Time for a new series! Let’s get started!! In this series, I will talk about  various formations, continents, geological structures and the prehistoric ecosystems they help us to reconstruct. I hope you enjoy!

Hello everyone, welcome to Stunning Strata #1. This time around we have the Candeleros Formation, a formation I have actually been studying for a while now (I’m really interested in its fauna):

The Candeleros Formation is part of the Neuquen group and outcrops in the Rio Negro, Mendoza, and Neuquen provinces of Argentina. It dates to around 99-92 million years ago. This formation was made famous (among the paleontological community, at least) through the discovery of Giganotosaurus carolinni. 

The Candeleros Formation dates to the Cenomanian stage of the Cretaceous, a time when the carcharodontosaurids were the top predators on land and titanosaurids were the most diverse sauropod group. The Candeleros Formation played host to many of these animals. From the formation we have the sauropod Andesaurus, a medium sized basal titanosaurid which probably fell prey to the menagerie of predatory animals also found in the formation.  Predatory dinosaurs found in the Candeleros Formation include the giganotosaurine carcharodontosaurid Giganotosaurus carolinni, the medium-sized abelisaurid Ekrixinatosaurus novasi, the small unenlagiine Buitreraptor gonzalezorum, and the large basal coelurosaurian (and possible tyrannosaurid) Bicentenaria argentina. The alvarezsaurid theropod Alnashetri cerropoliciensis is also known from the formation and was a possible omnivore.

Buitreraptor gonzalezorum by the author.  Pencils on paper, 2015.
Buitreraptor gonzalezorum by the author. Pencils on paper, 2015.

Based on the remains of theropod lineages found in other areas of South America (i.e. Oxalaia quiliombensis from the Cenomanian of Brazil) and by comparing the Candeleros Formation to other formations of the same time period which contain similar flora and fauna, we can infer that these theropod lineages probably co-existed with the animals found in the Candeleros Formation. Therefore, the Candeleros Formation represents an ecosystem with fauna similar to the Bahariya Formation of Egypt and/or the Kem Kem Beds of Morocco. This claim is also supported by the fact that the Candeleros Formation’s habitat is similar to that of the Bahariya Formation and the Kem Kem Beds. The habitat which the Candeleros Formation represents was a braided river system which a menagerie of fish, turtle, amphibian, mammal, arthropod, and dinosaur species called home. Some dinosaur forms like Buitreraptor had adaptations specially suited for living in a river ecosystem.

B. gonzalezorum had an elongated skull similar to herons which it may have used to catch fish. The primitive snake Najash rionegrina also may have been a predator of the wetlands, slithering through the water as it searched for prey. I should also note that there is ample evidence that suggests N. rionegrina assumed a subterranean lifestyle. Other animals, it seems, were more at home surviving off the land then off the wetlands…

Piney Lake in Vail, Colorado. The Candeleros Ecosystem was probably similar to that of Piney Lake's.  Photo by the author, 2014.
Piney Lake in Vail, Colorado. The Candeleros Ecosystem was probably similar to that of Piney Lake’s.
Photo by the author, 2014.

The Candeleros Formation played host to a number of terrestrial animals, namely dinosaurs. The first I want to mention is Bicentenaria argentina, a possible basal tyrannosaurid. I hypothesize this animal was a predator of small game, taking up a niche which would allow little (if not no) competition with the large macro-predators of the area such as Giganotosaurus. B. argentina was probably the leopard to G. carolinni’s African lion. Giganotosaurus itself is a pretty interesting animal. This highly derived carcharodontosaurid was the largest predatory animal found in the Candeleros ecosystem. Well for right now G. carolinni is, anyway. It is preposed that large carcharodontosaurid theropods (and large allosauroids in general, for that matter) were specialist hunters of sauropods. If so, G. carolinni lived in paradise. So far, 3 medium-sized sauropods have been formally described from the Candeleros Formation. These are the basal titanosaurid Andesaurus delgadoi, and the rebbechisaurids Limaysaurus tessonei and Nopcsaspondylus alarconensis. These sauropods took up a variety of herbivorous niches. The rebbechisaurids are famous for their rake-like jaws, which may have been adaptations for a grazing lifestyle. Titanosaurs had needle-like teeth, which were probably used to rip leaves off trees. All of these animals  may have fallen prey to G. carolinni. Indeterminate Iguanodont tracks have also been found from the formation. I’ve heard of partial, undescribed Iguanodont skeletons gaining dust in collections which are from the Candeleros Formation, but I haven’t been able to find any articles on the subject, so if you know of any please inform me in the comment section below. Nevertheless, the Iguanodont tracks tell us that the animals were there, and I am sure they also fell prey to G. carolinni. G. carolinni wasn’t always killing. It must have co-existed peacefully with sauropods at times, just like lion prides and zebra herds do in the modern African Savannah.

Giganotosaurus (foreground) rests in the antediluvian plains of the Candeleros Formation while Andesaurus browses in the background.  Illustration by the author.  Colored pencils on paper, 2015.
Giganotosaurus (foreground) rests in the antediluvian plains of the Candeleros Formation while Andesaurus browses in the background.
Illustration by the author.
Colored pencils on paper, 2015.

The abelisaurid Ekrixinatosaurus novasi was also a resident of the Candeleros Formation ecosystem. E. novasi may have competed with Giganotosaurus for prey, but was way smaller compared to the giant carcharodontosaurid.  At an estimated 26 feet long, a fully-grown Ekrixinatosaurus would be easily overpowered by a full grown 45 foot long, 8 ton Giganotosaurus carolinni. 

We should also look at the smaller animals which make up the prehistoric fauna of the Candeleros Formation. These include reptiles, turtles, fish, and amphibians (specifically frogs). Two species of the turtle Prochelidella have been found within the Candeleros Formation, as well as a variety of frogs, fish and mammals. The running crocodylomorph Araripesuchus patagonicus is known from the formation. It may have been a small predator of the wetlands, preying on the various animals which called the wetlands home. Alnashetri was a small alvarezsaurid that most liekly led an omnivorous lifestyle.  It is only known from its hind limbs, making it very hard to classify it among other coelurosaurs. The presence of the possible alvarezsaurid Alnashetri greatly increases the diversity of coelurosaurs in the Candeleros Formation.

Overall, the Candeleros Formation represents a very bio-diverse braided river ecosystem, and I hope more studies will be conducted on this formation. Thanks for reading!


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2. Baez, Ana M. , Muzzopappa, Paula, and Nicoli, Laura. 2007. “Anurans from the Candeleros Formation (?Cenomanian-Turonian) of west-central Argentina: new evidence for pipoid evolution.” Cretaceous Research 28 (2007): 1005-1016.

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