When is a Triassic fauna not Triassic?

In recent years among paleontologists who work on the Triassic/Jurassic boundary there has been some serious excitement about a new locality in northeastern Utah that hosts a wide variety of cool fossils. It has been named the Saint's and Sinners Quarry and has been actively worked by crews from Brigham Young University in Provo, Utah since 2009. Based on abstracts and news articles it is clear that the fauna is diverse and well represented by multiple specimens. Having been at SVP in recent years I have been able to see images of the fossils coming out of the quarry first hand. Over 11,500 fossils have been removed from the quarry which Brooks Britt (from BYU) and others estimate is only 33% excavated. Virtually all of the fossils are preserved in 3D, allowing us to have spectacular insights into animals we do not have much data from, due to crushing and other concerns. Most of the specimens are even articulated! My hat is off to all of the BYU and Dinosaur National Monument crews who have been literally working on the edge of a cliff to extract these remains.

But. You knew there was a "but" coming, didn't you? But while the fossils themselves are spectacular there has been a trend in the last couple years to refer to this bone bed as being Late Triassic in age.  Admittedly aeolian deposits are hard to date; they tend to lack any significant ash deposits and detritial zircons (which can be used to constrain ages in other sedimentary rocks) are not really useful in sand dunes. That is what the Nugget Sandstone is - a deposit of windblown sand in western North America that began during the latest Triassic Period and persisted well into the Early Jurassic (see Sprinkel et al., 2011 for more details). This sand sea expanded as paleolatitude changed and western North America drifted further away from the equator and into the "dry belt" where warm, arid climatic conditions exist. This pattern can even be seen in the Late Triassic Chinle Formation at Dinosaur National Monument, as presented on at SVP this year (Irmis et al., 2015).

The first reports of the quarry (Chambers et al., 2011) suggested that Britt and colleagues at first assigned an Early Jurassic age to the deposit. This date was keeping with the general consensus that the Triassic/Jurassic boundary was somewhere within the Nugget. By 2012, however, it appeared that the teams views changed. That year Engelmann and others (note -the actual abstract doesn't appear to be available any longer) presented an abstract at the GSA conference in Charlotte, NC. In the title they state that a new drepanosaur has been found in the Nugget Sandstone and state that it has biostratigraphic importance. They also explicitly question the Jurassic age of the Nugget (they literally put a question mark in front of the word Jurassic) based on this new find. This new drepanosaur is pretty dang cool! The team expanded on it in recent SVP meetings (Chure et al., 2013; Chure et al., 2015). This critter seems to show highly derived characters shared only with Drepanosaurus (a European form) that indicate it was a specialized fossorial (digging) animal. The kicker here is that all other known drepanosaurs come from definitive Triassic strata. The Nugget drepanosaur comes from a quarry 55 meters above the last reliably dated strata (the Bell Canyon Formation, which sits between the Chinle and Nugget in northeastern Utah).

So what's the problem? Well this year the team again presented on some more spectacular fossils from the Saints and Sinners Quarry, including a large toothed pterosaur that is very closely related to the Early Jurassic European pterosaur Dimorphodon (Britt et al., 2015). This story has been picked up by the national media who have been reporting this site as being Late Triassic in age. Let's do a quick review of the evidence for a Late Triassic age.

Evidence of a Triassic Age of the Saints and Sinners Quarry

• Presence of a drepanosaur
• Presence of several small sphenosuchians
• In a formation that is traditionally considered to span the Triassic/Jurassic Boundary

Okay...that's not really a convincing list. This is especially true if you are claiming that this extraordinary interdunal wetland deposit represents a Triassic assemblage unlike any other in western North America. In fact two of the "pros" can actually be taken as a "con" and the third I think is ambiguous.
Allow me to present a list of why I have concerns about a Triassic age for this quarry.

Why the Saints and Sinners Quarry may be Jurassic in age

• In a formation that is traditionally considered to span the Triassic/Jurassic Boundary
• Quarry located 55 meters above the last Triassic-dated rocks (~1/2 the thickness of the Nugget)
• Presence of the most-derived drepanosaur yet discovered
• Presence of a pterosaur that is most similar to a Jurassic pterosaur
• Presence of a medium-large bodied theropod in the quarry in addition to a coelophysoid
• Presence of several small sphenosuchians
• No phytosaurs
• No aetosaurs
• No metoposaurs
• Upper Nugget lacks a Triassic ichnofauna

Well, does this mean case closed? No. While my list may be longer it isn't the final word on anything. Several of these points rely on the absence of taxa like phytosaurs and we all know that the absence of evidence is not the evidence of absence. Still, taken as a suite of things, I am not convinced that this quarry is Triassic. There are a few ways that perhaps we could do to see if I'm wrong.

• Phylogenetic analysis of the sphenosuchians - closely related to Chinle or Kayenta taxa?
• Phylogenetic analysis of new drepanosaur compared to the still-unnamed Ghost Ranch form
• Phylogenetic analysis of the theropods - are they closer to Coelophysis or later taxa?
• Additional fieldwork to look for unambiguous biostratigraphic markers

To me this fauna looks like a typical Early Jurassic fauna from western North America with a drepanosaur thrown in. Could it be an impoverished Late Triassic fauna that also has several highly derived taxa in it? I suppose and I will happily eat my hat if that is the case. What a great collection of Triassic taxa it would be! With the data that have been presented thus far I just can't see it though.

Why does this matter? Timing is everything in evolution. One of the big ways we as paleontologists talk about paleobiogeography is in terms of dispersal and vicariance. Are animals (and plants, and fungi, etc.) slowly moving into new areas or are populations split up by new barriers, isolating groups that then adapt in their own directions? To put it in the context of the Nugget fossils, are we seeing evidence that many disparate clades were widespread in the Late Triassic, or are we seeing similar taxa from elsewhere in North America in the Early Jurassic adapting to new environments? These questions have serious implications for our understanding of the rate of evolution among all these groups. By tying down the date of the Saints and Sinners Quarry we will be better able to answer some of these questions.

Final caveat: this is all based off of abstracts, talks, and posters and conferences, some of which I was unable to attend or access (this is why people should archive their conference presentations on FigShare - but I digress). I am extremely excited to see the peer reviewed publications that should result from these finds. And it may very well be that their method for dating the quarry is more nuanced than they have already presented. As always, I suppose, "Wait for the paper."

Works Cited
Britt, B. B., Chure, D., Engelmann, G., Dalla Vecchia, F., Scheetz, R. D., Meek, S., Thelin, C., Chambers, M. A NEW, LARGE, NON-PTERODACTYLOID PTEROSAUR FROM A LATE TRIASSIC INTERDUNAL DESERT ENVIRONMENT WITHIN THE EOLIAN NUGGET SANDSTONE OF NORTHEASTERN UTAH, USA INDICATES EARLY PTEROSAURS WERE ECOLOGICALLY DIVERSE AND GEOGRAPHICALLY WIDESPREAD. Journal of Vertebrate Paleontology, Program and Abstracts, 2015 p. 97

Chure, D. J., Andrus, A. S., Britt, B. B., Engelmann, G. F., Pritchard, A. C., Scheetz, R., Chambers, M. MICRO CT IMAGERY REVEALS A UNIQUE MANUS MORPHOLOGY WITH DIGGING/SCRATCHING ADAPTATIONS IN THE SAINTS AND SINNERS QUARRY (SSQ) DREPANOSAUR, NUGGET SANDSTONE (LATE TRIASSIC), NORTHEASTERN UT Journal of Vertebrate Paleontology, Program and Abstracts, 2015 p. 107

Chure, D., Britt, B., Engelmann, G., Andrus, A., Scheetz, R. DREPANOSAURS IN THE DESERT: MULTIPLE SKELETONS OF A NEW DREPANOSAURID FROM THE EOLIAN NUGGET SANDSTONE (?LATE TRIASSIC - EARLY JURASSIC), SAINTS AND SINNERS QUARRY, UTAH: MORPHOLOGY, RELATIONSHIPS, AND BIOSTRATIGRAPHIC IMPLICATIONS Journal of Vertebrate Paleontology, Program and Abstracts, 2013 p. 106

Chambers, Mariah, Hales Kimberly, Brooks B. Britt, Daniel J. Chure, George F. Engelmann, and Rod Scheetz. "Preliminary taphonomic analysis of a Ceolophysoid theropod dinosaur bonebed in the Early Jurassic Nugget Sandstone of Utah." In Geological Society of America Abstracts with Programs, vol. 42, no. 4, p. 16. 2011.

Engelmann, G., Britt, B., Chure, D., Andrus, A., Scheetz, R. MICROVERTEBRATES FROM THE SAINTS AND SINNERS QUARRY (NUGGET SANDSTONE: ?LATE TRIASSIC–EARLY JURASSIC): A REMARKABLE WINDOW ONTO THE DIVERSITY AND PALEOECOLOGY OF SMALL VERTEBRATES IN AN ANCIENT EOLIAN ENVIRONMENT  Journal of Vertebrate Paleontology, Program and Abstracts, 2013 p. 122

Engelmann, George F., Daniel J. Chure, Brooks B. Britt, and Austin Andrus. "The biostratigraphic and paleoecological significance of a new drepanosaur from the Triassic-? Jurassic Nugget Sandstone of northeastern Utah." In 2012 GSA Annual Meeting in Charlotte. 2012.

Irmis, R. B., Chure, D. J., Wiersma, J. P. LATITUDINAL GRADIENTS IN LATE TRIASSIC NONMARINE ECOSYSTEMS: NEW INSIGHTS FROM THE UPPER CHINLE FORMATION OF

NORTHEASTERN UTAH, USA Journal of Vertebrate Paleontology, Program and Abstracts, 2015 p. 149

Sprinkel, Douglas A., Bart J. Kowallis, and Paul H. Jensen. "Correlation and age of the Nugget Sandstone and Glen Canyon Group, Utah." Utah Geological Association Publication 40 (2011): 131-149.

The Past Was Horrifying - Sounds of the Mesozoic

Okay, welcome to my part 2 of X on how the past was likely horrifying if we had lived through it. Today is going to be about what the Mesozoic Era might have sounded like. Apologies ahead of time but this will be a video-heavy post.

When we picture (or rather hear) what dinosaurs (and other prehistoric reptiles) may have sounded like most people will think back to dinosaur movies where the beasts are rampaging. Roaring, snorting, growling, and hissing creatures fill the screen with angry sounds. After the release of Jurassic Park, many of the sounds created by Universal's sound studio have been remixed and reused by other films both on large and small screens. Let's quickly review some of the iconic sounds that these creatures made back in the early 1990s.

Tyrannosaurus breaks out of its pen. Prepare to get T. rekt. Copyright Universal Studios.

My close friend (unfairly portrayed here) Dilophosaurus. Copyright Universal Studios.

The famous scene with Velociraptors in the kitchen. Copyright Universal Studios.

This gives us a great variety of sounds. From the deep bass rumbling roar of the Tyrannosaurus to the chirps of the Dilophosaurus, and the high-pitched screech of the Velociraptor we have great mood-appropriate sounds from our animal villains and protagonists. I especially love the sounds that the Tyrannosaurus in Jurassic Park makes. It gave me chills in the theater all those years ago and it still is exciting to me. But it also makes me question whether an actual Tyrannosaurus sounded like its cinematic depiction.

Since Tyrannosaurus and the other dinosaurs depicted in Jurassic Park are archosaurs, I figured it would be a reasonable place to start looking at the sounds our extinct friends might have made. If we can use extant phylogenetic bracketing for integument and parental care (among other things), why not the possible vocal capabilities? I decided to look at crocodiles and ratites + hoatzin, as my EPB.

What I found was frightening. The first thing I learned is that ratite sounds are not cute.

A modern Rhea, doing Rhea things.

Ostriches with their absurdly low booming sounds.

The frighteningly unexpected growls of the modern Cassowary.

The Hoatzin. Long video, but you can hear the sharp, chuffing near the start between parrot calls.

Being the glutton for punishment that I am, I decided to make myself listen to crocodilian sounds. Not only are they equally terrifying, but they also share some similarities to some of the ratite sounds.

Crocodilians have primeval sounding roars and the occasional hiss.

What is the takeaway from this investigation? For me, it is the idea that screeching, chirping, and otherwise boisterous dinosaurs may not be as plausible as Hollywood would like us to believe. Both croc and modern less-derived birds generally do not make "songs" or "calls" but rather deep rumbles/roars and occasional hisses/clicks. The shriek of the Jurassic Park Velociraptor, spliced together with dolphin and monkey sounds doesn't seem so plausible to me. Nor does the pretty sounding cry of our oddly-hopping Dilophosaurus (or it's rattlesnake-mincing attack cry) make much sense if the similarities between our EPB creatures represent a real signal. But what of our beloved Tyrannosaurus call?

A collection of all the Tyrannosaurus rex sounds from Jurassic Park

To me, this is the most convincing of all the theropod sounds produced for cinema. It sounds the most like the creatures I sampled for my EPB. But there is also another potential problem: size. Just as a tuba sounds deeper than a flute, the size of an animal's resonating chamber (larynx/sirynx) affects the deepness of the sounds it produces. Our largest terrestrial animal today, the African Elephant, is able to produce infrasound (sound too low to hear). The idea of large theropods or sauropods being able to produce infrasound is not itself unreasonable. The large birds and crocs I listened are already producing super-low frequency sounds and crocs are known to produce infrasound during mating season. The Mesozoic world may have been punctuated by low frequency roars and rumbles and silent periods interrupted by a strange feeling in your bones as a large sauropod or theropod let out a noise too low for our ears to hear.

"But wait," my ornithischian fans cry out (Pete, I'm looking at you...)! "What is this saurischian bias?" Well one reason for my saurischian bias is that most (but not all!) movie dinosaurs that make sounds are saurischians. Another is that we have to do a bit less speculation on the possible sounds some ornithischians would have made thanks to Sandia Labs and their 3D reproduction of a Paraaurolophus crest. While not perfect, it gives us an idea of what type of sounds large hadrosaurs may have been able to produce. It is worth noting that this reconstructed vocalization is a low sound, similar to what I've been suggesting for saurischians.

Ignore the metallic overtones...

Compared to the Jurassic Park Parasaurolophus cry...

Moral of the story: the Mesozoic would sound very little like what we imagine it to, based on depictions in cinema and television. Dinosaurs at least would have been making sounds more like their modern relatives than the mixed-up mammal sounds studios are fond of using. This would create an audio landscape deeply unfamiliar to our modern ears.

I'll leave you with one more clip: perhaps the most accurate dinosaur sounds in all of cinema history. Next time from me: discussion of a new tooth paper out in the Journal of Vertebrate Paleontology standardizing theropod tooth nomenclature, an issue near and dear to me at the moment!

1969's Valley of Gwangi, featuring an Allosaurus and a Styracosaurus

Richard Delgado's Age of Reptiles: Ancient Egyptians

I have been a fan of Richard Delgado's Age of Reptiles series for a little while now. If you are unfamiliar with the series it is a comic that focuses on recreating the prehistoric world. Delgado has looked at the Morrison and Clovery Formations in the past with his previous volumes but it has been several years. Now he takes aim at the paleoecosystems of North Africa in the Late Cretaceous.

The cover of Issue 1. Copyright Dark Horse Comics.

 The story follows, so far, the exploits of a lone Spinosaurus as it cruises around the mangroves and deltas of what is now Egypt. The first thing that jumped out at me is that the animals in Ancient Egyptians are far more accurate than in some of his earlier works. For example:

What is happening here? Anatomy? Physiology? MAKE THEM FIGHT! Copyright Dark Horse Comics.

While the artwork has always been pleasant to downright gorgeous in previous installments of Age of Reptiles, I find the accuracy and beauty of this latest outing is commendable. I will state that I am not someone who works on Cretaceous vertebrates from North Africa, but looking at the animals and scenes presented in the first two issues of Ancient Egyptians I don't see anything that immediately jumps out at me as being horrendously wrong either paleontologically or behaviorally. I am impressed at the care that Delgado has put into portraying his animals and scenes.

Scene from Ancient Egyptians, copyright Dark Horse Comics. Holy cow, look at the difference between the earlier work and now! Blood, poop, backgrounds!

Ancient Egyptians does suffer one setback. This series doesn't fully take into account how recent work has changed our understanding of what Spinosaurus looked like. The sail is shown as one uninterrupted convex bulge. The forelimbs are long but the hind feet show three functional digits and no webbing. Both of these are contra Ibrahim et al. (2014). To his credit(?), Spinosaurus is shown on all fours multiple times...but that may not be reasonable considering it is a theropod. And Delgado does like to pronate his theropod hands.

The cover of Issue 2. Copyright Dark Horse Comics. The two back animals show pronated hands.

 Regardless, Delgado does a great job of making Spinosaurus seem alive and an actual animal, not like a monstrous killing machine (I'm looking at you Jurassic Park III). His Spinosaurus seems real. It poops. It fights. It sleeps. It fails at hunting. It hides. It tries to mate. It has the wounds to prove it.

The scarred protagonist Spinosaurus. Copyright Dark Horse Comics.

It isn't just the main character that seems real. Herbivores are violent and protective - not dumb domestic cows with scales. Mating and rearing rituals are brutal but also in line with what we know about modern animals. It may be hard to look at some of the illustrations later in Issue 2 but on the other side they are in line with what we know about how some modern adult males act in the presence of unrelated juveniles.

Issue 3 just came out at the end of last week and Issue 4 comes out in September. I am looking forward to picking them up and finishing the tale which Delgado likens to Samurai and Western classic films. The absence of narrative text might put some off but for myself I find it adds to the immersion. Where will the lone Spinosaurus find himself at the end of his journey?

The cover of Issue 3. Copyright Dark Horse Comics.

References:

Delgado, Richard. "Age of Reptiles: Ancient Egyptians" Dark Horse Comics. (2015).

Ibrahim, Nizar, Paul C. Sereno, Cristiano Dal Sasso, Simone Maganuco, Matteo Fabbri, David M. Martill, Samir Zouhri, Nathan Myhrvold, and Dawid A. Iurino. "Semiaquatic adaptations in a giant predatory dinosaur." Science 345, no. 6204 (2014): 1613-1616.