Though in science objective thought is essential*, a great deal of my own mindset as a paleontologist is also very much emotionally invested in those creatures that myself and others seek to understand. One of my main goals in my field is not only to help research and piece together this puzzle that we call Life's History, but also to help take that information that leaves me with such wonder and translate the often dry scientific jargon into a medium that can enthrall the public at large (both to future interested students and curious laypersons).
Today's installment brings a great amount of the 'seriously cool' factor--simply, biological sharp things. ;-)
*Unrelenting dogma can be a scientist's downfall, especially so in paleontology--though many aspects and truths through the fossil record are likely to hold strong through time, we must always be careful to not feel that we have the whole truth in grasp: new evidence is always being lifted, and with new evidence comes new understanding.
1. C. Megaladon
Though the exact ancestry of this enigmatic ancient shark is still being debated (its teeth are remarkably similar in form to the modern great white, but increasingly mounting evidence suggests that its ancestry instead lies with an ancient form that had split into a separate evolutionary lineage from the extant predator that we love and love to hate).
In no stretched terms, it was mindblowingly massive.
Living from 18.5 to about 1.5 million years ago, C. Megaladon was far and away one of the largest sharks ever known. Though estimates of its length have varied quite substantially throughout time, conservative estimates consistently give it a length of 51 feet, and others have given it a maximum body size of as much as 75 feet.
Likely feeding on massive oceanic prey like whales and gigantic extinct sea turtles (along with assorted fish and other opportunistically exploited food items), C. Megaladon primarily occupied shallow warm coastal waters across the globe (fossil traces have been found anywhere from western North America to India and Jamaica).
Though the exact causes of its extinction, if ever we can uncover them, is still under discussion, it's highly likely that a global cooling trend caused by the convergence of North America and South America contributed a substantial amount to its eventual demise.
2. Carcharodontosaurus sarharicus
Carcharodontosaurus sarharicus ('Saharan shark-toothed reptile') was a massive carcharodontosaurid theropod that occupied what is now modern day Egypt, Algeria, and Morocco during the Albian and early Cenomanian periods, roughly 100-93 million years ago (though a southern species, Carcharodontosaurus iguidensis has been uncovered in the deserts of Niger, likely separated from its northern cousin by an ancient Northeast/Southwest trending seaway).
First named by a German paleontologist by the name of Ernst Stromer in the early 1900s (though a pair of teeth referable to the animal were briefly mentioned several years earlier, the genus they had attributed them to was later found to be invalid), Carcharodontosaurus saharicus takes its namesake from its distinctively shark-like teeth: the distal ('back') side flattened and its mesial ('front') side convex, both portions having a series of razor sharp serrations placed from the base to the apex (this is unusual for theropods--generally for those with serrated teeth, the mesial serrations end halfway through, likely because the rear and often recurved portion acts as the bulk of the cutting surface--what this means for the biomechanics of Carcharodontosaurus feeding has yet to be determined, and it's an area I hope to explore in the future).
3. Therizinosaurus cheloniformis
Therizinosaurus is likely one of the strangest dinosaurs in (ancient, long gone) existence. Though the majority of theropods known are carnivorous in nature, Therizinosaurus and its relatives are a bizarre exception, similar to the modern panda bear (though they are not the only group of theropods to have shied away from their carnivorous ancestry--the Ceratosaur Limusaurus, described in 2009, developed herbivory in an a very distantly related lineage).
However, the relationships of Therizinosaurus were not always known so clearly--when it was first discovered in the late Cretaceous fossil beds of Mongolia, it was thought to be a large turtle due to its bizarre massive scythe-like claws, some of which reach an astounding meter in length.
After an assortment of fossil discoveries, a closer picture of Therizinosaurus came into being: something of a cross between a pig, a bird, and the dude from Nightmare on Elm Street.
However, as with many other fossils, much of its skeleton is lacking; forcing us to look at close relatives to determine the missing pieces. With luck, further discoveries will help us get a better grasp on the nature of this utterly strange animal.
4. Suchomimus tenerensis
Suchomimus tenerensis, a massive theropod native to the Aptian period of central Niger (roughly 125-112 million years ago) is part of a group of tetanuran theropods called spinosaurids, most distinctly recognized by their elongate bilaterally flattened snouts with crocodile-like conical teeth that were almost certainly utilized for piscivory, or fish eating.
Through cladistic analysis (in which evolutionary pathways and relationships are determined by morphological similarities) the Spinosauridae can be split into two sub-groups: the Spinosaurinae (whose members include the South American Irritator and the north African Spinosaurus) and the Baryonichae (definitively comprised of European Baryonyx and Nigerian Suchomimus). Though there could be other differences given the current spotty material of spinosaurids through the fossil record, many of the most recognizable distinctions are based upon various variations of the skull (including things like the placement of the nostrils, or 'external nares' and the shape, form, and number of teeth in the jaws).
Another fascinating spinosaurid characteristic is a massive recurved thumb claw (scientifically dubbed 'Manual I ungual'), which was likely another adaptation for their largely piscivorous lifestyle (though they could probably be better described as fish-inclined generalist feeders ;-) ). Interestingly, this claw is also found in a closely related group of dinosaurs called torvosaurids.
Enjoy!