Paleontologists in Argentina have unveiled a new genus and species of armored thyreophoran dinosaur from the Cretaceous period.
Life reconstruction of Jakapil kaniukura. Image credit: Mauricio Álvarez / Gabriel Díaz Yanten.
Thyreophora is a group of small to large armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous period.
These dinosaurs are characterized by the presence of body armor lined up in longitudinal rows along the body.
Most thyreophorans were herbivorous and had relatively small brains for their body size.
“Thyreophora is a clade of ornithischian dinosaurs characterized by the presence of dermal bone armor on their backs,” said lead author Dr. Facundo Riguetti, a paleontologist in the Fundación de Historia Natural Félix de Azara at Universidad Maimónides and CONICET, and his colleagues.
“Although most thyreophorans are grouped within Eurypoda (Ankylosauria, the armored dinosaurs, and Stegosauria, the plated dinosaurs), their more basal relatives show unresolved phylogenetic placements.”
“The most representative of these forms are Scutellosaurus, Emausaurus and Scelidosaurus, from the Lower Jurassic of the United States, Germany and England, respectively.”
The newly-identified dinosaur species roamed Earth during the Late Cretaceous epoch, between 97 and 94 million years ago.
The ancient creature is the first definitive thyreophoran species from the Argentinian Patagonia.
Named Jakapil kaniukura, it had short arms, measured about 1.5 m (4.9 feet) long and weighted between 4 and 7 kg.
It shared many features with basal ornithischian and thyreophoran dinosaurs (even with ankylosaurids), but also had several novelties.
“The neck armor of this dinosaur is unique, and it protected that delicate area from predator attacks,” said co-author Dr. Sebastián Apesteguía, also from the Fundación de Historia Natural Félix de Azara at Universidad Maimónides and CONICET.
“Its arms were tiny, something that didn’t occur in the rest of the thyreophorans, the vast majority of which were quadrupeds.”
Speculative silhouette of Jakapil kaniukura showing preserved elements. Image credit: Riguetti et al., doi: 10.1038/s41598-022-15535-6.
The partial skeleton of Jakapil kaniukura — including skull bones, partial teeth and fragments — were recovered from the Candeleros Formation in Río Negro Province, North Patagonia.
Its proportions indicate that the species was likely bipedal as in Scutellosaurus.
“In Jakapil kaniukura, the relative dimensions of the forelimb, hind limb, and cranial remains bear a greater resemblance to those of the bipedal theropods, basal ornithischians and heterodontosaurids than thyreophorans,” they said.
“More complete material is needed to make accurate quantitative comparisons with other taxa and clarify its stance.”
Jakapil kaniukura also shows that early thyreophorans had a much broader geographic distribution than previously thought.
“This new species represents a previously unknown lineage of thyreophoran dinosaurs in South America,” the researchers said.
“Thyreophorans originated about 200 million years ago and rapidly evolved into various species distributed throughout the world.”
“However, of these early thyreophorans, the lineage represented by Jakapil kaniukura was the only one that lasted until at least 100 million years ago.”
The discovery is described in a paper published August 11, 2022 in the journal Scientific Reports.
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F.J. Riguetti et al. 2022. A new Cretaceous thyreophoran from Patagonia supports a South American lineage of armoured dinosaurs. Sci Rep 12, 11621; doi: 10.1038/s41598-022-15535-6
