Terrapene Carolina Putnami

Terrapene carolina putnami is the largest box turtle that ever existed. It walked through the wet pine flats and coastal marshes of what is now the southeastern United States during the Pleistocene, was described in 1906 from fossil bones by the palaeontologist Oliver Perry Hay, and is — as far as we can tell — completely extinct. There are no living animals. There is no surviving lineage. There is only a handful of carapace fragments in museum drawers and a body of literature about a turtle that may have been the size of a microwave.

By Hannah, with palaeo references checked against current Pleistocene literature.

The animal

If you have only ever seen modern Terrapene, picture a common box turtle. Now picture it scaled up so that the carapace would be 35–40 cm long instead of 11–14 cm. That is the rough scale of T. c. putnami based on the largest fossil carapaces recovered. Estimates put the largest individuals at roughly 380–400 mm carapace length — easily two to three times the size of any modern Terrapene carolina.

It is one of the clearest known examples of insular and Pleistocene gigantism in turtles. The southeastern United States during the late Pleistocene was a warmer, wetter, more productive environment with abundant arthropod and mast resources, and limited large terrestrial predators that targeted adult chelonians. Box turtles that were already at the upper end of the size distribution had room to grow.

Naming and description: Hay 1906

The original description is in O. P. Hay’s 1906 paper:

Hay, O. P. (1906). Descriptions of two new genera (Echmatemys and Xenochelys) and two new species (Xenochelys formosa and Terrapene putnami) of fossil turtles. Bulletin of the American Museum of Natural History 22(3): 27–31.

Hay originally named the species Terrapene putnami, recognising it as distinct from any living Terrapene. Subsequent work — primarily through the mid‑20th century — reclassified it as a subspecies of the common box turtle, T. carolina putnami, on the basis of carapace morphology. Some recent palaeontological work argues for restoring it to full species status, which would put the name back at Terrapene putnami; the older subspecies name remains common in citation. We use T. c. putnami through this article for continuity with the original page, while flagging that the taxonomy is contested.

Where it lived

Fossil records of T. c. putnami come from Florida, Georgia, and adjacent parts of the southeastern coastal plain, with the type material described from around the Savannah River area. Specimens have been recovered from late Pliocene and Pleistocene sediments, with the majority of finds dating to the late Pleistocene. The animal seems to have been a wet‑habitat generalist, much like its surviving relatives — coastal marshes, lowland pine flatwoods, swamp edge, river floodplain.

The southeast in the Pleistocene was unrecognisable compared to today. Mastodon, ground sloth, giant armadillo, dire wolf, sabretooth cat, and an enormous diversity of birds shared the landscape. T. c. putnami was a sympatric small‑to‑medium component of that fauna, large enough that its full‑grown adults probably had relatively few predators that could break the shell — which is exactly the size relief that allowed it to keep growing.

The carapace

The fossil carapaces of T. c. putnami share the basic morphology of the modern common box turtle: a single hinge across the plastron, a domed carapace, broad costal scutes. The differences are mostly scale and proportion:

• Carapace length consistently 30+ cm in adults, with the largest specimens approaching 40 cm.
• Shell thickness greater than in modern Terrapene — a defensive adaptation in an environment with more large predators.
• The plastral hinge appears to have functioned the same way as in living box turtles; whether the largest adults could fully close their shells is debated by palaeontologists.

That last point is interesting. There may be a hard upper size limit on a hinged plastron’s ability to seal — once the shell gets large enough, the mechanical loads on the hinge probably outpace the soft tissue’s ability to fully retract everything inside. Some palaeontologists have argued that very large adult T. c. putnami may have lost the ability to close fully, trading the defensive seal for sheer bulk. Others disagree. There is no living analogue to test against.

What it ate

Like every other Terrapene, T. c. putnami was almost certainly an opportunistic omnivore. The wild diet of modern Eastern and Florida box turtles is dominated by invertebrates (slugs, earthworms, beetles, isopods), fruits, fungi, and occasional vertebrate prey (small amphibians, hatchling birds, carrion). Inference from tooth‑like jaw structures and gut contents of more recent fossils suggests T. c. putnami ate the same kinds of food in larger quantities, with the larger body size likely opening up tougher mast (acorns, hickory nuts) and possibly larger vertebrate prey items.

Whether it ever actively predated mammals or hatchling birds, as some 20th‑century sources speculated, is genuinely unknown. Modern box turtles are perfectly capable of taking small vertebrate prey when offered. Scaling that behaviour to a 40 cm carapace is plausible but speculative.

Why it disappeared

The honest answer: we don’t fully know. The end of the Pleistocene saw a mass extinction event across North America that took out most of the megafauna, and T. c. putnami went with them. The leading hypotheses, none of them mutually exclusive:

• Climate change — the warming and drying of the southeastern coastal plain at the end of the Pleistocene altered the habitats that supported a large‑bodied wet‑habitat omnivore.
• Vegetation change — shifts in mast availability, swamp extent, and pine‑flatwood structure changed the food base.
• Human arrival — Paleoindian populations reached the southeast at roughly the same time as the species’s apparent decline. Large, slow, calorie‑dense turtles are exactly the kind of prey that human hunters exploit hard.
• Predator turnover — the collapse of the rest of the megafauna changed the predator/competitor balance in ways that may have disadvantaged a large slow‑breeding turtle.

The pattern in turtle phylogenies generally is consistent: large‑bodied insular and continental gigantism in turtles ends almost wherever human populations arrive. T. c. putnami fits that pattern. So do the giant tortoises of the Mascarenes, much of the Aldabran‑clade outside Aldabra itself, the giant horned turtles of Australia, and a host of others.

What its disappearance tells us about modern box turtles

This is the part of the putnami story that should matter to anyone who keeps or studies living Terrapene. The largest, longest‑lived, slowest‑breeding box turtle that ever existed survived something on the order of two to three million years of Plio‑Pleistocene climate cycling, and then was gone within a window of perhaps 10,000 years that coincides with rapid environmental change and the arrival of human hunters.

Modern Terrapene are smaller, faster‑maturing, and shorter‑lived than T. c. putnami, but they share the slow life history, the strong site fidelity, the long generation time, and the vulnerability to road mortality, collection, and habitat fragmentation. The genus is listed as IUCN Vulnerable, and several subspecies are in steeper decline than the genus average. The lesson the putnami record offers is uncomfortable: turtles like this can disappear quickly, and the conditions for their disappearance are conditions a modern reader recognises.

If you ever see one alive

You won’t. There is no credible argument for the survival of any population of T. c. putnami into the modern era. The fossil record stops at the end of the Pleistocene. If you find a very large turtle in coastal Georgia or northern Florida and you think it might be putnami, what you have almost certainly found is a large adult Gulf Coast or Florida box turtle, which can reach respectable sizes by living‑Terrapene standards but are nowhere near putnami‘s scale. Photograph it, leave it where it is, and contact a local herpetologist if you want a proper ID.

Quick facts

• Status: Extinct, late Pleistocene
• Type locality: Savannah River area, Georgia (Hay 1906)
• Range: Florida, Georgia, southeastern coastal plain
• Maximum carapace length: ~380–400 mm (largest known box turtle)
• Habitat: Pleistocene wet pine flats, coastal marsh, river floodplain
• Diet: Opportunistic omnivore (inferred from related Terrapene)
• Closest living relative: Terrapene carolina (common box turtle)

Common questions

How sure are we it’s extinct? Very sure. The fossil record ends in the late Pleistocene, the last credible specimens are roughly 11,000 years old, and no large-bodied Terrapene has been documented alive in the southeastern US in the historical record. There is no surviving population.

Could a large adult modern box turtle be mistaken for one? Yes, if you don’t have a tape measure. Adult Gulf Coast box turtles (T. c. major) can reach 16 cm carapace length, which is the upper edge of living Terrapene but still half the size of the smallest known adult putnami. The thickness and proportions of the shell also differ substantially.

Could ancient DNA still recover its genome? Possibly. Late Pleistocene chelonian remains from cool, dry contexts have yielded ancient DNA in other species. The southeastern US is neither cool nor dry, which makes preservation harder, but technical improvements in ancient DNA recovery from poorly preserved material are continuing. A genome from putnami would resolve a number of open questions about the genus’s evolutionary history.

Is the giant body size relevant to anything modern? Yes — comparative analysis of Pleistocene chelonian gigantism is informing current thinking on the upper size limit of hinged-plastron defence, on Pleistocene climate response in long-lived reptiles, and on how human arrival affects slow-breeding species. It is also a useful reminder that the genus we know today is the small remnant of a more diverse Plio-Pleistocene family.

Further reading on Box Turtles

• North American box turtles — the genus overview
• The 2013 Terrapene taxonomic revision — current understanding of the species relationships
• Box Turtle Conservation — why modern Terrapene need attention now, not later

Primary source

• Hay, O. P. (1906). Descriptions of two new genera (Echmatemys and Xenochelys) and two new species (Xenochelys formosa and Terrapene putnami) of fossil turtles. Bulletin of the American Museum of Natural History 22(3): 27–31. Available via the AMNH Digital Library.

Palaeontology is not our day job. If you spot a citation we’ve got wrong, write to Hannah via the contact page and we’ll fix it.