Jakapil

MEANING: Shield bearer

PERIOD: Late Cretaceous

CONTINENT: South America

Jakapil is a basal thyreophoran dinosaur from what is now Argentina. It has a novel morphotype among thyreophorans, including the presence of a predentary bone, large, low osteoderms, and a bipedal stance. These unique characteristics put into question its status as a thyreophoran, and its phylogenetic placement is still under some debate. It is estimated to be less than 1.5 m long and 4.5-7 kg in weight, based on femoral circumference. Due to its straight, narrow snout, it is suggested that Jakapil did not use its teeth and jaws to shear leaves, but likely processed tough plant material through chewing, as evidenced by the high amount of wear on the teeth.

Jakapil is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.

The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.

The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.

Jakapil is a thyreophoran. Thyreophora is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous. They are characterized by the presence of body armor lined up in longitudinal rows along the body. Early forms had simple, low, keeled scutes or osteoderms, whereas more derived forms developed more elaborate structures including spikes and plates. Most thyreophorans were herbivorous and had relatively small brains for their body size. In the Jurassic, Thyreophora diverged into two main groups: Ankylosauria and Stegosauria. In both the suborders, the forelimbs were much shorter than the hindlimbs, particularly in stegosaurs.

Basal thyreophorans were small to medium size dinosaurs with small, primitive plates. Many of them walked bipedally, or were facultatively quadrupedal. The majority of these are known from the Northern Hemisphere.