Apatosaurus Guide
November 14, 2024
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Sauropods were large, herbivorous dinosaurs that walked on four legs. They are best known for their very long necks and tails. Sauropods lived during the Jurassic and Cretaceous periods, and many species of sauropods are known from fossils. Some sauropod genera include Apatosaurus, Brachiosaurus, Diplodocus, and Mamenchisaurus.
Sauropods were the largest land animals of their time. They grew to be enormous, with some species reaching lengths of over 100 feet (30 meters) and body mass estimates weights of up to 80 tons (72 metric tons). Sauropods had long necks and tails, and most species had very tiny heads in comparison to their body size. They walked on all fours, and some species had four toes on each foot while others had five. Sauropods were plant-eaters, and they likely used their long necks to reach leaves high up in trees.
The earliest known indisputable sauropod dinosaurs appear in the Early Jurassic. By the end of the Jurassic period (roughly 150 million years ago), sauropods had become widely established (especially the diplodocids and brachiosaurids).
One species of sauropods, the titanosaurs, had supplanted all others by the Late Cretaceous and had a near-global presence. Much like all the other non-avian dinosaurs that lived at the time, titanosaurs went extinct during the Cretaceous–Paleogene mass extinction.
On every continent, including Antarctica, sauropod fossils remains have been discovered. The discovery of a complete sauropod skeleton is unusual; therefore, there are many incomplete skeletons. Many species, particularly the biggest ones, are known only from isolated and disassociated bones. The lack of heads, tail ends, and limbs in many near-complete specimens are typical.
All of the first fragments of sauropod fossils now recognized as sauropods originated in England and were originally thought to be a variety of things. Until recently, their relationship with other dinosaurs was largely overlooked.
The first sauropod fossil to be scientifically classified was a single tooth known as Rutellum implicatum, which was not described using Linnaean terminology. Although this fossil was first described by Edward Lhuyd in 1699, it was not recognized as a huge ancient reptile at the time. Dinosaurs would not be classified as a group until almost a century later.
In 1841, the English naturalist Richard Owen published descriptions of sauropods in a book and a paper, both of which were named for Cardiodon and Cetiosaurus. Cardiodon was discovered solely from two unusual, heart-shaped teeth (from which it received its name), which had no known origin. The smaller, scrappier remains of Cetiosaurus were previously known.
Owen named Cetiosaurus after the Greek word for “whale lizard,” believing it was a massive marine reptile akin to today’s crocodiles. A year later, Owen didn’t include Cetiosaurus and Cardiodon among the Dinosauria when he coined that name.
In 1850, Gideon Mantell realized that several sauropod bones attributed to Cetiosaurus by Owen belonged to dinosaurs. The discovery of this hollow structure in the leg bones led Mantell to believe that the creature was a land animal. He classified the sauropod bones into different species and designated a new genus, Pelorosaurus, for them. He also grouped the dinosaurs together with it in a new family. After this, Mantell still did not perceive a link between Cetiosaurus and Mesosaurus.
In 1878, The most comprehensive complete sauropod skeletons yet discovered and characterized by Othniel Charles Marsh was named Diplodocus. Marsh established a new genus and species for Diplodocus, Cetiosaurus, and their increasing cast of relatives in order to distinguish them from the other significant dinosaur families. Marsh named this group Sauropoda, also known as “lizard feet” in Latin.
The sauropods’ most distinctive feature was their enormous body size and their signature long sauropod necks. Even the dwarf sauropods, which were estimated to be 20 feet long (5-6 meters), were considered to be some of the largest animals in their ecosystem and to have some of the largest estimated body mass estimates of all animals recorded in history.
Sauropod species with incredibly lengthy tails, such as the diplodocids, might have been able to crack their tails like whips as a signaling or deterrent or to damage predators or cause sonic booms. The Supersaurus, at 108-112 feet long (33-34 meters), was the world’s longest sauropod known from reasonably complete sauropod fossil remains. Others, like the previous record holder, Diplodocus, were almost equally massive.
The longest sauropod dinosaur discovered from sufficient sauropod bones is Argentinosaurus huinculensis, with long bones that measure 115-118 feet (35-36 meters) based on the most up-to-date studies. For comparison, the biggest land animal alive today, the African elephant, reaches a maximum length of 24 feet (approx 7.3 meters).
However, the huge Barosaurus bones BYU 9024 might have been even larger, reaching lengths of 148-157 feet (45–48 meters). For reference, the giraffe (the tallest living land animal) measures between 4.8 and 5.6 m (15.74 and 18.3 ft) tall when standing upright on its hind legs.
Sauropod dinosaurs were huge descendants of tiny ancestors that grew to be with a surprisingly large body mass increase. The Middle Triassic of Argentina produced the Basal dinosauriformes Pseudolagosuchus and Marasuchus, both of which weighed around 2.2 pounds (1 kg).
The Saurischia were the next major group, and they developed into large bauplans. Despite this, more basic members like Eoraptor, Panphagia, Pantydraco, Saturnalia, and Guaibasaurus maintained a reasonable size at around 22 pounds (10 kg).
Even with these tiny, rudimentary forms, sauropodomorphs got larger during this time. However, little remains of this era make analysis difficult. Anchisaurus, for example, was beneath 50 kg (110 lb), even though it was closer to the sauropods than Plateosaurus and Riojasaurus (upwards of 1t).
Although sauropods were generally big, they occasionally grew to immense proportions throughout their history. The turiasaur Turiasaurus and the diplodocoids Maraapunisaurus, Diplodocus, and Barosaurus are just two of many enormous forms of sauropod gigantism that existed during the Late Jurassic (particularly Kimmeridgian and Turonian).
Through the Early to Late Cretaceous period, the massive giant sauropod dinosaurs Antarctosaurus giganteus, Notocolossus, Sauroposeidon, Argentinosaurus, Paralititan, Puertasaurus, Futalognkosaurus, schrani, and Dreadnoughtus lived, with all more than likely being titanosaur sauropods.
Huanghetitan ruyangensis, a sauropod dinosaur, known from 9.8 feet (3 meters) long ribs, is one of the world’s largest creatures. These enormous animals were present in the Late Jurassic to Late Cretaceous and evolved separately over a period of 85 million years.
According to a study by Michael D’Emic and his colleagues from Stony Brook University, sauropods evolved high tooth replacement rates to maintain pace with their voracious appetites. The findings indicated that Nigersaurus replaced each and every tooth around every 14 days, while on the other hand, the Camarasaurus replaced each tooth every 62 days, and Diplodocus replaced each tooth once every 35 days. Scientists discovered that the tooth’s characteristics influence how long it takes for a new tooth to develop. Because of their larger size, Camarasaurus teeth grew more slowly than those of Diplodocus.
The findings of D’Emic and his team indicated that the teeth of the sauropods varied in form, size, and shape. The differences between the tooth shapes indicate a shift in diet. Diplodocus fed on plants low to the ground, whereas Camarasaurus ate leaves from the top and middle branches. According to the researchers, specialized eating helped different herbivorous dinosaurs live together.
The long necks of sauropods were up to 49 feet long (15 meters), six times longer than the world’s longest giraffe neck. Several crucial physiological characteristics aided this. The large overall body size and quadrupedal stance provided a solid basis for the long neck, while the head was formed to be very small and light in order to lose the capacity to process food orally.
The sauropods’ heads were reduced to simple harvesting instruments that got the plants into their bodies, allowing them to lift their heads with less power and creating long necks with less thick muscle and connective tissue. This resulted in a significant reduction in neck mass and new neck posture allowing for further elongation.
Sauropods also had a wide range of improvements in the reconstructed skeletons owing to their bone structure. Sauropods had as many as 19 cervical vertebrae, whereas most animals have only seven. In addition, each vertebra was very long and had several empty areas that would have been filled solely with air. The air-sac system was connected to the spaces, which not only lightened the long necks but also effectively increased airflow through the trachea, allowing the animals to breathe enough for their size.
The sauropods’ vertebrae evolved to include more air, allowing them to minimize the quantity of dense, heavy bone while maintaining the ability to take big breaths to supply oxygen for the whole body.
Kent Stevens says that computer-modeled reconstructions of the sauropod skeletons using vertebrae show that their necks were capable of sweeping out significant feeding areas without having to shift their bodies, but they were unable to retract them much higher than the shoulders for investigating the territory or reaching higher.
Another suggested purpose for the sauropods’ long necks was to act as a heat radiator to handle the high amount of heat their enormous estimated body masses generated. Considering that the metabolism was working at a high rate, it would have generated a significant amount of heat, and the removal of this extra heat would have been necessary for survival. The long necks would have cooled the veins and arteries leading to the brain, preventing heated blood from reaching the head. It was discovered that the increased metabolic rate caused by sauropods’ necks was somewhat offset by an increased surface area where heat could dissipate.
There is a lot of disagreement about how sauropods held their tiny heads and long necks, as well as the postures they may have attained in life.
Some paleontologists have been suggesting that the sauropod dinosaurs long necks might have been used for browsing high-branch trees, based on calculations predicting that merely pumping blood up to the head in such a posture for lengthy would have required half of their energy intake.
To raise blood to such a height without auxiliary hearts in the long neck, a heart 15 times as big as a comparable-sized whale would be required. These same talking points have been used to claim that the long neck was held more or less horizontally and must have allowed feeding on plants over a wide area with less need to move about, resulting in a significant energy saving for such a big animal.
In the majority of instances, reconstructions of the necks of Diplodocus and Apatosaurus have been depicted in near-horizontal, so-called “neutral, undeflected posture” because of the similarity.
Sauropods developed specialized “graviportal” (weight-bearing) legs as massive quadrupeds. The hind feet were broad in most sauropod groups & species and retained three claws.
When compared to other animals, the highly modified front feet (manus) were unique. The front feet of sauropods were significantly distinct from those of modern big quadrupeds like elephants.
The manus bones of sauropods were positioned in distinctive vertically stacked columns, with very tiny finger bones (although it is uncertain if the most primitive sauropods, such as Vulcanodon and Barapasaurus, had such feet). Individual digits on the front feet were hidden by eusauropods and thus would not have been apparent in life.
The sauropod’s forefoot bone (metacarpal) columns were semi-circular, making sauropod forefoot imprints were horseshoe-shaped. Print evidence indicates that sauropods lacked any fleshy padding to support the front feet, making them concave in comparison to elephants.
The distinctive thumb claw (belonging to digit I) was the only claw that was visible in most sauropods. Such a claw was present in nearly all sauropods, although its function is unknown. The longest claw (as well as tall and laterally flattened) was in diplodocines, whereas it was tiny in brachiosaurids, some of which appear to have lost the claw entirely based on trackway evidence. The thumb claw, which had previously been present on all Titanosaurs, may have vanished completely (with the exception of early forms such as Janenschia).
The front foot of titanosaurians was one of the most unusual among sauropod dinosaurs since they lost not only the external claw but also all of the digits during their evolutionary history as a group. The digits and digit bones of the ancestral titanosaur were reduced in size, and it only walked on horseshoe-shaped “stumps” constructed of columnar metacarpal bones.
Portugal’s history of sauropod research has revealed that, at least in some sauropods (probably brachiosaurids), the bottom and sides of the forefoot column were covered in tiny, spiny scales which left score marks on the tracks. The metacarpal bones’ tips that made contact with the ground in titanosaurs were rather broad and rectangular-shaped, and certain fossils retain traces of soft tissue coverings over this region, implying that these animals had some sort of padding on their front feet.
Long bones of sauropods grew isometrically, which means there was little to no change in form as juvenile sauropods matured into adults. Bonnan speculates that this strange scaling pattern (most vertebrates show major shape changes in long bones associated with improved weight support) might be connected to a stilt-walker principle (advocated by amateur scientist Jim Schmidt), in which adult sauropods’ lengthy legs enabled them to easily traverse long distances without altering their fundamental mechanics.
Sauropod trackways and other footprints from sauropod fossils (known as “ichnites”) are widely recognized from the many traces discovered on most continents. Ichnites have aided in the study of sauropod biology, including the structural framework of their front and hind legs. The lower leg bones are frequently smaller in size and crescent-shaped than the upper leg bones. Occasionally, ichnites preserve traces of the claws, allowing researchers to determine which sauropods groups had claws or even digits on their forefeet.
The tracks of a sauropod family & herds from the Villar del Arzobispo Formation of the Berriasian age in Spain lend credibility to the group’s gregarious nature. The footprints are most comparable to those of Sauropodichnus giganteus, although they have been linked with a basal titanosauriform species.
The tracks are broad gauge, and the proximity to Sauropodichnus is confirmed by the manus-to-pes distance (the distance between the manus and foot). The lack of previous trackway individual age attribution makes it difficult to determine whether the herd’s footprints were created by youngsters, adults, or other sauropods.
The distance between opposite limbs is the defining characteristic of sauropod trackways, which are divided into three groups of sauropod diversity: narrow gauge, medium gauge, and wide gauge. The trackway’s gauge can help determine how big the limbs of various sauropods were and whether this may have affected the way they walked.
A 2004 study by Day et al. revealed that across the sauropod family, a general pattern might be detected, with each sauropod family characterized by distinct trackway gauges. They discovered that apart from titanosaur sauropods, most sauropods had narrow-gauge limbs with clear impressions of the big thumb claw on the forefeet.
While the majority of sauropods had thicker, heavier limbs and walked on two legs as modern elephants do, some primitive titanosauriformes evolved wider-set forelimbs with claws. The claw marks were placed on the front feet of these sauropod trackways, suggesting that they belonged to brachiosaurids or other early sauropod dinosaurs. True titanosaur sauropods retained their forefoot claw, yet they had fully developed broad gauge limbs. Advanced titanosaurs continued to use broad gauge limbs, as trackways with a wide gauge and no claws or digits on the forefeet are evident.
Trackways from the front feet are occasionally discovered only. According to Falkingham et al., this might be due to the substrate’s characteristics and hind foot anatomy. These have to be just perfect if tracks are to be preserved. Differences in limb surface area, especially on the hind limbs, may result in trackways being preserved only on the forefeet.
Bill Sellers, Rodolfo Coria, Lee Margetts, et al. conducted a study in PLoS ONE on October 30, 2013, to attempt for the first time to digitally reconstruct Argentinosaurus and test its movement. Bone histology and ichnology were previously used to determine the speed as the most popular technique.
Saucrodon bone histology and speed are frequently researched, with the postcranial skeleton being the primary focus. The postcranial skeleton has several unique characteristics, such as an enlarged ulnar process, a broad ilia lobe, an inward-slanting top third of the femur, and a rather ovoid femur shaft.
There are several difficulties when researching ichnology to calculate sauropod speed, including the fact that only certain gaits are estimated owing to preservation bias and that it is plagued with many more accuracy issues.
Armor was worn by some sauropod dinosaurs. Shunosaurus, for example, had a tiny club on the end of her tail, while several titanosaur species, such as Saltasaurus and Ampelosaurus, had little bony osteoderms that covered parts of their bodies.
From both bone beds and trackways, numerous lines of fossil evidence suggest that sauropods were social creatures that formed sauropod family herds. However, the composition of the herds varied among species. Some bone beds, for example, a site from Argentina’s Middle Jurassic period, appear to show congregations of individuals of various age groups, mixing juvenile sauropods and adults.
However, multiple fossil sites and trackways indicate that many sauropod species inhabited herds separated by age, with juvenile sauropods forming their own groups from adults. Many dinosaurs, such as Alamosaurus, Bellusaurus, and some diplodocids, have been observed employing separate herding techniques.
Myers and Fiorillo attempted to explain why sauropod dinosaurs tended to form separate herds in a study of the evidence for various herd types. Microscopic tooth wear studies suggest that juvenile sauropods ate differently from adult sauropods, so herding them together was less productive than herding them separately, where individual herd members could forage in a coordinated manner. The enormous variation in size between juvenile and adult seals may have influenced their different feeding and herding techniques.
Since adult and juvenile sauropods must have been separated soon after hatching, and considering that sauropod hatchlings are most likely precocial, Myers and Fiorillo inferred that species with age-segregated herds would not have provided much parental care. However, scientists who had studied herds of sauropod dinosaurs that include both juvenile and adult sauropod family claim that most sauropods may have cared for their young smaller sauropods for a lengthy amount of time before the youngsters reached adulthood.
According to a 2014 research, the time it took for an egg to hatch might have been between 65 and 82 days. The degree of segregation versus age-mixed herding among different sauropod species is unknown. In addition, more sauropod species will be required to identify any conceivable patterns of sauropod evolution and distribution.
The methods by which sauropods held their heads and necks are a matter of dispute, as well as the postures they could take in life.
However, a study of living animals indicates that almost all existing tetrapods keep their necks firmly flexed when awake, demonstrating just how unreliable any inference drawn from bones regarding “normal” postures is. Meanwhile, ostrich neck computer modeling has cast doubt on the flexibility required for stationary grazing.
The first phylogenetic definition of Sauropoda was produced in 1997 by Salgado and colleagues. They defined the clade as a node-based taxon, containing “the most recent shared ancestor of Vulcanodon karibaensis and Eusauropoda, as well as all of its descendants.”.
In recent years, the phylogenetic relationships of the sauropods have largely remained stable, although there are still some questions, such as Euhelopus’ position. More info on Sauropodomorpha’s characteristics here.
Sauropod dinosaurs are rarely known for having survived injuries or symptoms of sickness, but discoveries in recent years suggest they may have had such problems. “Dolly,” a Morrison Formation dinosaur from Montana, was named in 2022 and had evidence of an acute respiratory illness. Rib fractures caused by traumatic fracture, bone infection, and osteosclerosis have been observed among sauropod ribs from Yunyang County, Chongqing, in southwest China.
Neosauropoda was a titanosaurian sauropod dinosaurs clade that grew to enormous size according to body mass estimates. Smaller specimens are attributed to island dwarfism, although the trend in Titanosauria is downward growth.
The titanosaurians were some of the largest sauropod dinosaurs ever, while the titanosaurs were one of the biggest land animals that have existed. Dicraeosauridae is a subclass of diplodocoids that are characterized by both small size and titanosaurs. Even “dwarf” sauropod dinosaurs were much bigger than 1,100 lbs (500 kgs), a proportion achieved by roughly 10% of all mammal species’ body masses.
According to some researchers, sauropod dinosaurs may have reared up on their hind legs, utilizing the tail as a third ‘leg’ of a tripod since early in the field’s history.
The hypothesis that the diplodocid Barosaurus lentus reared up on its hind legs during life is represented by a skeletal mount from the American Museum of Natural History depicting the sauropod in this posture. In a 2005 paper, Rothschild and Molnar argued that if sauropod dinosaurs had walked upright on occasion, they would have suffered stress fractures in their forelimb “hands.” However, none were found after they assessed a large number of sauropod fossils.
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