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.

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