Thoughts and Ideas From a Paleo Punker

Shadow of Bagheera--the black leopards of the Malay Peninsula

2010-11-08T09:17:00.000-08:00

If there is one animal that that can be said to symbolize the mysterious wildness inherent in the deep jungle, it's the panther. The black coats seen in these animals have inspired myths and legends across many cultures throughout the ages. However, such a beast, as an independent entity, does not exist. Instead, these popular animals are in fact black morphs of more commonly known cats. Such coat colorings have been reported in the jaguar of the Americas and, more famously, in the leopard. However, in most areas melanism (the more formal name for such a coloring), a recessive trait in leopards, is a relatively rare occurrence. One remarkable exception can be found in the Malay Peninsula, a thin region of land comprising pieces of both Thailand and Malayasia found just south of the Isthmus of Kra.

Reports of a bounty of melanistic leopards in this area have been found as early as the 19th century. However, a scientific assessment of the status of these creatures is a remarkably difficult process. Leopards are solitary animals and incredibly reclusive by nature. For somebody to so much as catch a glimpse of a leopard is a fantastically rare event. As such, to assess the frequency of color patterns in a broad geographic region, searching for the animals on foot is not an option. Instead, an international team of scientists have opted for a higher-tech option: infrared imaging systems. Strategically placed, these cameras have been proven to be exceptionally useful for capturing images of otherwise elusive wildlife. To determine the frequency of this color pattern, the researchers pooled together data from camera trapping projects in over 22 separate locations throughout the Malay Peninsula and the regions bordering it to the north. Taken together, they recorded some 474 images of leopards over 42,565 collective camera trapping nights. What they found was quite remarkable.

Of the 22 camera trapping sites in the study, 16 captured images of leopards. The melanistic morph was found in all camera trapping sites that recorded leopards, but the spotted morph was only found in those areas north of the Isthmus of Kra. This suggests that though one cannot conclude that spotted leopards are entirely absent with the present dataset (indeed, they have been previously reported in the area), they are rare enough that it's likely that the recessive allele for melanisim is 'nearly fixed' in the population. One possibility that could explain the prevalence of melanistic leopards is through genetic drift, wherein genes are shuffled about the population, and through chance, change in frequency. The authors ran a variety of scenarios, using different population sizes to determine the amount of time required for genetic drift alone to account for the unique status of the Malay leopards. These ranged from 1,100 years with a population of 100 (which would have lead to a severe bottleneck) to 100,000 years with a population of 5,000, with a myriad of scenarios in between.

Therefore, the question remains--to what degree is the frequency of melanism in the leopard population due to genetic drift (which would require a high amount of geographic, and therefore reproductive isolation), and to what degree was the near fixation due to natural selection? Genetic studies of tigers have suggested that gene flow has indeed been very much reduced between the two areas, and as such it seems likely that genetic drift had at least some play in this evolutionary event. Suggested causes for these genetic bottlenecks include the rise of sea levels caused by the end of the last ice age and the volcanic winter that would have occurred when Mount Toba erupted 74,000 years ago. These bottlenecks would have detectible signatures in the genes of the Malay leopards, and future genetic studies will help test for such a possibility. However, there have been selective benefits of melanism postulated, including increased camouflage in densely forested environments. This too may have helped meld the leopard population of the Malay Peninsula.

The authors conclude that "it is likely that both genetic drift and natural selection have been involved at different stages in the history of leopard melanism, providing a unique system for studying the adaptive genetics of carnivore coloration." Surely, many surprises and wonders await in the study of Malay's secretive leopards

Different lions react in different ways to territorial intrusions.

2010-09-17T09:47:00.000-07:00

Ask a given person to name one of the four big cats, and the lion (Panthera leo) is likely to top the list. They're fierce, large, and remarkably charismatic. Throughout history, lions were integrated into the symbology of many cultures, representing such ideal traits as nobility and courage. And indeed, however much one can say such a thing, these traits can be found in lions at large. But it does no good to anthropomorphize. Lions are living organisms that fight for survival each day. To truly understand the nature of the lion requires biological research, and this research has created a vast and fascinating body of data.

Lions live in what are called 'fission-fusion' societies, in which a group separates and reforms throughout their daily activities. Lion prides comprise 1-22 adult females, their collective offspring, and a coalition of 1-9 males. These males will defend the pride against invading males, while the females will protect their offspring from infanticide by invading males, and intrusions by the females of other prides. Territory quality has been linked to reproductive success and survival, and is therefore key in the overall quality of lion lives. Because of this, when an invasion occurs, one could suggest that it would be overall better for the maximum number of pride members to respond to territorial intrusions. The more lions that respond, the better the chances of driving off a given number of invaders. However, an experiment performed by researchers from the University of Minnesota and the Australian National University suggests that the true nature of lion responses is more complex.

To simulate a territorial threat, researchers recorded the roars of a single female as well as three separate females. These roars were then played through a loud speaker within the territories of eight prides throughout Serengeti National Park and Ngorongoro Crater, Tanzania. To measure the responses of female lions, the researchers recorded the amount of time it took a given lion to reach the midpoint between the speaker and the lions ('latency'), the differences in the times it took each given lion to reach that midpoint (the 'lag time'), the order within the group that each lion reached the midpoint, and the number of backwards glances given by each lion within the group.

They then analyzed these standardized ranks to determine the degree of responsiveness to these intrusions. Some lions were consistently on the ball when a roar was played, immediately adopting an aggressive response while moving towards the playback. However, others were what were dubbed "laggards": lions that are less likely to rush towards the source of the threat. Laggards consistently slowed the approach of more active lions, causing them to pause and look back to verify that the laggard was still approaching.

Response times and actions of lions responding to territorial roars.

Interestingly, not all laggards lagged equally in every situation (though some did). Some were more likely to approach the speaker quickly when there were more invaders (and would therefore be more in need), while others lagged more when there were more invading lions relative to responders (lending an injury more likely).

This study suggests that though logic may dictate immediate responses to a territorial invasion, the responses of lions may vary substantially depending on the situation. Lion society is complex, and the consequences of that complexity are many. This kind of research helps unlock the secrets to lion behavior, and though they may certainly have applications to lion conservation, the more of nature's hidden facets we can uncover the better.

Updates!

2010-09-16T17:56:00.000-07:00

Hi everyone.

Sorry about the long break--this summer has been very eventful. Amongst other things, I spent two months working the famous Egg Mountain site with the Museum of the Rockies, submitted (and revised) a review paper on the Spinosauridae, and slightly altered my career trajectory by switching to an Ecology and Evolution major. So, though updates may be periodic, expect updates on life in all its forms, ancient or modern.

In the mean time, here are some pictures of my various adventures.

As we say, tearing it down.

Mountain goats in the Beartooths, a half hour or so outside Egg Mountain.

Sunset just outside our camp. In the distance lie the foothills of the Rockies.

Hiking near my home in eastern Montana.

Your humble author near the falls in Yellowstone National Park.

Turbulence and chaos all.

One of the many ravens native to Yellowstone.

Yellow-bellied marmot.

The famous Lamar Valley, home of the now defunct Druid Peak wolf pack. Though alas, the wolves were with the elk in the high country.

No real content, but here's a joke:

2010-05-20T10:55:00.001-07:00

(an original, too!)

****

A hardware store manager, on his day off, visits the local Sea World. While strolling about and enjoying the various sights, he gasps as he sees one of his employees throwing boxes of Swiss Army Knives into one of the pools.

"What are you doing?!" he asks his employee angrily.

"Well boss," the employee explains, "You said yourself that they're tools for multiple porpoises."

"No vestige of a beginning, no prospect of an end..."

2010-05-06T09:31:00.001-07:00

Nothing like a punk band quoting James Hutton. Did I mention their lead singer is a professor of evolutionary biology?

Suchomimus (Baryonyx?) tenerensis manual ungual I description attempt.

2010-05-02T16:32:00.000-07:00

So, having read that describing a bone is one of the best ways to learn its features well, this is something I wrote up last night. Obviously it's a cast, but it's a very well done cast, so most of the features I describe should be in the real bone.

I'll note that because my access to the kind of literature I need to make any kind of comparative basis is currently limited (at least until the Fall), I've only focused on the features of the claw itself, and not how they relate to other theropod dinosaur groups.

With that said, I'd appreciate any comments/tips you may have!

*****

The element, a robust left manual ungual I missing the distal tip (which is fractured at a point transversely distal from the ventral margin of the articular facet and flexor tubercle), measures 190 mm in a line perpendicular to the articular facet and 305 mm across its convex, recurved dorsal margin. Its ventral portion, with the exception of the flexor tubercle (which is convex and robust in form), is flattened across its length. Distinctive rugosities cover the ungual's surface, though they are most apparent on the posterior regions. Possibly due to erosion, these pits are shallower on the medial side of the bone than on the lateral one.

A deep groove extends from the dorsomedial margin of the flexor tubercle, terminating just posterior to the missing distal tip. At its inception, this groove is placed in the lower 1/3 of the dorso-ventral complex, a form maintained for 3/4 of the claw’s curvature. However, this placement rapidly migrates dorsally at the 3/4 point until it reaches the top 1/3 of the bone. The groove reaches its maximum width halfway through the claw’s total length. A similar groove can be found on the lateral side of the claw. However, this groove is much deeper, a feature that may also be in part due to erosion of the medial surface. The lateral groove differs substantially from the medial one in that it thins radically to a ‘crack-like’ form 3/4 of the way through the medial groove’s duration.

The flexor tubercle is large and robust, being subequal in width to the dorsal margin of the articular facet. Its form, whose posterior margin is placed anterior to the articular facet, is subtriangular in both posterior and ventral views. A deep, median ridge divides the articular facet, which is oval-shaped in posterior view. The ventral portion of this ridge is especially bulky, being twice as thick as the maximum width reached by the midline. The articular surface for the condyles of the penultimate phalanx is deeper on the medial side than its lateral counterpart. Given the overall proportions of the ungual and its articular surfaces, the phalanx to which it was connected in life was likely equally robust.

The problem with interpreting trackways--redux.

2010-04-23T21:10:00.000-07:00

I want you to imagine for a moment that you are a wildlife photographer observing a waterhole in the Serengeti. The waterhole is positioned roughly 50 feet from the open plains. Much of the pool is surrounded by a thick belt of vegetation, with the exception of a 15 foot stretch of soft muddy shoreline. Given that this is the only water source in several miles, you tentatively assume that it would be a good place to capture photos of the various creatures native to the area.

As your luck would have it, after only a few minutes of waiting, a zebra approaches and, being wary of predators, approaches the hole for a drink. The zebra drinks its fill, and almost as quickly as he came, is gone. A moment later, another zebra approaches from the same direction, spends a short time drinking (from a spot 5 feet adjacent from the first zebra), and also departs the way he came (after all, it's easier to walk across the sandy beach than transverse through the thickets).

Then finally, just before you call the day to a successful close, a final zebra arrives for the much needed water, drinks what it needs, and walks away.

Looking at the tracks left behind by the animals, you begin to wonder: what would somebody who had only seen the traces they left while walking to and from the pool have thought? After all, these were animals that were roughly the same size, walking at roughly the same speed, spaced roughly equally from each other (4-5 feet between trackways), and all with similar goals/geographic restrictions. You know that they were three lone ungulates. You saw them yourself! But somebody, were they to visit this hole themselves would not have this information. It would be a reasonable conclusion that they walked in together.

Now, in this same thought experiment, transport yourself several millions of years into the future. The plains have long since gone, and the pool long dried. An observer (human or otherwise), while hiking through the now uplifted sediments derived from this pool sees these tracks. Unlike the previous viewer from the past, this person doesn't have access to the past geographic constraints. He doesn't know of the thick vegetation that proved to be such a limitation to the zebras. All he sees are three sets of tracks, each equally spaced, and formed by the same variety of foot, all walking in the same direction, turning in the same direction, and leaving.

He has several conclusions that he can make: either a. the track makers were walking in formation of a group of three, or b. there was a single track maker followed by two track makers (or vice versa). or c. there were three individual track makers, each of which either independently arrived at the waterhole at the same time and left at different times or arrived at different times and left at roughly the same time.

The point is: how can he possibly decide between these? Each scenario, though very different in life, would leave an identical trace. He may decide that they traveled as a group, or he may decide that they were individual creatures on their own schedules. The most he can accurately say is that it is possible that the track makers traveled as a group.

Of course, many more track makers over a much larger distance traveling for a much longer length of time would make the possibility of a group derived trackway more likely. But, like Schrödinger's cat, we won't be able to know without the possibility of doubt until we observe

the event. Problem is, we don't have that option.

First lecture was a success!

2010-04-22T21:13:00.000-07:00

And only two people walked out when I used the word 'evolution.' Go me!

Ever just wish there was a biologist out there to listen?

2010-04-22T06:41:00.000-07:00

Well, as luck would have it, there is!

As a child, I was always hyper enthusiastic about asking questions regarding the natural world; some were answerable by the non-experts at hand, but many sadly were not. Dave Hone from Dave Hone's Archosaur Musings and others have put together an online resource to do just this. They've got a mix of categories in which questions can be placed, each of which have been flowing with questions and answers in the last several days.

So, if the inquisitive muse moves you, go out there and Ask a Biologist!

The problem with interpreting trackways...

2010-04-18T12:27:00.001-07:00

Modified from Myers & Fiorillo 2009.

Wow.

2010-04-15T18:13:00.001-07:00

Equine criminals are the worst kind.

2010-04-11T11:47:00.001-07:00

Ending slavery.

2010-03-30T11:29:00.000-07:00

No updates just yet, soon!

Incoming: Carnotaurus.

2010-03-23T08:54:00.000-07:00

Need to dig up some publications first, but stay tuned.

Denizens of the pale blue dot.

2010-03-20T20:22:00.000-07:00

Nothing more, nothing less.

Where have I been?

2010-03-18T16:47:00.000-07:00

A good question!

Last semester here at Northwest, so things have been pretty crazy. Spinosaur review is nearing completion (waiting on a few photographs, some fantastic artwork, and a bit of statistics), and have started a new project that also deals with the certified Most Awesome Clade™ (using GIS techniques to find ideal locations for North American spinosaurs should they exist, a possibility I find quite likely).

I'll be gone roughly from the middle of May to the beginning of August, doing fieldwork in southern Utah (the Grand Staircse-Escalante National Monument area) and joining a crew from the Museum of the Rockies to work on the famous Egg Mountain site in northwestern Montana. From what I understand, the MOR field program usually offers satellite based internet services, so likely expect periodic updates as the field season progresses.

Swear I'll write about something until that time comes. Peace out, Blogland.

Science and punk rock brought to you by Bad Religion.

2009-10-20T22:29:00.000-07:00

You've got to quit your little charade and join the freak parade
Now that your road has been paved from conception to your grave.
Enormous things to do, others' practices to eschew,
To be better than you is impossible to do,

But the world won't stop without you.
No, the world won't stop without you.

Your achievements are unsurpassed, you are highly-ordered mass,
But you can bet your ass your free energy will dissipate.
Two billion years thus far, now mister here you are,
An element in a sea of enthalpic organic compounds.

The world won't stop without you.
The world won't stop without you.

You're only as elegant as your actions let you be
A piece of chaos related phylogenetically
To every living organ system, we're siblings, don't you see?
The earth rotates and will revolve without you constantly.
Two billion years thus far, now mister here you are,
An element in a sea of enthalpic organic compounds.

The world won't stop without you.
No, the world won't stop without you.
I said the world won't stop without you.

****

Some relatively personal thoughts on the convergence of punk rock and science and what they both my mean within the confines of my own life are coming within a few days for any of those interested.

The Paleo paper Challenge.--

2009-10-04T23:40:00.000-07:00

Andy Farke and Dave Hone are putting together a project called the (you guessed it!) Paleo Paper Challenge. The idea? Finish a paper and get it published by the beginning of next year. It's especially a new (and thus far quite interesting) challenge for me because I've never before attempted a formal scientific publication--until now I've strictly dealt with translating the information I've been learning (my interest in paleontology, especially as a life's path, was rekindled by a chance event last spring) into a medium aimed for the curious layperson.

Basically, the paper is a review on a group of ancient prehistoric animals called the Spinosauridae (I've blogged about Spinosaurus here before, so you shouldn't be entirely unfamiliar!). From the first discoveries through the century following, it details a multitude (and a half) of finds that have been made by paleontologists spanning the globe and adds my own thoughts and interpretations behind them--their form, evolution, and biotic history.

So, give it a chance! Even if you've never tried it before, there's no better time to start than now.

-Tor

Eocarcharia.

2009-09-23T20:30:00.000-07:00

The Carcharodontosauridae, a group of enigmatic and titanic theropod dinosaurs (whose members included Giganotosaurus and Mapusaurus, amongst others) were one of the most successful predatory dinosaurian clades of all time. While the Tyrannosaurids dominated the niche of large predator in the northern hemisphere throughout the Cretaceous (the last of the three major periods of the non-avian dinosaurs' existence; lasting 145.5-65.5 million years ago), the Carcharodontosaurids, Abelisaurids, and Spinosaurids formed a frequently found biological triumverate in the Southern hemisphere; creating a fascinating and as it would appear, alarmingly successful example of a phenomenon called niche partitioning, in which multiple animals of similar (in this case massive) body size can operate in the same ecosystem with minimal to no competition by utilizing different niches (one of the most important aspects of which includes a differential food source). One of these Carcharodontosaurids, Eocarcharia dinops ('Fierce-Eyed Dawn Shark'), is the subject of this blog.. Eocarcharia, discovered in the western Ténéré Desert of Niger by paleontologist Paul Sereno and his field crew based out of the University of Chicago, is a remarkable animal. As one of the most basal members (those that display many early evolutionary characteristics of an individual group--much like the Platypus represents the basal, egg-laying mammalian condition) of the Carcharodontosauridae, it embodies a fantastic image of the early (but not earliest) development of the traits we associate with the group.

One of the most distinctive of these traits has to do with several bones of the skull--the orbit, the lacrimal, and the frontals. Archosaurs (like the crocodilians and the only living clade of dinosaurs, the birds) are partly characterized by a large opening in the skull called the Antorbital Fenestra (the first hole just behind the nares, or 'nose holes' ;-) , though the fenestra does not exist in living crocodilians). The two bones that border the eye socket, or the orbit (the large opening behind the Antorbital Fenestra) are the Lacrimal and the Postorbital-- from the front and back of the orbit respectively, each of which are attached to the frontals, a pair of bones on the top of the skull.

In late Carcharodontosaurids, these two bones meet together to form a greatly enlarged shelf that separates the frontals from the orbit region entirely (in many other dinosaurs, the frontals aren't excluded!). As hypothesized by Sereno, it's very possible that this evolution of a thickened 'brow' above the eyes to that degree suggests an adaptation for lateral impacts--sideways headbutting Carcharodontosaurs! (though I should note that a similar, but much less prominent brow is found in some Abelisaurids and Tyrannosaurids, suggesting that the development of the feature is partly related to reaching large body and skull size)

As you can see from the above diagram (below the Carcharodontosaurus skull), the frontals of Eocarcharia are separated from the orbit, but only by a small degree--though the Lacrimal of the animal itself wasn't found, Sereno and crew were able to determine its basic shape and size by the way it articulates or attaches to the post orbital and frontal. 50 million years later, this brow-like condition was greatly developed and enhanced in its relatives. Though there are many other features of note, one thing that really strikes me as fantastic about Eocarcharia is its teeth--as much as it is easily referable as a Carcharodontosaurid, the distinctive teeth of later ('derived') Carcharodontosaurs have serrations that stretch from the base of the tooth to the tip and back up the front to the base once more (thus giving the clade its name--a similar pattern is found in many modern day sharks!), a straight 'distal' end (the portion of the tooth that faces away from the snout) and a series of deep wrinkles that stretches up to the length of the tooth. Eocharia on the other hand, did not yet develop these very unique teeth.

When one considers the sheer unlikelihood of fossil preservation combined with the unlikelihood that the preserved fossils are not only exposed to the mercy of nature, but found by a far younger species of bipedal mammal with enough knowledge to either extract it and study it or tell people who can... the fact that we can trace the history of evolution as efficiently as we can never ceases to amaze me, and probably never will.

Busy, busy, busy...

2009-09-18T23:14:00.001-07:00

So here's a dramatic sloth.

The most open dinosaurs you've ever seen!

2009-09-08T16:57:00.000-07:00

Ye happy few (band of brothers, etc.):

Mike Taylor, Matt Wedel, and Andrew Farke have put together a project whose sheer scope and most importantly accessibility is absolutely remarkable. The basic idea is to create a massive database of Ornithischian bone measurements for various lines of research (both their own, and in the future, anyone who can use them!), starting out with an in depth statistical look into the development of quadrupedalism within the Ornithischia (when it was done, what strategies were used, which groups utilized these morphologic changes sooner in their development... all sorts of possible questions can be answered). And most importantly, anyone can contribute (and potentially be listed amongst the authors)--to find out more, visit their website!

http://opendino.wordpress.com/

Hope you're as thrilled about this as I am!

Giant theropod trackway found in the Upper Jurassic of Morocco.

2009-09-03T09:37:00.000-07:00

This isn't just exciting and seriously awesome--it's seriously exciting and slightly more than seriously awesome.

Several researchers have just reported on a series of trackways found in the Upper Jurassic beds of Morocco--though there are several different varieties of tracks found in the area (a huge theropod, a smaller theropod and a sauropod), the tracks of the largest theropod are absolutely massive--the largest measuring 80 cm (from the posterior to anterior margins) by 76 cm (medio-laterally).

Though the exact size of trackways can be distorted by the substrate the trackway was found in (more on that later), in contrast a probable Tyrannosaur footprint found in the Hell Creek Formation (described by Philip Manning amongst several others) measures 72 cm anterior-posteriorly and 76 medio-laterally.

Though Morocco is no stranger to massive theropods (for example, Carcharodontosaurus is estimated at as much as 45 feet in adult length, with a skull several inches over five feet), this trackway's position in time shows that African Gondwanan theropods achieved a massive size fairly early in their evolution (though the exact identity of the track's owner can't be directly confirmed).

Considering the spotty record of African dinosaurs in general, especially in the Jurassic, this is beyond remarkable!

References--

Boutakiout, M., Hadri, M., Nouri, J., Díaz-Martínez, I. & Pérez-Lorente, F. 2009. Rastrilladas de icnitas terópodas gigantes del Jurásico Superior (Sinclinal de Iouaridène, Marruecos). [Gigantic theropod footprints from Upper Jurassic trackways (Iouaridène syncline, Morocco).] Revista Española de Paleontología, 24 (1), 31-46. ISSN 0213-6937.

Manning, Phillip L., Ott, Christopher, Falkingham, Peter L.-- A Probable Tyrannosaurid Track from the Hell Creek Formation (Upper Cretaceous), Montana, United States--PALAIOS 2008 23: 645-647

So it turns out...

2009-08-27T18:48:00.001-07:00

That archaeologists are also constantly mixed up for paleontologists.

Real content coming soon, I promise!

Every geology lesson you'll ever need to know--

2009-08-20T06:51:00.001-07:00

Dinosaur of the Week--Kryptops.

2009-08-15T18:22:00.000-07:00

Back from the field! Working on resizing some photos for a photo post tomorrow.

*****

Evolution is a funny thing. It's sensitive to countless conditions, both based on one's environment and purely random chance (we owe our entire existence to one of these catastrophic chance events). But if there is one thing that truly forces diversity amongst animals (given the time, of which the Earth has plenty), it's separation--something that possibly no animals have seen more of throughout their evolutionary history than the dinosaurs. They saw the Earth as one massive continent (the famously known Pangea) and they saw it torn apart, sent in all directions. These separation events isolate populations of animals, who are then able to interbreed independently--and with the newly found selective pressures added to them within their own individual environment, evolution accelerates to new levels (possibly one of the best evolutionary accelerants outside mass extinctions!). This effect is known as vicariance. It was this vicariance effect (spurred by the opening of the Tethys ocean--which separated Africa, South America, Australia, Antarctica, India, and Madagascar from the rest of the world--forming the now long gone continent Gondwana) that helped spawn the subject of this week's blog--Kryptops.

Kryptops, discovered in the Ténéré Desert of central Niger, is the oldest known member of the Abelisauridae, a group of dinosaurs that look uncannily like large bipedal semi-reptilian (more dinosaurian) pitbulls, with short snouts and stout skulls. Take, for example, this Carnotaurus (though its crazy amount of cranial kinesis is something relatively unique to the genus)--

One of the most distinctive features of the skeletal remains discovered thus far of Kryptops are the short grooves and pits that cover the external surface of the Maxilla--one of the bones in the upper jaw. Though this sort of rough surface is something that is characteristic of Abelisaurids and some Carcharodontosaurids, they indicate that Kryptops may have been covered with a sort of Keratin-style mask on its face (thus the name--'Covered Face').

Like all dinosaurs, Kryptops was equipped with a sort of internal tooth factory--in which teeth grew and fell out constantly. Broken teeth are very common finds at various dig sites, which are often used as indicator of scavenging activity--the tooth would break off the hard bone and either fall on the ground or become swallowed with the meat (which in turn eats the enamel coating--if you ever chance upon a fossil tooth without, it's very likely that it's spent some time in the innards of a dinosaur!)

(Quick snapshot of an example--tooth on the left is most likely from the Tyrannosaurid Albertosaurus with the enamel still attached, while the tooth on the right belongs to Daspletosaurus sans enamel--both were collected in the field this last week)

Kryptops, like other Abelisaurids, likely had 17-18 teeth on the Maxilla--its discoverer removed a small portion of the jawbone to expose the tooth replacement system (in this case, in the 8th alveolus--or tooth socket) for its published scientific description.

The discovery of Kryptops helps shed some light on dinosaur evolution, showing that the derived (most evolutionary recent) features of the Abelisauridae existed before the Early Cretaceous ended. And as little as we know about the history of Mesozoic life on Africa, any information at all is a treasure. Even still, it's largely a blank slate with many new fascinating discoveries to be found in years to come.

Off to the field.

2009-07-28T20:11:00.000-07:00

Will be back on the 9th of August; with luck I'll have photos and such of the trip!

Dinosaurian death in decidedly drenched dirt.

2009-07-26T05:40:00.000-07:00

Well, make that just wet enough for some less than ideal results for at least one group of dinosaurs!

Just got done reading a paper entitled Mud Trapped Herd Captures Evidence of Distinctive Dinosaur Sociality, and it's a really cool read; especially if you have an interest in both taphonomy (what happens to an animal--in this case fossilized--after it dies) and dinosaurian behavior.

An excavation done in the Ulansuhai formation (late Cretaceous in age) of inner Mongolia turned up a group of at least thirteen separate specimens of the ornithomimid Sinornithomimus who were all found on a single geologic horizon and in very close proximity. Utilizing the sort of detective work essential for a field like paleontology (like a sleuth in some crime thriller, we have to use as many tools and conceptions as we can to get to the bottom of the case!), the paleontologists steadily unearthed a fascinating story.

First off, the geology of the locality held many different hints of information--like the presence of fine-grained layered deposits of rock and dirt that would alternate between very thick and very thin sections laid down in such a way as to suggest a non-fluvial (non-river caused) depositional environment. Various fossil ostracods (a sort of shrimp-like animal) helped support this.

However, the rocks told more of a story--in one layer in particular, this lakeside was drying up and fast--leaving various features of an arid environment (evaporites and the like). It was this horizon where the dinosaurs were found.

Twelve of the thirteen ornithomimids were found in an upright posture, stuck in a highly viscous material created by certain kinds of drying clays. Most (ten out of thirteen) of the skeletons were angled between 87º and 188º, which also lends itself towards a mass death at a single instant in time (a chance alignment for that number of specimens within that range of direction is very, very low).

One of the many really neat things about this find is the fact that the directionality the animals died in greatly influenced the bones and pieces that were missing from the skeletons--animals that died with their belly facing the ground most often had their gastralia (ribs found in front of the gut) and their stomach contents at the time of death preserved, but were missing dorsal (back) vertebrae and their respective ribs. On the other hand, the animal that was found on its left side had right rib elements missing. This is highly indicative of scavenging--after death and before complete burial, the exposed surfaces were eaten by opportunistic feeders.

Interestingly, the ilium (the largest of the hip bones) was missing in most of the specimens, and --though it can't be said for certain--this is also likely due to scavenging given that a. it probably would have been exposed to the surface on most of the specimens and b. it has a massive amount of muscle tissue to attract local carnivores. However, several of the Ilia appear to have weathered off, and very well may have survived to the point of burial.

Bone histology studies (research into the microstructure of the animal's bones) as well as relative size comparisons show that these animals were all juveniles or sub-adults, which is absolutely awesome in many ways--many bone beds containing the skeletons of non-avian juvenile dinosaurs have been found before, but because there was little taphonomic evidence to say for certain that they dead as a group or if it was a chance washing, this aspect of dinosaurian behavior was still slightly up in the air. But because this bone bed also contains similar age ranges, and the detail of taphonomy is so intense, it helps prove that previous similar finds were no accident!

All of this information helps us paint a picture of the scene--a drying lake bed, many millions of years ago attracts a roaming group of juvenile Sinornithomimus (the adults and infants are presumably nesting and traveling elsewhere). They're parched, thirsty beyond belief--and in temperatures well over 100 degrees, water is not common. They reach the watering hole, and though the water is stagnant and awful tasting, it was the most water they've had in days--but something goes wrong: they're stuck. They struggle, letting out distress calls in hopes that others are near--and as they try to pull themselves away from the sticky mud's grasp, they push themselves further in yet. After what could be hours, they fall over dead--struck by overexerting themselves in the scalding desert heat. The lake bed progressively dries further, and scavengers take the opportunity to snag a meal of what's exposed. Eventually the bodies are entirely buried with mud, and become fossilized over the aeons--lost in memory until a chance encounter with an entirely different group of bipedal animals, who map and detail their discovery for the world to see.

Reference--

Varricchio, D.J., Sereno, P. C., Zhao, X., Tan, L., Wilson ,J. A.,and Lyon, G. H.2008.Mud−trapped herd captures evidence

of distinctive dinosaur sociality. Acta Palaeontologica Polonica 53 (4): 567–578.

Dinosaur of the Week--Spinosaurus.

2009-07-21T20:39:00.000-07:00

This is Egypt, a largely desert-covered country in Northern Africa, possibly most famous for its pyramids and other traces of ancient, long gone civilizations.

And this, roughly, is Egypt 110 million years ago.

Through a study of its geology and evaluations of the local fossil record, we've determined that in aeons past Egypt was very similar in appearance to the modern day Florida Everglades, with scattered mangrove swamps and intensely widespread vegetation.

However, there were some fairly recognizable differences. For example, you're not likely to find this guy in Florida--

Spinosaurus, a giant theropod dinosaur famously featured in Jurassic Park III. Spinosaurus is the last known member of a group of dinosaurs known as the Spinosauridae, whose members stretched from modern day Europe (Baryonyx) to Niger and Morocco in northwestern Africa (but was then called Gondwana). Though we have slightly more information on the animal now than has been the case in the past, Spinosaurus is still something of an enigma, with an absolutely enthralling and fascinating history. It was first discovered in the isolated deserts of Egypt by German paleontologist Ernst Stromer in 1912, known from a fragment of its skull and several vertebrae characterized by an absolutely massive spinous process (the portion of the top of the vertebrae that sticks up, or as we paleontologists unnecessarily put it 'extends dorsally') that stretched up to seven feet in length--these vertebrae would form together to create a large sail structure. Along with the holotype (the original find that a group of dinosaurs is based on) of Carcharodontosaurus, Stromer left the Egyptian desert, and had the specimens shipped back to Germany years later (after running through many hurdles to get them returned).

However, when they finally arrived, Stromer saw practically every single specimen in pieces--destroyed by the bumpy roads and inefficient carrying. For the next several years, he would reassemble and scientifically document and describe each of them, taking both photographs and producing detailed drawings.

But for all his work, every one of them were demolished into fine dust during World War II, when an Allied bombing run missed its mark and destroyed the museum that contained them. For years, it was all that had been found of this dinosaur, and was shrouded in mystery through those few remaining photographs and drawings. But very recently (within the last couple decades), new specimens of Spinosaurus have been unearthed, helping shed some light on the animal. These find include several more vertebrae, and and a couple jaw fragments (one of which--a bottom jaw, or 'dentary'--may represent a new species of the genus).

By the shape of its skull and teeth, it's been suggested that Spinosaurus was a largely piscivorous (fish-eating) animal, but was large enough (estimates put it as much as 58 feet long) that it could have certainly predated on smaller prey as well (a modern day analog would be the Grizzly Bear).

Dinosaur bite marks--

2009-07-20T01:08:00.000-07:00

One aspect of paleontological research that has always fascinated me is how amazingly similar many of the events that occurred countless millions of years ago are to those found in modern ecosystems--in this case that of the countless and wide-varied interactions between predators and their prey, and even those between the predators themselves. One of these behaviors is something known as 'head biting'--a behavior observed amongst living animals in which competing rivals (over a mate, territory, a corpse, many things) fight amongst each other for control over whatever it is that they have their eyes set on. And because each of these animals are trying to assert their dominance over the other and would like to keep themselves as intact as possible, the head is a frequent target (keeping the rival in their sights). Also, because carnivores of aeons past had the same goals in mind as those living today (self-preservation and reproduction) and very similar tools to do so with (teeth and jaws!), they very likely ran into similar encounters and bouts of combat. As it turns out, we can find signs of these encounters throughout the fossil record!

This is a drawing of the partially reconstructed skull of an animal called Sinraptor, found in the deserts of northwest China. Each of the dark black lines outline the path of bite wounds that Canadian paleontologist Phillip Currie believes were caused by a conspecific (another Sinraptor). What is unique and so absolutely cool about this find is the fact that it allowed Currie to reconstruct the event in fascinating detail (given that it occurred over a hundred million years ago!)--two carnivorous dinosaurs faced off over a number of possible things (food, territory, etc.)--the tensions breaks, and one of the pair snaps its teeth at the other on the right side of the face and lower jaw with the right side of its mouth (measured by the angle and direction of the bite marks). However, as evidenced by the fact that the injuries were partially healed we know that the dinosaur in question (somehow) fled the scene. On the other hand, not all conspecific combat avoids mortality. In fact, we have evidence of outright cannibalism by this guy--

Majungasaurus, a large theropod dinosaur that lived in modern day Madagascar 70-65 million years ago. One find in particular viscerally fleshed out the defleshing of one such animal by another of its own species--the tooth marks on the bone match the dinosaur's teeth perfectly. Looking at today's ecosystems, this sort of thing is none too surprising--it occurs more frequently than many realize. What is exceptional (being that fossilization alone is very rare) is the signs of its existence being preserved after so long! However, encounters were certainly not limited between the carnivorous dinosaurs themselves--we have also uncovered fantastically detailed evidence of predator/prey interactions (both of animals that were scavenged and animals that escaped attack). At the centerpiece of a pseudo-debate involving the feeding behavior of the Late Cretaceous dinosaur Tyrannosaurus is a skeleton re-described by paleontologist Ken Carpenter (which was first discovered by a man called Barnum Brown in 1933)--a series of its caudal (tail) vertebrae was fractured, with at least one portion of the 'spinous process' completely broken and still several others kinked. On these spines were several tooth marks that match the exact shape and size of those belonging to Tyrannosaurus. But, because the bones show signs of healing, we know that it escaped for at least some time (and possibly died due to a bone infection) created by the bite. Also like many carcasses found in the wild today, bones of various dead animals would have scattered to the four winds by both assorted predators and scavengers, and as much of the bone as possible would have been picked clean. One such find is quite indicative of just that--a Triceratops pelvis collected by the Museum of Pennsylvania with a bare minimum of twelve bite marks, and as many as 33.

Fossils Encased in Mudstone--Part I

2009-05-20T19:11:00.000-07:00

Started preparation work on this bastard last week--and armed with a nothing but a chisel, hammer, and a few brushes... it's slow going.

I won't be removing the fossils themselves from the block to give a visual representation of the deposition and burial of whatever may lie inside.

Thus far I have exposed a large chunk of fairly unidentifiable bone, a diminutive rib of something or another (possibly some sort of small lizard), and a tiny three-chambered shellfish.

Will update with new photos as progress is made!

PS--I will accept any an all air compressor donations.