Sunday, September 25, 2016

Machairoceratops: Beast of the Week

This week we will be looking at another recently discovered horned dinosaur.  Enter Machairoceratops cronusi!

Machairoceratops was a ceratopsian dinosaur, which means it was in the same group as the more famous, Triceratops.  Within this group, however, it was more closely related to Diabloceratops and NasutoceratopsMachairocearatops' name translates to "Bent Knife Horned Face".  This is in reference to the shape of the two horns that grew from the top of the dinosaur's frill.  The species name, "cronusi" is after the mythical Greek god, Cronus, who cut off his dad's testicles with a curved sword.  (Next time you think your family has drama, remember that.)  In life, Machairoceratops would have been a plant-eater.  It lived in what is now Utah, USA, during the Cretaceous period, about 77 million years ago.  From beak to tail it would have measured about twenty feet long based on the skull. (Only the skull was found.)

Two rival Machairoceratops use their horns to lock into one another as they engage in a shoving match.

Like its relatives, Machairoceratops had a beak, a frill behind its head, and horns...very unique horns.  I know I say "unique" a lot in reference to ceratopsians, but it holds true!  Especially when it comes to this genus.  The two horns on the top of the frill curve forward and downward.  Frill horns aren't unheard of ceratopsians...but this exact orientation and curvature combined with their length, is.  It also had one horn over each eye which curved slightly upwards.  Due to the fragmentary remains of the skull, we sadly don't know what kind of horn ornamentation Machairoceratops had over its snout, if any at all.

Known fossil material from Machairoceratop's skull.  Image is from the paper by Eric K. Lund, Patrick M. O’Connor, Mark A. Loewen, Zubair A. Jinnah, referenced below.

As is the case with all ceratopsians, we don't know exactly why Machairoceratops' horns and frill evolved the way they did.  But it is very likely it had something to do with interacting with other members of its species.  If ceratopsian horns and frills were purely for defense against predators, they would likely be more uniform from species to species.  But this isn't the case.  Typically, when a variety of different, but related animals have the same sort of trait that is unique in form to each species, it has to do with some sort of intraspecies communication, like sexual display.  Just look at modern songbirds and their variety of colors and calls, or ungulates and their horns/antlers as modern comparisons. When it came to Machairoceratops, I felt that the overall shape that the brow and frill horns made together looked like it might serve well for combating rivals in head-to-head pushing behavior.  The antlers of modern reindeer also form this forward-facing crescent form, and they use them similarly.  Can I prove this was exactly how Machairoceratops used its horns?  Of course not.  But it's possible and also fun to think about.

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

References

Eric K. Lund, Patrick M. O’Connor, Mark A. Loewen and Zubair A. Jinnah (2016). "A New Centrosaurine Ceratopsid, Machairoceratops cronusi gen et sp. nov., from the Upper Sand Member of the Wahweap Formation (Middle Campanian), Southern Utah". PLoS ONE. 11 (5): e0154403.

 

Sunday, September 4, 2016

Palaeosaniwa: Beast of the Week

This week we shall be checking out a prehistoric reptile whose lineage continues to this day.  Enter Palaeosaniwa canadensis.

Palaeosaniwa was a lizard that lived in what is now North America, including Alberta, Canada, and Wyoming and Montana, USA, during the Late Cretaceous Period, from 75 all the way to 66 million years ago.  Within this time there may have been multiple species within the genus, but canadensis is the most well known.  Palaeosaniwa was a relatively large lizard, capable of growing to over eleven feet long from snout to tail, judging by the remains of it that have been found.  The genus name translates to "Ancient Saniwa".  Saniwa being another, slightly younger by a few million years, but still very much prehistoric, kind of lizard.  When alive, this Palaeosaniwa would have been a meat-eater.

Palaeosaniwa getting chased by an angry Anatotitan.

Palaeosaniwa was a kind of veranoid lizard, in the same family that includes living monitors, like the Komodo Dragon, as well as the extinct marine lizards, the mosasaurs.  Like the modern Komodo Dragon, Palaeosawina had long, curved, serrated teeth which were probably adept at grabbing and tearing mouthfuls of meat off carcasses.  It likely had other adaptations in common with its modern relative, but unfortunately venomous saliva and forked tongues have never fossilized.

Me comforting my modern varanoid friend, Bruno, the Black-Throat Monitor (Varanus albigularis ionidesi)  He would have been way too emotionally sensitive to survive the Cretaceous.

There is something to be respected about a lizard that lived for such a long span of time amongst dinosaurs.  Despite the fact that an eleven-foot lizard is nothing to scoff at, it still coexisted with some of the largest and potentially dangerous dinosaurs of all time.  Veranoids historically tend to be very adaptable.  Their strong arms and legs, each ending in five curved claws are great for climbing, digging, and running.  Their long muscular tails are an effective weapon against enemies and also allow them to be strong swimmers.  This combination of adaptations would have made this lizard a jack-of all trades, opportunistic meat-eater, a very good place to be in the long run.  Because Palaeosawina was a mid-to-small scale meat-eater, pretty much every other creature in its community probably had some sort of beef with it.  Large plant-eaters like ceratopsians and hadrosaurs likely would have seen it as a threat to their eggs and babies and may have tried to chase or even kill it if spotted, while large predators like tyrannosaurids and even Dakotaraptor would have likely hunted it for food in addition killing it to protect young.  Despite this, this lizard still managed to carve a prominent niche that remains intact to this day thanks to its modern kin.  Palaeosawina would have had to be an extremely tough lizard!

That's all for this week.  As always feel free to comment below or on the facebook page.

References

Archibald, J. David (2011). Extinction and Radiation: How the Fall of Dinosaurs Led to the Rise of Mammals. JHU Press. p. 43.

Michael Joseph Balsai, The phylogenetic position of Palaeosaniwa and the early evolution of the Platynotan (Varanoid) anguimorphs (January 1, 2001). Univ. of Pennsylvania - Electronic Dissertations. Paper AAI3031637.