Dinosaur of the Week--Acrocanthosaurus.

Community (This content is not subject to review by Daily Kos staff prior to publication.)

Wednesday August 12, 2009 · 10:19 AM PDT

2009/08/12 · 10:19

One of many of a series devoted to all things dinosaurian!

Prounounced Ack-Roh-Kan-Tho-Sorus.

Oklahoma has brought us a great many things--inspiration for famous musicals, the dust bowl, Droogie... but for all of its famous articles of culture and pizazz, it was also the home to something much larger.

Acrocanthosaurus, a massive carnivorous theropod dinosaur native to the Early Cretaceous period (roughly 125-110 million years ago)--informally dubbed 'The Terror of the South' (though some contend that the title may have been usurped by George W. Bush).

The exact position of Acrocanthosaurus within the always branching tree of life is still debated, but many scientists place it as one of the older members of the prior diaried Carcharodontosauridae--the 'shark toothed reptiles', while others place it as being closer related to the Late Jurassic theropod Allosaurus. My own thoughts of its placement are still somewhat on the fence.

But whether within the Allosauridae or Carcharodontosauridae, there is one crucial fact that most everyone can agree on--it was big. Really big.

Though the type specimen (found in Oklahoma) was smaller, the latest finds suggest that it was roughly 38 feet long and weighed around 5300 pounds.

And though they would certainly not push aside a smaller, less dangerous meal (indeed, some recent research suggests that much like modern day carnivores, juvenile dinosaurs or other small prey may have been preferred--doubly so when you consider the far greater number of offspring produced compared to placental mammals), some evidence suggests that they may have periodically preyed upon absolutely massive dinosaurs--sauropods, the group containing the largest animals to have ever walked the Earth.

A footprint trackway (one of many to be found in Glen Rose, Texas) appears to hold direct evidence of such an attack--a set of footprints attributed to Acrocanthosaurus (due to both their size and location) steadily stalks a herd of sauropods through the damp mud. But suddenly, one of the theropod's footprints disappears as soon as it meets that of one of the sauropods--suggesting that it grabbed hold of the sauropod's side and was dragged a step. Though there is no evidence suggesting that the theropod's attack was immediately successful, it may well have died from infection later or escaped to heal its wounds.

It was this scenario that led to the following sculpting, located in the Museum of Natural History in Raleigh, North Carolina.

On the other hand, some scientists doubt this interpretation, suggesting that the Acrocanthosaurus merely crossed the same patch of mud soonafter the sauropod--pointing to the lack of gait change during the postulated moment of attack.

However, not all footprints reported as belonging to Acrocanthosaurus are based upon rigorous scientific truth--in fact, some are outright laughably false (a side effect of being found smack dab in the middle of the bible belt!).

For an example, by measuring its size and looking at the known dinosaurs of the formation in which it was found we can often suggest the owner of a footprint (though sometimes this is impossible when there are multiple contenders).

This is a footprint attributed to Acrocanthosaurus.

Dinosaurs walked on their toes (like, unsurprisingly, their direct modern day avian descendants)--with their metatarsals (the bones just above the phalanges or toe bones) raised above the ground. Note the angled centralized meeting point in the back, which is then followed by the three toes--heel first.

This is also seen in this Acrocanthosaurus footprint (which partially refilled after the foot was pulled out!)--

This on the other hand...

Resides in a creationist museum nearby where its 'discoverer' claims to have found it--proving once and for all that humans and dinosaurs coexisted (other than birds!).

Problem is... not only is it a fake, it's a horribly made fake. Note the 'dinosaur's' absolutely enormous heel compared to the following toes--which also lack claws (those thin lines in the prior two pictures). Its toes are also facing the wrong direction--dinosaurs walk with one central toe pointing forward with the other two angled from it--all the toes in the last 'footprint' are facing forward.

And that's just the dinosaur footprint! Especially of amusement is the enormously deep largest toe compared with the rest of the human's. The hoax's crafter could try to claim that the footprint's maker was angling his toe downward, but it's the size and shape one would expect were it to be held fully horizontal--just 5x deeper than it should be.

However, frauds like this shouldn't keep the public from enjoying the fascinating natural history and the traces of the remarkable ancient fauna that once inhabited this planet countless millions of years ago. When tracing the rocks, we paleontologists are merely letting loose a soft whisper of what once was, but we do everything we can to let the voice and our understanding of these long-gone aeons grow stronger.