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Post by OldGreenGrolar on Feb 12, 2023 7:04:20 GMT -5
When Tyrannosaurus Chomped Sauropods.Even though Tyrannosaurus missed Apatosaurus by many millions of years, the tyrant still had a chance to feed on long-necked giants Tyrannosaurus rex never crunched into Stegosaurus. Despite what Walt Disney’s animators so dramatically depicted in Fantasia, the two dinosaurs were separated by about 83 million years. The same is true for Apatosaurus, Diplodocus, Barosaurus, Brachiosaurus and Camarasaurus—all of these 150-million-year-old icons flourished during a time when tyrannosaurs were tiny, fuzzy creatures that could have tackled only much smaller fare. It wasn’t until millions of years later—when the famous Morrison Formation dinosaurs were long gone—that tyrannosaurs became gargantuan apex predators. But this doesn’t mean that Tyrannosaurus never ate sauropods. Discoveries in New Mexico, Utah, Texas and Mexico have not only placed sauropods back in southwestern North America at the very end of the Cretaceous, but rare bits of tooth and bone have confirmed that Tyrannosaurus prowled many of the same places. Tyrannosaurus almost certainly preyed on titanic sauropods. Tyrannosaurus tears a mouthful out of Alamosaurus. Art by Michael Skrepnick. The potential tyrannosaur prey goes by the name of Alamosaurus. This dinosaur, which may have reached lengths of 100 feet or more, marked the return of sauropods to North America after a 30-million-year hiatus. Even though sauropods were the dominant herbivores in North America during the Late Jurassic, and though various forms persisted through the Early Cretaceous, the entire group vanished from the continent about 100 million years ago. Horned dinosaurs and hadrosaurs eventually replaced the long-necked herbivores, but the disappearance of sauropods in North America doesn’t mean that they went extinct on a global scale. Sauropods persisted on other continents, most prominently South America, and sometime around 70 million years ago Alamosaurus, or the precursor of Alamosaurus, trod northward to arrive in the American Southwest. This was the southern limit of Tyrannosaurus. Most Tyrannosaurus skeletons—and certainly the most famous ones—have been found in Montana and South Dakota. But in 2005, paleontologists Scott Sampson and Mark Loewen described a partial Tyrannosaurus skeleton found in Utah’s North Horn Formation. Since Alamosaurus bones had already been found at the same site, this cinched the connection between predator and prey. Unfortunately, dinosaur fossils found in the North Horn are frequently scrappy and brittle. Much remains unknown about the dinosaurs that lived in Utah at the very end of the Cretaceous. The record of Alamosaurus and Tyrannosaurus in Texas and New Mexico is also quite fragmentary, but, in a press release that accompanied his recent paper about the size of Alamosaurus, paleontologist Denver Fowler mentioned that his team found a tyrannosaur tooth in association with an Alamosaurus vertebra at a New Mexico site. Was the tooth just washed into that position during burial, or might the connection show that the tyrant was feeding on the sauropod’s carcass? For the moment, that’s unclear, but the coincident burial reinforces the ecological connection between the animals. Tyrannosaurus to the north might have been specialists in taking down Edmontosaurus and Triceratops, while their southern cousins had the option of long-necked fare. www.smithsonianmag.com/science-nature/when-tyrannosaurus-chomped-sauropods-67170161/#:~:text=Discoveries%20in%20New%20Mexico%2C%20Utah,certainly%20preyed%20on%20titanic%20sauropods. How true would this article be?
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Post by brobear on Feb 27, 2023 19:36:00 GMT -5
Dinosaur claws had many functions, but now a team from the University of Bristol and the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing has shown some predatory dinosaurs used their claws for digging or even for display. www.sciencedaily.com/releases/2023/02/230227132633.htm The study focused on two groups of theropod dinosaurs, the alvarezsaurs and therizinosaurs, that had weird claws whose function had been a mystery up to now. It turns out that alvarezsaurs used their rock-pick-like claws for digging, but their close relatives, the giant therizinosaurs, used their overdeveloped, metre-long, sickle-like claws for display. The new work is led by Zichuan Qin, a PhD student at the University of Bristol and the IVPP. He developed a new, computational approach in biomechanics to identify functions based on detailed comparison with living animals. First, the claws were modelled in three dimensions from CT scans, then modelled for stress and strain using engineering methods, and finally matched to functions of pulling, piercing and digging by comparison with modern animals whose claw functions are known. "Alvarezsaurs and therizinosaurs are definitely the strangest cousins among dinosaurs," said Professor Michael Benton, one of Zichuan's supervisors. "Alvarezsaurs were the tiniest dinosaurs ever, the size of chickens, with stubby forelimbs and robust single claws, but their closest relative, the therizinosaurs, evolved in the exact opposite path." "Therizinosaurus is famous for its sickle-like claws, each as long as a samurai sword: Edward Scissor-hands on speed. We all saw Therizinosaurus in 'Jurassic World' hitting deer and killing the giant predator Giganotosaurus. However, this is unlikely. These long, narrow claws were too weak for combat." said Dr Chun-Chi Liao, an expert on therizinosaurs from IVPP who co-authored this study. "Our engineering simulation shows that these claws could not withstand much stress." "Not all therizinosaur hand claws were so useless in combat, but most other related species could use their claws as powerful hooking tools when feeding on leaves from the trees.," Dr Chun-Chi Liao added, "so, we conclude that the largest claws of any animal ever were actually useless in mechanical function, and so must have evolved under sexual selection to be used in display. The adult Therizinosaurus I guess could wave the claws at a competitor and effectively say, 'look at me, back off' or wave them around in some way like a peacock can use its tail in display to attract females for mating." "Our previous work has shown that alvarezsaurs evolved to become the tiniest dinosaurs by the end of the Cretaceous, and these dinosaurian midgets were using their punchy little claws for digging into ant hills and termite mounds. They were ant-eaters." said Zichuan Qin. "Our study shows that the early alvarezsaurs, like Haplocheirus from the Jurassic, had multifunctional hands, but they were not good at digging. Their much smaller descendants had the efficient digging hands so they could feast on the Late Cretaceous termites." added Zichuan Qin. "Science and technology cannot bring dinosaurs back to life, but advanced computing and engineering techniques can show us how extinct animals lived," said Professor Emily Rayfield, one of Zichuan's supervisors, and an expert of dinosaur biomechanics. "Especially for extinct animals like alvarezsaurs and therizinosaurs, they are so bizarre that we even can't find any living animals like them. Luckily, advanced technology can help us to simulate, on a computer, the functioning of extinct animals using fundamental engineering and biomechanical principles. This study shows very well how selection for function can lead to the emergence of specific, sometime very bizarre, forms."
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Post by OldGreenGrolar on Mar 10, 2023 17:38:33 GMT -5
Reply 200. I just watched that movie yesterday.
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Post by brobear on Mar 10, 2023 18:07:08 GMT -5
Reply 200. I just watched that movie yesterday. Looks like a good one. What was your take on it?
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Post by OldGreenGrolar on Mar 11, 2023 0:29:22 GMT -5
Reply 200. I just watched that movie yesterday. Looks like a good one. What was your take on it? Honestly it was fun but average. It is similar to After Earth film.
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Post by OldGreenGrolar on Mar 13, 2023 7:19:58 GMT -5
I know it is fiction but it might give us a rough indication on how a tree interacts with different dinosaurs.
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Post by brobear on Mar 13, 2023 8:29:01 GMT -5
Quote; "I know it is fiction but it might give us a rough indication on how a tree interacts with different dinosaurs." I'm left totally clueless as to what this line means; but there were three scenes that really ticked me off. 1- When Spinosaurus killed T-rex in a face-off - total bull-droppings. 2- When the genetically created Frankenstein of a dinosaur wannabe - Indominus rex - killed T-rex. Why did the Hollywood idiots do that? 3- When Giganotosaurus defeated T-rex... then T-rex needed help to defeat Giganotosaurus - more bull-droppings.
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Post by OldGreenGrolar on Mar 15, 2023 1:15:45 GMT -5
/\ Some of them are off course exaggerations, I just forgot to mention that .
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Post by OldGreenGrolar on Mar 15, 2023 1:17:04 GMT -5
Reply 207. The indominus rex was in the end killed by a manousaur after a velociraptor, Blue and the T rex worked together.
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Post by brobear on Jun 13, 2023 3:52:00 GMT -5
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Post by arctozilla on Jun 13, 2023 8:46:38 GMT -5
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Post by brobear on Jul 13, 2023 1:48:55 GMT -5
Spinosaurus is not an aquatic dinosaur elifesciences.org/articles/80092?fbclid=IwAR1U_3ITAuLqN6KhuMhbKDqkG23dMs_B_5DSCqRQ4OrM0xkTa7Y3TOvRm3k Discussion In 1915 Ernst Stromer highlighted the remarkable adaptations in the jaws and neural spines of S. aegyptiacus for piscivory and ostentatious display, respectively, citing modern analogs for both (Stromer, 1915). Nothing close to this morphology had ever been described among nonavian dinosaurs at that time. More recently, a sequence of investigators have gone further, attempting to fathom the manner in which the lifestyle of this large predatory dinosaur engaged coastal waters. All have been hamstrung by the scarcity and fragmentary nature of the specimens, as all of Stromer’s Egyptian fossils were destroyed in World War II. Indeed, the unveiling of a new partial skeleton from Morocco (Ibrahim et al., 2014) and its tail 6 years later (Ibrahim et al., 2020b) generated hypotheses for semiaquatic and aquatic interpretations, respectively. The superficially eel-like morphology of the tail, viewed as a ‘novel propulsor organ,’ provided the inspiration for the ‘aquatic hypothesis,’ which envisioned S. aegyptiacus as a tail-propelled, diving predator ‘that pursued and caught its prey in the water column’ (Ibrahim et al., 2020b). Conversely, as would be requisite for status as a secondarily aquatic reptile, its terrestrial capabilities were regarded as seriously diminished by a trunk-positioned center of body mass (Ibrahim et al., 2014; Ibrahim et al., 2020b) that would require a quadrupedal stance on land and the use of long-clawed forelimbs not at all designed for weight support. Presented as support for the aquatic hypothesis, Fabbri et al used bone compactness to assert that S. aegyptiacus was a ‘subaqueous forager’ with diving bona fides (Fabbri et al., 2022). The aquatic hypothesis, nonetheless, requires far more than proving its tail was a high-powered source of propulsion or its bones a bit more compact. In order to conclude that S. aegyptiacus was an aquatic diver and pursuit predator, one also must understand its buoyancy, stability, velocity, maneuverability, and diving performance in water. Those calculations require an accurate flesh rendering, which in turn is built over an accurate skeletal model. Therefore, we began with CT scans of the fossils to piece together an accurate skeletal model, discovering major discrepancies with the original 3D skeletal model (Ibrahim et al., 2014) and the 2D skeletal silhouette used by the aquatic hypothesis (Fabbri et al., 2022). Comparisons to the 2D model with the more accurate tail show that skeletal regions anterior to the hips are enlarged in length and depth beyond the dimensions of our CT-based reconstruction, shifting the CM in the resulting flesh model forward from the hips to the trunk. Trunk length was increased in both previous models of S. aegyptiacus due to unnatural ventroflexion of the dorsal column that also spread further the neural spines of the sail (Figure 9). When neotype (CT-scanned) or rebuilt holotype dorsal vertebrae of S. aegyptiacus are rearticulatd in an osteological neutral pose, the shorter torso has a straighter column with less spread neural spines. The ribcage, in addition, is not as deep, based on the preserved rib pieces of the holotype and neotype and the nearly complete ribcage known for S. tenerensis (Figures 1F and 9). These proportions effectively reduce the volume of the trunk in our flesh model (Figure 2). The flesh model used by the aquatic hypothesis, likewise, underestimated the muscle mass at the base of the tail, judging from our study of CT scans of crocodylians and a range of other reptiles (Díez Díaz et al., 2020). These differences are far from trivial when considering centers of mass and buoyancy in S. aegyptiacus. The dinosaur, in fact, stood back up on its hind legs like all other theropods. With a more accurate flesh model in hand, we embarked on a range of biomechanical tests of its performance in water, determining that it fell short in all critical measures by huge margins. S. aegyptiacus failed spectacularly by factors from four- to tenfold for maximum swimming speed on the surface or underwater (Figure 3A), for the capacity to right and remain stable or maneuver underwater (Figure 3B), and for generating the force needed to overcome buoyancy and fully submerge. S. aegyptiacus was an unstable, slow swimmer without the capacity to submerge. These are stiff biomechanical hurdles for the aquatic hypothesis to overcome. We thought of other comparative means to test the aquatic hypothesis, plotting S. aegyptiacus against various extant and extinct secondarily aquatic amniotes to consider appendage area (Figure 5), the size of foot and tail paddles in crocodylians (Figure 6), tail structure (Figure 4C and D), and the habitats occupied by large-bodied secondarily aquatic vertebrates (Figure 7A). S. aegyptiacus fails all of these comparative tests as well because it resembles other theropod dinosaurs in limb size, other reptiles that use midline sails for display, and semiaquatic reptiles in the diversity of coastal and inland habitats occupied. Although additional fossils of S. aegyptiacus and other spinosaurids will surely come to light, the overall skeletal proportions and form of S. aegyptiacus are largely known. Although many fine points on the structure and function of this interesting clade of predators will surely continue to engender controversy. The aquatic hypothesis, for that reason, is unlikely to survive as a plausible lifestyle interpretation. What then is our lifestyle interpretation for S. aegyptiacus? Our study and that of Hone and Holtz, 2021 envision S. aegyptiacus as a bipedal, semiaquatic dinosaur using ambush predation of large fish while wading into shallow coastal and riverine waters.
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Post by brobear on Jul 13, 2023 1:52:04 GMT -5
Spinosaurus is not an aquatic dinosaur Thirteen principal conclusions can be drawn from this study, all of which may be tested:
1- Adult S. aegyptiacus had a body length of under 14 m with the axial column in neutral pose.
2- The reduced hind limb long bones in neotypic skeleton of S. aegyptiacus are infilled likely as an adaptation to weight support on land rather than functioning as ballast to increase density in water.
3- The segment-crossing caudal neural spines in S. aegyptiacus suggest that its tail functioned more as a pliant billboard than flexible fluke.
4- S. aegyptiacus, like S. tenerensis and other spinosaurids, was bipedal on land with its CM positioned over its hind feet. The long-clawed forelimbs of S. aegyptiacus were not used in weight support on land.
5- S. aegyptiacus could wade into shallow water for feeding with flotation occurring at water depth greater than ~2.6 m.
6- An adult flesh model of S. aegyptiacus has a body mass of ~7400 kg and average density of ~830 kg/m3, which is considerably less than the density of saltwater (1026 kg/m3).
7- S. aegyptiacus was incapable of diving, given its buoyancy and incompressible trunk. Full submergence would require 15–25 times the maximum force output of its tail, depending on estimated lung volume. 8- S. aegyptiacus was unstable in deeper water with little ability to right itself, swim, or maneuver underwater. Maximum power from its tail, assuming it could undulate as in Alligator, is less than 700 N, which would generate a top speed of ~1 m/s, an order of magnitude slower than extant large-bodied pursuit predators.
9- All extant and extinct large-bodied (>2 m long) secondarily aquatic vertebrates are strictly marine, whereas fossils pertaining to Spinosaurus have been found in inland basins distant from a marine coast.
10- Transition to a semiaquatic lifestyle, as occurred in the evolution of spinosaurid theropods, can occur at any body size. Transition to an aquatic lifestyle among tetrapods, in contrast, has only occurred at relatively small body size (<3 m) with subsequent radiation once in the marine realm into larger body sizes.
11- S. aegyptiacus is interpreted as a semiaquatic shoreline ambush predator more closely tied to waterways than baryonychine spinosaurids.
12- Spinosaurids flourished over a relatively brief Cretaceous interval (~35 My) in circum-Tethyan habitats with minimal impact on aquatic habitats globally.
13- Two phases are apparent in evolution of aquatic adaptations among spinosaurids, the second distinguishing spinosaurines as the most semiaquatic of non-avian dinosaurs.
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