Today we return to the long-vanished summer world of the Eocene (the third epoch of the Cenezoic era). During most of the Eocene, there was no polar ice on Earth: a balmy temperate summer held sway from Antarctica to Svalbard. British Colombia was covered by a tropical rainforest where palm trees and cycads contended with warm weather conifers (and with the ancestors of elms, cherries, maples, and alders). Within this warm diverse forest, which thrived between 55 and 50 million years ago, lived numerous strange magnificent birds and insects. Shoals of tropical fish thronged in the acidic foaming waters (which were practically carbonated—since the atmospheric carbon dioxide levels of the Eocene were probably double that of the present). The mammals of this lovely bygone forest were equally splendid–strange proto-carnivores not closely related to today’s mammalian predators, weird lemur analogs, and strange ur-rodents. This week the discovery of two new mammal species was announced. These remarkable fossil finds provide us with an even better picture of the time and place.
One of the two creatures discovered was a tapir-like perissodactyl from the genus Heptodon. The newly discover tapir was probably about the size of a large terrier. I really like tapirs (and their close relatives) but these remains are not a huge surprise–since many perissodactyls thrived in North America during the Eocene. The other fossil which paleontologists found is a surprise—an adorable surprise! Within a stone within a coal seam was a tiny jaw the size of a fingernail. Such a fossil would have been all but impossible to study in the past, but the paleontological team led by David Greenwood, sent the little fossil to be scanned by a CT scanner and then imaged with a 3D scanner. The tiny jaw was from a diminutive hedgehog relative since named Silvacola acares. The little hedgehog grew to a maximum adult size of about 6 cm (2.3 inches) long or approximately thumb-sized. Since it probably lacked spines, this miniature hedgehog was a bit different than the modern hedgehog, but it was definitely a relative.
As discussed in previous posts, I like to imagine the balmy Eocene, when so many mammals which are now the mainstay of our familiar Holocene/Anthropocene world got their first start. It makes it even better to imagine that the thickets were filled with endearing hedgehogs the size of bumble bees.