. Besides, the curiosity that something rare or lost arouses is an important factor to define a theme of interest to someone. Those two combined factors are the foundation that sustains a great interest on my part in extinct species of psittacids, mainly in those ones with little evidence of their doubtful existence.

Several psittacid species inhabitant of island paradises were extinct in the last centuries mainly due to hunting for food, trade to become pets and habitat loss. In this post I’ll deal with a specific species that’s said to have inhabited the Dominica Island, in the Lesser Antilles (Caribbean).

Dominica was firstly inhabited by the Caribbean Indians and later colonized by French and English. Hunting by the Indians is usually sustainable, not representing a great threat for the species.

The colonization by the Europeans, however, has been proved devastating, a common scenario not only in those islands, but also in several other points of the planet.

A forest in Dominica

A forest in Dominica. Photo by Dirk.heldmaier, from Wikipedia.

The Dominican Green-and-Yellow Macaw (also known as Atwood’s Macaw or simply Dominican Macaw), Ara atwoodi, is known only from the report of Thomas Atwood. In his work “The history of the island of Dominica. : Containing a description of its situation, extent, climate, mountains, rivers, natural productions, &c. &c. Together with an account of the civil government, trade, laws, customs, and manners, of the different inhabitants of that island. Its conquest by the French, and restoration to the British dominions” from 1791, Atwood describes the local fauna, whose elements can be associated to the species currently known to the region, with the exception of a kind of psittacid no more found there and that differs from the other ones known in the island (Amazona arausiaca and A. imperialis, which Atwood probably considered a single species in his description) or anywhere else on the planet. The following is the excerpt, adapted to the modern English:

‘’The macaw is of the parrot kind, but larger than the common parrot, and makes a more disagreeable, harsh noise. They are in great plenty, as are also parrots in this island; have both of them a delightful green and yellow plumage, with a scarlet-colored fleshy substance from the ears to the root of the bill, of which color is likewise the chief feathers of their wings and tails. They breed on the tops of the highest trees, where they feed on the berries in great numbers together; and are easily discovered by their loud chattering noise, which at a distance resembles human voices. The macaws cannot be taught to articulate words; but the parrots of this country may, by taking pains with them when caught young. The flesh of both is eat, but being very very fat, it wastes in roasting, and eats dry and insipid; for which reason, they are chiefly used to make soup of, which is accounted very nutritive.’’

Atwood's Description

Atwood's Description in ''The History of the Island of Dominica'', 1791.

It’s believed that it became extinct by the end of the 18th century or beginning of the 19th century. As there are no extant species of green and yellow plumage (excluding hybrids induced by humans), Austin Hobart Clark assumed that it belonged to a species not yet known to science, firstly including it in Ara guadeloupensis (which is said to inhabit the neighboring island Guadeloupe). With the discovery of Atwood’s account, it was considered distinct, receiving the status of species in 1908.

Considered a hypothetical species by most authors, Ara atwoodi usually isn’t included in non-specific publications that mention recently extinct macaws, which almost always only mention the Cuban macaw Ara tricolor, for being the only one known from preserved specimens, and subfossil forms like A. autocthones. Joseph Forshaw highlight that’s not even safe to associate the species to the genus Ara, due to the absence of specimens, either stuffed or bones, or even illustrations. The association was made by deduction, based on the term “mackaw” used by Atwood, where Clark notices that “his macaw is a bona fide member of the genus Ara”. That, however, didn’t exclude the possibility of being a similar but separated genus that evolved by isolation in the island.

Reconstruction following the picture published in David Day's ''The Doomsday Book of Animals''. Picture by Rafael Silva do Nascimento, 2009.

From the excerpt describing its physical characteristics and based in close species, some reconstructions of how it looked started to appear, though in shyer steps than in other more popular extinct birds. The most widely known is the one present in David Day’s work “The Doomsday Book of Animals” (1981), which depicts a macaw well distinguished from the species whose appearance was known, not having the portion of bare skin on its face, consisting merely of a closed portion, but following the color pattern described by Atwood. Most posterior reconstructions are based on this picture. Other obscure species with a similar history are portrayed, like Ara erythrocephalus from Jamaica, which was also reported having green and yellow feathers, but with a red head. The color as it was described and the observation of extant species suggest a pattern similar to the one found in Ara ararauna and maybe in A. martinicus from the neighbor island Martinica (another hypothetical extinct species), with blue replaced by green. Also reported from Jamaica, but not creditable by most sources, is A. erythrurus, said to be similar to A. ararauna, but with an entirely red tail. Julian Hume in his book “Extinct Birds” to be released in February 2012, which also have Michael Walters as author, portrayed the species according to this idea, however without having the portion of bare skin on the face painted red, but only the forehead of this color. Since I didn’t have access to the work of Walters and Hume, I’m not aware of the reason for such a reconstruction, but considering that the reddish facial portion, usually seen as a distinct feature of A. atwoodi, may be simply excitation as observed in A. ambiguus, A. militaris and A. rubrogenys, this macaw may have been represented in a “calm” situation. Both A. ararauna and A. glaucogularis can show traces of redness on the face, being more evident in the last, so if A. atwoodi was truly a close relative, this feature might be more advanced in this species. A color pattern that recalls the described by Atwood is found in the pet market as in the hybrids Catalina (A. ararauna x A. macao) and Harlequin (A. ararauna x A. chloropterus), where the back is green and the belly varies from shades of yellow to bright orange.

Ara atwoodi by Rafael Silva do Nascimento

I've made this reconstruction following the theory that A. atwoodi was closely related to A. ararauna. Some elements, such as the black patch below the bill, are highly speculative.

While I see sufficient evidences to declare the existence of a different form of macaw that once inhabited Dominica, its real appearance will remain a mystery until new evidences came to the surface, whether they are lost reports or subfossil bones.

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References:

Atwood, T. 1791: The History of the Island of Dominica. London: Frank Cass and Co.

BirdLife International (2011) Species factsheet: Ara atwoodi. Available on-line in: < www.birdlife.org/datazone/speciesfactsheet.php?id=30080>.  Acess on December 6th, 2011.

Clark, A. H. 1908. The Macaw of Dominica Auk, 25, 309-311

Forshaw, J. M. & Cooper, W. T. 1977: Parrots of the World. T.F.H. Publications, Inc. New Jersey.

Fuller, E. 1987: Extinct Birds. Facts on Files Publications. New York.

Maas, P. H. J. 2007: Dominican Green-and-Yellow Macaw. In: TSEW. The Sixth Extinction Website. Available on-line in: <www.petermaas.nl/extinct/speciesinfo/dominicanmacaw.htm>. Acess on December 6th, 2011.

Many-feathers. Catalina Macaw. Available on-line in: < www.many-feathers.com/Catalina-Macaw.htm>. Acess on December 6th, 2011.

Rothschild, W. 1907: Extinct Birds. Hutchison, London.

Williams, M. I. & Steadman, D. V. 2001: The historic and prehistoric distribution of parrots (Psittacidae) in the West Indies. Pp 175-489 in Biogeography of the West Indies: patterns and perspectives. 2nd ed. (Woods, C. A. & F. E. Sergile, eds.) Boca Raton, FL: CRC Press.

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