La Huérguina Formation

The La Huérguina Formation (also known as the Calizas de La Huérguina Formation, La Huérguina Limestone Formation or as the Una Formation) is a geological formation in Spain whose strata date back to the Barremian stage of the Early Cretaceous. [1] Las Hoyas is a Konservat-Lagerstätten locality within the formation located near the city of Cuenca, Spain which is mostly known from its exquisitely preserved dinosaurs, especially enantiornithines.[2]

La Huérguina Formation
Stratigraphic range: Late Barremian
129.4–126.3 Ma
Type Geological formation
Underlies Contreras Formation or Unconformity with the Utrillas Group
Overlies Tragacete Formation
Thickness 60 - 100 m
Primary Limestone, Marl
Other Conglomerate
Coordinates 40°05′23″N 1°53′52″W / 40.0897°N 1.8978°W
Region Europe
Country  Spain
Extent Province of Cuenca
Type section
Named for Huérguina


As a Konservat-Lagerstätten, the preservation is exceptional. This may be a result of three factors: Microbial mats, Obruption and Stagnation.

Microbial mats may be responsible for the preservation of soft tissue in many fossils from Las Hoyas, like Pelecanimimus' crest. The iron carbonate depositions, a result from bacterial metabolism which covered the dinosaur's crest enhanced the preservation of those soft tissues. Evidence of these mats comes from the studies on microfacies and the fossils themselves.

Obruption is notable in the formation, due to the presence of highly articulated specimens. From actuotaphonomy studies on several different organisms it can be estimated that the burial of most entities was quick. Concornis may have been buried in less than 15 days, after a period of sub-areal exposition.


Las Hoyas was an inland lacustrine environment which presents an important aquatic and terrestrial flora (with many specimens of Charophytes, Montsechia, Weischelia or Frenelopsis) and diverse fauna, with specimens of at least five or six Phyla: Arthropods, Molluscs, Chordata and many vermiform soft bodied animals which might be Nemertines or Annelids.

Among vertebrates the most abundant and diverse group are fish. The presence of mostly articulated skeletons, exceptional preservation of tissue and lack of any other signs of transportation may indicate that these are demic and autochthonous entities (meaning that they lived and died in the same place where they fossilized).

Crocodylomorphs are the most abundant amniotes from Las Hoyas.

Dinosaurs from Las Hoyas (avian and non avian) are unique in many ways. The first ornithomimid dinosaur described in Europe, Pelecanimimus polyodon, shows some characters previously unknown in these dinosaurs which enhanced the knowledge on the evolution of the group, such as a high number of teeth. Concavenator corcovatus presents two unique features: very tall neural spines on the vertebrae near the hip, which look like a hump, and a structure on its forearm, which if homologous to quill knobs would push back the origin of feathers earlier in theropod evolution.

Las Hoyas birds are enantiornithes, the most diverse Cretaceous bird clade, which became extinct at the end of the period. Iberomesornis romerali shows both derived ("avian") and primitive ("dinosaurian") characters. Within the derived characters we can underline the presence of a pygostile, although it is still very large compared to that of modern neornithines and the presence os quilled sternum. Eoalulavis hoyasi shows the first report of an alula or "bastard wing", which means it had a flight manoeuvrability analogous to that of modern birds.


Las Hoyas Formation has been studied for more than two decades by researchers from the Universidad Autónoma de Madrid, the Universidad Complutense de Madrid and the National University of Distance Education, in collaboration with the Museo de las Ciencias de Castilla-La Mancha, which is responsible for the fossil record from the area.

Vertebrate paleofauna

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Many fish and lizards also have been found.

See also


  1. ^ Martínez, Marian Fregenal; Meléndez, Nieves; Muñoz-García, M. Belén; Elez, Javier; de la Horra, Raúl (2017). "The stratigraphic record of the Late Jurassic-Early Cretaceous rifting in the Alto Tajo-Serranía de Cuenca region (Iberian Ranges, Spain): genetic and structural evidences for a revision and a new lithostratigraphic proposal". Rev. Soc. Geol. Esp. 30: 113–142.
  2. ^ Weishampel, David B; et al. (2004). "Dinosaur distribution (Early Cretaceous, Europe)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 556-563. ISBN 0-520-24209-2.
  3. ^ Thomas Martin, Jesús Marugán-Lobón, Romain Vullo, Hugo Martín-Abad, Zhe-Xi Luo & Angela D. Buscalioni (2015). A Cretaceous eutriconodont and integument evolution in early mammals. Nature 526, 380–384. doi:10.1038/nature14905
  4. ^ a b Ortega F., Escaso, F. and Sanz, J.L. (2010). "A bizarre, humped Carcharodontosauria (Theropoda) from the Lower Cretaceous of Spain." Nature, 467: 203-206. doi:10.1038/nature09181 PMID 20829793
  5. ^ a b c d e f g h i j "15.9 Provincia de Quenca, Spain; 4. Calizas de La Huergina Formation," in Weishampel, et al. (2004). Pages 561-562.
  6. ^ a b "Table 11.1," in Weishampel, et al. (2004). Page 212.
  7. ^ a b Listed as "cf. Euronychodon sp." in "15.9 Provincia de Quenca, Spain; 4. Calizas de La Huergina Formation," in Weishampel, et al. (2004). Page 561.
  8. ^ "Table 11.1," in Weishampel, et al. (2004). Page 213.
  9. ^ "Table 6.1," in Weishampel, et al. (2004). Page 138.
  10. ^ a b Listed as "cf. Paranychodon sp." in "15.9 Provincia de Quenca, Spain; 4. Calizas de La Huergina Formation," in Weishampel, et al. (2004). Page 561.
  11. ^ a b Listed as "cf. Ricardoestesia sp." in "15.9 Provincia de Quenca, Spain; 4. Calizas de La Huergina Formation," in Weishampel, et al. (2004). Page 561.

External links


  • Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.
  • Perez-Moreno, B. P., Sanz, J. L., Buscalioni, A. D., Moratalla, J. J., Ortega, F., and Raskin-Gutman, D. (1994). "A unique multitoothed ornithomimosaur from the Lower Cretaceous of Spain." Nature, 30: 363-367.
  • Sanz, J. L. & Bonaparte, José F. (1992): A New Order of Birds (Class Aves) from the Lower Cretaceous of Spain. In: Jonathan J. Becker (ed.): Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Contributions in Science 36: 38-49.
  • Sanz, J. L. & Buscalioni, A.D. (1992): A new bird from the Early Cretaceous of Las Hoyas, Spain, and the early radiation of birds. Palaeontology 35(4): 829-845. PDF fulltext
  • Sanz, José L.; Chiappe, Luis M.; Pérez-Moreno, Bernardino P.; Buscalioni, Ángela D.; Moratalla, José J.; Ortega, Francisco & Poyato-Ariza, Francisco J. (1996): An Early Cretaceous bird from Spain and its implications for the evolution of avian flight. Nature 382(6590): 442-445. doi:10.1038/382442a0 (HTML abstract)
  • Ortega, F., Escaso, F. & Sanz, J. L. (2010): A bizarre, humped Carcharodontosauria (Theropoda) from the Lower Cretaceous of Spain Nature 467: 203-206. HTML abstract

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