Doedicurus clavicaudatus

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Doedicurus clavicaudatus


© @ Rodrigo-Vega

Temporal range: Pleistocene (0.781-0.0117Ma)

Scientific classification:

Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Superphylum: Deuterostomia
Phylum: Chordata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Synapsida
Clade: Eupelycosauria
Clade: Sphenacodontia
Clade: Sphenacodontoidea
Order: Therapsida
Suborder: Cynodontia
Clade: Prozostrodontia
Clade: Mammaliaformes
Class: Mammalia
Legion: Cladotheria
Sublegion: Zatheria
Infralegion: Tribosphenida
Subclass: Theria
Clade: Eutheria
Infraclass: Placentalia
Subcohort: Exafroplacentalia
Superorder: Xenarthra
Order: Cingulata
Family: Chlamyphoridae (Delsuc et al., 2016)
Subfamily: †Glyptodontinae (Delsuc et al., 2016)
Genus: †Doedicurus
Species: †D. clavicaudatus

Doedicurus clavicaudatus ("pestle tail") is an extinct species of glyptodont that lived in South America from the Pleistocene to the very end thereof. Doedicurus is one of the most well-known Pleistocene megafauna. Like all glyptodonts, Doedicurus was herbivorous. It was estimated to have weighed ~1,900-2,370 kilograms.[1] The glyptodont's girth was covered with a huge round carapace and the bony armor around the tail region was flexible in order to allow Doedicurus to swing its tail. Another one of the most notable features of Doedicurus was the spiked distal end of its tail. Some Doedicurus specimens had carapaces with evidence that they were hit by the tails of conspecifics, providing direct evidence that they were used in intraspecific conflict. Likewise, there was even a layer of fat underneath the carapace to help cushion tail blows. Despite this, the tail would supposedly have been of limited use as a defensive weapon against predators, as the glyptodont's field of vision was apparently too limited to the extent that it would have to blindly swing its tail.[2]

References:

[1] www.sbpbrasil.org/revista/edicoes/15_1/9_Soibelzon_et_al.pdf
[2] "Tail blow energy and carapace fractures in a large glyptodont (Mammalia, Xenarthra)" (Alexander et al., 1999).

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The signature tail spikes actually appear to be conjectural, although they're not out of the question.

"Those spikes at the end of Doedicurus' tail are largely conjectural. While the spiky tail design had more appeal for early and mid 20th century artists, more recent scientific restorations show the tail extremity in modified form. Did Doedicurus even sport a spiky tail? If so, is there fossil evidence for a mace or spikes? While at least two specimens show the mace region, there are no "spikes" preserved as fossils. The reason is that while the caudal tube is bony, the spikes would have been composed not of bone but of dermal tissue such as tightly woven hair follicles, rather like rhino horn which doesn't readily fossilize. So what justification is there for endowing my Doedicurus model with a spiky mace?

Well, there are "spike scars" on the fossilized bony tail extremity. According to British Museum paleo-mammalogist Andy Currant, "You would not be flying the face of scientific opinion if you put spikes on their tails, but you could just as easily put lumpy knobs on them-they would have been just as effective. They probably started off as conical structures and got rounded off with the passage of time. I would imagine there was as much individual variation as there is from one set of rhino horns to another." (28)

Indeed, the "knobby" (instead of "prickly") look has been in vogue lately, as in a 1996 restoration by Mauricio Anton(29). Another recent restoration, by an identified artist, that is published on the Internet shows a tail with protuberances of intermediate design, that are "bulbous-prickly"(30). South American leading glyptodont researcher, Sergio Vizcaino claims the scars, "...suggest the presence of big stings." His colleague, Farina, who modeled his own miniature Doedicurus, lacking a spiky mace, now claims that if he were to redo the model, he would furnish it with spikes(31). Another artist, Carlos Vildoso Morales, now the Director of Lima's Natural History Museum, in Peru, chose not to include the spikes on the tail in his 1998 restorations of the Panochthus and Doedicurus,(32) but instead embedded the preserved "scars" with thickly rounded studs, a design reminiscent of John Ryder's 19th century restoration, appearing in the June 1878 issue of Popular Science Monthly.(33)"
Source

Emphasis mine.

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Extinct glyptodonts really were giant armadillos, ancient DNA shows

Summary: Extinct glyptodonts really were gigantic armadillos, according to researchers who have reconstructed the family tree of glyptodonts based on their mitochondrial genome, reconstructed from small fragments of DNA extracted from bits of a protective, bony carapace.

If you could travel back in time to South America thousands of years ago, you might have caught a glimpse of an animal known as a glyptodont living alongside giant ground sloths and saber-toothed cats. Glyptodonts looked like gigantic and fearsome armadillos; one of the largest species, Doedicurus, weighed as much as a ton and had a powerful club-shaped and spiky tail.

There's a good reason for the resemblance to armadillos, according to researchers who have reconstructed the family tree of these ancient beasts based on their mitochondrial genome, reconstructed from small fragments of DNA extracted from bits of a protective, bony carapace. The molecular evidence reported in the Cell Press journal Current Biology on February 22 confirms that gigantic armadillos are exactly what glyptodonts were. "Glyptodonts in fact represent an extinct lineage that likely originated about 35 million years ago within the armadillo radiation," says Hendrik Poinar of McMaster University in Canada. "Glyptodonts should probably be considered a subfamily of gigantic armadillos," adds Frédéric Delsuc of CNRS in France. "We speculate that the peculiar structure of their unarticulated carapace might have evolved as a response to the functional constraint imposed by the size increase they experienced over time." Poinar and Delsuc have had a long interest in living and extinct xenarthrans (a group including armadillos, anteaters, and sloths) and in their evolutionary relationships to each other. Recent advances in DNA capture and genome sequencing technology are now making it possible to fish DNA fragments out of fossil remains to help put those evolutionary family trees together. In the new study, the researchers used a technical trick allowing them to specifically fish Doedicurus mitochondrial DNA out of an extract containing plenty of DNA from other sources. They used RNA baits designed from computationally reconstructed ancestral DNA sequences based on known modern sequences of glyptodonts' living relatives. Their phylogenetic analysis establishes that glyptodonts are in fact deeply nested within the armadillo crown group, representing a distinct subfamily (Glyptodontinae) within the family known as the Chlamyphoridae, represented today by the dwarf pink fairy armadillo and the giant armadillo, for instance. Molecular dating suggests that glyptodonts diverged no earlier than about 35 million years ago, the researchers report, in good agreement with their known fossil record. Their findings also highlight the impressive increase in glyptodonts' size over evolutionary time. The researchers estimate that the last common ancestor of glyptodonts and their living armadillo relatives weighed in at a mere 6 kilograms, suggesting a "spectacular increase in glyptodont body mass." That's consistent with the fossil record, which shows glyptodonts evolved from medium-sized forms (about 80 kilograms) to become true megafauna in the Pleistocene (reaching 2,000 kilograms) before their disappearance at the end of the last ice age. Poinar and Delsuc say they'll continue to explore ancient DNA lifted from numerous other fossil xenarthrans, including giant ground sloths.

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The phylogenetic affinities of the extinct glyptodonts (Delsuc et al., 2016)

Among the fossils of hitherto unknown mammals that Darwin collected in South America between 1832 and 1833 during the Beagle expedition were examples of the large, heavily armored herbivores later known as glyptodonts. Ever since, glyptodonts have fascinated evolutionary biologists because of their remarkable skeletal adaptations and seemingly isolated phylogenetic position even within their natural group, the cingulate xenarthrans (armadillos and their allies). In possessing a carapace comprised of fused osteoderms, the glyptodonts were clearly related to other cingulates, but their precise phylogenetic position as suggested by morphology remains unresolved. To provide a molecular perspective on this issue, we designed sequence-capture baits using in silico reconstructed ancestral sequences and successfully assembled the complete mitochondrial genome of Doedicurus sp., one of the largest glyptodonts. Our phylogenetic reconstructions establish that glyptodonts are in fact deeply nested within the armadillo crown-group, representing a distinct subfamily (Glyptodontinae) within family Chlamyphoridae. Molecular dating suggests that glyptodonts diverged no earlier than around 35 million years ago, in good agreement with their fossil record. Our results highlight the derived nature of the glyptodont morphotype, one aspect of which is a spectacular increase in body size until their extinction at the end of the last ice age.
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