Tuesday, March 21, 2017

Livyatan: Beast of the Week

This week we will be voyaging back to the Miocene to observe an amazing whale.  Make way for Livyatan melvillei!

Livyatan was a large, toothed, whale that swam in oceans that covered what is now South America and Australia (likely most of the southern hemisphere given that range) during the Serravalian stage of the Miocene epoch, between thirteen and twelve million years ago.  However, teeth that appear to be from Livyatan, found in Australia are dated at only between five and six million years old, pushing this animal's success much further through time. (If it is, in fact, the same genus, and if not it's still from an extremely close relative.)  Only teeth and parts of the skull have been found, but based on this, experts have estimated the animal's body length to have been between forty four and fifty seven feet long from snout to tail.  The genus name is the Hebrew spelling of the word, Leviathan, which was an enormous sea monster from biblical mythology.  The species name, melvillei, is in honor of Herman Melville, the author of the classic novel, Moby Dick...which is about a huge whale...in case you didn't know.

Livyatan immobilizing a young megalodon shark.  Painting by Christopher DiPiazza.

Livyatan was in the same major family of whales as the modern Sperm Whale.  Sperm whales (which Moby Dick was based on) are the largest living toothed whales.  However, they only have teeth on the lower jaw.  Sperm Whales eat almost exclusively giant squid.  Unfortunately we don't know exactly how they hunt because a Sperm Whale has never been observed in the act due to the fact that they dive down too deep, where the squid live, for us to observe the hunting behavior.  We know large squid make up most of their diets, however, because humans used to hunt Sperm Whales for their oil and during dissection/butchering, squid have always been found upon cutting open the stomach.  We also see scars and marks from giant squid tentacles on the faces of many Sperm Whales from their prey fighting back before being consumed.


Livyatan, on the other hand, despite being a close relative to Sperm Whales, may not have behaved, let alone, hunted the same way as their modern family members.  One very striking difference is that Livyatan had proportionally larger, more robust teeth, and a full set of them at that, on the lower and upper jaws.  Some of these teeth measure fourteen inches long!  This suggests it was not a squid specialist.  The fact that the teeth are so large and thick, points to Livyatan being more of a hunter of larger, more general prey that it would utterly pulverize via monstrous bites.  This makes sense, since we know Livyatan coexisted with plenty of other large sea creatures, including seals, sea lions, sharks, dolphins, and slightly smaller whales.  That's right, Livyatan, may have been a hunter of other whales!  (Which isn't unheard of. Orcas do it all the time.)   I find it worth noting that Carcharodon megalodon, (the giant predatory shark that is most certainly NOT still alive today, despite what Discovery Channel's idiotic shows suggest) was a contemporary of Livyatan's.  It is likely that the two were competitors, being similarly-sized predators.  They may have even preyed on each other depending on the circumstances!

Cast of Livyatan's skull on display at the Museo di Storia Naturale e del Territorio, in Italy.

The rest of Livyatan's skull was shaped similarly to that of a modern Sperm Whales.  This suggests that in life it had a large mass of soft tissue taking up most of the front of it's head, called a spermaceti organ.  This body part is full of oil and fat that helps whales use echolocation to navigate underwater.  Because of this it is likely Livyatan could do the same.  It also probably used complex vocalizations to communicate to members of its own species, as well.

I did this quick sketch just to show how much of a whale's head can be soft tissue compared to the skull.  The Sperm Whale's (pictured on the left) iconic rectangular profile is due to soft tissue mostly. (I actually botched the Sperm Whale's profile.  The shaded blue soft tissue part should go beyond the tip of the jaws even.)  It is likely, judging by the skull, that Livyatan, pictured left, had something similar. 

That is all for this week!  As always comment below or on our facebook page!

References

Lambert, Olivier; Bianucci, Giovanni; Post, Klaas; de Muizon, Christian; Salas-Gismondi, Rodolfo; Urbina, Mario; Reumer, Jelle (1 July 2010). "The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru Nature466 (7302): 105–108. 

Norris, K.S. & Harvey, G.W. (1972). "A theory for the function of the spermaceti organ of the sperm whale". In Galler, S.R; Schmidt-Koenig, K; Jacobs, G.J. & Belleville, R.E. Animal orientation and navigation. NASA, Washington, D.C. pp. 397–417.

Tuesday, March 14, 2017

Sphaerotholus: Beast of the Week

This week we shall be checking out a relatively small, but successful round-headed dinosaur.  Say hello to Sphaerotholus!

Sphaerotholus, was a pachycephalosaurid dinosaur, related to the much more famous, Pachycephalosaurus, that lived in what is now North America, including New Mexico and Montana, USA, as well as Alberta and Saskatchewan, Canada, during the late Cretaceous period.  The genus includes three species, that together, spanned from 76 to 66 million years ago.  When alive, Sphaerotholus would have been a plant-eater and could have measured roughly six feet from beak to tail, based on the very fragmented fossil material that is actually known from it. (basically just the top of the skull.) We can also guess roughly how large it was by comparing it to more completely-known, similarly-sized pachycephalosaurids, like Prenocephale and StegocerasSphaerotholus' genus translates to "ball dome" in reference to the top of it's head...which was quite spherical.

Sphaerotholus goodwini, from New Mexico, life reconstruction by Christopher DiPiazza.

Unfortunately not too much is known from this dinosaur.  Despite the fact that there are three named species, all the specimens consist of fragments of the top of the skull and very little else.  What we do know, is that even for a pachycephalosaurid, it had a particularly rounded and thick skull.  The arrangement of nodes (small horns/bumps surrounding the dome) were arranged in a unique way, as well.  Interestingly, pachycephalosaurids actually exhibit quite a bit of variation amongst species when it comes to head ornamentation, and Sphaerotholus was at the derived end of this family tree, when it came to cranium thickness. Some experts have suggested that Sphaerotholus is should really be sunken into the same genus as a more completely known, close relative, called Prenocephale, which was native to what is now Mongolia, but so far the material from Sphaerotholus has proven to be different enough to hold this off for now.

Dorsal view photo of a Sphaerotholus buchholtzae dome, from Canada, held at the American Museum of Natural History, from Paterson's 2013 paper.  Arrows are pointing to injuries possibly from head-butting behavior.

So why such a thick skull?  This question has been asked and debated by paleontologists since the first pachycephalosaurid was discovered.  The knee-jerk conclusion was that these dinosaurs were using their heads as weapons to ram each other with, similar to the behavior seen in many horned mammals today, like goats and muskox.  In fact, the skulls of many of these pachycephalosaurids, including Sphaerotholus, have been found with injuries on them, in the form of small lesions on the tops of their domes that became infected and possible healed in life, suggesting they were, indeed smashing their noggins together.  However, some other paleontologists think that if these dinosaurs actually rammed their skulls in that way, it would seriously injure, or even kill both animals.  It is possible they still used their heads as weapons, but rather aimed for softer parts of their rivals' bodies, like the flanks, or maybe at shorter range, swinging their necks around like clubs, instead of ramming with a running start.  It is also possible the skulls were at least partially for display within the species, as signs of sexual maturity, or even sex. (Although we have no idea if the males and females actually looked different from each other at this time.  Remember, we only have dome tops!)

That is all for this week!  As always feel free to comment below or on the facebook page!

References

Carr T. E.; Williamson T. D. (2002). "A new genus of highly derived pachycephalosaurian from western North America". Journal of Vertebrate Paleontology. 22 (4): 779–801.

Longrich N. R.; Sankey J. T.; et al. (2010). "Texacephale langstoni, a new genus of pachycephalosaurid (Dinosauria: Ornithischia) from the upper Campanian Aguja Formation, southern Texas, USA". Cretaceous Research. 31: 274–284.

Mallon Jordan C.; Evans David C.; Tokaryk Tim T.; Currie Margaret L. "First pachycephalosaurid (Dinosauria: Ornithischia) from the Frenchman Formation (upper Maastrichtian) of Saskatchewan, Canada". Cretaceous Research. 56: 426–431.

Peterson, Joseph E., Collin Dischler, and Nicholas R. Longrich. "Distributions of Cranial Pathologies Provide Evidence for Head-Butting in Dome-Headed Dinosaurs (Pachycephalosauridae)." Docs.com. N.p., 16 July 2013. Web.