Shell Games

One of those questions a herpetologist gets too often is the one about the difference between tortoises and turtles.  The short answer to this is that there isn’t much, technically speaking.  Herpetologists work with a more varied idea of the diversity of these shelled reptiles than can fit neatly into just two categories.  However, culturally, the use of the English language does have conventions on what is a tortoise and what is a turtle, but culture being what it is, those usages depend on which English-speaking culture you are from and have much less to say about any big dichotomy in the evolutionary history of these highly specialised and durable reptiles. This little review is aimed at explain how we came to use these names, and how they are currently applied.

First a bit of biological background. This discussion concerns the group of highly specialised reptiles technically called the Testudines (tes-TUDE-in-ees), reptiles with very highly modified bodies covered by a bony shell.  There are two major groups of living members of this group, distinguished by the way that the head and neck retract into the safety of the shell. The fossil history of the Testudines reveals that pulling your head in was something that these animals evolved sometime after they had the rest of their anatomical specialisations, including the shell and the modifications of the limbs and limb girdles that go with it. Retraction of the neck requires specialised joints that enable it to fold back on itself, and in the Testudines this evolved twice.

In the group that is most widespread today, the Cryptodira (“hidden-necks”) the neck developed a vertical fold – as the neck contracts, the head is pulled straight back into folds of skin between the front legs, the “elbow” of the neck actually ending up in the middle of the shoulder girdle – the ultimate shrug. In the second group, the Pleurodira (“side-necks”), today confined to the three major Southern Hemisphere landmasses of South America, Africa-Madagascar and Australia-New Guinea, the neck folds sideways, and the head ends up facing either right or left and under the overhanging front of the shell.  As it happens, in Australia the traditional use of the term “tortoise” was applied to the freshwater species with webbed, clawed feet, all¹ of them side-necks, while the term “turtle” was applied to the marine species with flippers, which are all hidden-necks.  Neat. But accidental, and only applies to Australia. 

Here’s where culture creeps in. An American looking at our testudinate fauna would see all of them as turtles, because where he is from, tortoises are purely terrestrial creatures with pillar-like, short-toed legs. An English naturalist who had been reading her semi-technical literature would also not recognise our tortoises as the same thing she would call a tortoise; she might be inclined to call our freshwater species terrapins, a term that has come into use among reptile keepers to refer to aquatic/amphibious species that have clawed feet instead of flippers. In fact we would need a lot of names if we wanted to parcel out the variation in the 353 living Testudines into English names that match their evolutionary diversity.

Today, apart from those two major neck-based subdivisions, the Testudines are broken up further into 14 families, each with a characteristic set of anatomical and ecological specialisations (see the Table at the end of the article). There are the sea turtles (Cheloniidae and Dermochelyidae) and Australian side-necked turtles (Chelidae) we have already mentioned, plus the other Australian species, a flipper-bearing freshwater hidden-neck called the pig-nose turtle (Carettochelys insculpta), the only living member of its family (Carettochelyidae).  Elsewhere  in the world there are two other side-necked families, both freshwater pond and river dwellers, and among the hidden-necks, the peculiar soft-shelled turtles which have shells of greatly reduced thickness and extent to make them faster underwater swimmers, and the land-dwelling, even desert-dwelling, members of the  Testudinidae that includes the giant species of the Galápagos and Aldabra.  Most numerous are the several families of semiaquatic river and pond dwelling hidden-necks that occur across North America and Asia.

So the two popular names we use don’t have roots that are based on the differences that arose among the living species because of their biological evolution.  They originate in the much more quirky world of language evolution.  And as a start we can say that the two English words ultimately have the same etymological origin – strictly, we should just have one word for the Testudines, as is the case with some other European languages, like French, Italian and German. 

No members of the Testudines occur naturally in the British isles or adjacent Norman France or the Germanic and Scandinavian states, the three places whence our English words mainly derive. So there is no unique word for these animals that can be traced back to these founding sources. France, it seems, is the ultimate source of both of our English words, and for them it all starts with Latin. The Roman Empire introduced their subjugated peoples to the fauna of pretty much all of western Europe, the Middle East and North Africa, and many of those unfamiliar animals had no names in the local languages of north-western Europe.  Naturally, Latin words (or local dialect versions) were used to label the exotic species. The original Latin word for the animals we are talking about is testudo, from the Romans’ word for a shell, testa. But oddly, that is not the name that came into use in modern European languages, following the breakup of the Empire.

Although pet tortoises are popular in western Europe today, in Mediaeval times they seem to have had a darker reputation. Something in local story-telling viewed the tortoise as a symbol of the forces of darkness.  In early Christian iconography, Hell was often referred to using the Greek mythological term, Tartaros (Latin: Tartarus), the underworld, and the tortoise was the tartaruca: “beast from Tartaros”.  Modern Italian still uses essentially same word, tartaruga, as their all-purpose name for a member of the Testudines.

A common occurrence as languages develop is the phenomenon of homophones, words that have different origins and meanings but sound the same or similar (e.g. son and sun, hear and here). Sometimes a more familiar word can echo the sound of a less familiar word and, eventually, usage makes the sound of the two words identical. For the people of southern France, the name for the tortoise had lost a syllable and become, in old Provençal, tartuga or when written in Latin, tortuca (the source of the modern Spanish word, tortuga).  This word is not dissimilar to the shorter and more everyday Old French adjectives tortue, meaning crooked, and tordu, meaning twisted.  So pretty soon, for French people, seemingly across a variety of Latin-related, regional languages, the word tortue used as a noun came to mean the shelled reptile.   In modern French, the single word is applied to all members of the Testudines as the common distinguishing term. If not the Romans, then the Normans would have brought both their word and possibly the animals themselves as curiosities as they spread into the British isles following the 1066 conquest. An Anglo-Norman word appeared, written down as tortouse, and this evolved into the Middle English word tortuce and, with modified spelling, the modern English ‘tortoise’. 

So English has had a generic word for a member of the Testudines for almost as long as the French.  Why are there now two vernacular words?  Why turtle as well? In fact we had ‘turtle’ for as long as we had ‘tortoise’, and from the same ultimate source, the Romans.  But until the 17^th Century, ‘turtle’ was not the name for a reptile, it was the name for a bird. The Romans were familiar with a widespread small European species of dove that had a distinctive, purring call, for which they named it turtur. In old English, the word became ‘turtle’, often expressed as ‘turtle dove’,  and today it has become ‘turtledove’.  In Shakespeare’s day (and in his plays) mention of turtles refers to these birds that had become a symbol of fidelity in love. As the British started to sail warmer oceans from the 16^th Century onwards, they regularly exploited the large marine turtles at their nesting beaches, or the giant land tortoises that roamed some islands. In seeking a name for these desirable animals they borrowed the names used by Spanish (tortuga) and French (tortue) mariners. The names were unfamiliar, but close enough to ‘turtle’, a word they did know, and the reptiles were soon being referred to by the bird’s name (first record of this was in 1605 at Bermuda).   

Over the 17^th to the 19^th Centuries, the two terms appear to have been interchangeable, a good example being the commodity derived from the shell plates of the marine hawksbill turtle becoming referred to as ‘tortoise-shell’.  By this time the British had colonised areas that did have endemic Testudines, and so local English usage began to apply the names to particular subgroups, but did so somewhat differently. Today, everyone seems to agree that the marine species in the families Cheloniidae and Dermochelyidae are ‘turtles’, and that the highly terrestrial, club-footed Testudinidae are ‘tortoises’.  In Australia, with no typical land tortoises, settlers evidently settled on tortoise for the freshwater species that did not have flippers and were small in size, while continuing with turtle for the giant marine species.  In the New World, there were land tortoises like the Mediterranean ones, and so tortoise became quite narrowly applied to just those few species, while everything else was a turtle.  

North America also provided that third word I used earlier – terrapin. This is word was picked up by the British colonists of the 1600s from the Native American speakers of the Algonquian language group of the northeast coast of the United States. Their word torope (TO-ro-pay) applied specifically to one species, now known by zoologists as the diamondback terrapin, Malaclemys terrapin. This species is a member of one of the main northern hemisphere families, the Emydidae, but is unusual in living in brackish coastal waters and so is neither marine nor freshwater but something in-between, making it a useful word to add to North American English for this particular species. In British English, it is sometimes more generally applied to the Testudines that are neither marine nor strictly terrestrial, which in practice would be almost all Testudines.  However the name is inconsistently applied and its use has stayed mainly among those with a particular interest in Testudines rather than the wider English speaking public.

So, to sum up, English usage across the world agrees that the big marine species with flippers (the typical sea turtles, Cheloniidae, and the giant leatherback, Dermochelyidae) are turtles, and that the members of the  Testudinidae, that have strictly terrestrial habits, pillar-like legs, and mostly high-domed shells, are tortoises. If you want to move towards a more technical usage, American English tends to dominate the technical literature, so turtle is the default word unless you want to refer specifically to one of the Testudinidae, in which case you would use tortoise.  But for most situations most of the time – either word will do.

TESTUDINES (353 species)

Cryptodira (hidden-neck turtles)

• Chelydridae (Snapping Turtles) (5 species)
• Emydidae (Pond Turtles/Box and Water Turtles) (53 species)
• Testudinidae (Tortoises) (60 species)
• Geoemydidae (Asian River Turtles, Leaf and Roofed Turtles, Asian Box Turtles) (71 species)
• Platysternidae (Big-headed Turtles) (1 species)
• Carettochelyidae (Pignose Turtles) (1 species)
• Trionychidae (Softshell Turtles) (33 species)
• Dermatemydidae (River Turtles) (1 species)
• Kinosternidae (Mud and Musk Turtles) (27 species)
• Cheloniidae (Sea Turtles) (6 species)
• Dermochelyidae (Leatherback Turtles) (1 species)

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Pleurodira (side-necked turtles)

• Chelidae (Austro-American Side-neck Turtles) (59 species)
• Pelomedusidae (Afro-American Side-neck Turtles) (27 species)
• Podocnemididae (Madagascan Big-headed and American Side-neck River Turtles) (8 species)

Sources:
Ernest Weekley – An Etymological Dictionary of Modern English
Larousse French dictionary – définition ‘tortue’
Wikipedia – Diamondback Terrapin
Wikipedia – Algonquian languages
YouTube – Video of the Burmese peacock softshell turtle