It's #MammalMonday #MesozoicMammalMonday and I'm thrilled to share my paper on #multituberculates from #EggMountain, published today @NatureEcoEvo! These incredible fossils provide the earliest evidence of mammalian social behavior
https://www.nature.com/articles/s41559-020-01325-8

This paper was many years in the making, HUGE shoutout to the team that made it a reality: @gpwilson11, Dave Varricchio, Eric Sargis, @freewillie643, and @Meng_Chen_ . And big thanks to @UW, @UWBiology, @burkemuseum, @NSFGRFP, @NSF for the support. #UWpaleo

#EggMountain was made famous when @dustydino et al. discovered the first #dinosaur nests from North America. The site also produces beautiful lizards ( https://doi.org/10.1098/rspb.2016.1902) and abundant trace fossils ( https://doi.org/10.1016/j.palaeo.2019.109262 ; https://doi.org/10.1017/jpa.2020.26)

We describe new #multituberculate #mammal #fossils from the site, all belonging one species, #Filikomys primaevus (new genus). For the #MesozoicMammals lovers amongst us, this taxon helps resolve some persistent taxonomic issues (checkout the Supplement!)

The #Filikomys #fossils occur as multi-individual aggregates of skulls and skeletons, representing both adults and subadults. Most #multituberculate fossils are #teeth! These represent the most complete #MesozoicMammal fossils from North America

These multi-individual aggregates occur throughout the #EggMountain quarry, but are especially concentrated at one horizon. All specimens from this horizon are exceptionally complete and preserve individuals of different ontogenetic ages

The #geology and #taphonomy of the site and fossils indicate that these remains did not accumulate via physical processes (e.g., wind, water, attrition, debris flows) or via predation (e.g., regurgitates, poop). Read the paper for details on this stuff!

Instead, the evidence points to these animals congregating together in life and being preserved in #burrows! In fact, the #EggMountain #multituberculate assemblage resembles that of modern-day, small #mammal colonies (e.g., some #rodents)

That #Filikomys was a burrower is supported by its skeletal #anatomy, which reveals that it was adapted for scratch #digging, similar to #chipmunks. Multivariate analyses of the #skeleton also shows that #Filikomys clusters with extant burrowers

Together, this represents the earliest evidence for mammalian social behavior and the first evidence for sociality in a #mammal that is not a #placental or #marsupial! #Multituberculates are an ancient group that went extinct ~35 million years ago

Since we're social animals, mammalian #sociality is often thought to be somehow unique to our evolutionary stock, and probably didn't arise until after the #extinction of non-avian #dinosaurs. This paper continues a trend of dismantling that narrative!

If you want to read my short "Behind the Paper" blog for @NatureComm, check out this link: https://go.nature.com/37JoI2j 

Bob Masek was responsible for the incredible #fossil #preparation on these very delicate specimens. Misaki Ouchida created the beautiful artistic reconstructions I've been using throughout this thread ( https://www.misakiouchida.com/ ).

So many others to thank, but those on Twitter: @MuseumRockies, @dustydino, @Alex_Brannick, @mererivin, @johnscannella, @AmyLynnAtwater, @PatriciaHolroyd, @ucmpberkeley, @AMNH, @yalepeabody, @Cimexomys, @_megwhit_, @TheOxyprimest, @WaigePilson, @caestromberg

This was my first real #thread, but I was too excited not to try it! I'm super proud of this paper and hope you all enjoy it. I'd love to chat about it more if you have any comments or questions. Please DM me or shoot me an email!