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Tyrannosaurids and Other Big Ancient Predators

Started by Recusant, March 16, 2016, 01:12:53 PM

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Recusant

#15
The largest and oldest (in terms of longevity) Tyrannosaurus rex is reported from Canada. I wonder whether the Tyrannosaurs were like sharks--growing their entire lives.

"Paleontologists report world's biggest Tyrannosaurus rex" | ScienceDaily

Quote


The towering and battle-scarred 'Scotty' reported by UAlberta paleontologists is the world's largest Tyrannosaurus rex and the largest dinosaur skeleton ever found in Canada.
Image credit: Amanda Kelley





QuoteUniversity of Alberta paleontologists have just reported the world's biggest Tyrannosaurus rex and the largest dinosaur skeleton ever found in Canada. The 13-metre-long T. rex, nicknamed "Scotty," lived in prehistoric Saskatchewan 66 million years ago.

"This is the rex of rexes," said Scott Persons, lead author of the study and postdoctoral researcher in the Department of Biological Sciences. "There is considerable size variability among Tyrannosaurus. Some individuals were lankier than others and some were more robust. Scotty exemplifies the robust. Take careful measurements of its legs, hips, and even shoulder, and Scotty comes out a bit heftier than other T. rex specimens."

Scotty, nicknamed for a celebratory bottle of scotch the night it was discovered, has leg bones suggesting a living weight of more than 8,800 kg, making it bigger than all other carnivorous dinosaurs. The scientific work on Scotty has been a correspondingly massive project.

The skeleton was first discovered in 1991, when paleontologists including T. rex expert and UAlberta professor Phil Currie were called in on the project. But the hard sandstone that encased the bones took more than a decade to remove -- only now have scientists been able to study Scotty fully-assembled and realize how unique a dinosaur it is.

It is not just Scotty's size and weight that set it apart. The Canadian mega rex also lays claim to seniority.

"Scotty is the oldest T. rex known," Persons explains. "By which I mean, it would have had the most candles on its last birthday cake. You can get an idea of how old a dinosaur is by cutting into its bones and studying its growth patterns. Scotty is all old growth."

[Continues . . .]
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Recusant

A new Allosaurus.  :sidesmile:

"New species of Allosaurus discovered in Utah" | Phys.org

Quote

Idealized skull of Allosaurus jimmadseni in lateral (A), dorsal (B) and posterior (C) views. Skeletal reconstructions of DINO 11541 (D) and MOR 693 (E). Missing elements in indicated in gray. A–C original artwork by Samantha Zimmerman; D and E are modified from artwork by Scott Hartman. Scale bar equals 10 cm for A–C; one m for D and E. [PeerJ]

QuoteA remarkable new species of meat-eating dinosaur has been unveiled at the Natural History Museum of Utah. Paleontologists unearthed the first specimen in early 1990s in Dinosaur National Monument in northeastern Utah. The huge carnivore inhabited the flood plains of western North America during the Late Jurassic Period, between 157-152 million years ago, making it the geologically oldest species of Allosaurus, predating the more well-known state fossil of Utah, Allosaurus fragilis. The newly named dinosaur Allosaurus jimmadseni, was announced today in the open-access scientific journal PeerJ.

The species belongs to the allosauroids, a group of small to large-bodied, two-legged carnivorous dinosaurs that lived during the Jurassic and Cretaceous periods. Allosaurus jimmadseni, possesses several unique features, among them a short narrow skull with low facial crests extending from the horns in front of the eyes forward to the nose and a relatively narrow back of the skull with a flat surface to the bottom of the skull under the eyes. The skull was weaker with less of an overlapping field of vision than its younger cousin Allosaurus fragilis. Allosaurus jimmadseni evolved at least 5 million years earlier than fragilis, and was the most common and the top predator in its ecosystem. It had relatively long legs and tail, and long arms with three sharp claws. The name Allosaurus translates as "different reptile," and the second part, jimmadseni, honors Utah State Paleontologist James H. Madsen Jr.

[. . .]

George Engelmann of the University of Nebraska, Omaha initially discovered the initial skeleton of the new species within Dinosaur National Monument in 1990. In 1996, several years after the headless skeleton was collected, the radioactive skull belonging to the skeleton using a radiation detector by Ramal Jones of the University of Utah. Both skeleton and skull were excavated by teams from Dinosaur National Monument.

[Continues . . .]

The full paper: "Cranial anatomy of Allosaurus jimmadseni, a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America" | PeerJ
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Tank

If religions were TV channels atheism is turning the TV off.
"Religion is a culture of faith; science is a culture of doubt." ― Richard P. Feynman
'It is said that your life flashes before your eyes just before you die. That is true, it's called Life.' - Terry Pratchett
Remember, your inability to grasp science is not a valid argument against it.

Recusant

It's the season, apparently.

"Argentine researchers find distant Tyrannosaurus relative" | Phys.org

QuoteThe remains of a 90-million-year-old carnivorous dinosaur distantly related to Tyrannosaurus rex has been discovered in Argentine Patagonia by a team of paleontologists.

The four-meter-long (13-foot-long) theropod was discovered in February 2018 in the central Argentine province of Rio Negro.

Scientists have christened it Tralkasaurus cuyi, the National University of La Matanza's Scientific Disclosure Agency said on Thursday.

Tralkasaurus means "thunder reptile" in the indigenous Mapuche language common in Patagonia. Cuyi relates to the place the fossil remains were found, El Cuy.

Tralkasaurus would have been dwarfed by its distant cousin Tyrannosaurus rex which could grow to 14 meters in length.

"The size of the Tralkasaurus body is smaller than other carnivores in its group—the abelisaurids," said Dr Federico Agnolin, an investigator from the Argentine Museum of Natural Sciences.

[Continues . . .]

Maybe there's some discussion in the paper (paywalled, unfortunately) on why they believe this is an adult, rather than a juvenile of a known species.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Recusant

A new paper describes fossil trackway evidence of bipedal ancestors of the crocodile. I'm sure they were very well mannered. I suppose this jolly bipedal crocodilomorph qualifies as "mysterious" because it's an ichnospecies: A species for which there are no bone fossils, only fossilized footprints or other fossilized evidence such as coprolites or nests.

"Mysterious crocodile relative may have walked on two legs" | National Geographic

Quote

Reconstruction of Batrachopus grandis, a proposed crocodylomorph that lived over 110-million-years ago and left tracks in the Jinju Formation of South Korea.
Illustration by Anthony Romilio, University of Queensland, Brisbane, Australia




Over 110 million years ago, during the Cretaceous period, the southern coastal area of South Korea, near the city Jinju, was covered by extensive lakes. The muddy shores were inhabited by frogs, lizards, turtles, and dinosaurs, all of which left their tracks in the muck. Whenever the water level rose, some of these footprints were filled with sand, allowing a fraction of them to be preserved.

Today, thousands of tracks can be found in this area, known as the Jinju Formation, says Martin Lockley, a paleontologist who specializes in trace fossils like footprints—known as an ichnologist—at the University of Colorado Denver. Lockley and colleagues in South Korea have studied the tracks at Jinju for decades, and for many years, they've been mystified by some of the largest footprints.

In 2019 they finally discovered detailed imprints from the creature, reported today in Scientific Reports. The tracks provide an impression of the animals' toes, the pads on the bottoms of their feet, and even the occasional patch of skin. These details have convinced Lockley and his colleagues that the footprints likely were left by crocodylomorphs, crocodile relatives, that were over nine feet long. They appear to have been unusual crocodilians, leaving imprints only from their hind feet, suggesting the animals were bipedal.

"[The imprints] really do look like they were made by big crocodilians," says ichnologist Anthony Martin, of Atlanta's Emory University, who was not involved in the new study. "Indeed, by ones that were walking on their rear feet and on land. That's pretty weird. But then again, the Cretaceous was a weird and wondrous time."

[Continues . . .]

The paper is open access:

"Trackway evidence for large bipedal crocodylomorphs from the Cretaceous of Korea" | Scientific Reports

QuoteAbstract:

Large well-preserved crocodylomorph tracks from the Lower Cretaceous (? Aptian) Jinju Formation of South Korea, represent the well-known crocodylomorph ichnogenus Batrachopus. The Korean sample includes multiple, narrow-gauge, pes-only trackways with footprint lengths (FL) 18–24 cm, indicating trackmaker body lengths up to ~3.0 m.

Surprisingly, the consistent absence of manus tracks in trackways, with well-preserved digital pad and skin traces, argues for bipedal trackmakers, here assigned to Batrachopus grandis ichnosp. nov.

No definitive evidence, either from pes-on-manus overprinting or poor track preservation, suggests the trackways where made by quadrupeds that only appear bipedal. This interpretation helps solve previous confusion over interpretation of enigmatic tracks of bipeds from younger (? Albian) Haman Formation sites by showing they are not pterosaurian as previously inferred. Rather, they support the strong consensus that pterosaurs were obligate quadrupeds, not bipeds.

Lower Jurassic Batrachopus with foot lengths (FL) in the 2–8 cm range, and Cretaceous Crocodylopodus (FL up to ~9.0 cm) known only from Korea and Spain registered narrow gauge trackways indicating semi-terrestrial/terrestrial quadrupedal gaits. Both ichnogenera, from ichnofamily Batrachopodidae, have been attributed to Protosuchus-like semi-terrestrial crocodylomorphs. The occurrence of bipedal B. grandis ichnosp. nov. is evidence of such adaptations in the Korean Cretaceous.

[Paragraph breaks added. - R]
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Recusant

Hat-tip to Lark for this one.  :boaterhat:

"Unusual New Species of Dinosaur Discovered – 'We Were Struck by Just How Hollow This Animal Was'" | SciTechDaily


Quote

Artists impression of the dinosaur's final moments.
Image credit: Trudie Wilson




Scientists in Southampton believe four bones recently found on the Isle of Wight belong to a new species of theropod dinosaur.

A new study by Palaeontologists at the University of Southampton suggests four bones recently found on the Isle of Wight belong to new species of theropod dinosaur, the group that includes Tyrannosaurus rex and modern-day birds.

The dinosaur lived in the Cretaceous period 115 million years ago and is estimated to have been up to four meters long.

The bones were discovered on the foreshore at Shanklin last year and are from the neck, back, and tail of the new dinosaur, which has been named Vectaerovenator inopinatus.

The name refers to the large air spaces in some of the bones, one of the traits that helped the scientists identify its theropod origins. These air sacs, also seen in modern birds, were extensions of the lung, and it is likely they helped fuel an efficient breathing system while also making the skeleton lighter.

The fossils were found over a period of weeks in 2019 in three separate discoveries, two by individuals and one by a family group, who all handed in their finds to the nearby Dinosaur Isle Museum at Sandown.

The scientific study has confirmed the fossils are very likely to be from the same individual dinosaur, with the exact location and timing of the finds adding to this belief.

[Continues . . .]

The paper "A highly pneumatic 'mid Cretaceous' theropod from the British Lower Greensand" is noted as being "published soon" and apparently will be open access, but I haven't found it as yet.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Recusant

A recently discovered large carnivorous dinosaur doesn't have really big teeth, but they're big enough. Sort of reminds me of Venom, the comic book alien. It's looks scary, so that's what they called it. Llukalkan means "one who causes fear" in the Mapuche language of the locals.

"New Species of Carnivorous Dinosaur Unearthed in Argentina" | Sci-News

Quote

Life reconstruction of Llukalkan aliocranianus.
Image credit: Jorge Blanco.




Llukalkan aliocranianus roamed our planet during the Late Cretaceous epoch, about 80 million years ago.

The dinosaur was a member of Abelisauridae, a family of big predators known from the ancient supercontinent Gondwana.

It grew to about 5 m (16.4 feet) in length, and had extremely powerful bite, very sharp teeth, huge claws, and keen sense of smell.

It also had a strange short skull with rough bones, so in life its head had bulges and prominences like some living reptiles.

"But the most distinctive feature of Llukalkan aliocranianus is a small posterior air-filled sinus in the middle ear zone that has not been seen in any other abelisaurid found so far," said Dr. Ariel Mendez, a paleontologist at the Patagonian Institute of Geology and Palaeontology.

"It means that this dinosaur likely heard differently to other abelisaurids — most probably better and similar to that of a modern day crocodile."

"This finding implies a different hearing adaptation from other abelisaurids, and likely a keener sense of hearing."

The fossilized cranial remains of Llukalkan aliocranianus were recovered from the Bajo de la Carpa Formation at La Invernada fossil area in northwestern Patagonia, Argentina.

According to the team, the ancient predator lived in the same small area and period of time as Viavenator exxoni, another species of furileusaurian abelisaurid from the Bajo de la Carpa Formation.

"This is a particularly important discovery because it suggests that the diversity and abundance of abelisaurids were remarkable, not only across Patagonia, but also in more local areas during the dinosaurs' twilight period," said Dr. Federico Gianechini, a paleontologist at the National University of San Luis.

[Continues . . .]
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Recusant

A newly discovered large spinosaur from the Isle of Wight.  ;D


Image credit: Anthony Hutchings

"Europe's 'largest ever' predator dinosaur found on Isle of Wight" | BBC

QuoteRemains of Europe's largest ever land-based predator dinosaur have been discovered on the Isle of Wight, scientists say.

Palaeontologists at the University of Southampton identified the remains, which measured more than 32ft (10m) long and lived 125 million years ago.

The prehistoric bones belonged to a two-legged, crocodile-faced, predatory spinosaurid dinosaur.

PhD student Chris Barker, who led the research, said it was a "huge animal".

The remains, which include pelvic and tail vertebrae, were discovered on the south-west coast of the Isle of Wight.

The carnivore has been dubbed the "white rock spinosaurid", after the geological layer in which the remains were found.

"This was a huge animal, exceeding 10m in length and probably several tonnes in weight," Mr Barker said.

"Judging from some of the dimensions, it appears to represent one of the largest predatory dinosaurs ever found in Europe - maybe even the biggest yet known."

It would have lived at the beginning of a period of rising sea levels and would have stalked lagoonal waters and sandflats in search of food.

Co-author of the research, Darren Naish, said: "Because it's only known from fragments at the moment, we haven't given it a formal scientific name. We hope that additional remains will turn up in time."

Most of the fossils were found by Isle of Wight dinosaur hunter Nick Chase, who died just before the Covid pandemic.

[Continues . . .]

The paper is open access:

"A European giant: a large spinosaurid (Dinosauria: Theropoda) from the Vectis Formation (Wealden Group, Early Cretaceous), UK" | PeerJ

QuoteAbstract:

Postcranial elements (cervical, sacral and caudal vertebrae, as well as ilium, rib and limb bone fragments) belonging to a gigantic tetanuran theropod were recovered from the basal unit (the White Rock Sandstone equivalent) of the Vectis Formation near Compton Chine, on the southwest coast of the Isle of Wight. These remains appear to pertain to the same individual, with enormous dimensions similar to those of the Spinosaurus holotype and exceeding those of the largest European theropods previously reported.

A combination of features—including the presence of spinodiapophyseal webbing on an anterior caudal vertebra—suggest that this is a member of Spinosauridae, though a lack of convincing autapomorphies precludes the identification of a new taxon. Phylogenetic analysis supports spinosaurid affinities but we were unable to determine a more precise position within the clade weak support for a position within Spinosaurinae or an early-diverging position within Spinosauridae were found in some data runs.

Bioerosion in the form of curved tubes is evident on several pieces, potentially related to harvesting behaviour by coleopteran bioeroders [insect scavengers].

This is the first spinosaurid reported from the Vectis Formation and the youngest British material referred to the clade. This Vectis Formation spinosaurid is unusual in that the majority of dinosaurs from the Lower Cretaceous units of the Wealden Supergroup are from the fluviolacustrine deposits of the underlying Barremian Wessex Formation. In contrast, the lagoonal facies of the upper Barremian–lower Aptian Vectis Formation only rarely yield dinosaur material. Our conclusions are in keeping with previous studies that emphasise western Europe as a pivotal region within spinosaurid origination and diversification.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


billy rubin



more people have been to berlin than i have

Recusant

Another large beastie with big teeth and tiny arms--suggests that there is a connection between the two traits. :D

"Big head, small arms: A newly discovered gigantic dinosaur evolved in a similar manner to Tyrannosaurus rex" | The Conversation

QuoteThe fossil record represents an amazing window into the endless forms of life that have existed across countless ages. By studying ancient species and ecosystems we can increase our understanding of what lived in the past and how the Earth was different compared to today. We can also use fossils to understand how evolution works and what is most likely to evolve under particular sets of circumstances.

This context is what makes Meraxes gigas, a newly named theropod dinosaur, so important for our understanding of dinosaur evolution and biodiversity.

I was part of the international team of palaeontologists, led by Juan Canale of the Ernesto Bachmann Palaeontological Museum, that named and described Meraxes gigas. The specimen was collected between 2012 and 2014 near Villa El Chocón in Argentina, in rocks of the ~95 million year old Huincul Formation.

[. . .]

Meraxes is particularly notable in what it tells us about the evolution of large size in dinosaurs. Its body plan — a large head and small arms — is very similar to that seen in tyrannosaurids like Tyrannosaurus rex, and abelisaurids like Carnotaurus.

These three groups of theropod dinosaurs are all distant relatives. Each independently evolved both large body size and the combination of a large head and small arms.

We analyzed the evolution of these changes in these three groups by examining changes in arm size relative to other body measurements, such as leg and body size. We found that not only did each group experience similar changes through evolution, but there appears to be a lower limit for how small the arms can be relative to the rest of the body. This may represent a developmental or mechanical constraint: the arm can only get so small relative to the body, regardless of other evolutionary pressures in this context.

There are several potential explanations for the size of the arms; the forelimbs themselves may have retained some function despite their reduced size. Our data most directly support the idea that arm reduction in these dinosaur groups is more likely tracking other traits rather than being the subject of evolutionary selective pressure itself. In other words, as the relative size of the skull increased over evolution, the arms decreased proportionally in size as an evolutionary trade-off.

[Continues . . .]

The paper is behind a paywall.

QuoteSummary:

Giant carnivorous dinosaurs such as Tyrannosaurus rex and abelisaurids are characterized by highly reduced forelimbs that stand in contrast to their huge dimensions, massive skulls, and obligate bipedalism. Another group that follows this pattern, yet is still poorly known, is the Carcharodontosauridae: dominant predators that inhabited most continents during the Early Cretaceous and reached their largest sizes in Aptian-Cenomanian times.

Despite many discoveries over the last three decades, aspects of their anatomy, especially with regard to the skull, forearm, and feet, remain poorly known. Here we report a new carcharodontosaurid, Meraxes gigas, gen. et sp. nov., based on a specimen recovered from the Upper Cretaceous Huincul Formation of northern Patagonia, Argentina. Phylogenetic analysis places Meraxes among derived Carcharodontosauridae, in a clade with other massive South American species.

Meraxes preserves novel anatomical information for derived carcharodontosaurids, including an almost complete forelimb that provides evidence for convergent allometric trends in forelimb reduction among three lineages of large-bodied, megapredatory non-avian theropods, including a remarkable degree of parallelism between the latest-diverging tyrannosaurids and carcharodontosaurids. This trend, coupled with a likely lower bound on forelimb reduction, hypothesized to be about 0.4 forelimb/femur length, combined to produce this short-armed pattern in theropods.

The almost complete cranium of Meraxes permits new estimates of skull length in Giganotosaurus, which is among the longest for theropods. Meraxes also provides further evidence that carchardontosaurids reached peak diversity shortly before their extinction with high rates of trait evolution in facial ornamentation possibly linked to a social signaling role.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken