Ancient DNA Puts Glyptodonts Firmly in the Armadillo Family Tree

It has proved more difficult to trace than the pattern of osteoderms on the giant, armoured back of Glyptodon but thanks to a new study published in the journal “Current Biology” scientists have been able to establish that glyptodonts nestle well and truly within the family tree of modern armadillos.  It had long been suspected that these heavily armoured animals, many of which possessed fearsome, spiky tail clubs, were closely related to extant armadillos, but this new research, based on the analysis of 12,000 year old mitochondrial DNA extracted from a Doedicurus fossil, identifies them as a subfamily with the armadillos.

Doedicurus

Placing the Glyptodonts in the Armadillo Family

Good old “pestle tail” has a home.

Picture credit: Safari Ltd

The picture above shows a model of the glyptodont called Doedicurus (D. clavicaudatus), by Safari Ltd.  Doedicurus was one of the larger representatives of this group of strange prehistoric animals that originated in South America.  At over three metres in length and weighing in at approximately 1,400 kilogrammes, this herbivore was around the size of a Volkswagen Beetle car.

Earlier studies based on the shape of fossil bones indicated that the glyptodonts were members of the Xenarthra Order.  A group of mammals that includes anteaters, sloths and armadillos, but there were considerable anatomical differences between members of this Order, which led to confusion as to how closely related to the armadillos the extinct glyptodonts were.

The Key is the Carapace

That large, dome-shaped shell, (carapace) certainly resembles that seen in modern armadillos, but it lacks the articulation.  However, it was a fragment of fossilised carapace, believed to come from a Doedicurus that roamed some 12,000 years ago that has unlocked this mystery.  Scientists from the National Centre of Scientific Research (CNRS) and Montpellier University in France in collaboration with colleagues from McMaster University (Ontario, Canada), were able to reconstruct the entire mitochondrial genome based on computer modelling that could predict likely mitochondrial DNA sequences.

Studying Glyptodonts

The researchers had to develop RNA probes capable of identifying potential genetic material from the target species from within the heavily contaminated fossil sample.  Possible ancestral sequences were plotted against the genomes of present-day Xenarthra (sloths, anteaters and armadillos) and slowly and surely the composition of the mitochondrial genome of Doedicurus was pieced together.

The Family Tree of the Armadillos (Cingulata)

Phylogenetic analysis places the glyptodonts firmly in the Armadillo family.

Picture credit: Current Biology

The picture above shows a phylogeny and molecular timescale of extant armadillos including the extinct glyptodont Doedicurus sp. (in red).

DrcFrederic Delsuc, one of the authors of the scientific paper explained:

“Glyptodonts should probably be considered a subfamily of gigantic armadillos.”

The resulting phylogenetic analysis places the Glyptodontinae as a subfamily but a distinct lineage within the Cingulata (armadillos).  The closest living relative to the giant glyptodonts according to this new research, is the Pichiciego, otherwise known as the Dwarf Pink Fairy Armadillo (Chlamyphorus truncatus) an inhabitant of the grasslands of central Argentina.  Ironically, the Pichiciego, is the smallest species of Armadillo alive today, with adults rarely measuring in excess of twelve centimetres long and weighing around 120 grammes, that’s around 1,160 times lighter than the giant Doedicurus!

Implications for this Study

This research has wider implications when it comes to piecing together the evolutionary relationships between long extinct animals and their modern relatives.  This ancient DNA identification and mapping technique pioneered in this research  can help unlock and reconstruct a range of other ancient genomes, allowing scientists a much better understanding of the diversification, evolution and radiation of vertebrate species.

To view the range of prehistoric animals made by Safari Ltd including that splendid Doedicurus replica: Wild Safari Prehistoric World Figures.