- Janaki Lenin and Jack Frazier
They are the largest native herbivores on the island they inhabit in the Indian Ocean – Aldabra Atoll – and amongst the largest living tortoises on the planet. As four of these Aldabra tortoises deliberately and calmly munch their way through leaves at the Madras Crocodile Bank, an international debate on their scientific name, which has been simmering for more than two decades, is now raging.
Biologists give every living thing a “scientific name,” usually based on Latin or Greek words. This allows them to cut through the babel of names in various languages (there are 17 names recorded for the flap-shelled turtle,
Lissemys punctata, in Indian languages alone!). But the case of the Aldabra tortoise has made a mockery of this practice, for there are nearly a dozen “scientific names” in use for the same animal. There is so much confusion that some scientists have used more than one name in the same chapter or even on the same page! So, now the reverse is true: the common name of the Aldabra tortoise has far more universality than its scientific names.
The saga begins with the expansion of European colonial powers and Napoleon’s conquest over much of Europe. About 1809 August Friedrich Schweigger, a German botanist, visited the Paris Museum and did the first scientific study of turtles. Among the dozens of specimens that he described was one that had formerly been part of the King of Portugal’s collection, but after Napoleon’s army claimed Portugal, this tortoise, along with various other scientific specimens, was taken to Paris. Schweigger called this spoil of war
Testudo gigantea and recorded the country of origin as “Brasilia” (modern day Brazil). His Latin description of the animal has been variously interpreted and reinterpreted by different experts over the years because Schweigger did not clearly distinguish
gigantea from the other large tortoises found on islands of the Western Indian Ocean, Galapagos, mainland Africa or South America.
More than 20 years after Schweigger’s classic study of turtles was published in 1812, André Marie Constance Duméril and Gabriel Bibron, two renowned French biologists, described
T. gigantea on the basis of another, larger specimen also lodged in the Paris Museum. There are no records that indicate the origin of this second specimen, and in 1855, A.M.C. Duméril and Auguste Henri André Duméril referred to the same specimen again as the only one of this species in the Paris Museum. For nearly two centuries following Schweigger’s description of
T. gigantea the original specimen was never mentioned again. Meanwhile, Duméril and Bibron had also described a new species of giant tortoise,
T. elephantina said to be native to islands in the Mozambique Channel, including Anjouan, Comores and “Aldebra”. Could Schweigger’s
T.gigantea be the same as Duméril and Bibron’s
T. elephantina? This line of thought occurred to Duméril and Bibron as well as to Albert Charles Ludwig Gotthilf Günther, another important 19th century zoologist working in the Natural History Museum in London. A few years later, Ambrosius Arnold Willem Hubrecht in Holland and George Albert Boulenger, yet another important figure at the Natural History Museum, London, concluded that
T. gigantea lived on Aldabra. For the next 100 years, the Aldabra tortoise was routinely known by the name of
Testudo gigantea.
In 1957, Arthur Loveridge and Ernest E. Williams, from the Museum of Comparative Zoology at Harvard University, reorganized tortoises of the genus
Testudo into seven different genera; the large, or giant, tortoises were now in the genus
Geochelone. In addition, Loveridge and Williams created a new subgenus –
Aldabrachelys – specifically for the Aldabra tortoise and its close relatives; understandably, they designated
T. gigantea as the “type species” for their new subgenus.
In 1982, Roger Bour of the Paris Museum declared that Schweigger’s 1812 specimen was not an Aldabra tortoise, but was “unquestionably” an extinct tortoise,
Geochelone (Cylindraspis) indica, from the Mascarene islands; this group of volcanic islands, which includes Mauritius, lies east of Madagascar and is distant from and unrelated to Aldabra and the Seychelles. Bour thus argued that the Aldabra tortoise could not be called
T. gigantea (or
Aldabrachelys) anymore, and that the appropriate name was
T. elephantina, the name coined by his famous compatriots Dúmeril and Bibron 150 years earlier. To fill the void left by rendering
Aldabrachelys irrelevant to the Aldabra tortoise, Bour created a new genus,
Dipsochelys. Bour based his assumptions on his interpretation of Schweigger’s description of
T. gigantea, by no means an unequivocal source.
In 1986, Peter Pritchard agreed with Bour’s conclusion that the 1812 Latin description did not refer to the Aldabra tortoise, but he disagreed that Schweigger had described an extinct tortoise from the Mascarenes. Since the locality for the Napoleonic war trophy was “Brasilia”, Pritchard argued that the specimen in question was the largest tortoise of that country: the yellow-legged tortoise,
Chelonoidis denticulata. However, since the name
Aldabrachelys had been expressly created for the Aldabra tortoise and was in use, Pritchard appealed for its continued usage. That same year, Chuck Crumly explained that Schweigger’s original 1812 description in Latin was not that easy to interpret, and he went on to clarify that
gigantea was the established species name by which the Aldabra tortoise had been regularly known for many years; thus, he argued that the name should continue to be used on the grounds of “nomenclatural stability and universality”.
There is yet another name that complicates the history of the Aldabra tortoise even more: one that had been forgotten for 150 years. In 1831, John Edward Gray, the curator at the Natural History Museum in London, had included
T.gigantea with a host of other tortoises under the name
T. indica. Gray believed that all giant tortoises, whether those from the Galapagos Archipelago in the eastern Pacific or those from the Seychelles (which includes Aldabra Atoll) in the Indian Ocean, were all the same species. He thought that the virtually global distribution of the single species was from translocations of tortoises among the islands by sailors. Among the different names for tortoises that Gray included as synonyms of
T. indica was
T. dussumieri. In 1984, Bour declared the name
T. dussumieri to be a forgotten name (“nomen oblitum”) – after all, it had not been used for nearly 150 years. But in 1995, confusion escalated again when Justin Gerlach declared
Dipsochelys dussumieri as the correct name for the Aldabra tortoise.
Hence, the name of this distinctive tortoise had become a tower of scientific babel. By now five generic names (
Aldabrachelys, Geochelone, Dipsochelys, Megalochelys and Testudo) and three specific names (
elephantina, gigantea, and dussumieri), combined in at least eight different combinations, were being used to refer to just one tortoise. And, there were yet other names in the running (
Testudo daudinii, T. hololissa, T. ponderosa, T. sumeirei, T. gouffei and Dipsochelys arnoldi). In one year alone (2003), Bour used both
Aldabrachelys gigantea and
Dipsochelys dussumieri in two different publications to refer to the Aldabra tortoise. Yet, whichever name was used, the authors routinely took pains to clarify that they were indeed referring to the animal also known as
gigantea.
In 2006, Jack Frazier tried to bring some order by nominating a specimen of an Aldabra tortoise from Dune Patates, Aldabra Atoll, lodged at the Smithsonian Institution as the neotype: since the Schweigger specimen was widely presumed to be lost, the neotype would provide a clear reference for the name
T. gigantea.
Inexplicably, within months of the declaration of the neotype, Bour reversed his earlier position and agreed with Gerlach that the long forgotten name
dussumieri should be used for the Aldabra tortoise henceforth. At the same time he described in great detail a stuffed tortoise that he claimed had been overlooked in the Paris Museum for over a century. This specimen had a catalogue entry from about 1864 and the museum label stated that it was
Testudo carbonaria, the red-legged tortoise from South America. However, Bour pointed out that this old specimen, evidently studied by Dúmeril and Bibron, is really a yellow-legged tortoise (
Chelonoidis denticulata), evidently from Brazil. Since the size of the specimen and locality matched the 1812 description of
T. gigantea, Bour claimed to have “rediscovered” the long-lost specimen that Schweigger had described, and changing his earlier held opinion, now agreed with Pritchard’s reinterpretation of Schweigger’s 1812 description. Bour also identified Duméril and Bibron’s 1835 specimen of
gigantea, and he claimed that these two doyens of herpetology had made a terrible mistake; he said, they were the first to describe the Aldabra tortoise but wrongly named it as
T. gigantea.
If Bour’s purported rediscovery of the long-lost Schweigger specimen were accepted, then
gigantea can never be used to refer to the Aldabra tortoise again. However, several museum curators and chelonian experts are not convinced of Bour’s and Pritchard’s claim (which would first require a clear understanding of Schweigger’s description). Whether or not the “rediscovery” can ever be proven, various taxonomists, conservationists, zoo curators, and other educators have argued that stability of the name is the fundamental concern, not the “pedantic legalistic” speculations about what may have happened 200 years ago. They argue that to avoid confusion, it is important to continue calling the Aldabra tortoise by a name that has been in continuous usage for more than a century:
gigantea. The rules of the International Commission on Zoological Nomenclature (ICZN) also give primary importance to “nomenclatural stability”. The simple and straight forward mechanism to accomplish this stability is to set aside the “rediscovered” holotype in favour of the 2006 neotype which conserves the name that has immediate and universal recognition:
gigantea.
That is the essence of Case 3463 that was submitted to the ICZN in March of this year. Letting the status quo continue with endless debates about whether or not the original specimen from 1812 has or has not been rediscovered and different names being used by various factions does nothing for the future of a species that is threatened by many different risks, including global climate change and rising sea levels on an atoll that is but a few meters above sea level.
Source: Frazier, J. (2009) ‘Case 3463:
Testudo gigantea Schweigger, 1812 (currently
Geochelone (Aldabrachelys) gigantea; Reptilia, Testudines): proposed conservation of usage of the specific name by maintenance of a designated neotype, and suppression of
Testudo dussumieri Gray, 1831 (currently
Dipsochelys dussumieri)’. Bulletin of Zoological Nomenclature 66(1): 34-50.
(a PDF of this document is available on request)
