Some Mesozoic mammal news
Kalaallitkigun jenkinsi diagram from Sulej et al 2020.
So we have two developments that greatly progressed our understanding of early mammals this year:
- The description of Kalaallitkigun jenkinsi, a basal mammaliaform from Greenland and currently the earliest such synapsid from there. This animal displays an intermediate state between the simple triconodont dentition seen in morganucodonts and eutriconodonts and the multicusped teeth seen in ‘allotheres’, suggesting that at least mammaliaformss with multituberculate-like teeth evolved from ancestors with triconodont teeth. This is huge because it confirms that triconodont dentitions are in fact the basal condition in mammals and their shift into the broad, complex molars we have is the result of increasing tendency towards omnivorous and herbivorous diets, mammals thus joining other vertebrate groupss with an ancestrally carnivorous condition. Nonetheless the tribosphenic condition we therians have seems still to have been derived from the symmetrodont condition seen in, well, symmetrodonts; ‘allothere’ conditions meanwhile seem to have evolved independently multiple times as seen in ‘haramiyidans’ and multituberculates.
- A study that demonstrates that molars and shoulder girdles are in fact unreliable as phylogenetic signals. Seeing as both have been extensively used to characterise mammal phylogeny and evolution, this has massive consequences in future studies.