#FossilAdventCalendar Day 24

Our journey #north ends with one of the most important #fossils ever found. Like Puijila, Tiktaalik roseae is known from #Nunavut 🇨🇦, has an #Inuktitut name (meaning "large freshwater #fish"), and records an important #evolutionary transition, this time from #sea to #land. #Tiktaalik shares traits with both fish and #tetrapods, making it a close relative of all of us land-living #vertebrates. This replica and model are from the #CanadianMuseumOfNature.

#FossilAdventCalendar Day 23
#FossilFriday

The #Canadian 🇨🇦 #Arctic has yielded some especially important #fossils documenting major #evolutionary changes. This 3D-printed replica of a #fossil from #Nunavut and displayed in the #CanadianMuseumOfNature is one of these. It's Puijila darwini, whose name means "young sea #mammal" in #Inuktitut. It looks like an otter, but it's one of the earliest relatives of #seals and #sealions - with still-functional hands and feet, unlike modern #pinnipeds.

#FossilAdventCalendar Day 22 (delayed due to time with the family)

Our first #fossil from north of the #Arctic Circle is from the most iconic of #IceAge #megafauna. This woolly #mammoth, Mammuthus primigenius, was found over a century ago in the far #north of Siberia and gifted to Paris' #MuseumNationalD'HistoireNaturelle by the tsar. Like the squirrel featured yesterday, this mammoth was partially preserved in #permafrost; you can see its #mummified face and leg in the case at the right.

#FossilAdventCalendar Day 21 (delayed by a busy travel day)

As we move towards the far #North we encounter one of the (literally) coolest kinds of #fossilization. When the #frozen ground known as #permafrost forms, it can #freeze dry #animals buried in it. This ground #squirrel, Urocitellus undulatus from #Alaska 🇺🇸 and displayed in the #AmericanMuseumOfNaturalHistory, burrowed into the ground in life and was #mummified by it after death, providing a remarkable window into life in the #IceAge.

#FossilAdventCalendar Day 20
#Terrestrial Tuesday

Today we think of #lions as predators of the African savanna, but during the last #IceAge, they had a much wider distribution. Some lived in what's now the continental US, while another - the so-called cave #lion - lived in cold environments across the #Northern Hemisphere. This skull, displayed in the #AmericanMuseumOfNaturalHistory in front of its distant relative Smilodon, was found in #Alaska 🇺🇸 - our first specimen from the Last Frontier!

#FossilAdventCalendar Day 19

It's appropriate that this #MarineLifeMonday our journey #north reaches the shores of #Hudson'sBay at #Churchill, #Manitoba 🇨🇦. It's here that the largest complete #trilobite #fossil ever found was uncovered from #Ordovician rocks. If you want to see the more than two foot long Isotelus rex in person, head to #Winnipeg's #ManitobaMuseum, where it's displayed in all its splendor.

#FossilAdventCalendar Day 18

The original of this cast #skeleton, displayed in the #ArizonaMuseumOfNaturalHistory, was found along the Northern Dvina River. It's from Inostrancevia alexandri, a #gorgonopsian from the #Permian. Its huge size is the first thing you'll notice about it; this #animal and its relatives were clearly among the most imposing #predators of their time. Look closer and you'll see that it shares many traits with #mammals, of which it was a not-very-distant relative.

#FossilAdventCalendar Day 17

This #whale-sized #marine #reptile in the #RoyalTyrrellMuseum is the #ichthyosaur Shastasaurus sikkaniensis. Unusually, it was not only one of the earliest members of its group, but one of the very largest. Its #species name comes from where it was found, along the Sikanni Chief River which flows out of the #RockyMountains of #BritishColumbia 🇨🇦. Its #genus name comes from Mt. #Shasta in the #CascadeRange, where other species of this Triassic titan have been found.

#FossilAdventCalendar Day 16
#FossilFriday

This exploration of #fossils from the #Arctic nations wouldn't be complete without one of the most spectacular #dinosaur fossils ever found that happens to be named for the #North. Borealopelta, meaning "#Northern Shield," is a #nodosaur, a type of #ankylosaur, or #armored dinosaur. This #fossil, uncovered in the tar sands of #Alberta 🇨🇦 and displayed in the #RoyalTyrrellMuseum, preserves much of that armor in incredible detail.