''Jakapil'' (meaning "shield bearer" in Puelchean) is a genus of basal thyreophoran dinosaur from the

Candeleros Formation The Candeleros Formation (formerly known as the Candeleros Member of the "Río Limay Formation") is a geologic formation that crops out in the Río Negro, Neuquén, and Mendoza provinces of northern Patagonia, Argentina. It is the oldest formati ...

of Argentina. The type species is ''Jakapil kaniukura''.

Discovery and naming

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, MPCA-PV-630, is a partial skeleton including several

osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct ...

and a complete lower jaw, which were found on land owned by the Mariluan family in 2012 and excavated between 2014 and 2019/2020. The finds were prepared by L. Pazo and J. Kaluza. The generic name, "''Jakapil''", is derived from "Ja-Kapïl", a Puelchean word meaning "shield bearer". This is also the literal meaning of the clade name

Thyreophora Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous. Thyreophorans are characterized by the presence of body ...

. The specific name, "''kaniukura''", means "crest stone" in

Mapudungun Mapuche (, Mapuche & Spanish: , or Mapudungun; from ' 'land' and ' 'speak, speech') is an Araucanian language related to Huilliche spoken in south-central Chile and west-central Argentina by the Mapuche people (from ''mapu'' 'land' and ''che ...

, in reference to its uniquely deep jaw.

Description

''Jakapil'' represents a novel morphotype among thyreophorans, including, among other things, the presence of a

predentary Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...

bone (absent or cartilaginous in other basal thyreophorans), large, low osteoderms, and a bipedal stance, similar to ''

Scutellosaurus ''Scutellosaurus'' ( ) is a genus of thyreophoran ornithischian dinosaur that lived approximately 196 million years ago during the early part of the Jurassic Period in what is now Arizona, USA. It is classified in Thyreophora, the armoured di ...

''. Its describers estimate it to be less than long and in weight, based on femoral circumference.

Classification

Due to a combination of features seen in basal

ornithischians Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek st ...

, basal thyreophorans, and ankylosaurs, a

phylogenetic analysis In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

placed it, according to most data matrices, as a basal thyreophoran, outside the clade Eurypoda. Riguetti ''et al''. (2022) suggest that ''Jakapil'' represents a member of a previously unknown thyreophoran clade. This clade may have diverged from the rest of the thyreophorans during the

Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and is ...

. The status of ''Jakapil'' as a thyreophoran has been disputed by some researchers; paleontologist

Susannah Maidment Susannah Catherine Rose Maidment is a British palaeontologist at the Natural History Museum, London. She is internationally recognised for her research on ornithischian dinosaur evolution, and was awarded the 2016 Hodson Award of the Palaeontologic ...

of the

Natural History Museum A natural history museum or museum of natural history is a scientific institution with natural history collections that include current and historical records of animals, plants, fungi, ecosystems, geology, paleontology, climatology, and more. ...

London London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...

has instead suggested that it may be an armored, basal

ceratopsian Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. ...

(based on jaw anatomy), or that it may even belong to an entirely distinct, previously unknown clade of

Paleobiology

In light of its straight, narrow snout, Riguetti ''et al.'' (2022) suggest that ''Jakapil'' did not use its teeth and jaws to shear leaves, but instead likely processed tough plant material via

mastication Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, th ...

, as evidenced by the high amount of wear on the teeth.

Paleoenvironment

The

is interpreted as an ancient

desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...

known as the Kokorkom desert, with some

oases In ecology, an oasis (; ) is a fertile area of a desert or semi-desert environment'ksar''with its surrounding feeding source, the palm grove, within a relational and circulatory nomadic system.” The location of oases has been of critical imp ...

in it, and its

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

represent a faunal assemblage typical of Middle Cretaceous ecosystems in the western remnants of

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

. Other animals from this formation include the rhynchocephalians '' Tika'' and ''

Priosphenodon ''Priosphenodon'' is an extinct rhynchocephalian known from the early Late Cretaceous of Argentina. It is believed to have been a fairly large herbivore, having a longer snout than modern tuatara, with teeth specialised for shearing plant mat ...

'', the snake ''

Najash ''Najash'' is an extinct genus of basal snake from the Late Cretaceous Candeleros Formation of Patagonia. Like a number of other Cretaceous and living snakes it retained hindlimbs, but ''Najash'' is unusual in having well-developed legs that e ...

'', the

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

'' Cronopio dentiacutus'', the theropods ''

Alnashetri ''Alnashetri'' is an extinct genus of alvarezsaurid coelurosaurian theropod dinosaur known from the early Late Cretaceous ( Cenomanian stage) of La Buitrera, Río Negro Province, Argentina. It contains one known species, ''Alnashetri cerropolici ...

'', ''

Buitreraptor ''Buitreraptor'' (meaning "La Buitrera seizer") is a genus of dromaeosaurid dinosaurs that lived during the Late Cretaceous of Argentina at the Candeleros Formation. ''Buitreraptor'' was described in 2005 and the type species is ''Buitreraptor go ...

'', ''

Ekrixinatosaurus ''Ekrixinatosaurus'' ('explosion-born reptile') is a genus of abelisaurid theropod which lived approximately 100 to 97 million years ago during the Late Cretaceous period. Its fossils have been found in Argentina. Only one species is currently ...

,'' and ''

Giganotosaurus ''Giganotosaurus'' ( ) is a genus of theropod dinosaur that lived in what is now Argentina, during the early Cenomanian age of the Late Cretaceous period, approximately 99.6 to 95 million years ago. The holotype specimen was discovered in the ...

'', as well as the sauropods ''

Andesaurus ''Andesaurus'' ( ; "Andes lizard") is a genus of basal titanosaurian sauropod dinosaur which existed during the middle of the Cretaceous Period in South America. Like most sauropods, belonging to one of the largest animals ever to walk the Eart ...

'' and ''

Limaysaurus ''Limaysaurus'' ("Limay lizard") is a genus represented by a single species of rebbachisaurid sauropod dinosaurs, which lived during the mid-Cretaceous period, about 99.6 to 97 million years ago, in the Cenomanian, in what is now South America ( ...

''.

References

{{Thyreophora, S. Thyreophorans Ornithischian genera Late Cretaceous dinosaurs of South America Cretaceous Argentina Fossils of Argentina Fossil taxa described in 2022