Saturday, November 7, 2015

Fortunate Son

Elsewhere in the Mesozoic, parts of the field crew were working away at Cretaceous dinosaurs in the Mussentuchit Member of the Cedar Mountain Formation. In may we worked at Crystal Geyser Quarry, which is in the Yellow Cat Member of the same formation and is about 125 million years old, in a part of the Cretaceous called the Barremian. In contrast, the Mussentuchit Member is about 98 million years old, or Cenomanian in age. The Cedar Mountain Formation is a giant unit of rock, and the dinosaur faunas changed dramatically throughout!

The dinosaur fauna of the Mussentuchit is still poorly known, and we still don't know very much about the dinosaurs of the 'middle' Cretaceous compared to the Jurassic (like the Morrison Formation) or the Late Cretaceous (like my previous fieldwork in Alberta and Mongolia). There are still many new dinosaurs to be discovered here! This quarry has produced a new small iguanodontian, nicknamed Fortunate Son for the time being while we prepare its bones and until it is formally described.

The views from this quarry are terrible. Just awful.

The Fortunate Son quarry was about a 30-40 minute hike from camp and generally a very pleasant place to work. However, when the weather looks like this, you're probably going to get wet.

This particular thunderstorm was threatening us for a long time, but when the sky opened up it was worse than expected and an almost instantaneous drenching. Here we are hiding from the lightning! For extra bonus fun, we had to walk over the highest hill in the vicinity in order to return to camp, so we had to wait this one out for a long time until we thought it was safe. When we finally tried heading home, the slick wet mud made us very slow, and the lightning started again by the time we got to the top of the hill. GOOD TIMES. Lindsay also posted about our stormy weather at the Expedition Live blog!

  
Camp wasn't much drier!

Later that day, a second thunderstorm rolled through, throwing hail onto us like I haven't experienced before. Grape-sized hail came down for at least 15 minutes straight, so we figured we may as well try to get some free ice for our drinks.

Haviv made the best of the bad weather with some mud sculpting!

We also spent some time prospecting for new localities, although I didn't find anything particularly exciting. The strata here are much more deformed than what I'm used to, making for some steep hiking! The red rocks towards the bottom are Jurassic Morrison Formation, and the buff coloured rocks above are largely the Ruby Ranch Member of the Cedar Mountain Formation, with Mussentuchit Member rocks closer to the top.

Here's a kind of ok 180-panorama from the highest point I climbed to one day. Click to embiggen!

Next time, we meet a Decepticon.

15 comments:

  1. Very pretty scenery!

    For those of us who don't win the survey, will the Galactic Coelacanth be available for purchase later?

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  2. From what I've heard the Mussentuchit fauna was Jurassic aspect, minus the stegosaurs. Siats faced the big Abydosaurus--around the same time Carcharodontosaurus faced Paralititan and Mapusaurus faced Argentinosaurus. A small iguanodont isn't so out of place; camptosaurs were in the Morrison.

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    1. The Mussentuchit fauna is probably better described as transitional between the endemic North American Early Cretaceous faunas and the Late Cretaceous faunas with a lot of immigrant Asian taxa.

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    1. I don't know if I would say the Mussentuchit is saurischian dominated - most of what we find there is the early hadrosauroid Eolambia! And there are sauropods in the other Cedar Mountain members too - Cedarosaurus in the Yellow Cat, and Brontomerus in the Ruby Ranch. I wouldn't say that the Musseuntuchit really looks a lot like the Morrison - it has the first appearances of things like tyrannosaurs, so it really represents a blending of the Early Cretaceous and Late Cretaceous ecosystems.

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  5. Any chance Abydosaurus and Siats are stratigraphically separated from Eolambia and tyrannosaurs i.e. occur lower in the unit?

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    1. Given that there's only one Siats specimen known at the moment, I don't think there's any way we could say whether or not the two are stratigraphically separated.

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  6. But do known Abydosaurus and Siats remains occur lower than hadrosauroid/tyrannosaur material? Wouldn't be surprising in view of subsequent history but it's falsifiable.

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    1. I don't think at the moment there's any evidence for stratigraphic separation of the taxa in the Mussentuchit. But like I said, with only a single occurrence of Siats, it would be a bit harder to show stratigraphic separation - even in the Dinosaur Park Formation, some of the taxa that are stratigraphically separated can overlap in range a little bit. What you need to see is the overall pattern using lots of specimens. I don't know the exact distributions of all of the specimens in the Mussentuchit because studies of this unit are still in the early stages, but from my experience there this summer there is Eolambia everywhere. The Mussentuchit is also much more tectonically deformed than something like the Dinosaur Park Formation, which may make correlations tricky. May I ask, why the insistence that the Mussentuchit represents a saurischian-dominated, Jurassic-like landscape, despite the information I've given you?

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  7. Lol, if hadrosauroids are the most common dinosaurs at all levels in the Mussentuchit, it is obviously NOT a saurischian dominated unit. A Jurassic like community was my initial impression because of the presence of Abydosaurus and Siats. That would only be true for the the lower level IF they were dominant then, which may not be likely.

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  8. There is another possibility--taphonomic bias. If ornithopods preferred riparian habitat, they may be over represented in some fluvial units, relative to sauropods, which lived farther away. I wonder if Eolambia was more likely to be preserved than the big saurischians, not only because it was more easily buried but lived nearer the streams where sediment accumulated. I'm not assuming that though. :)

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  10. From what I've read, Abydosaurus came several million years before Eolambia and Siats, and almost certainly faced a different, unknown theropod, possibly descended from A. atokensis.

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