Scientists have uncovered fossils believed to provide a vital evolutionary link to the contemporary koala, shining a light on a 30-million year chasm in the creature’s evolution that until now, remained dark. Named Lumakoala blackae, this ancient relation to the modern-day koala was decidedly more diminutive, approximating the size of a common house cat, according to a study recently published.
Lumakoala blackae sported a lithe weight of nearly 2.5 kilograms, revealed Arthur Crichton, the lead researcher and a PhD student out of Flinders University. He unexpectedly came across fossilized teeth belonging to this new species at the Pwerte Marnte Marnte fossil site in Australia’s Northern Territory, considered to house traces of the earliest terrestrial mammals from an epoch known as the Oligocene, roughly dated between 33.7 million years to 23.8 million years in the past.
Despite its small stature, Lumakoala blackae had a hearty appetite, favoring tender leaves while not shying away from indulging in the odd insect. Moreover, it’s suggested this minuscule marsupial is a part of the koala family or at least, a close kin. Although its appearance echoes that of bygone marsupials, the Thylacotinga and Chulpasia, who from their fossils, are known to possess a 55-million-year lineage.
Pwerte Marnte Marnte is indeed a treasure trove of fossils, albeit removing them from the limestone proves notably arduous. Exceptionally careful processing using a variety of tools freed these findings from their rocky confines, a task running from 2020 to 2022 conducted at the Palaeontology Lab at Flinders University. Examining the field samples also revealed the existence of two other premature koala relatives, Madakoala and Nimiokoala.
A prevailing theory stemming from this research hypothesizes that Lumakoala blackae may have been a transitional link between older marsupials such as those found in Tingamarra and today’s koalas. The traces of shared characteristics, especially in the structure of molars, between Lumakoala blackae and these ancestors found at Tingamarra could substantiate this connection.
Australia is known as a haven for an extraordinarily diverse range of marsupials. Diprotodontia, a marsupial order boasting around 155 species including kangaroos, wallabies, possums, koalas, wombats and many more, is the largest of its kind. However, a conspicuous absence of fossils from earlier periods has made it difficult to determine the initial stages of their evolution.
Genetic analysis indicates that Diprotodontia separated from Agreodontia, another marsupial order, during a timeframe stretching from the late Cretaceous epoch to the early middle Eocene. This evolutionary branching is speculated to have taken place before Australia’s final split from Antarctica about 30 million years back. This continental isolation catalyzed a unique evolution path for Australia’s marsupials and other species.
The newly discovered koala species could offer significant insights into the evolution of early marsupials. One hypothesis suggests that two 55 million-year-old species, Thylacotinga and Chulpasia could be ancient relatives of Australian herbivorous marsupials due to the key similarities found between their molars and that of Lumakoala blackae.
Interestingly, fossil specimens resembling the enigmatic Chulpasia have shown up as far away as Peru, pinning a potential South American connection. Crichton muses, “The discovery of Lumakoala suggests that Thylacotinga and Chulpasia could actually be early relatives of Australian herbivorous marsupials such as koalas, wombats, kangaroos and possums.”
The study invites intrigue about the roots of the koala stretching back to South America and Antarctica, marking the first ancient koala relative found in Australia’s Northern Territory. Although only one modern koala species remains, the existence of many species has been identified, with seven known to have been active in the late Oligocene. This newly discovered relative of the koala family points to a more interconnected and complex past that will undoubtedly inspire continued exploration and understanding in the evolutionary history of marsupials.
