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Zupaysaurus
Zupaysaurus
Zupaysaurus
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Zupaysaurus
Temporal range: Norian
~221–206 Ma
The skull of Zupaysaurus
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Neotheropoda
Genus: †Zupaysaurus
Arcucci & Coria 2003
Species:
†Z. rougieri
Binomial name
†Zupaysaurus rougieri
Arcucci & Coria 2003

Zupaysaurus (/ˌzuːpeɪˈsɔːrəs/; "ZOO-pay-SAWR-us") is an extinct genus of early theropod dinosaur living during the Norian stage of the Late Triassic in what is now Argentina. Fossils of the dinosaur were found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. Although a full skeleton has not yet been discovered, Zupaysaurus can be considered a bipedal predator, up to 4 metres (13 ft) long. It may have had two parallel crests running the length of its snout.

Discovery

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Discovered in May 1997 by Santiago Reuil ("Vultur"), part of the crew of Guillermo Rougier, it was later described by Arcucci and Coria and published in 2003. The name Zupaysaurus is composed of the Quechua word supay meaning "devil" and the Greek word sauros (σαυρος) meaning "lizard"; thus "devil lizard". In Incan mythology, supay was both the god of death and ruler of the ukhu pacha, the Incan underworld. The type species was named Z. rougieri in the honor of Guillermo Rougier, the scientist who led the expedition which discovered and collected the holotype (original specimen) PULR-076. Zupaysaurus was first described and named in the scientific journal Ameghiniana by Argentine paleontologists Andrea Arcucci and Rodolfo Coria in 2003.[1]

Description

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Skull diagram

Zupaysaurus was a medium-sized theropod. An adult skull, measured approximately 450 mm (18 in) in length, suggesting a body length of approximately 4 m (13 ft) from its snout to the tip of its tail. In 2010 Gregory S. Paul gave a length of 6 meters (20 ft) and a weight of 250 kg (550 lbs).[2] In 2016 it was given a much smaller size of 4.2 meters (14 ft) and 70 kg (154 lbs).[3] Like all theropods, Zupaysaurus walked only on its hindlegs, leaving its forelimbs free to grasp its prey. The length of the neck bones recovered suggests that this genus has a rather long neck. Like the coelophysoids, Zupaysaurus has a kink in its snout, between the premaxillary and maxillary bones of the upper jaw. It is estimated that Zupaysaurus had 24 teeth and an intermandibular hinge is present in the lower jaw.[1] Only one specimen of Zupaysaurus is known to science. The holotype specimen was designated PULR-076, which consists of a nearly complete skull which was very well preserved, the right shoulder girdle, the lower right leg and ankle, and twelve vertebrae from the neck, back, and hips. Additional material of a smaller individual found at the same site may or may not belong to Zupaysaurus. As Zupaysaurus was originally described, the head bore two thin parallel crests on top of the skull, similar to theropods like Dilophosaurus and Coelophysis kayentakatae. These crests are thought to have been formed by the nasal bones solely, unlike those of many other theropods which also incorporated the lacrimal bones. Crests on the skull were pervasive among theropods and may have been used for communicative purposes such as species or gender recognition.[4] However, more recent analysis of the skull has cast doubt on the presence of these crests in Zupaysaurus. An unpublished abstract presented at a recent conference indicated the structures initially identified as crests were in fact the lacrimal bones displaced upwards during the process of fossilization.[5] Other cranial ornamentation included a rugose laterally-projecting lacrimal ridge on the top of the skull.

Life restoration of Zupaysaurus in a resting pose

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group. According to Ezcurra (2006) and Ezcurra and Novas (2006), Zupaysaurus can be distinguished based on the following characteristics: the maxillary fenestra is within the antorbital fossa (according to Ezcurra, 2006), the rostral process of the lacrimal is ventrally bowed (according to Ezcurra, 2006), the ventral process of the squamosal is kinked (according to Ezcurra, 2006), wide contact between squamosal and quadratojugal (according to Ezcurra, 2006). The maxillary-jugal ventral margin describes an obtuse angle in lateral view (according to Ezcurra and Novas, 2006), a notch on the dorsal margin of the ascending process of the maxilla, relating to horizontal ramus of the lacrimal is rostrally tapering onto the forked caudal tip of the ascending process of the maxilla; (according to Ezcurra and Novas, 2006), a lacrimal with a highly pneumatized antorbital recess (according to Ezcurra and Novas, 2006), a short and square-shaped retroarticular process of the mandible (according to Ezcurra and Novas, 2006), the cnemial crest is poorly developed (according to Ezcurra and Novas, 2006).

Classification

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Zupaysaurus was classified as the earliest known tetanuran theropod due to several features of its skull, dentition, and hindlimb. However, several features typical of more basal theropods were also noted by the original authors.[1] Analyses by Carano (2005), Tykoski (2005), and Ezcurra and Novas (2005) have classified Zupaysaurus as a coelophysoid related to Segisaurus and probably Liliensternus, though more basal than Coelophysis.[5][6][7] Yates (2006) found Zupaysaurus to form a group with Dilophosaurus and Dracovenator, placing it in a monophyletic Dilophosauridae.[8] But later studies found Zupaysaurus to be a sister taxon sister to a clade containing dilophosaurids, ceratosaurs and tetanurans.[9][10]

Below is a cladogram based on the phylogenetic analysis conducted by Sues et al. in 2011, showing the relationships of Zupaysaurus:[11]

Theropoda

Paleoecology

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Zupaysaurus was discovered in red siliciclastic sediments at the "Quebrada de los Jachaleros" locality within the Los Colorados Formation of the La Rioja province in Argentina. This formation has been shown by magnetostratigraphy to date to the Norian stage of the Late Triassic period, approximately 228 to 208 million years ago.[12] but has also been assigned to the slightly younger Rhaetian stage, which was approximately 208 to 201 million years ago.[13] Both specimens assigned to this genus are housed in the collection of the National University of La Rioja in La Rioja, Argentina.[1]

The Los Colorados Formation was interpreted as an ancient floodplain and it was home to several types of early sauropodomorph dinosaurs (including Riojasaurus, Coloradisaurus, and Lessemsaurus), all of which shared the same paleoenvironment with Zupaysaurus.[12] It is recognized as one of the earliest known faunal assemblages dominated by dinosaurs, which were 43% of the number of tetrapod species currently known. The non-dinosaurs that inhabited this locality included pseudosuchians, therapsids like Cynodontia, other early reptiles, and possible archosaurs.

References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Zupaysaurus

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Zupaysaurus rougieri is an extinct genus of basal neotheropod known from the stage of the epoch, approximately 225–213 million years ago, in what is now northwestern . This medium-sized bipedal is represented primarily by a nearly complete and fragmentary postcranial elements, with an estimated total body length of about 4 meters and a skull measuring roughly 45 cm in length. The specimen (PULR 076) was discovered in the Los Colorados Formation of the Agua de la Peña Group, in Quebrada de los Jachaleros, La Rioja Province, and formally described in 2003 by Andrea B. Arcucci and Rodolfo A. Coria. The generic name Zupaysaurus derives from "Zupay," a demon from Andean mythology, combined with the Greek "sauros" meaning lizard, while the specific epithet honors paleontologist Guillermo W. Rougier. Key anatomical features include a large , a pneumatized , and a with a deep caudal fossa, indicating adaptations for agile predation. The skull exhibits a slight kink in the snout, a trait shared with coelophysoids, and CT scans of the braincase reveal a short, tall endocranium with well-developed in the , providing insights into early theropod . Initially classified as a basal tetanuran due to features like the position of the tooth row and pneumatized bones, Zupaysaurus was later reinterpreted through phylogenetic analyses as a non-coelophysid member of , a basal theropod dominant in the . This placement highlights its role as one of the earliest known coelophysoids in and contributes to understanding theropod diversification during the , bridging basal forms with more derived carnivores. As a rare South American representative of early theropods, Zupaysaurus underscores the global distribution of neotheropods by the Norian and their evolutionary adaptations for terrestrial predation.

Taxonomy and Discovery

Etymology

The genus name Zupaysaurus is derived from the Quechua word zupay, meaning "devil" or "subterranean spirit" in Andean indigenous mythology, combined with the Greek sauros, meaning "lizard," thus translating to "devil lizard." This etymological choice reflects the cultural context of the fossil's discovery in the Andean region of , where Quechua linguistic influences persist. The species epithet rougieri honors paleontologist Guillermo W. Rougier, who directed the field expedition that recovered the specimen. Zupaysaurus rougieri was formally named and described in 2003 by Andrea B. Arcucci and Rodolfo A. Coria.

Discovery and Naming

The specimen of Zupaysaurus rougieri, designated PULR-076, was discovered in May 1997 by field assistant Santiago Reuil during a paleontological expedition led by Guillermo W. Rougier in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin, specifically at Quebrada de los Jachaleros, approximately 7 km west of National Route 126 in Province, northwestern . This partial skeleton includes elements such as a nearly complete (lacking premaxillae), 12 vertebrae, the left scapulocoracoid, manual unguals, and portions of the hindlimbs including distal femora, proximal left , distal right and , and the right astragalocalcaneum. The specimen was formally described and named six years later, in 2003, by Argentine paleontologists Andrea B. Arcucci and Rodolfo A. Coria in a paper published in the journal Ameghiniana. Additional material, including a left scapulocoracoid, a fragmentary right ilium, a proximal right pubis, distal femora, and a proximal left , has been collected from the same locality and tentatively associated with Zupaysaurus but remains unassigned pending further study.

Classification

Zupaysaurus is recognized as an early within the , dating to the stage of the period. In its initial description, Zupaysaurus rougieri was interpreted as a basal member of based on features of the skull and hindlimb, marking an early appearance of this group. Subsequent phylogenetic analysis reclassified it as a non-coelophysid coelophysoid, emphasizing resemblances in cranial and postcranial anatomy to other early theropods. Proposed affinities place Zupaysaurus possibly within or more basally as a dilophosaurid, with close relations to taxa such as , Liliensternus, and , supported by shared traits including a slender build and specific tarsal and tibial morphologies. A from Sues et al. (2011) positions it near the base of , consistent with its early evolutionary role among neotheropods. Classification remains uncertain due to the limited material, consisting primarily of a single partial , which has fueled ongoing debates regarding its exact family-level placement. No major phylogenetic updates have emerged since 2011, highlighting a research gap for this .

Description

Skull and Dentition

The skull of Zupaysaurus rougieri measures approximately 450 mm in length and is preserved as a nearly complete specimen lacking only the premaxillae, including key elements such as the maxillae, nasals, lacrimals, jugals, dentaries, and other associated cranial bones. The structure features a proportionally long and low profile, with the preorbital region comprising over 75% of the total length and an internal exceeding 30% of the 's length, contributing to a build. The consists of an estimated 23–24 teeth in total, with 15 preserved in the right alone, representing a high count characteristic of early theropods. The teeth are laterally compressed, recurved, and bear fine serrations along both mesial and distal margins, features indicative of a carnivorous diet suited for slicing . The largest preserved maxillary reaches about 30 mm in height and 10 mm in width, with the crowns showing moderate curvature that increases posteriorly. A long, narrow dominates the cranial morphology, suggesting adaptations for an agile predator capable of precise, rapid strikes, consistent with the animal's estimated body length of around 4 meters. Initial descriptions noted parasagittal crests formed by the above the , potentially serving a display function akin to that in Dilophosaurus, but subsequent reanalysis has interpreted these structures as postmortem artifacts due to displaced lacrimal bones or preservation effects from the specimen's incomplete state. Additional features include a pneumatic lacrimal and a maxillary , enhancing the skull's lightness without confirmed ornamental elements.

Postcranial Skeleton

The postcranial skeleton of Zupaysaurus rougieri is represented by fragmentary but informative elements preserved in the holotype specimen (PULR 076), including parts of the axial column and hindlimb, which collectively indicate a slender, bipedal theropod adapted for agile locomotion. The axial skeleton comprises ten presacral vertebrae, encompassing several cervicals and anterior dorsals, along with the atlas, axis, and fused cervical ribs. The cervical centra are notably elongated and low in height, with a constriction at mid-length that likely conferred flexibility to the neck; the axis alone measures 11 cm in length. Dorsal centra are amphicoelous and bear laterally extensive transverse processes, features consistent with the lightweight vertebral architecture typical of early theropods. Elements of the further emphasize a gracile, build optimized for bipedal speed. The is partially preserved, with the proximal portion of the right unfused to the and featuring a deep, narrow glenoid cavity; the possesses a prominent lateral process. remains include the distal portions of the right and , a fused right astragalus-calcaneum, and proximal parts of two pedal unguals. The 's distal end is transversely expanded with a posterolaterally concave surface, while the astragalus has a robust posteromedial process that interlocks with a tibial notch, suggesting stable ankle articulation for rapid movement. The overall proportions of these long elements point to adaptations, with no bones preserved but likely reduced in size based on close relatives. Body size estimates for Z. rougieri derive from scaling the 45 cm skull length against comparably built early theropods like Coelophysis bauri, yielding an approximate total length of 4 m and a lightweight frame weighing between 70 and 250 kg according to varying reconstructions.

Paleoecology

Geological Context

The Zupaysaurus fossils were recovered from the Los Colorados Formation, a Upper Triassic stratigraphic unit within the Ischigualasto-Villa Unión Basin in northwestern , spanning the provinces of and San Juan. This basin represents a continental rift system developed during the breakup of western , with the Los Colorados Formation marking the post-rift phase of sedimentation following the and earlier syn-rift deposits like the Los Rastros Formation. The formation consists of a thick sequence of red sandstones, siltstones, and mudstones, overlain unconformably by Cretaceous units such as the Cerro Rajado Formation and underlain by the . Stratigraphically, the Los Colorados Formation is assigned to the stage of the , with magnetochronological data indicating an age range of approximately 227 to 213 million years ago (Ma). This temporal framework is derived from correlation with the Newark Astrochronological Polarity Time Scale (APTS). Direct within the Los Colorados is limited, relying instead on indirect methods such as paleomagnetic correlations to dated beds in adjacent formations, leading to ongoing debates about its precise placement within the Norian sub-stages. The sedimentary deposits of the formation reflect an alluvial floodplain environment dominated by meandering to systems, with multistory sandstones indicating channel fills and overbank mudstones suggesting periodic flooding events. These fluvial settings were influenced by a semi-arid to subhumid characterized by seasonal , as evidenced by calcrete paleosols and episodic fluvial , though interpretations vary with some earlier views emphasizing more arid conditions based on the pervasive red coloration of the sediments. Fossils from the Los Colorados Formation, including those of Zupaysaurus, are preserved primarily in the of fine-grained sandstones and mudstones, consistent with rapid burial in distal fluvial channels and settings that minimized post-mortem transport and . This depositional context favored the preservation of articulated skeletal elements, though exposure to in semi-arid conditions contributed to fragmentation in some specimens.

Faunal Assemblage and Habitat

The Los Colorados Formation preserves a diverse tetrapod assemblage, dominated by herbivorous sauropodomorph dinosaurs such as incertus and Coloradisaurus brevis, which co-occurred with the theropod Zupaysaurus rougieri in the upper levels of the unit. Pseudosuchians were abundant, including armored aetosaurs like Neoaetosauroides engaeus and large predatory rauisuchians such as Fasolasuchus tenax, alongside smaller crocodylomorphs including Pseudhesperosuchus jachalensis and Hemiprotosuchus lealli. Recent discoveries include additional crocodylomorph remains and a new traversodontid cynodont from 2022, enhancing understanding of the synapsid diversity. Non-mammalian synapsids, particularly derived therapsids like the chiniquodontid cynodont Chaliminia musteloides, further contributed to this community, reflecting a mix of archosaurian and synapsid dominance typical of Gondwanan ecosystems. The habitat consisted of fluvial-lacustrine environments along riverside floodplains, where meandering rivers and seasonal water bodies supported a variety of vertebrates adapted to semi-arid to subhumid conditions with periodic flooding. Within this setting, Zupaysaurus, a bipedal theropod estimated at 4–5 meters in length, likely occupied the role of a , preying on smaller herbivores like juvenile sauropodomorphs or scavenging remains in open terrains suitable for agile pursuit. Its adaptations for speed and maneuverability, inferred from limb proportions, positioned it amid potential competition from larger pseudosuchian predators like , which may have targeted similar prey or exerted top-down pressure on the . Theropod diversity in the formation remains sparse, with Zupaysaurus representing one of the few well-documented examples alongside fragmentary remains of other indeterminate theropods, suggesting incomplete sampling of the carnivorous niche despite the overall richness of the assemblage. This limited record highlights gaps in our understanding of predatory dynamics, as the formation's transitional bridges radiations but lacks the abundance of theropod taxa seen in contemporaneous North American deposits.
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