Huayracursor jaguensis

Huayracursor jaguensis is an early sauropodomorph dinosaur from the late Carnian stage of the Late Triassic, discovered in the Santo Domingo Formation at Quebrada Santo Domingo, Northern Precordillera Basin, La Rioja Province, northwestern Argentina. Represented by holotype CRILAR-Pv 580 – a nearly complete, articulated skeleton of a subadult individual – this taxon provides the oldest evidence of simultaneous body mass increase and cervical elongation in Sauropodomorpha. Larger and longer-necked than typical Carnian sauropodomorphs, Huayracursor bridges the morphological gap between small, short-necked forms like Buriolestes schultzi and later Norian giants, highlighting rapid early diversification in a newly recognized Andean basin.

Etymology

The generic name Huayracursor combines Quechua “huayra” (wind) with Latin “cursor” (runner), alluding to the windy environment of the discovery site and the animal’s lightly built, cursorial limbs. The specific epithet jaguensis refers to Jagüé, the nearest village to Quebrada Santo Domingo.

Physical Characteristics

Huayracursor jaguensis was a slender, bipedal dinosaur with a lightly built frame suited for agile movement in fluvial environments. The holotype, a subadult individual, preserves nearly the entire skeleton in articulation, offering one of the most complete views of a Carnian sauropodomorph. Standing about 0.8–1 m (2.6–3.3 ft) at the hip, it featured proportionally long hindlimbs and a tail that balanced its forward-leaning posture.

The skull was small and triangular, with large orbits and nares indicating good vision and possibly keen senses. The jaws held serrated, leaf-shaped teeth for cropping vegetation, and the lower jaw had a downturned tip – typical of early sauropodomorphs. The neck, comprising 10 cervical vertebrae, showed incipient elongation: centra were longer than in contemporaries like Eoraptor lunensis or Buriolestes schultzi, representing an intermediate stage toward the extremely long necks of later sauropods.

The trunk was short with 14 dorsal vertebrae, supporting a compact body. The forelimbs were relatively long (about 60% hindlimb length) with grasping hands – five digits, though the outer two reduced – suggesting some manipulative ability for feeding. The pelvis was robust, with a broad ilium, and the hindlimbs were elongated for bipedal locomotion, featuring a femur slightly shorter than the tibia and a metatarsus nearly as long as the crus.

Overall body size for the subadult holotype is estimated at 2.5–3 m (8–10 ft) long and 20–40 kg (44–88 lb) in mass, significantly larger than most Carnian sauropodomorphs (typically <2 m and <20 kg). Adults may have approached 3.5 m (11.5 ft) and 50–60 kg (110–132 lb), based on growth patterns in related taxa. This combination of increased mass and neck length distinguishes Huayracursor as a transitional form in sauropodomorph evolution.

Diet and Feeding Habits

Herbivore or omnivore; Huayracursor jaguensis likely browsed low vegetation such as ferns, horsetails, and seed ferns, using its serrated teeth to strip leaves. The elongated neck allowed access to higher foliage than shorter-necked contemporaries, hinting at niche partitioning in diverse Carnian ecosystems.

Habitat and Distribution

South America, Argentina, La Rioja Province, Northern Precordillera Basin, Santo Domingo Formation (Quebrada Santo Domingo site).

Paleoenvironment

Fluvial-lacustrine deposits with alluvial fans and palustrine carbonates in a rift basin under semi-arid to humid conditions; co-occurring taxa include hyperodapedontine rhynchosaurs (e.g., cf. Teyumbaita), gomphodontosuchine traversodontids, probainognathians, aetosaurs, and another small sauropodomorph.

Behavior and Social Structure

Inferred from clade: likely solitary or small-group forager exploiting mid-level vegetation; cursorial limbs suggest evasion-based anti-predator strategy in open floodplains.

Discovery and Research

Holotype CRILAR-Pv 580 (near-complete articulated skeleton) collected from lower Santo Domingo Formation; described in 2025. No referred material. Phylogenetic analyses recover it as an early-diverging sauropodomorph, sister to more derived Norian forms, emphasizing rapid acquisition of large size and neck elongation post-Carnian Pluvial Episode.

Discovery Context

Excavated from ~230 Ma fluvial sediments in a newly identified rift basin; part of diverse Carnian assemblage expanding known dinosaur geographic range into the Andes.

Significance and Interesting Facts

• Oldest evidence of concurrent body size increase and cervical elongation in Sauropodomorpha, bridging Carnian “dwarf” forms and Norian giants.
• First dinosaur-bearing fauna from Northern Precordillera Basin, extending early dinosaur records into Andean highlands.
• Near-complete skeleton (one of the best for Carnian sauropodomorphs) preserves delicate details like gastralia and hyoid apparatus.
• Coexists with typical Carnian taxa (rhynchosaurs dominant, dinosaurs rare), reflecting pre-dominance ecosystems.
• Highlights role of regional rifts in preserving early dinosaur diversification.
• Name honors local Quechua culture and Jagüé community.

Huayracursor jaguensis

Huayracursor jaguensis is an early sauropodomorph dinosaur from the late Carnian stage of the Late Triassic, discovered in the Santo Domingo Formation at Quebrada Santo Domingo, Northern Precordillera Basin, La Rioja Province, northwestern Argentina. Represented by holotype CRILAR-Pv 580 – a nearly complete, articulated skeleton of a subadult individual – this taxon provides the oldest evidence of simultaneous body mass increase and cervical elongation in Sauropodomorpha. Larger and longer-necked than typical Carnian sauropodomorphs, Huayracursor bridges the morphological gap between small, short-necked forms like Buriolestes schultzi and later Norian giants, highlighting rapid early diversification in a newly recognized Andean basin.

Etymology

The generic name Huayracursor combines Quechua “huayra” (wind) with Latin “cursor” (runner), alluding to the windy environment of the discovery site and the animal’s lightly built, cursorial limbs. The specific epithet jaguensis refers to Jagüé, the nearest village to Quebrada Santo Domingo.

Physical Characteristics

Huayracursor jaguensis was a slender, bipedal dinosaur with a lightly built frame suited for agile movement in fluvial environments. The holotype, a subadult individual, preserves nearly the entire skeleton in articulation, offering one of the most complete views of a Carnian sauropodomorph. Standing about 0.8–1 m (2.6–3.3 ft) at the hip, it featured proportionally long hindlimbs and a tail that balanced its forward-leaning posture.

The skull was small and triangular, with large orbits and nares indicating good vision and possibly keen senses. The jaws held serrated, leaf-shaped teeth for cropping vegetation, and the lower jaw had a downturned tip – typical of early sauropodomorphs. The neck, comprising 10 cervical vertebrae, showed incipient elongation: centra were longer than in contemporaries like Eoraptor lunensis or Buriolestes schultzi, representing an intermediate stage toward the extremely long necks of later sauropods.

The trunk was short with 14 dorsal vertebrae, supporting a compact body. The forelimbs were relatively long (about 60% hindlimb length) with grasping hands – five digits, though the outer two reduced – suggesting some manipulative ability for feeding. The pelvis was robust, with a broad ilium, and the hindlimbs were elongated for bipedal locomotion, featuring a femur slightly shorter than the tibia and a metatarsus nearly as long as the crus.

Overall body size for the subadult holotype is estimated at 2.5–3 m (8–10 ft) long and 20–40 kg (44–88 lb) in mass, significantly larger than most Carnian sauropodomorphs (typically <2 m and <20 kg). Adults may have approached 3.5 m (11.5 ft) and 50–60 kg (110–132 lb), based on growth patterns in related taxa. This combination of increased mass and neck length distinguishes Huayracursor as a transitional form in sauropodomorph evolution.

Diet and Feeding Habits

Herbivore or omnivore; Huayracursor jaguensis likely browsed low vegetation such as ferns, horsetails, and seed ferns, using its serrated teeth to strip leaves. The elongated neck allowed access to higher foliage than shorter-necked contemporaries, hinting at niche partitioning in diverse Carnian ecosystems.

Habitat and Distribution

South America, Argentina, La Rioja Province, Northern Precordillera Basin, Santo Domingo Formation (Quebrada Santo Domingo site).

Paleoenvironment

Fluvial-lacustrine deposits with alluvial fans and palustrine carbonates in a rift basin under semi-arid to humid conditions; co-occurring taxa include hyperodapedontine rhynchosaurs (e.g., cf. Teyumbaita), gomphodontosuchine traversodontids, probainognathians, aetosaurs, and another small sauropodomorph.

Behavior and Social Structure

Inferred from clade: likely solitary or small-group forager exploiting mid-level vegetation; cursorial limbs suggest evasion-based anti-predator strategy in open floodplains.

Discovery and Research

Holotype CRILAR-Pv 580 (near-complete articulated skeleton) collected from lower Santo Domingo Formation; described in 2025. No referred material. Phylogenetic analyses recover it as an early-diverging sauropodomorph, sister to more derived Norian forms, emphasizing rapid acquisition of large size and neck elongation post-Carnian Pluvial Episode.

Discovery Context

Excavated from ~230 Ma fluvial sediments in a newly identified rift basin; part of diverse Carnian assemblage expanding known dinosaur geographic range into the Andes.

Significance and Interesting Facts

• Oldest evidence of concurrent body size increase and cervical elongation in Sauropodomorpha, bridging Carnian “dwarf” forms and Norian giants.
• First dinosaur-bearing fauna from Northern Precordillera Basin, extending early dinosaur records into Andean highlands.
• Near-complete skeleton (one of the best for Carnian sauropodomorphs) preserves delicate details like gastralia and hyoid apparatus.
• Coexists with typical Carnian taxa (rhynchosaurs dominant, dinosaurs rare), reflecting pre-dominance ecosystems.
• Highlights role of regional rifts in preserving early dinosaur diversification.
• Name honors local Quechua culture and Jagüé community.

Conclusion

Huayracursor jaguensis reveals an unexpectedly advanced stage in sauropodomorph evolution during the Carnian, with its larger body and elongating neck foreshadowing the giant sauropods of the Jurassic. Discovered in a previously unrecognized Andean basin, this near-complete skeleton expands the geographic and morphological scope of early dinosaurs, underscoring rapid adaptation following climatic shifts. As a transitional form in size and posture, Huayracursor illuminates the origins of one of dinosauria’s most successful lineages, just as they began their ascent to ecological dominance.

Huayracursor jaguensis reveals an unexpectedly advanced stage in sauropodomorph evolution during the Carnian, with its larger body and elongating neck foreshadowing the giant sauropods of the Jurassic. Discovered in a previously unrecognized Andean basin, this near-complete skeleton expands the geographic and morphological scope of early dinosaurs, underscoring rapid adaptation following climatic shifts. As a transitional form in size and posture, Huayracursor illuminates the origins of one of dinosauria’s most successful lineages, just as they began their ascent to ecological dominance.