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A 380-million-year old predatory fish from Central Australia is finally named after decades of digging
More than 380 million years ago, a sleek, air-breathing predatory fish patrolled the rivers of central Australia. Today, the sediments of those rivers are outcrops of red sandstone in the remote outback.
Our new paper, published in the Journal of Vertebrate Paleontology, describes the fossils of this fish, which we have named Harajicadectes zhumini.
Known from at least 17 fossil specimens, Harajicadectes is the first reasonably complete bony fish found from Devonian rocks in central Australia. It has also proven to be a most unusual animal.
Meet the biter
The name means “Min Zhu’s Harajica-biter”, after the location where its fossils were found, its presumed predatory habits, and in honour of eminent Chinese palaeontologist Min Zhu, who has made many contributions to early vertebrate research.
Harajicadectes was a fish in the Tetrapodomorpha group. This group had strongly built paired fins and usually only a single pair of external nostrils.
Tetrapodomorph fish from the Devonian period (359–419 million years ago) have long been of great interest to science. They include the forerunners of modern tetrapods – animals with backbones and limbs such as amphibians, reptiles, birds and mammals.
For example, recent fossil discoveries show fingers and toes arose in this group.
Devonian fossil sites in northwestern and eastern Australia have produced many spectacular discoveries of early tetrapodomorphs.
But until our discovery, the poorly sampled interior of the continent had only offered tantalising fossil fragments.
A long road to discovery
Our species description is the culmination of 50 years of tireless exploration and research.
Palaeontologist Gavin Young from the Australian National University made the initial discoveries in 1973 while exploring the Middle-Late Devonian Harajica Sandstone on Luritja/Arrernte country, more than 150 kilometres west of Alice Springs (Mparntwe).
Packed within red sandstone blocks on a remote hilltop were hundreds of fossil fishes. The vast majority of them were small Bothriolepis – a type of widespread prehistoric fish known as a placoderm, covered in box-like armour.
Scattered among them were fragments of other fishes. These included a lungfish known as Harajicadipterus youngi, named in honour of Gavin Young and his years of work on material from Harajica.
There were also spines from acanthodians (small, vaguely shark-like fish), the plates of phyllolepids (extremely flat placoderms) and, most intriguingly, jaw fragments of a previously unknown tetrapodomorph.
Many more partial specimens of this Harajica tetrapodomorph were collected in 1991, including some by the late palaeontologist Alex Ritchie.
There were early attempts at figuring out the species, but this proved troublesome. Then, our Flinders University expedition to the site in 2016 yielded the first almost complete fossil of this animal.
This beautiful specimen demonstrated that all the isolated bits and pieces collected over the years belonged to a single new type of fish. It is now in the collections of the Museum and Art Gallery of the Northern Territory, serving as the type specimen of Harajicadectes.
A strange apex predator
Up to 40 centimetres long, Harajicadectes is the biggest fish found in the Harajica rocks. Likely the top predator of those ancient rivers, its big mouth was lined with closely-packed sharp teeth alongside larger, widely spaced triangular fangs.
It seems to have combined anatomical traits from different tetrapodomorph lineages via convergent evolution (when different creatures evolve similar features independently). An example of this are the patterns of bones in its skull and scales. Exactly where it sits among its closest relatives is difficult to resolve.
The most striking and perhaps most important features are the two huge openings on the top of the skull called spiracles. These typically only appear as minute slits in most early bony fishes.
Similar giant spiracles also appear in Gogonasus, a marine tetrapodomorph from the famous Late Devonian Gogo Formation of Western Australia. (It doesn’t appear to be an immediate relative of Harajicadectes.)
They are also seen in the unrelated Pickeringius, an early ray-finned fish that was also at Gogo.
The earliest air-breathers?
Other Devonian animals that sported such spiracles were the famous elpistostegalians – freshwater tetrapodomorphs from the Northern Hemisphere such as Elpistostege and Tiktaalik.
These animals were extremely close to the ancestry of limbed vertebrates. So, enlarged spiracles seem to have arisen independently in at least four separate lineages of Devonian fishes.
The only living fishes with similar structures are bichirs, African ray-finned fishes that live in shallow floodplains and estuaries. It was recently confirmed they draw surface air through their spiracles to aid survival in oxygen-poor waters.
That these structures appeared roughly simultaneously in four Devonian lineages provides a fossil “signal” for scientists attempting to reconstruct atmospheric conditions in the distant past.
It could help us uncover the evolution of air breathing in backboned animals.
Brian Choo, Postdoctoral fellow in vertebrate palaeontology, Flinders University; Alice Clement, Research Associate in the College of Science and Engineering, Flinders University, and John Long, Strategic Professor in Palaeontology, Flinders University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Scientists shocked to discover new species of green anaconda, the world’s biggest snake
The green anaconda has long been considered one of the Amazon’s most formidable and mysterious animals. Our new research upends scientific understanding of this magnificent creature, revealing it is actually two genetically different species. The surprising finding opens a new chapter in conservation of this top jungle predator.
Green anacondas are the world’s heaviest snakes, and among the longest. Predominantly found in rivers and wetlands in South America, they are renowned for their lightning speed and ability to asphyxiate huge prey then swallow them whole.
My colleagues and I were shocked to discover significant genetic differences between the two anaconda species. Given the reptile is such a large vertebrate, it’s remarkable this difference has slipped under the radar until now.
Conservation strategies for green anacondas must now be reassessed, to help each unique species cope with threats such as climate change, habitat degradation and pollution. The findings also show the urgent need to better understand the diversity of Earth’s animal and plant species before it’s too late.
An impressive apex predator
Historically, four anaconda species have been recognised, including green anacondas (also known as giant anacondas).
Green anacondas are true behemoths of the reptile world. The largest females can grow to more than seven metres long and weigh more than 250 kilograms.
The snakes are well-adapted to a life lived mostly in water. Their nostrils and eyes are on top of their head, so they can see and breathe while the rest of their body is submerged. Anacondas are olive-coloured with large black spots, enabling them to blend in with their surroundings.
The snakes inhabit the lush, intricate waterways of South America’s Amazon and Orinoco basins. They are known for their stealth, patience and surprising agility. The buoyancy of the water supports the animal’s substantial bulk and enables it to move easily and leap out to ambush prey as large as capybaras (giant rodents), caimans (reptiles from the alligator family) and deer.
Green anacondas are not venomous. Instead they take down prey using their large, flexible jaws then crush it with their strong bodies, before swallowing it.
As apex predators, green anacondas are vital to maintaining balance in their ecosystems. This role extends beyond their hunting. Their very presence alters the behaviour of a wide range of other species, influencing where and how they forage, breed and migrate.
Anacondas are highly sensitive to environmental change. Healthy anaconda populations indicate healthy, vibrant ecosystems, with ample food resources and clean water. Declining anaconda numbers may be harbingers of environmental distress. So knowing which anaconda species exist, and monitoring their numbers, is crucial.
To date, there has been little research into genetic differences between anaconda species. Our research aimed to close that knowledge gap.
Untangling anaconda genes
We studied representative samples from all anaconda species throughout their distribution, across nine countries.
Our project spanned almost 20 years. Crucial pieces of the puzzle came from samples we collected on a 2022 expedition to the Bameno region of Baihuaeri Waorani Territory in the Ecuadorian Amazon. We took this trip at the invitation of, and in collaboration with, Waorani leader Penti Baihua. Actor Will Smith also joined the expedition, as part of a series he is filming for National Geographic.
We surveyed anacondas from various locations throughout their ranges in South America. Conditions were difficult. We paddled up muddy rivers and slogged through swamps. The heat was relentless and swarms of insects were omnipresent.
We collected data such as habitat type and location, and rainfall patterns. We also collected tissue and/or blood from each specimen and analysed them back in the lab. This revealed the green anaconda, formerly believed to be a single species, is actually two genetically distinct species.
The first is the known species, Eunectes murinus, which lives in Perú, Bolivia, French Guiana and Brazil. We have given it the common name “southern green anaconda”. The second, newly identified species is Eunectes akayima or “northern green anaconda”, which is found in Ecuador, Colombia, Venezuela, Trinidad, Guyana, Suriname and French Guiana.
We also identified the period in time where the green anaconda diverged into two species: almost 10 million years ago.
The two species of green anaconda look almost identical, and no obvious geographical barrier exists to separate them. But their level of genetic divergence – 5.5% – is staggering. By comparison, the genetic difference between humans and apes is about 2%.
Preserving the web of life
Our research has peeled back a layer of the mystery surrounding green anacondas. This discovery has significant implications for the conservation of these species – particularly for the newly identified northern green anaconda.
Until now, the two species have been managed as a single entity. But each may have different ecological niches and ranges, and face different threats.
Tailored conservation strategies must be devised to safeguard the future of both species. This may include new legal protections and initiatives to protect habitat. It may also involve measures to mitigate the harm caused by climate change, deforestation and pollution — such as devastating effects of oil spills on aquatic habitats.
Our research is also a reminder of the complexities involved in biodiversity conservation. When species go unrecognised, they can slip through the cracks of conservation programs. By incorporating genetic taxonomy into conservation planning, we can better preserve Earth’s intricate web of life – both the species we know today, and those yet to be discovered.
Bryan G. Fry, Professor of Toxicology, School of the Environment, The University of Queensland
This article is republished from The Conversation under a Creative Commons license. Read the original article.
If humans disappeared, what would happen to our dogs?
Shutterstock Bradley Smith, CQUniversity Australia and Mia Cobb, The University of MelbourneFor many of us, dogs are our best friends. But have you wondered what would happen to your dog if we suddenly disappeared? Can domestic dogs make do without people?
At least 80% of the world’s one billion or so dogs actually live independent, free-ranging lives – and they offer some clues. Who would our dogs be if we weren’t around to influence and care for them?
What are dogs?
Dogs hold the title of the most successful domesticated species on Earth. For millennia they have evolved under our watchful eye. More recently, selective breeding has led to people-driven diversity, resulting in unique breeds ranging from the towering Great Dane to the tiny Chihuahua.
Humanity’s quest for the perfect canine companion has resulted in more than 400 modern dog breeds with unique blends of physical and behavioural traits. Initially, dogs were bred primarily for functional roles that benefited us, such as herding, hunting and guarding. This practice only emerged prominently over the past 200 years.
Some experts suggest companionship is just another type of work humans selected dogs for, while placing a greater emphasis on looks. Breeders play a crucial role in this, making deliberate choices about which traits are desirable, thereby influencing the future direction of breeds.
Are we good for dogs?
We know certain features that appeal to people have serious impacts on health and happiness. For instance, flat-faced dogs struggle with breathing due to constricted nasal passages and shortened airways. This “air hunger” has been likened to experiencing an asthma attack. These dogs are also prone to higher rates of skin, eye and dental problems compared with dogs with longer muzzles.
Many modern dogs depend on human medical intervention to reproduce. For instance, French Bulldogs and Chihuahuas frequently require a caesarean section to give birth, as the puppies’ heads are very large compared with the mother’s pelvic width. This reliance on surgery to breed highlights the profound impact intensive selective breeding has on dogs.
And while domestic dogs can benefit from being part of human families, some live highly isolated and controlled lives in which they have little agency to make choices – a factor that’s important to their happiness.
Dogs without us
Now imagine a world where dogs are free from the guiding hand of human selection and care. The immediate impact would be stark. Breeds that are heavily dependent on us for basic needs such as food, shelter and healthcare wouldn’t do well. They would struggle to adapt, and many would succumb to the harsh realities of a life without human support.
That said, this would probably impact fewer than 20% of all dogs (roughly the percentage living in our homes). Most of the world’s dogs are free-ranging and prevalent across Europe, Africa and Asia.
But while these dogs aren’t domesticated in a traditional sense, they still coexist with humans. As such, their survival depends almost exclusively on human-made resources such as garbage dumps and food handouts. Without people, natural selection would swiftly come into play. Dogs that lack essential survival traits such as adaptability, hunting skills, disease resistance, parental instincts and sociability would gradually decline.
Dogs that are either extremely large or extremely small would also be at a disadvantage, because a dog’s size will impact its caloric needs, body temperature regulation across environments, and susceptibility to predators.
Limited behavioural strategies, such as being too shy to explore new areas, would also be detrimental. And although sterilised dogs might have advantageous survival traits, they would be unable to pass their genes on to future generations.
No more designer breeds
Ultimately, a different type of dog would emerge, shaped by health and behavioural success rather than human desires.
Dogs don’t select mates based on breed, and will readily mate with others that look very different to them when given the opportunity. Over time, distinct dog breeds would fade and unrestricted mating would lead to a uniform “village dog” appearance, similar to “camp dogs” in remote Indigenous Australian communities and dogs seen in South-East Asia.
These dogs typically have a medium size, balanced build, short coats in various colours, and upright ears and tails. However, regional variations such as a shaggier coat could arise due to factors such as climate.
In the long term, dogs would return to a wild canid lifestyle. These “re-wilded” dogs would likely adopt social and dietary behaviours similar to those of their current wild counterparts, such as Australia’s dingoes. This might include living in small family units within defined territories, reverting to an annual breeding season, engaging in social hunting, and attentive parental care (especially from dads).
This transition would be more feasible for certain breeds, particularly herding types and those already living independently in the wild or as village dogs.
What makes a good life for dogs?
In their book A Dog’s World, Jessica Pierce and Marc Bekoff explore the idea of “doomsday prepping” our dogs for a future without people. They encourage us to give our dogs more agency, and consequently more happiness. This could be as simple as letting them pick which direction to walk in, or letting them take their time when sniffing a tree.
As we reflect on a possible future without dogs, an important question arises: are our actions towards dogs sustainable, in their best interests, and true to their nature? Or are they more aligned with our own desires?
By considering how dogs might live without us, perhaps we can find ways to improve their lives with us.
Bradley Smith, Senior Lecturer in Psychology, CQUniversity Australia and Mia Cobb, Research Fellow, Animal Welfare Science Centre, The University of Melbourne
This article is republished from The Conversation under a Creative Commons license. Read the original article.