FOSSILS
New koala relative fills a branch of Australia’s unique marsupial story
IMAGE: COMPARISON OF UPPER MOLAR MORPHOLOGY BETWEEN CHULPASIA JIMTHORSELLI, LUMAKOALA BLACKAE AND THE MODERN KOALA. view more
CREDIT: A CRICHTON (FLINDERS UNIVERSITY)
Koalas are endangered in much of Australia now but in in the past there were multiple species living across the continent. The discovery of an ancient relative of the koala helps fill a 30 million year gap in the amazing evolution of Australia’s marsupials, according to a new study by Australian and British scientists published in Scientific Reports.
The study was led by Flinders University PhD student Arthur Crichton, who found fossil teeth of the new species at the Pwerte Marnte Marnte fossil site south of Alice Springs, thought to be about 25 million years old.
“The new species, which has been named Lumakoala blackae, weighed roughly 2.5 kg (about the size of a modern day brushtail possum, or a small domestic cat), and probably ate mostly soft leaves, but wouldn’t have turned down an insect given the chance,” says Mr Crichton, who analysed field samples collected in 2014 and 2020.
“Our computer analysis of its evolutionary relationships indicates that Lumakoala is a member of the koala family (Phascolarctidae) or a close relative, but it also resembles several much older fossil marsupials called Thylacotinga and Chulpasia from the 55 million-year-old Tingamarra site in northeastern Australia.
“In the past, it was suggested the enigmatic Thylacotinga and Chulpasia may have been closely related to marsupials from South America.
“However, 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.”
“This group (Diprotodontia)is extremely diverse today, but nothing is known about the first half of their evolution due to a long gap in the fossil record.”
“If our hypothesis is correct, it would extend the diprotodontian fossil record back by 30 million years. We would really expect early diprotodontians to have been around at the time; molecular information suggests koalas, wombats, kangaroos and possums split off from other marsupials between about 65 million and 50 million years ago.”
Co-author Associate Professor Robin Beck, from England’s University of Salford, says the discovery of Lumakoala helps fill a major 30 million-year-old gap in Australian marsupial evolution.
“These Tingamarran marsupials are less mysterious than we thought, and now appear to be ancient relatives of younger, more familiar groups like koalas,” says Dr Beck.
“It shows how finding new fossils like Lumakoala, even if only a few teeth, can revolutionise our understanding of the history of life on Earth.”
The study raises important new questions, including whether these relatives of Australian herbivorous marsupials once lived in South America and Antarctica, Dr Beck says, adding there are South American fossils that look very similar to the Tingamarran marsupials.
The new study also reports the presence of two other types of koala – Madakoala and Nimiokoala – that lived alongside Lumakoala, filling different niches in the central Australian forests that flourished 25 million years ago.
Professor Gavin Prideaux, director of the Flinders University Palaeontology Laboratory, describes the late Oligocene (23–25 million years ago) as a “kind of the koala heyday”.
“Until now, there’s been no record of koalas ever being in the Northern Territory; now there are three different species from a single fossil site,” says Professor Prideaux.
“While we have only one koala species today, we now know there were at least seven from the late Oligocene – along with giant koala-like marsupials called ilariids.
Iliariids were the largest marsupials in Australia at the time, weighing in at up to 200 kg. They lived alongside a strong-toothed wombat relative named Mukupirna fortidentata and bizarre possum, Chunia pledgei.
The article, A probable koala from the Oligocene of central Australia provides insights into early Diprotodontia evolution (2023) ) by Arthur I Crichton, Robin MD Beck, Aidan MC Couzens, Trevor H Worthy, Aaron B Camens and Gavin J Prideaux has been published in Scientific Reports. DOI: 10.1038/s41598-023-41471-0.
Photos, map and graphics at the link: Reconstruction illustration by Peter Schouten
Reconstruction of the 25 million year old Ditjimanka Lumakoala blackae, featuring (left to right) the wallaby-sized herbivore Muramura williamsi, extinct koala relative Madakoala devisi and the calf-sized ilariid (Ilaria lawsone). Courtesy of Peter Schouten
CREDIT
Illustration courtesy of Peter Schouten
Flinders University palaeontology researcher Arthur Crichton, who found fossil teeth of the new species at the Pwerte Marnte Marnte fossil site south of Alice Springs, thought to be about 25 million years old.
CREDIT
Flinders University
JOURNAL
Scientific Reports
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Animals
ARTICLE TITLE
A probable koala from the Oligocene of central Australia provides insights into early Diprotodontia evolution
Chinese paleontologists find new fossil link in bird evolution
IMAGE: LIFE RECONSTRUCTION OF THE 150-MILLION-YEAR-OLD AVIALAN THEROPOD FUJIANVENATOR PRODIGIOSUS view more
CREDIT: ZHAO CHUANG
Birds descended from theropod dinosaurs by the Late Jurassic, but our understanding of the earliest evolution of the Avialae, the clade comprising all modern birds but not Deinonychus or Troodon, has been hampered by a limited diversity of fossils from the Jurassic.
As of now, no definitive avialans have been reported except from the Middle–Late Jurassic Yanliao Biota in northeast China (166–159 million years ago; Ma) and the slightly younger German Solnhofen Limestones, which preserve Archaeopteryx. Consequently, there is a gap of about 30 million years before the oldest known record of Cretaceous birds. However, the Jurassic avialans are key to deciphering the evolutionary origin of the characteristic avialan body plan. More importantly, they are key to reconciling the phylogenetic controversy about the origin of birds.
A joint research team from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences in Beijing and the Fujian Institute of Geological Survey (FIGS) described and analyzed a new 150-million-year-old avialan theropod from Zhenghe County, Fujian Province.
The findings were published in Nature on Sept. 6.
The new species, named Fujianvenator prodigiosus, exhibits a bizarre assembly of morphologies that are shared with other avialans, troodontids, and dromaeosaurids, showing the impact of evolutionary mosaicism in early bird evolution.
"Our comparative analyses show that marked changes in body plan occurred along the early avialan line, which is largely driven by the forelimb, eventually giving rise to the typical bird limb proportion," said Dr. WANG Min from IVPP, lead and corresponding author of the study. "However, Fujianvenator is an odd species that diverged from this main trajectory and evolved bizarre hindlimb architecture."
The surprisingly elongate lower leg and other morphologies, in combination with other geological observations, suggest that Fujianvenator lived in a swamp-like environment and was a high-speed runner or a long-legged wader, representing a previously unknown ecology for early avialans.
"Besides Fujianvenator, we have found abundant other vertebrates, including teleosts, testudines and choristoderes," said XU Liming from FIGS, lead author of the study.
During the Late Jurassic–Early Cretaceous, southeastern China underwent intensive tectonic activities due to subduction of the paleo-Pacific plate, resulting in widespread magmatism and coeval fault-depression basins, where Fujianvenator was found. This geological background is essentially the same as in the Late Jurassic in north and northeastern China, where the older Yanliao Biota is preserved.
"The extraordinary diversity, unique vertebrate composition, and paleoenvironment strongly indicate that this locality documents a terrestrial fauna, which we named the Zhenghe Fauna," said Dr. ZHOU Zhonghe from IVPP, co-author of the study. In-situ radioisotopic dating and stratigraphic surveys constrain the Zhenghe Fauna to the period from 150–148 Ma. Therefore, Fujianvenator documents one of the stratigraphically youngest and geographically southernmost members of the Jurassic avialans.
The discovery of the Zhenghe Fauna opens a new window into the Late Jurassic terrestrial ecosystem of the planet, and the joint research team from IVPP and FIGS plan to continue their exploration of Zhenghe and nearby areas.
Photograph and interpretive line drawing of the 150-million-year-old avialan theropod Fujianvenator prodigiosus, with a phylogeny and paleomap showing the locality of the Zhenghe Fauna (red star)
Morphometric space of body plan and cursoriality of Fujianvenator prodigiosus, compared with other Mesozoic theropods
Stratigraphic log and vertebrate fossil assemblage discovered in the Late Jurassic Zhenghe Fauna
CREDIT
WANG Min
JOURNAL
Nature
ARTICLE TITLE
A new avialan theropod from an emerging Jurassic terrestrial fauna
ARTICLE PUBLICATION DATE
6-Sep-2023
