Los Colorados Formation

Los Colorados Formation
Stratigraphic range: Norian
~227–213 Ma
Type Geological formation
Unit of Agua de la Peña Group
Underlies Cerro Rajado Formation
Overlies Ischigualasto Formation
Thickness 600 m (2,000 ft)
Lithology
Primary Sandstone, siltstone, mudstone
Other Conglomerate, gypsum
Location
Coordinates 29°48′S 67°54′W / 29.8°S 67.9°W / -29.8; -67.9Coordinates: 29°48′S 67°54′W / 29.8°S 67.9°W / -29.8; -67.9
Approximate paleocoordinates 38°54′S 31°24′W / 38.9°S 31.4°W / -38.9; -31.4
Region San Juan & La Rioja Provinces
Country  Argentina
Extent Ischigualasto-Villa Unión Basin

The Los Colorados Formation is a sedimentary rock formation found in the provinces of San Juan and La Rioja in Argentina. It has a Norian age (Late Triassic), and is notable for its fossils of early dinosaurs, including the coelophysoid Zupaysaurus and the "prosauropods" Coloradisaurus, Lessemsaurus, and Riojasaurus.[1] Magnetostratigraphic analysis suggests that the Los Colorados Formation was deposited between 227 and 213 million years ago.[2]

Description

Los Colorados Formation is a unit with an approximate thickness of 600 metres (2,000 ft) of the Agua de la Peña Group in the Ischigualasto-Villa Unión Basin, where it is exposed in the Ischigualasto Provincial Park, a World Heritage site in Argentina. The formation gradually overlies the Ischigualasto Formation and is unconformably overlain by the Cretaceous Cerro Rajado Formation. The formation comprises red-colored, fine- to medium-grain–size sandstones together with siltstones and ancillary floodplain mudstones with early calcisol development. The formation was deposited in a fluvial to lacustrine environment.[2]

Paleofauna

Anapsids

Anapsids of the Los Colorados Formation
Genus Species Location Stratigraphic position Material Notes Images

Paleochersis

P. talampayensis

 [3]

Synapsids

Synapsids of the Los Colorados Formation
Genus Species Location Stratigraphic position Material Notes Images

Jachaleria

J. colorata

Eucynodontia

Eucynodonts of the Los Colorados Formation
Genus Species Location Stratigraphic position Material Notes Images

Chaliminia

C. musteloides

Archosauromorphs

Archosauromorphss of the Los Colorados Formation
Taxa Presence Notes Images

Genus:

  1. F. tenax
  1. Geographically present in the Provincia de la Rioja.[1]

Genus:

  1. N. engaeus
  1. Geographically present in the Qda. de los Jachaleros, El Salto (San Juan).

Genus:

  1. R. tenuisceps

Crocodylomorpha

Crocodylomorphs of the Los Colorados Formation
Taxa Presence Notes Images

Genus:

  1. H. leali
  1. Geographically present in the Qda. de los Jachaleros, El Salto (San Juan).

Genus:

  1. P. jachaleri
  1. Geographically present in the Qda. de los Jachaleros, El Salto (San Juan).

Dinosaurs

Indeterminate theropod remains present in the Provincia de la Rioja.[1]

Dinosaurs of the Los Colorados Formation
Taxa Presence Notes Images

Genus:

  1. C. brevis
  1. Geographically present in the Provincia de la Rioja.[1]

"Skull, adult."[4]
Lessemsaurus
Riojasaurus
Zupaysaurus

Genus:

  1. L. sauropoides
  1. Geographically present in the Provincia de la Rioja.[1]

"Partial cervical, dorsal, and sacral vertebrae, adult."[4]

Infraorder:

  1. Indeterminate remains.[1]
  2. Indeterminate remains.[1]
  1. Geographically present in the Provincia de la Rioja.[1]
  2. Geographically present in the Provincia de San Juan.[1]
  1. Includes Strenusaurus procerus.[1] "Dorsals, caudals, partial fore- and hindlimb."[5]

Genus:

  1. P. podocitus
  1. Geographically present in the Ischigualasto-Villa Unión Basin[6]
 Known from previously undescribed partial hindlimbs.

Genus:

  1. R. incertus
  1. 1. Geographically present in the Provincia de la Rioja.[1]

Genus:

  1. Z. rougieri
  1. Geographically present in the Provincia de la Rioja.[1]

Ichnofossils

See also

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 Weishampel et al., 2004, pp.527-528
  2. 1 2 Kent et al, 2014, p.7959
  3. ↑ 2 km NE of La Esquina at Fossilworks.org
  4. 1 2 "Table 12.1," in Weishampel, et al., 2004. Page 234.
  5. ↑ "Table 12.1," in Weishampel, et al., 2004. Page 237.
  6. ↑ Martín D. Ezcurra (2017). "A new early coelophysoid neotheropod from the Late Triassic of northwestern Argentina". Ameghiniana. in press. 10.5710/AMGH.04.08.2017.3100
  7. ↑ Río de los Tarros tracksite at Fossilworks.org
  8. ↑ Leonardi locality 15 at Fossilworks.org

Bibliography

  • Kent, Dennis V.; Paula Santi Malnis; Carina E. Colombi; Oscar A. Alcober, and Ricardo N. Martínez. 2014. Age constraints on the dispersal of dinosaurs in the Late Triassic from magnetochronology of the Los Colorados Formation (Argentina). Proceedings of the National Academy of Sciences 111. 7958–7963. Accessed 2018-09-08.
  • Weishampel, David B; et al., 2004. "Dinosaur distribution (Late Triassic, South America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 527–528. ISBN 0-520-24209-2

Further reading

  • A. B. Arcucci, C. A. Marsicano, and A. T. Caselli. 2004. Tetrapod association and palaeoenvironment of the Los Colorados Formation (Argentina): a significant sample from western Gondwana at the end of the Triassic. Géobios 37:557-568
  • A. B. Arcucci and R. A. Coria. 2003. A new Triassic carnivorous dinosaur from Argentina. Ameghiniana 40(2):217-228
  • J. F. Bonaparte. 1999. Evolución de las vértebras presacras en Sauropodomorpha [Evolution of the presacral vertebrae in Sauropodomorpha]. Ameghiniana 36(2):115-187
  • J. F. Bonaparte and J. A. Pumares. 1995. Notas sobre el primer craneo de Riojasaurus incertus (Dinosauria, Prosauropoda, Melanorosauridae) del Triasico Superior de La Rioja, Argentina [Notes on the first skull and jaws of Riojasaurus incertus (Dinosauria, Prosauropoda, Melanorosauridae), Late Triassic of La Rioja, Argentina]. Ameghiniana 32(4):341-349
  • J. F. Bonaparte. 1981. Descripción de "Fasolasuchus tenax" y su significado en la sistematica y evolución de los thecodontia. Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" 3(2):55-101
  • J. F. Bonaparte. 1978. Coloradia brevis n. g. et n. sp. (Saurischia–Prosauropoda), dinosaurio Plateosauridae de la Formacion Los Colorados, Triasico Superior de La Rioja, Argentina [Coloradia brevis n. g. et n. sp. (Saurischia–Prosauropoda), a plateosaurid from the Upper Triassic Los Colorados Formation of La Rioja, Argentina]. Ameghiniana 15(3-4):327-332
  • J. F. Bonaparte. 1971. Los tetrapodos del sector superior de la Formacion Los Colorados, La Rioja, Argentina (Triásico Superior) [The tetrapods of the upper part of the Los Colorados Formation, La Rioja, Argentina (Upper Triassic)]. Opera Lilloana 22:1-183
  • J. F. Bonaparte. 1969. Dos nuevas "faunas" de reptiles triasicos de Argentina [Two new reptilian "faunas" of the Argentine Triassic]. Gondwana Stratigraphy (IUGS Symposium, Buenos Aires) 2:283-306
  • J. B. Desojo and A. M. Baez. 2007. Cranial morphology of the Late Triassic South American archosaur Neoaetosauroides engaeus: evidence for aetosaurian diversity. Palaeontology 50:267-276
  • J. B. Desojo and A. M. Baez. 2005. El esqueleto postcraneano de Neoaetosauroides (Archosauria: Aetosauria) del Triásico Superior del centro-oeste de Argentina. Ameghiniana 42:115-126
  • M. D. Ezcurra and C. Apaldetti. 2012. A robust sauropodomorph specimen from the Upper Triassic of Argentina and insights on the diversity of the Los Colorados Formation. Proceedings of the Geologists' Association 123:155-164
  • A. G. Martinelli and G. W. Rougier. 2007. On Chaliminia musteloides (Eucynodontia: Tritheledontidae) from the Late Triassic of Argentina, and a phylogeny of Ictidosauria. Journal of Vertebrate Paleontology 27:442-460
  • G. W. Rougier, M. S. de la Fuente, and A. B. Arcucci. 1995. Late Triassic turtles from South America. Science 268:855-858
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