The Dinosaur Graveyards at Las Águilas, Mexico Were a Campanian Cretaceous River Delta Environment

Age and depositional environment of the “dinosaur graveyard” at Las Águilas, southern Coahuila, NE Mexico

Authors:

Vogt et al

Abstract:

Here we provide a detailed description of the upper Campanian sediment succession at Las Águilas, southern Coahuila, northeastern Mexico, including the first absolute age dating for this interval, paleoenvironmental reconstructions and taphonomic observations on the abundant dinosaur remains at the locality. Stratigraphic investigations of the dinosaur-bearing succession at the Las Águilas vertebrate fossil area near Porvenir de Jalpa reveal a diverse vertebrate assemblage, including dinosaurs, crocodilians and turtles. New findings in adjacent sites include eusuchian crocodylomorphs, four different kinds of turtles, dromaeosaurids, lambeosaurines, pterosaurs and elasmosaurid plesiosaurs. Strontium isotope measurements on fossil oyster shells provide an absolute age of 73 ± 1 Ma for the lower part of the Las Águilas section. The locality is thus of late Campanian age. The vertebrate, invertebrate and plant materials as well as the sediment structures observed in a 50 m thick predominantly siliciclastic succession of the Cerro del Pueblo Formation suggest deposition in an extensive delta plain environment. The facies succession indicates a short-termed cyclicity of limnic, brackish and shallow marine environments during the late Campanian–early Maastrichtian Cerro del Pueblo Formation with numerous layers containing dinosaur fossil remains.

The Curious Case of Tribrachidium "Boneyards" From Ediacaran NeoProterozoic South Africa

Paleoecology of the enigmatic Tribrachidium: New data from the Ediacaran of South Australia

Authors:

Hall et al

Abstract:

Tribrachidium is a monospecific genus of the Ediacara biota found globally. In the Ediacara Member of the Rawnsley Quartzite, Flinders Ranges of South Australia, the spatial distribution of Tribrachidium across the seafloor is best described as patchy. Although Tribrachidium is the dominant fossil on two of the twenty-six beds currently excavated and is present in large numbers on another, the genus most commonly occurs as no more than a handful of specimens on a bed. Tribrachidium size frequency distributions of each of the three beds with more than 5 specimens are all statistically distinguishable from one another. Additionally, the size range on any given bed is smaller than the overall size range observed for the genus. These patterns suggest that these organisms lived in populations composed of single generations. The beds with numerous Tribrachidium come from different facies and are characterized by the presence of dissimilar mixes of taxa and textured organic surfaces, indicating that Tribrachidium was a generalist, able to adapt to a variety environments. Uniquely, the base or internal structure of Tribrachidium is also found preserved in both positive and negative relief as a sequence of concentric ridges on beds where Tribrachidium is the dominant genus. The most parsimonious explanation for the presence of these concentric ridge fossils is that they are the fossilized form of a Tribrachidium preserved when the organism was buried upside-down, flipped over, or dead and partially decayed prior to burial.

REMINDER! BONE YARD!

Reminder, folks. John Hawks is hosting the Bone Yard on Friday at his web log. Get your posts to him if you want to be included!

Bone Yard XVI

Welcome to the 16th Boneyard Paleo Carnival. Let us dig back through time and strata to see what the blogosphere has worked out of the sediments of knowledge. Like my last hosting, this BY will follow the convention that the posts that deal with the more recent eras and periods will come first. So let us begin.

First up, not even out of the Holocene, Dr Micheal Ryan from Paleoblog brings our attention to the hands bones of Hadropithecus stenognathus, one odd lemur.

(Picture added for clarity for the following; pic credit, AMNH)

We wander back further and find ourselves looking in the mirror of our past in the Pleistocene, following the evolution and bushy branching of the hominid line. The controversy over our relatives, the so-called Hobbits, rages on. Greg Laden discusses the recent paper that staked out the claims that Homo floresiensis is in fact a separate species. John Hawks also weighs in on the H floresiensis and Palau pygmy population discoveries. John has been a busy beaver in general. He also has interesting posts on the Neandertals: their linguistic capabilities and whether or not genetic drift was responsible for their divergence from Homo sapiens. He also found the time to discuss the paleoecology at Hadar and the new study about Orrorin's bipediality. Afarensis also has a good post on the Palau island dwarfed skeletons.

Diverging from the hominid line, we find that over at The World We Don't Live In, there's a very good discussion of the deinotheres being tapir convergent probisceans. Also discussed there are the ever fascinating second attempt at theropods in the Cenozoic and whether or not Megatherium americanum was a carnivore specializing in glyphodonts!

Over at Nimravid's Blog, we have the discussion of a rather interesting and unique carnivore, Simocyon. Also discussed is the diet of big sabre tooth felids.

Chris Taylor over at Catalogue of Organisms has the odd ball of a whale that seems to thought it was a walrus!

Over at Archaeozoology, the discussion of the oldest known fossil of the rabbit family is quite interesting. Equally interesting, the discovery of fossil rhino bones has brought into question whether or not Anatolia was truly isolated up to the Oligocene as has been thought.

Transition backing across the iridium layer, we find ourselves working through the Mesozoic strata. Therein lies some interesting posts themselves. First up is whether or not the Deccan Traps were responsible for the demise of the dinosaurs over at Everything Dinosaur. My own post on the subject languished alas.

Amanda at Self-designed Student titillates us with another discussion of Dino Teen Sex. (degenerate dinos must repent!)

The ever reputable Darren Naish of Tetrapod Zoology comments on dual discoveries of the Cretaceous. The first being Nemicolopterus crypticus with Darren pointing out this fossil looks a lot like an underage representative of a known pterosaur and he continues on the uber sized anuran of Madagascar. He also has the most unforgivable set of pictures under the title of LOLSAUROPOD!

Zach Miller up at When Pigs Fly Returns has a great drawing (and the reasoning behind it) of Nyctosaurus. He also has up his latest Guess the Dino (no, that's not what its called).

Both Brian Switek of Laelaps and Manabu Sakamoto of the Raptor's Nest have good posts (here and here) about Megalosaurus and its problematic status. Manabu goes on to delightfully discuss Velociraptor mongoliensis and whether or not the uber alligatoroid Deinosuchus was cotemporal with T rex. Brian turns his attention to the newly discovered Cretaceous plesiosaur, Nichollsia borealis.

Over at the Sauropod Vertebra Picture of the Week, there is a fascinating expose on whether or not all giant sized sauropods exhibited pneumaticity. There's a uber tease about a giant vertebra found at the earliest Jurassic!

My own The Dragon's Tales has the OMG moment that the pterosaurs also had teen sex! Bad archosaur! Bad!

In the very early Mesozoic, Scott at the Coherent Lighthouse gives us a wonderful head study of Euparkaria.

Straddling the Mesozoic/Paleozoic transition with the Permian Extinction, I raised the question, based on the very recent research on the genetics of casein and the pseudogenes for vitellogenin, whether or not the nonmammalian therapsids might have been nursed their young. Just how basal is milk in the synapsid line?

Over at Real Climate, they take a hammer out to yet another claim of periodicity.

Brian Switek and Nimravid both blog about the complexity and evolution at the Ediacaran and Cambrian Explosions (here and here).

In the Vendian, Micheal Ryan at Paleoblog highlights the Ediacaran life form of Funisia dorothea.

And that, my fossilized friends, is the Boneyard Carnival for this edition. If I missed anyone, please drop me a note, and I will add your post. The Bone Yard XVII will be appearing at Greg Laden's place in two weeks. Until then, enjoy! And post more original work, folks! We're also lacking for Paleozoic posts here!