Doedicurus: the armoured giant with a club on its tail

Lived about 2 million to 7 800 years ago the youngest dates may be too young, and the true end may lie in the Late Pleistocene [1]

Length about 3.6 to 4 m the higher figure is for the largest individuals [3]

Height about 1.5 m [1]

Weight about 1.4 to 2.4 tonnes estimates differ; one very large arm bone gives 1.9 to 2.37 tonnes [4]

Tail club 105 cm in the specimen studied a single fused sheath of bone, estimated at about 65 kg with the soft tissue inside it but without the spikes; 48 to 72 kg in alternative models [5]

Tail blow about 2.5 kJ an estimate from the tail muscles; the tip may have reached about 15 m/s [1]

Diet probably grass teeth that never stopped growing, and a broad muzzle that suggests bulk feeding [1]

Range Argentina, Brazil and Uruguay the cold, humid Chaco-Pampean plains [1]

Named 1847, by Owen from a partial tail; Burmeister gave it its own genus in 1874 [1]

Closest living relatives armadillos from ancient DNA; the line split off about 34 to 35 million years ago [10]

About the pictures. The close view of the tail shows a heavy club and spikes, inferred from the rough discs on the fossil club; the number, length and shape of the spikes are unknown. Its rings run right up to the club, where most of the real tail was one fused tube, and the flower-like plates above it follow other glyptodonts: the plates of Doedicurus were smooth with large pores. The open plain with its tussocks and shallow lake shows the kind of cold, humid country the animal lived in, without the animal itself. Plants, light and all colours are imagined.

Doedicurus was among the largest of the glyptodonts, the giant armoured relatives of armadillos that once lived in South America. It probably grazed the cold, humid plains of what are now Argentina, Uruguay and Brazil from about 2 million years ago until the end of the last Ice Age or shortly after, under one rigid dome of bone. Its tail is what sets it apart: the end was a solid club about a metre long, which has given researchers an unusual chance to work out how an extinct animal fought.

A tail before an animal

The species was named from its tail. In 1847 Owen described a partial tail that seemed to come from a massive club and called the animal Glyptodon clavicaudatus, “club-tailed”. In 1874 Burmeister moved it to a genus of its own, Doedicurus, “pestle tail”.

The tail began as a series of bony rings that could move against one another, so the base could bend. Further along, the rings were fused into a single sheath of bone with the tail vertebrae bound inside it. A specimen measured by Blanco and colleagues in 2009 is 105 cm long, and they estimated its mass, with the soft tissue inside it, at about 65 kg. Very large, deep, rough discs towards its end are read as the seats of horny spikes. The spikes themselves do not fossilise well, any more than the horn of a rhinoceros, so their shape and length are guesswork.

Aiming the blow

A bat has a point where a hit does its work with the least jolt to the handle, called the centre of percussion. Blanco’s team calculated that on this club it lay about 77 cm from the base, very close to the centre of the largest socket, on the side of the club towards its far end. That suits an animal swinging its tail from side to side. An earlier study by Alexander and colleagues estimated that the tail muscles could deliver a blow of about 2.5 kJ, with the tip perhaps moving at 15 m/s.

Who received those blows is less certain. Fractures on some glyptodont shells match the calculated force, which points to fights between rivals. Blanco’s team argued that so precise a weapon would be inefficient against fast-moving sabre-toothed cats and better suited to ritualised contests, a hypothesis that has not been confirmed. Predators were certainly around: a 2026 study of bones from Salto de Piedra in Argentina reports a conical groove about 3 cm long and 8 mm deep on a Doedicurus ankle bone, most likely made by Smilodon.

Between 1.4 and 2.4 tonnes

Doedicurus stood about 1.5 m tall and was about 3.6 m long overall, with the largest perhaps reaching 4 m. Its weight is less settled. Fariña and colleagues estimated 1.4 tonnes in 1998. In 2012 Soibelzon and colleagues described the end of a very large upper arm bone from Los Pozos in Buenos Aires Province and calculated 1.9 to 2.37 tonnes for its owner. The Natural History Museum in London gives up to 2.4 tonnes, slightly more than a fully grown black rhinoceros.

The shell was built from many tightly fitted bony plates, smooth-surfaced with large pores in this group of glyptodonts, and it was anchored firmly to the hips but only loosely at the shoulders. The head could not be pulled inside and carried armour of its own.

An armadillo, according to its DNA

Two studies published in 2016 recovered ancient DNA from Doedicurus and reached the same answer: glyptodonts sit inside the family tree of living armadillos, not beside it. Delsuc and colleagues placed them as a subfamily of the family Chlamyphoridae and dated their split to no earlier than about 35 million years ago. Mitchell and colleagues found anatomical features linking them to the tiny fairy armadillos.

The last glyptodont, perhaps

Doedicurus may have been the last glyptodont to survive. The date usually preferred comes from La Moderna in Argentina, where a Doedicurus was butchered on the edge of a swamp, and works out at about 7 800 calibrated years. If those dates hold, people and Doedicurus shared the Pampas for thousands of years. Politis and colleagues argued in 2019, as a later study did, that such Holocene ages are too young because of contamination, and that the animals really belong to the Late Pleistocene. Hunting and climate change are the causes usually proposed for its disappearance.

Where it sits in deep time

Doedicurus: About 2 million to 7 800 years ago, with the last dates disputed, in the Pleistocene.

Doedicurus

Earth forms, 4.57 billion years agoToday

Each step to the right is ten times closer to today, so the last few million years get as much room as the first billion.

If Earth's history were one day

Squeeze all of Earth's history, about 4.6 billion years, into 24 hours, starting at midnight. Doedicurus runs from 23:59:22.2 to 23:59:59.85, ending 0.15 seconds before midnight.

On this clock one second is about 52 862 years. All of written history fits into the last tenth of a second.

How big

Overall length and standing height of Doedicurus next to a person.

Doedicurus, overall length 3.6 m
Doedicurus, standing height 1.5 m
Person, for scale 1.7 m

The largest individuals may have reached about 4 m.

Reconstructions

Close-up of a thick, armoured tail made of bony rings ending in a heavy, rounded club with blunt spikes, the edge of a domed shell of small, rosette-patterned plates above it, an impression of the tail club of Doedicurus. AI-generated painting.

A wide, flat plain of pale grass tussocks and a shallow lake under towering white clouds, distant hills on the horizon, an impression of the Pampas of Ice Age South America where Doedicurus grazed. AI-generated painting.

Questions people ask

How big was Doedicurus?

It stood about 1.5 m tall and was about 3.6 to 4 m long. Weight estimates run from about 1.4 tonnes, the figure from Fariña and colleagues in 1998, to 2.4 tonnes, the upper figure given by the Natural History Museum in London. A very large upper arm bone from Argentina points to 1.9 to 2.37 tonnes.

What was the tail club of Doedicurus used for?

Probably for fighting others of its kind, and perhaps for defence. A 2009 study found that the best striking point lay very close to the largest spike socket on the club, which suits hard, aimed blows, and fractures on some glyptodont shells match the force of such a blow. The authors thought the club would be inefficient against fast-moving predators. The idea of ritual fights remains a hypothesis.

Is a glyptodont an armadillo?

In effect, yes. Ancient DNA from Doedicurus, published in 2016, places glyptodonts inside the family tree of living armadillos, as a subfamily of the family Chlamyphoridae. Their line split off about 34 to 35 million years ago.

What is the difference between Doedicurus and Glyptodon?

Doedicurus was larger and carried a long, solid club on its tail, and its shell plates were smooth with large pores. Glyptodon had eight or nine movable rings of conical plates around its tail, ending in a short tube and no club, and its plates sometimes show a rosette pattern.

Did people hunt Doedicurus?

Probably. At La Moderna in Argentina a Doedicurus was butchered on the edge of a swamp, at a site usually dated to about 7 800 calibrated years ago. Later studies argue that Holocene dates like this one from the Pampas are too young because of contamination, so the butchery may be older than that.

Did Smilodon attack Doedicurus?

There is evidence that it did. A 2026 study of bones from Salto de Piedra in Argentina reports a conical groove on a Doedicurus ankle bone, and names Smilodon as the most likely cause. The authors date Smilodon's feeding at the site to about 22 000 to 13 000 years ago.