Monthly Archives: December 2011

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.

– – –

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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Filed under Extinction, Ornithology

The Stiff-Tailed Dinosaur Syndrome

by Carlos Augusto Chamarelli

Hello everyone, PK here, which means it’s time for some good old paleoartistic criticism and bashing of current ideas! So enjoy today’s topic: dinosaurs tails.

As everyone knows, for the longest time since their formal description in the mid-19th century, dinosaurs were thought to be tail-draggers in the same fashion as reptiles, because reptiles are lazy and so should be dinosaurs since they were reptiles. Or so it seemed, as it was about in the 70’s when the “dinosaur renaissance” came into scene, replacing the slow-moving and swamp-dwelling giant lizards for active, warm-blooded animals.

And considering the topic, the most important of all these changes is that they now had their tails off the ground, but then things sort of went downhill from there: artists started to depict their dinosaurs with increasingly elevated tails, to the point where, in the last 10 years or so, dinosaurs are always pictured as having their tails completely parallel to the ground and almost pointing upwards!

I, for one, am convinced that this idea was something paleoartists – both amateur and professionals – simply misunderstood. Namely – while dinosaurs may very well been able to maintain their tails parallel to the ground, they may not have done so at all the time.

There’s one important factor about dinosaurs that I have the slight feeling some artists overhead, or just plain ignore for a more dramatic effect, is that dinosaurs are animals just like the ones that live today, and as such, dinosaurs most certainly would get very tired sometimes. See, there is not a single animal in the world that maintains any of its limbs in a certain position for too long, and dinosaurs would be no exception: maintaining their tails elevated in a horizontal posture for so long would be exhaustive.

In other words, dinosaurs were able maintain their tails above the ground, but just enough; namely, they had droopy tails for the most part.

I went to brainstorm with RSN about this possibility, and he reminded me of an important detail: some dinosaurs were found with fossilized tendons on their tails. So naturally I had to research about that and what it would mean for the droopy-tail idea. One such evidence is found in the first ever Corythosaurus remains discovered by Barnum Brown in 1912, which is nice because for me ornithopods are the worst offenders of the rigid-tail idea. Now, please, take a look at this picture:

Picture of a giant helmeted duck.

Corythosaurus casuarius skeleton, by Barnum Brown, 1916.

Not only the creature’s skeleton was found almost complete, skin impressions are also present, but take a closer look at the tail; specifically the base, right above the ischium. Those distinct line markings you see were made by tendons which, supposedly, helped the animal maintain his tail in the same horizontal position as seen in this skeleton. But where exactly does this leave the idea that dinosaurs had droopy tails then? Go ahead, I’ll give you a few seconds…

You see it yet? Ok, I’ll make it more clear with this other picture:

Corythosaurus

Drawing of the fossil, by Barnum Brown, 1916.

Yes, as you can see, those tendons were present mainly at the very base of the tail. Not only that, but consider the caudal vertebrae also have a slight irregular shape when lined horizontally, but not so much if you curve it downwards – this also happens in other dinosaurs such as sauropods. In other words, the tendons only helped the Corythosaurus to maintain the first half or so of its tail elevated.

From what could be inquired from mummified hadrosaurid findings, duck-billed dinosaurs (as they are informally called) had a longer digestive system than other plant-eating dinosaurs. The elevated tail base means there is some more free room for processing the plant matter. Maybe not for much, but it was a very welcome addition.

But naturally dinosaurs didn’t had tails to digest plants. Tails are primarily used for balance, and in some animals it can also serve as a weapon, other might use them to call attention of mates or signalizing for each other in a group. Some animals, however, have no need for any of these, so what usually happen is that the tails have so little impact on its lifestyle that they quickly degenerate, resulting in stumps or completely disappearing. Just like what happened to us humans.

But dinosaurs had big tails – except for those who became birds and other not-quite-bird-yet small theropods such as Epidexipteryx – it’s one of their trademarks that make them so different from any other large animal today. But not all dinosaurs used their tails for balancing.

Epidexipteryx hui skeleton, discovered in 2008. Notice the shortened tail, compensated by the elongated feathers. Photo from National Geographic.

For example, armored dinosaurs such as ankylosaurids, nodosaurids and stegosaurids. With a low profile and sturdy legs, having a tail for balance isn’t needed, but they still had well formed tails for a single reason: they were mortal weapons. Stegosaurids had piercing spikes, nodosaurids had rows of sharp blades and ankylosaurids had a mass of bone at the tip that formed a fearsome weapon against predators.

Tail club of Euoplocephalus tutus, an ankylosaurid. Photo by Ghedoghedo, from Wikipedia, 2011.

Sauropods, at least the ones without extreme long neck lenghts, wouldn’t need such a long tail for counterbalancing; their torso might have been enough. These would then be free to be used as weapons since they couldn’t back-off predators with sheer size alone, and surely enough, some sauropods such as Diplodocus had elongated tails that ended in thin bones that could be used as whips, and the chinese Shunosaurus had a bone club similar to that of ankylosaurids. Both dinosaurs, while much larger than any living terrestrial animal, are visibly rather small for sauropod standards.

Skeletal reconstruction of the Spinophorosaurus nigerensis from Africa, which closely resembles the chinese Shunosaurus both in size and weaponry. Souce: Remes K, Ortega F, Fierro I, Joger U, Kosma R, et al. (2009).

On the same note, brachiosaurids had huge front legs which supported an extreme neck, but their tails were very small compared to other sauropods. So small in fact, they couldn’t be used for anything and one wouldn’t be surprised if their tails became stumps had they survived long enough.

Brachiosaurus brancai (now Giraffatitan brancai). Picture by Paul Olsen, 1988.

Now there are the odd ones: Ceratopsians. The larger ceratopsian that dominated North America in the late Cretaceous period landscape are known for their huge frills and huge horns and sturdy bodies… and for having rather pathetic-looking tails. These were relatively short and thin, and it’s hard to imagine that ceratopsians used them for counterbalancing their skull – which is in some way confusing since they might have been quite heavy even with the “windows” on the frills to decrease the weight.

And even odder ones: Pachycephalosaurids. These dinosaurs are known for their thick skulls which they used for head-butting contests (yes), but they are also known for the woven net of tendons at the tip of their tails. The total opposite of what usually happens.

So where do ornithopods such as Corythosaurus fall in all of this? My guess is that they used them for balance, but only when running on their hind legs. See, duck-billed dinosaurs had very small arms compared to his legs, with hoof-like hands, which is good evidence that they could walk on four legs as well as two legs.

A grazing Corythosaurus did not need their tails to be parallel to the ground; their arms would enable them to stand with a droopy tail. But on the sign of danger, things change: unsuitable to handle the stress that running on all four would cause, they would stand on two legs and run; the tail tendons then would enable the animal lift his tail to counterbalance its body while running. In this respect, the dinosaur would then function more like a theropod rather than a ceratopsian, per se. When away from danger, the tendons relax and the animal tail goes back to its droopy position. Corythosaurus would then look something like this (thanks RSN for the picture!):

Corythosaurus in relaxed position (above) and running from danger (below). Picture by Rafael Silva do Nascimento, 2011.

So there you have it. Dinosaurs had many uses for their tails, and just because they had tendons and warm blood it doesn’t mean they had steel rod for tails. While Corythosaurus is used as a starting point for the idea, keep in mind other dinosaurs also could have droopy tail, including the ones that used their tails for balance such as theropods.

So if you ever see a picture of a dinosaur, any kind of dinosaur, standing still or having a nice stroll, and said dinosaur is doing it while having their tails completely parallel to the ground, you’re allowed to shout “WRONG!”, because that dinosaur must be tired as heck of having his tail like that.

Hope everyone enjoyed reading my article; if you have any questions just comment and I’ll answer it.

Thanks for reading!

– – –

References:

Leonardo, the mummified dinosaur. Available on-line in: <www.youtube.com/watch?v=ihifMrV3-pY>. Acess on December 1st, 2011.

Paul, G. S. et al. 2010: The Princeton Field Guide to Dinosaurs. Princeton University Press.

Wikipedia. Corythosaurus. Available on-line in: <en.wikipedia.org/wiki/Corythosaurus>. Acess on December 1st, 2011.

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A Brief History of the Kingdoms of Life

by Piter Kehoma Boll

Since ancient times, living beings were classified as either plants or animals and Linnaeus retained this system in his great work Systema Naturae in the 18thcentury, where he divided nature in three kingdoms: Regnum Animale (animal kingdom), Regnum Vegetabile (plant kingdom) and Regnum Lapideum (mineral kingdom). This system was not intended to reflect natural relationships among living organisms, since Linnaeus was a Christian and believed that all life forms were created separately by God himself just as they are today, but was created to make the study of living beings easier.

Linnaeus and the two kingdoms of life. Painting by Alexander Roslin, 1775.

When the first unicellular organisms were discovered by Antoine van Leeuwenhoek in 1674, they were placed in one of the two kingdoms of living beings, according to their characteristics. It remained so until until 1866, when Ernst Haeckel proposed a third kingdom of life, which he called Protista, and included all unicellular organisms in it.

Haeckel and the three kingdoms. Photo by the Linnean Society, 1908.

Later, the development of optic and electronic microscopy showed important differences in cells, mainly according to the presence or absence of distinct nucleus, leading Édouard Chatton to distinguish organisms in prokaryotes (without a distinct nucleus) and eukaryotes (with a distinct nucleus) in a paper from 1925. Based on it, Copeland proposed a four-kingdom system, moving prokaryotic organisms, bacteria and “blue-green algae”, into the kingdom Monera. The idea of a ranking above kingdom came from this time and so life was separated in two empires or superkingdoms, Prokaryota (Monera) and Eukaryota (Protista, Plantae, Animalia).

Two empires and four kingdoms

Since Haeckel, the position of fungi was not well established, oscillating between kingdoms Protista and Plantae. So, in 1969, Robert Whittaker proposed a fifth kingdom to include them, the called Kingdom Fungi. This five-kingdom system remained constant for some time; Monera were prokaryotes; Plantae were multicellular autotrophs (producers); Animalia multicellular consumers; and Fungi multicellular saprotrophs (decomposers). Protista was like the  trash bag, where anything that doesn’t fit in the other 4 kingdoms was placed in.

Whittaker and the five kingdoms. Photography source: National Academy of Sciences: Robert H. Whittaker (1920—1980) – A Biographical Memoir by Walter E. Westman, Robrt K. Peet and Gene E. Likens.

With the dawn of molecular studies around 1970, significant differences were found inside the Prokaryotes, regarded, for example, to the cell membrane structure. Based on those studies, Carl Woese divided Prokaryota in Eubacteria and Archaeobacteria, emphasizing that the differences between those two were as high as the ones between them and the eukaryotes. This later gave rise to a new higher classification of life in three domains, Bacteria, Archaea and Eukarya.

Woese and the three domains. Photo from Photo from News Bureau – University of Illinois, given by IGB (Institute for Genomic Biology).

By the end of the 20th century, Thomas Cavalier-Smith, after intense study of protists, created a new model with 6 kingdoms. Bacteria and Archea were put together in the same kingdom, called Bacteria. Protists were divided in two kingdoms: (1) Chromista, including Alveolates (Apicomplexa, parasitic protozoa like Plasmodium; Ciliates and Dinoflagellates), Heterokonts or Stramenopiles (brown algae, golden algae, diatoms, water moulds, etc) and Rhizarians (like Radiolaria and Foraminifera), among others; and (2) Protozoa, including Amoebozoa (amoebas and slime moulds), Choanozoa (choanoflagellates) and a set of flagellated protozoa called Excavata. Glaucophytes, red and green algae were classified inside the kingdom Plantae.

Cavalier-Smith and his two new kingdoms. Photo from Department of Zoology – University of Oxford.

From the 21th century on, a phylogenetic approach to classify living beings has gained strength. After a lot of molecular analyses using different genes, the real evolutionary relationship among Eukaryotes is still not clear. However, the following groups are supported by most phylogenetic trees:

(1) Archaeoplastida (or Plantae): glaucophytes (Glaucophyta), red algae (Rodophyta) and green plants and algae (Viridiplantae)

(2) Chromalveolata: Stramenopiles or Heterokonta, haptophytes (Haptophyta), cryptomonads (Cryptophyta) and Alveolata.

(3) Rhizaria: Foraminifera, Radiolaria and some amoeboid protozoa

(4) Amoebozoa: amoebas and slime moulds

(5) Opisthokonta: animals, fungi, choanoflagelates

(6) Excavata: many flagellate protozoa. This group, however, isn’t as well supported as the other ones.

The current (maybe not so) well-established groups of organisms

So, as we can see, the Eukaryotes’ case is yet to be solved, but we hope that further molecular studies will help us understand better how the tree of life branches.

– – –

References:

Baldauf, S. L. et al. 2000: A Kingdom-Level Phylogeny of Eukaryotes Based on Combined Protein Data. Science 290, 972-977.

Cavalier-Smith, T. 2004: Only six kingdoms of life. Proceedings of the Royal Society B 271, 1275-1262.

Rogozin, I. B. et al. 2009: Analysis of Rare Genomic Changes Does Not Support the Unikont–Bikont Phylogeny and Suggests Cyanobacterial Symbiosis as the Point of Primary Radiation of Eukaryotes. Genome, Biology and Evolution 1, 99-113.

Wikipedia. Kingdom (Biology). Available on-line in: <en.wikipedia.org/wiki/Kingdom_(biology)>. Acess on December 5th, 2011.

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Exotic Species: Are they always a trouble?

by Piter Kehoma Boll

In the last decades, non-native species became victims of discrimination by conservationists, land managers, policy makers, as well as among scientist, being condemned for driving native species to extinction and ‘polluting’ natural environments. However, current management approaches need to consider that natural systems are changing without return thanks to climatic changes, urbanization, eutrophication and other changes due to land use.

Certainly many species introduced by humans lead to extinctions and reduced valuable ecological services. The avian malaria, introduced in Hawaii with non-native birds brought by Europeans, kill more than half of the native species. The zebra mussel Dreissena polymorpha, originally native from Russia and introduced in North America, and the golden mussel Limnoperna fortunei, native from Southern Asia and introduced in South America, became a a great problem for clogging water pipes.

Zebra mussel, an invasive species in North America

Zebra Mussel, an invasive species in North America. Photo by GerardM, from Wikipedia.

But the majority of claims about the destructive role of invasive species is based on Wilcove et al. (1998) who claim that invasive species are the second greatest threat to endangered species after habitat loss, but that’s little supported by data. Actually, in many cases the introduction of species increased the species richness in a region.

The effects of an invasive species that doesn’t cause troubles now can became a harm in the future, but the same applies to native species. Nativeness is not a sign of a necessarily positive effect. The insect suspected of killing more trees than any other in North America is the native beetle Dendroctonus ponderosae. Many species of introduced fruit trees became important feeding sources for local birds, attracting them and so even helping the dispersion of native species.

The idea is not to defend invasive species in all cases, but to incite a more analytical approach of the situation. Instead of blindly condemning a species just for not being native, the management plans need to be based in empirical evidences and not in unsubstantiated claims.

– – –

Reference:

Davis et al. 2001: Don’t judge species on their origins. Nature, 474, 153-154.

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Earthling Nature!


Welcome aboard! We present this blog with the intention to serve as a journal about the life on our planet. While we are not (yet) experts in the field, our enthusiasm and interest on the different lifeforms around this world came to provide texts and comments on new and relictic subjects.

This blog came from the idea of entereing the blogroll of science writting and reviving our past sites in the subject, all in Portuguese language: BioData by Rafael and Biolista by Piter. The blog will serve as a sibling to our other existing journals: Poisor Tristesi, as well for discussing the representation of both extinct and extant life in art.

Presenting the friends and editors of the blog:

Carlos Augusto Chamarelli
Piter Kehoma Boll
Rafael Silva do Nascimento

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