We received an email earlier this week with an enquiry about the term allometric growth which had been found in a scientific paper the emailer had been reading. Our emailer wrote to ask what did this term mean?
Allometric growth is a term used to describe the growth of an organism whereby different parts develop at different rates. The appearance of the organism will change as it grows and matures.
Triceratops Allometric Growth
In the picture (above) a model of a juvenile Triceratops is compared with a model of a fully-grown, mature Triceratops. In the juvenile the head is proportionately larger and the skull frill and horns are very different in their morphology compared to the adult. This is an example of allometric growth. Allometry is the study of body size relative to body shape, it is often partnered in scientific papers with ontogeny which is the term used to describe how organisms develop and grow.
The Chinese model-making company PNSO have recently introduced some replicas that demonstrate how dinosaurs changed as they grew and matured. For example, the company recently introduced (2022), a 1:35 scale replica of an adult chasmosaurine ceratopsian (Torosaurus latus) and a juvenile. The models, entitled Aubrey and Dabei were supplied with posters and a full-colour, illustrated booklet.
In episode four (Ice Worlds) of the acclaimed television series “Prehistoric Planet”, a troodontid dinosaur is depicted deliberately spreading a forest fire. Is this behaviour plausible? This Apple TV+ series has been praised for depicting prehistoric animals not as movie monsters but as animals capable of complex behaviours as seen in living relatives. The behaviour of many of the dinosaurs in the documentary series reflects behaviour observed and documented in birds.
Lead scientific consultant for the five-part, nature documentary series, vertebrate palaeontologist and author Darren Naish has used his extensive knowledge of the living world to create realistic scenarios illustrating behaviours of long extinct creatures.
For example, the troodontid is depicted carefully selecting a burning ember and carrying it to another, as yet unburnt, part of the forest in order to deliberately start a fire. Fire starting is a behaviour that has been observed in some species of birds.
Forest Fires Provide an Opportunity for Hunters
Flames and smoke from a forest fire, presumably started by lightning would cause animals to flee and a hunter like a troodontid could patrol the fringes of the fire and ambush any small mammal, lizards or birds that had been panicked and were attempting to avoid the flames.
In the scene which features the troodontid, this clever little dinosaur (troodontids having relatively large brains in proportion to their body size), chooses an ember and deliberately carries it to another part of the forest to in order to spread the fire.
Australian Fire Hawks
Indigenous Australians have reported that certain types of bird intentionally spread fires in order to exploit feeding opportunities. People in northern Australia have considered the black kite (Milvus migrans), the whistling kite (Haliastur sphenurus) and the brown falcon (Falco berigora) to be “fire hawks” picking up smouldering debris moving it some distance and then dropping it in a bid to spread the conflagration. Some of the observations and anecdotes were reported in a scientific paper published in the “Journal of Ethnobiology”.
The paper attempted to document evidence supporting the theory that many birds of prey used fires to help them find food, making easy meals out of insects and other small animals attempting to avoid the blaze.
Co-author of the scientific paper, which was published in 2017, Mark Bonta (Pennsylvania State University), commented:
“We’re not discovering anything. Most of the data that we’ve worked with is collaborative with Aboriginal peoples. They’ve known this for probably 40,000 years or more.”
Other Scientists are Sceptical
Some experts have expressed scepticism, whether these birds were intentionally spreading fires or were seen to pick up sticks as a consequence of darting down to capture prey but missing their intended target.
Anthony Molyneux of the Alice Springs Desert Park commented:
“If [hawks] have missed the prey and perhaps grabbed a stick, they will drop that stick or rock. If the stick is smouldering or on fire, then it will start another fire.”
In a 2016 interview with the Australian Broadcasting Corporation, Bob Gosford, an Australian indigenous-rights lawyer and ornithologist explained that these raptors thrive in areas where wildfires are common.
In the interview he stated:
“It’s a feeding frenzy, because out of these grasslands come small birds, lizards, insects, everything fleeing the front of the fire.”
There have been many first-hand accounts of hawks and other birds of prey picking up burning sticks in their claws and dropping them in a fresh area of dry grass several hundred metres away to start another fire.
No one can ever know whether troodontids or other theropod dinosaurs indulged in this fire-spreading behaviour, but research is on-going to determine whether their close relatives (birds) deliberately spread fires.
It certainly made an intriguing and thought-provoking segment in the documentary series.
The scientific paper: “Intentional Fire-Spreading by “Firehawk” Raptors in Northern Australia” by Mark Bonta, Robert Gosford, Dick Eussen, Nathan Ferguson, Erana Loveless, Maxwell Witwer published in the Journal of Ethnobiology.
One in five species of reptile is threatened with extinction. A team of international scientists including researchers from the Zoological Society of London, the University of Witwatersrand (Johannesburg, South Africa), Monash University (Victoria, Australia) and the Biodiversity Assessment Unit, IUCN-Conservation International based in Washington DC (USA), have conducted a comprehensive extinction-risk assessment of the class Reptilia. Writing in the academic journal “Natural” the team conclude that at least 1,829 out of 10,196 species of reptile (21.1%) are threatened.
Agriculture, Logging, Urban Development and Invasive Species
A global assessment of the risk of extinction to species of reptile has been lacking, although similar studies have been undertaken for the other tetrapods such as amphibians, mammals and birds. The researchers conclude that reptiles are threatened by the same major factors that threaten other tetrapods— agriculture, logging, urban development and invasive species, although the threat posed by climate change remains uncertain. Many species of reptile live in extremely arid or desert regions, this comprehensive study reveals that it is those reptiles that live in forests that face the greatest threat.
Reptiles Threatened with Extinction
The scientists discovered that birds, mammals and amphibians are unexpectedly good surrogates for the conservation of reptiles. The study revealed that efforts to conserve other threatened tetrapods (mammals, birds and amphibians) are more likely than expected to co-benefit many threatened species of reptile. Although reptiles are well known to inhabit arid habitats such as deserts and scrubland, most reptile species occur in forested habitats, where they and other vertebrate groups, suffer from threats such as logging and conversion of forest to agriculture. The study found that 30% of forest-dwelling reptiles are at risk of extinction, compared with 14% of reptiles in arid habitats.
An Urgent Multifaceted Plan is Needed
Neil Cox, co-leader of the study and Manager of the IUCN-Conservation International Biodiversity Assessment Unit in Washington DC stated:
“The results of the Global Reptile Assessment signal the need to ramp up global efforts to conserve them. Because reptiles are so diverse, they face a wide range of threats across a variety of habitats. A multifaceted action plan is necessary to protect these species, with all the evolutionary history they represent.”
The report states that although some reptiles including most species of crocodiles and turtles require urgent, targeted action to prevent extinctions, efforts to protect other tetrapods, such as habitat preservation and control of trade and invasive species, will probably also benefit many reptiles.
Everything Dinosaur acknowledges the assistance of a media release from the International Union for Conservation of Nature (IUCN) in the compilation of this article.
The scientific paper: “A global reptile assessment highlights shared conservation needs of tetrapods” by Neil Cox, Bruce E. Young, Philip Bowles, Miguel Fernandez, Julie Marin et al published in Nature.
At Everything Dinosaur, we are always amazed by the variety of prehistoric animal themed products that are available to fans of prehistoric life. Take for example, a new board game in development that has been inspired by palaeontology. We were contacted by Brett, one of the developers of “Holotype”, a fast-paced, worker placement game designed for 2-5 participants. Players get the chance to role play the life and work of a vertebrate palaeontologist.
A Kickstarter Project
This innovative, light-strategy board game has its own kickstarter funding page and the project has already received hundreds of backers.
Brett very kindly provided more details to Everything Dinosaur, commenting that the object of the game was to further the field of palaeontology by collecting specimens, undertaking research and getting findings published in scientific journals. “Holotype” focuses on the major fossil formations and prehistoric animals associated with North America, but other regional variations of this game, such as a version exploring the prehistoric animals of Europe, have been proposed.
Throughout the gameplay, players deploy their palaeontologist, graduate student and field assistant workers to perform various actions. Players can search for fossils by rolling fossil dice on field expeditions, conduct research at the university library and access museum collections to exchange fossils and to further their ambitions.
A Palaeontology Board Game – “Holotype”
By making discoveries and expanding scientific knowledge, players ultimately aim to have their research on holotypes published in prestigious scientific journals. Victory points are awarded as the player’s career in palaeontology advances.
As the game progresses, special milestones are unlocked to make each player’s gameplay unique. Semi-collaborative global objectives and private personal objectives ensure that every game will be different.
With a playing time estimated at around 1-2 hours, the winner is the person who has gained the most points through their research which resulted in published holotypes and the achievement of personal and global objectives.
The media release sent to Everything Dinosaur states:
“The goal of the developers was to create a game that would appeal to avid board gamers and palaeontology fans alike. The game features 60 unique dinosaurs and marine reptiles from the Mesozoic Era across North America, fossil-bearing geologic formations, and objectives referencing modern palaeontology concepts such as cladistics and taxonomy.”
Scientists from the University of Tel Aviv in collaboration with colleagues from the University of Napoli have published a study that suggests having a small brain relative to your body size predisposed Late Quaternary mammals to extinction. If you were a “smart” mammal, with a relatively big brain in proportion to your body size, you were less likely to become extinct.
The Extinction of Megafauna
The Late Quaternary is marked by a drastic global extinction event, mainly of large-bodied, land mammals. Causes proposed for these extinctions include overhunting by an increasing human population, particularly in areas such as the Americas and Oceania where modern humans had been largely absent previously. Earlier papers had proposed that species with traits that make them less prone to human hunting (arboreal, nocturnal, or forest dwelling) were more likely to survive.
However, the rapid decline and extinction of large, terrestrial animals is linked to the end of the last glacial period (25,000 to 12,000 years ago) which saw dramatic climate change. The research team hypothesised that the large mammals that survived the extinctions might have been endowed with larger brain sizes than those that perished. Larger brains might have helped these animals to adapt better and to cope with the wild fluctuations in climate.
To test this idea, the scientists assembled data on the brain size of 291 living mammal species plus 50 more that went extinct during the Late Quaternary.
The team found that models that used brain size in addition to body size predicted extinction status better than models that used only body size. It was concluded that possessing a large brain was an important, yet so far neglected and rarely studied characteristic of surviving megafauna species.
Implications for Large Mammals Living Today
One prominent feature shared by many extinct taxa was their large body size. In mammals, body size is correlated with several traits, including low population density, small population size, long lifespans, extended gestation periods along with prolonged inter-birth intervals and low fecundity.
Brain size is strongly correlated with body size as well and yet, mammals of similar size can have greatly different brain sizes.
In studies of modern birds and mammals, large brains have been found to improve survivability as these animals can modify their behaviour and adapt to rapidly changing environments and new threats such as an expanding human population.
When considering which animals around today might be under the most severe threat of extinction, brain-size should be considered when calculating the risk factors.
The paper published as an open access document in “Scientific Reports”
The scientific paper: “Small brains predisposed Late Quaternary mammals to extinction” by Jacob Dembitzer, Silvia Castiglione, Pasquale Raia and Shai Meiri published in Scientific Reports.
An almost perfectly preserved specimen of the very bird-like theropod Caudipteryx has provided researchers with evidence of organic molecule preservation at a cellular and nuclear level. Writing in “Communications Biology”, scientists from the Institute of Vertebrate Palaeontology and Palaeoanthropology of the Chinese Academy of Sciences, in collaboration with colleagues from the Shandong Tianyu Museum of Nature (Shandong Province, eastern China), report on a study of fossilised cells from cartilage associated with a Caudipteryx thigh bone that reveal exquisite molecular preservation.
Fragments from a Femur
The specimen (number STM4-3), is in the Shandong Tianyu Museum of Nature vertebrate fossil collection, one of the largest collections of dinosaur fossils in the world. It was collected from the Yixian Formation near Chaoyang City, Dapingfang Town (Liaoning Province) and is almost complete and partially articulated. Gastroliths are preserved in the stomach cavity and the outline of some feathers can also be seen. A right femur, measuring 15 cm in length was examined, a fragment removed representing cartilage and divided into three portions to permit detailed scanning electron microscopy (SEM), histochemical staining, energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) along with chemical analysis.
The research team realised that some cells had been mineralised by silicification after the death of the animal. This silicification is most likely what permitted the excellent preservation of these cells.
Li Zhiheng, an Associate Professor at the Institute of Vertebrate Palaeontology and Palaeoanthropology and a co-author of the study commented that the discovery of cellular preservation in the cartilage was not unexpected stating:
“Geological data has accumulated over the years and shown that fossil preservation in the Jehol Biota was exceptional due to fine volcanic ashes that entombed the carcasses and preserved them down to the cellular level”.
Healthy Cells and Unhealthy, Dying Cells
The researchers discovered two main types of cells, cells that were healthy at the time of fossilisation, along with unhealthy cells that were porous and fossilised while in the process of dying.
Co-author Alida Bailleul (Institute of Vertebrate Palaeontology and Palaeoanthropology), explained:
“It is possible that these cells were already dying even before the animal died”.
Cell death is a process that occurs naturally throughout the lives of all organisms. But being able to identify a fossilised cell at a specific life stage within the cell cycle is quite new in palaeontology.
Staining the Nuclei of Dinosaur Cells
The team isolated some cells and stained them with a purple chemical used by biologists to identify nuclei material. This chemical, hematoxylin, is known to bind to the nuclei of cells. Cells from a chicken were also stained to provide an extant comparison. One dinosaur cell showed a purple nucleus with some darker purple threads. This provides strong evidence to support the idea that the 125-million-year-old dinosaur cell has a nucleus so well-preserved that it retains some original biomolecules and threads of chromatin.
Chromatin is found within the cells of all living organisms. It consists of tightly packed DNA molecules. The results of this study thus provide preliminary data suggesting that remnants of original dinosaur DNA may still be preserved.
Much Further Work is Required
Whilst highlighting the significance of this study, after all discovering that 125-million-year-old dinosaur cells react to hematoxylin staining in the same way as living cells is remarkable, the researchers concede that a much more refined and precise approach will be required if dinosaur DNA is to be identified and recovered in any quantity.
In 2020, Everything Dinosaur reported upon the discovery of chromosome-like chromatin threads preserved in the fossilised cartilage of a 75-million-year-old hadrosaur (Hypacrosaurus stebingeri). This study identified nuclear and cellular preservation which was previously unknown in a Cretaceous fossil specimen. To read our article: Cartilage, Proteins and Potential Dinosaur DNA?
The scientific paper: “Nuclear preservation in the cartilage of the Jehol dinosaur Caudipteryx” by Xiaoting Zheng, Alida M. Bailleul, Zhiheng Li, Xiaoli Wang and Zhonghe Zhou published in Communications Biology.
New research published in the journal “Nature Communications” suggests that all extant snakes evolved from just a handful of species that survived the K-Pg extinction event 66 million years ago. The researchers conclude that this catastrophic extinction event, that wiped out the non-avian dinosaurs and something like 75% of all terrestrial life, was a form of “creative destruction” leading to a burst of evolutionary development within the Serpentes.
Snakes benefited from the extinction event, the loss of so many competitors allowed them to diversify rapidly and to occupy new niches in food chains.
The Snake Fossil Record
The fossil record of snakes is relatively poor because snake skeletons are typically small and fragile making the preservation of fossil material a rare event.
It is generally accepted that snakes (Suborder Serpentes), evolved from lizards. Snakes gradually losing their limbs, whether the first snakes were burrowers and evolved from burrowing lizards or whether the first snakes were adapted to a life in marine environments is an area of on-going debate between vertebrate palaeontologists. For example, in 2016 a team of scientists challenged the conclusions from the paper that described Tetrapodophis amplectus, a primitive snake-like animal from the Lower Cretaceous of Brazil. It had been suggested that T. amplectus, which had been described and named the year before, was adapted to a life underground, however, researchers from Canada and Australia challenged this view and proposed a marine habit for this 20 cm long animal that has been classified as being close to the base of the evolutionary lineage of true snakes.
The research, led by scientists at the University of Bath in collaboration with researchers from Cambridge, Bristol and Germany, involved examining snake fossils and an analysis of the genomes of living snakes to pinpoint genetic differences permitting a picture of modern snake evolution to be built up.
The results indicate that despite the great variety of snakes alive today – cobras, vipers, pythons, boas, sea snakes and blind, burrowing snakes for example, all extant snakes can be traced back to a handful of species that survived the K-Pg extinction event that took place 66 million years ago.
Snake Survival Strategy
The authors postulate that the ability of snakes to shelter underground and go for long periods without food helped them survive the destructive effects of the bolide impact event. In the aftermath, the extinction of their competitors including Cretaceous snakes and small theropod dinosaurs, permitted snakes to move into new niches, new habitats and new parts of the world. Today, snakes are found in all but the highest latitudes and are present on every continent except Antarctica.
The researchers, which included lead author Dr Catherine Klein, a former graduate of Bath University but now based at the Alexander-Universität Erlangen-Nürnberg (FAU) in Germany, state that modern snake diversity – including tree snakes, sea snakes, venomous vipers and cobras, and huge constrictors like boas and pythons – emerged only after the non-avian dinosaur extinction.
Dr Klein commented:
“It’s remarkable, because not only are they surviving an extinction that wipes out so many other animals, but within a few million years they are innovating, using their habitats in new ways.”
A Change in Snake Vertebrae
Fossils also show a change in the shape of snake vertebrae in the aftermath, resulting from the extinction of Cretaceous lineages and the appearance of new groups, including giant sea snakes, such as Gigantophis garstini from the Eocene of northern Africa which may have reached a length of ten metres. Gigantophis was scientifically described in 1901, it was thought to have been the largest snake to have ever lived, until in 2009 when the giant, South American boa – Titanoboa cerrejonensis was described.
Rapidly Spreading Around the Globe
The research team also suggest that snakes began to spread rapidly around the globe. The “Greenhouse Earth” conditions that occurred close to the boundary between the Palaeocene and Eocene Epochs that led to the establishment of extensive tropical forests in the Northern Hemisphere, would have facilitated the geographical spread of cold-blooded animals such as snakes.
Although the ancestor of living snakes probably lived somewhere in the Southern Hemisphere, snakes first appear to have spread to Asia after the extinction event.
Corresponding author, Dr Nick Longrich, from the Milner Centre for Evolution (University of Bath), explained:
“Our research suggests that extinction acted as a form of “creative destruction”- by wiping out old species, it allowed survivors to exploit the gaps in the ecosystem, experimenting with new lifestyles and habitats. This seems to be a general feature of evolution – it’s the periods immediately after major extinctions where we see evolution at its most wildly experimental and innovative. The destruction of biodiversity makes room for new things to emerge and colonise new landmasses. Ultimately life becomes even more diverse than before.”
Further Serpentes Evolution Driven by Climate Change
The researchers also found evidence for a second major diversification event around the time that the world shifted from a warm and moist climate to a colder, more seasonal climate (Oligocene Epoch).
It seems, that for the snakes at least, global catastrophes can have their upsides. The patterns seen in snake evolution hint at the key role played by mass extinction events – they are the catalysts for driving rapid evolutionary changes.
The scientific paper: “Evolution and dispersal of snakes across the Cretaceous-Paleogene mass extinction” by Catherine G. Klein, Davide Pisani, Daniel J. Field, Rebecca Lakin, Matthew A. Wills and Nicholas R. Longrich published in Nature Communications.
Specimens of a strange, recently extinct crocodile housed at the American Museum of Natural History (New York), have helped unravel a mystery surrounding the evolutionary relationships of crocodilians. The skulls belong to the horned crocodile of Madagascar (Voay robustus) and a research team has demonstrated that it was closely related to “true crocodiles” – Crocodylus, making it the closest species to the common ancestor of the crocodile genus.
When the first Europeans came to Madagascar the native Malagasy people told them about two distinct types of crocodiles that lived on their island. There was a gracile form that preferred rivers, this was identified as a population of Nile crocodiles (Crocodylus niloticus), but the swamps and lakes were home to a crocodile that the early explorers had never seen before. This second type was a much more heavy-set and powerful animal with two, bony bumps at the top of its skull.
When first named and described in 1872 (Grandidier and Vaillant), it was thought to be a species of true crocodile – a member of the Crocodylus genus. More recent studies have suggested affinities with the dwarf crocodiles (Osteolaeminae), however, with an estimated length of around 5 metres V. robustus was much larger than any other species assigned to this group.
New research published in the academic journal Communications Biology, which used DNA extracted from the American Museum of Natural History specimens, has resolved the phylogeny of this enigmatic reptile. Carbon dating of the material used in the study confirms that the horned crocodile probably survived until just a few hundred years ago.
One of the authors of the scientific paper, Evon Hekkala, a research associate at the American Museum of Natural History stated:
“This crocodile was hiding out on the island of Madagascar during the time when people were building the pyramids and was probably still there when pirates were getting stranded on the island. They blinked out just before we had the modern genomic tools available to make sense of the relationships of living things. And yet, they were the key to understanding the story of all the crocodiles alive today.”
Mitochondrial DNA extracted from sub-fossil specimens found during a Franco-Anglo-American expedition to south-western Madagascar (1927 to 1930), demonstrates that V. robustus was not a true crocodile but very closely related to that lineage that led to them. Being placed next to the true crocodiles on an evolutionary tree suggests that it was the closest species to the common ancestor of extant members of the Crocodylus genus.
Co-author George Amato, (American Museum of Natural History), explained:
“This is a project we’ve tried to do on and off for many years, but the technology just hadn’t advanced enough, so it always failed. But in time, we had both the computational setup and the paleogenomic protocols that could actually fish out this DNA from the fossil and finally find a home for this species.”
“Teasing apart the relationships of modern crocodiles is really difficult because of the physical similarities,” Hekkala added. “Many people don’t even realise that there are multiple species of crocodiles, and they see them as this animal that’s unchanging through time. But we’ve been trying to get to the bottom of the great diversity that exists among them.”
The close affinity of Voay to Crocodylus lends weight to the idea that Crocodylus originated in Africa and then dispersed into the Americas and Asia/Australia. Competing theories have proposed an Asian origin for Crocodylus but as Voay was restricted to Madagascar and has been cited as the closest species to the true crocodiles, this DNA analysis lends weight to the “African origins” idea.
The scientific paper: “Paleogenomics illuminates the evolutionary history of the extinct Holocene “horned” crocodile of Madagascar, Voay robustus” by E. Hekkala, J. Gatesy, A. Narechania, R. Meredith, M. Russello, M. L. Aardema, E. Jensen, S. Montanari, C. Brochu, M. Norell and G. Amato published in Communications Biology.
Scientists have proposed that the bizarre, chicken-sized alvarezsaurid Shuvuuia (S. deserti) had amazing eyesight and owl-like hearing, adaptations for a nocturnal hunter in its Late Cretaceous desert environment.
A Very Bizarre, Tiny Theropod
Named and described in 1998 from fossil material associated with the famous Djadochta Formation (Campanian faunal stage), Shuvuuia has been assigned to the Alvarezsauridae family of theropods. It may have been small (around 60 cm in length), but its skeleton shows a range of bizarre anatomical adaptations. It had long legs, a long tail, short but powerful forelimbs that ended in hands with greatly reduced, vestigial digits except for the thumb which was massive and had a large claw. The skull was very bird-like with disproportionately large orbits.
Writing in the academic journal “Science” a team of scientists led by Professor Jonah Choiniere (University of Witwatersrand, Johannesburg, South Africa), used sophisticated computerised tomography to examine the skull of Shuvuuia and to map this dinosaur’s sensory abilities, as part of a wider study into non-avian dinosaur sensory abilities.
The international team of researchers used CT scanning and detailed measurements to collect data on the relative size of the eyes and inner ears of nearly 100 living bird and extinct dinosaur species. There are more than 10,000 species of bird (avian dinosaurs) alive today, but only a few have evolved sensory abilities that enable them to track and hunt prey at night. Owls are probably the best known, but not all owls are nocturnal.
Kiwis hunt at night using their long, sensitive beaks to probe in the leaf litter for worms, whilst another bird endemic to New Zealand, the large, flightless Kakapo (a member of the parrots – Order Psittaciformes), is also nocturnal. Other birds active at night include the globally widespread black-capped night heron and the Stone-curlew (Burhinus oedicnemus) which is an occasional visitor to East Anglia in the UK.
To measure hearing ability, the team measured the length of the lagena, the organ that processes incoming sound information (known as the cochlea in mammals). The barn owl, which can hunt in complete darkness using hearing alone, has the proportionally longest lagena of any bird.
To examine vision, the team looked at the scleral ring, a series of bones surrounding the pupil, of each species. Like a camera lens, the larger the pupil can open, the more light can get in, enabling better vision at night. By measuring the diameter of the ring, the scientists could estimate how much light the eye can gather.
The researchers found that many carnivorous theropods such as large tyrannosaurs and the much smaller Dromaeosaurus had vision optimised for the daytime, and better-than-average hearing presumably to help them hunt.
However, Shuvuuia, had both extraordinary hearing and night vision. The extremely large lagena of this species is almost identical in relative size to today’s barn owl, suggesting that Shuvuuia could have been a nocturnal hunter. With many predators sharing its Late Cretaceous desert environment, a night-time existence may have proved to be an effective strategy to avoid the attentions of much larger theropods.
Commenting on the significance of this discovery, joint first author of the scientific paper, Dr James Neenan exclaimed:
“As I was digitally reconstructing the Shuvuuia skull, I couldn’t believe the lagena size. I called Professor Choiniere to have a look. We both thought it might be a mistake, so I processed the other ear – only then did we realise what a cool discovery we had on our hands!”
Extremely Large Eyes
The eyes of Shuvuuia were also remarkable. Skull measurements suggest that this little dinosaur had some of the proportionally largest pupils yet measured in birds or dinosaurs, This suggests that they could likely see very well at night.
The Alvarezsauridae remain one of the most unusual of all the types of non-avian dinosaur known to science. Their place within the ecosystems of the Late Cretaceous remains controversial. Geographically widespread, a recently described alvarezsaurid from China Qiupanykus zhangi may have been a specialised ovivore (egg-eater), whilst other palaeontologists have postulated that these theropods used their strong forelimbs and large thumb claws to break into termite mounds. Perhaps, these small (most probably feathered), dinosaurs occupied a number of niches within Late Cretaceous ecosystems – including that of a nocturnal hunter of small vertebrates and insects.
To read Everything Dinosaur’s blog article about Qiupanykus zhangi and the evidence behind the egg-eating theory: Did Alvarezsaurids Eat Eggs?
Everything Dinosaur acknowledges the assistance of a media release from the University of Witwatersrand in the compilation of this article.
The scientific paper: “Evolution of vision and hearing modalities in theropod dinosaurs” by Jonah N. Choiniere, James M. Neenan, Lars Schmitz, David P. Ford, Kimberley E. J. Chapelle, Amy M. Balanoff, Justin S. Sipla, Justin A. Georgi, Stig A. Walsh, Mark A. Norell, Xing Xu, James M. Clark and Roger B. J. Benson published in the journal Science.
The Amazon rainforest is an extremely important low latitude habitat with a huge diversity of animals, fungi and plant species. Described as the “lungs of the planet”, this tropical rainforest is at the very centre of many global conservation efforts. New research suggests that it was the extra-terrestrial impact event some 66 million years ago that led to the rise of this angiosperm dominated ecosystem.
K/Pg Extinction Event
Approximately 66 million years ago a rock from space smashed into our planet. This triggered a sudden mass extinction event devastating around 75% of all the animal and plant terrestrial species, many of which subsequently became extinct. At this time the dinosaurs, their cousins the pterosaurs and the majority of marine reptiles died out.
Analysis of Fossil Pollen and Study of Fossil Leaves
Writing in the journal “Science”, researchers from the Southern Methodist University (Texas) and the University of Wyoming report on the study of tens of thousands of fossil pollen specimens along with thousands of leaf fossils from Cretaceous-aged strata and deposits laid down after the K/Pg extinction event. The scientists, which include co-author Dr Ellen Currano (Department of Botany, University of Wyoming), found that the types of plant creating tropical forests were very different pre and post the extra-terrestrial impact. In the Late Cretaceous tropical forests were dominated by conifers and they were much more open than the dense, angiosperm forests that came about during the Palaeocene.
A Thick Forest Canopy Denying Access to Light
The scientists discovered that the fossil pollen and leaves show a marked transition in tropical forest flora. After the extra-terrestrial impact forests developed a thick canopy blocking much of the light from reaching the ground and angiosperms became more dominant.
How Did These Changes Come About?
As well as the documenting the turnover in flora and the transition from one tropical forest environment to a different type of rainforest in the Palaeocene, the researchers propose three possible explanations for this change:
The absence of large megaherbivores, specifically dinosaurs allowed plant densities in forests to increase. The extinction of giant plant-eating dinosaurs such as the Ceratopsia, hadrosaurs, armoured dinosaurs and the titanosaurs allowed plants to grow at lower levels as they were not being trampled or consumed by herbivorous dinosaurs.
Several types of fern and conifer became extinct during the K/Pg transition permitting new types of angiosperm (flowering plants) to evolve and exploit the vacated niches.
Falling ash from the impact enriched soils throughout the tropics, provided an advantage to faster-growing angiosperms.
The scientists conclude that the three hypotheses are not mutually exclusive and that a combination of factors could have led to the change in the flora as recorded in the fossil record.
A Significant Lesson for Today
Today, a rapidly changing climate, largely caused by the actions of our own species is having a dramatic effect on the world’s forests. The researchers note that the fossil record demonstrates that rainforests do not simply “bounce back”, after a catastrophe. They can take millions of years to recover and a very different type of ecosystem is likely to emerge.
The scientific paper: “The impactful origin of neotropical rainforests” by Bonnie F. Jacobs and Ellen D. Currano published in the journal Science.