That picture of it looks so unbalanced. But I measured it out and the tail is actually significantly further back than the head is forward, so I guess it's plausible. Probably just a case where human judgement does a poor job of estimating things!
I always find it odd that generalizations can be made such as "[this] was the most abundant animal to be found 145 million years ago" when it is based on so infinitesimal a fraction of the evidence. Perhaps this article is simply missing the bulk of the data, but it strikes me as odd that a corner of the Andes could be accurately representative of the world so very, very long ago.
"[...] was the most abundant animal to be found 145 million years ago, in what is now the Aysén region of Patagonia."
I read that as it was the most abundant animal found in the region.