Open Paleo

Bicharracosaurus

Reutter et al., 2026 bee-chah-RAH-koh-SOR-us

From Spanish 'bicharraco' (informal term for 'big animal', used by discoverer Dionide Mesa to refer to the large size of the fossils) and Greek 'sauros' meaning 'lizard'.

161.5–149.2 million years ago Oxfordian–Kimmeridgian, Late Jurassic
Late Jurassic stages

Bicharracosaurus is a genus of macronarian sauropod dinosaur, possibly a brachiosaurid, that existed during the Late Jurassic of Cañadón Calcáreo Formation in what is now Argentina. The genus is monotypic with the type species being Bicharracosaurus dionidei.

Under dispute

Bicharracosaurus is recovered as a macronarian by its describers (Reutter and colleagues, 2026), but its position oscillates between a basal macronarian, allied with Tehuelchesaurus and Janenschia, and a member of Brachiosauridae depending on the matrix and weighting scheme, and a brachiosaurid identity is considered possible.

Diagnosis

  1. CDF in middle and posterior cervical vertebrae pierced by a triangular coel (autapomorphy)
  2. Distal portion of PODL with a small dorsally oriented protuberance in posteriormost cervical vertebrae (autapomorphy)
  3. Boat-like articular facets of sacral centra — wider than high, with straight dorsal margin giving a non-oval outline (autapomorphy)
  4. Ventrally bifurcated postzygodiapophyseal lamina (PODL) in posterior cervical vertebrae
  5. Small triangular fossa anteroventral to pleurocoel in middle to posterior dorsal vertebrae
  6. Second sacral rib with dual contribution from Sa1 and Sa2; ilium with semi-horizontal preacetabular process

Species

Bicharracosaurus dionidei Reutter et al., 2026

Type species

Honors Dionide Mesa, the local farmer who discovered the holotype on Mesa's farm.

Holotype
MPEF-PV 1730 , Museo Paleontológico "Egidio Feruglio"
Material
Seven middle to posterior cervical vertebrae, four cervical ribs, complete dorsal column of ten vertebrae, ten dorsal ribs, five articulated sacral centra with sacricostal yoke fused to preacetabular process of right ilium, nine caudal vertebrae, one fragmentary chevron
Horizon
upper Cañadón Calcáreo Formation, Oxfordian–Kimmeridgian, Late Jurassic , 161.5–149.2 million years ago
Locality
Dionide 3, Chubut, Argentina

References

  1. Reutter, A.; Carballido, J. L.; Windholz, G. J.; Pol, D.; Rauhut, O. W. M. (2026). Bicharracosaurus dionidei, gen. et sp. nov., a new macronarian (Dinosauria, Sauropoda) from the Late Jurassic Cañadón Calcáreo Formation of Argentina and the problematic early evolution of macronarians. PeerJ 14: e20945. PeerJ. doi:10.7717/peerj.20945 reutter2026a