Ecology Dental microwear texture analysis (DMTA) performed on a titanosauriform sauropod from the Turonian-aged Tamagawa Formation suggests that the sauropod fed on plant material that was softer than insect exoskeletons or mollusc shells, with the diet likely consisting of ferns and gymnosperms. The DMTA results also suggested that sauropods likely masticated more energetically than present-day
lepidosaurs do. When sauropods were first discovered, their immense size led many scientists to compare them with modern-day
whales. Most studies in the 19th and early 20th centuries concluded that sauropods were too large to have supported their weight on land, and therefore that they must have been mainly
aquatic. Most life restorations of sauropods in art through the first three quarters of the 20th century depicted them fully or partially immersed in water. This early notion was cast in doubt beginning in the 1950s, when a study by Kermack (1951) demonstrated that, if the animal were submerged in several metres of water, the pressure would be enough to fatally collapse the lungs and airway. However, this and other early studies of sauropod
ecology were flawed in that they ignored a substantial body of evidence that the bodies of sauropods were heavily permeated with
air sacs. In 1878, paleontologist E.D. Cope had even referred to these structures as "floats". Beginning in the 1970s, the effects of sauropod air sacs on their supposed aquatic lifestyle began to be explored. Paleontologists such as Coombs and Bakker used this, as well as evidence from
sedimentology and
biomechanics, to show that sauropods were primarily terrestrial animals. In 2004, D.M. Henderson noted that, due to their extensive system of air sacs, sauropods would have been buoyant and would not have been able to submerge their torsos completely below the surface of the water; in other words, they would float, and would not have been in danger of lung collapse due to water pressure when swimming. Studies published in 2021 suggest sauropods could not inhabit polar regions. This study suggests they were largely confined to tropical areas and had metabolisms that were very different to those of other dinosaurs, perhaps intermediate between mammals and reptiles. New studies published by Taia Wyenberg-henzler in 2022 suggest that sauropods in North America declined due to undetermined reasons in regards to their niches and distribution during the end of the Jurassic and into the latest Cretaceous. Why this is remains unclear, but some similarities in feeding niches between
iguanodontians,
hadrosauroids, and sauropods have been suggested and may have resulted in some competition. However, this cannot fully explain the full decline in distribution of sauropods, as competitive exclusion would have resulted in a much more rapid decline than what is shown in the fossil record. Moreover, it must be determined as to whether sauropod declines in North America was the result of a change in preferred flora that sauropods ate, climate, or other factors. It is also suggested in this same study that iguanodontians and hadrosauroids took advantage of recently vacated niches left by a decline in sauropod diversity during the late Jurassic and the Cretaceous in North America.
Herding and parental care '', formed herds segregated by age. Many lines of fossil evidence, from both bone beds and trackways, indicate that sauropods were gregarious animals that formed
herds. However, the makeup of the herds varied between species. Some bone beds, for example a site from the
Middle Jurassic of
Argentina, appear to show herds made up of individuals of various age groups, mixing juveniles and adults. However, a number of other fossil sites and trackways indicate that many sauropod species travelled in herds segregated by age, with juveniles forming herds separate from adults. Such segregated herding strategies have been found in species such as
Alamosaurus,
Bellusaurus and some
diplodocids. In a review of the evidence for various herd types, Myers and Fiorillo attempted to explain why sauropods appear to have often formed segregated herds. Studies of microscopic tooth wear show that juvenile sauropods had diets that differed from their adult counterparts, so herding together would not have been as productive as herding separately, where individual herd members could forage in a coordinated way. The vast size difference between juveniles and adults may also have played a part in the different feeding and herding strategies. A 2014 study suggested that the time from laying the egg to the time of the hatching was likely to have been between 65 and 82 days. Exactly how segregated versus age-mixed herding varied across different groups of sauropods is unknown. Further examples of gregarious behavior will need to be discovered from more sauropod species to detect possible distribution patterns.
Rearing stance , 1911 Since early in the history of their study, scientists, such as
Osborn, have speculated that sauropods could rear up on their hind legs, using the tail as the third 'leg' of a tripod. A skeletal mount depicting the
diplodocid Barosaurus lentus rearing up on its hind legs at the
American Museum of Natural History is one illustration of this hypothesis. In a 2005 paper, Rothschild and Molnar reasoned that if sauropods had adopted a bipedal posture at times, there would be evidence of stress fractures in the forelimb 'hands'. However, none were found after they examined a large number of sauropod skeletons. '', depicted in a rearing tripodal stance Heinrich Mallison (in 2009) was the first to study the physical potential for various sauropods to rear into a tripodal stance. Mallison found that some characters previously linked to rearing adaptations were actually unrelated (such as the wide-set hip bones of
titanosaurs) or would have hindered rearing. For example, titanosaurs had an unusually flexible backbone, which would have decreased stability in a tripodal posture and would have put more strain on the muscles. Likewise, it is unlikely that brachiosaurids could rear up onto the hind legs, as their center of gravity was much farther forward than other sauropods, which would cause such a stance to be unstable. Diplodocids, on the other hand, appear to have been well adapted for rearing up into a tripodal stance. Diplodocids had a center of mass directly over the hips, giving them greater balance on two legs. Diplodocids also had the most mobile necks of sauropods, a well-muscled pelvic girdle, and tail vertebrae with a specialised shape that would allow the tail to bear weight at the point it touched the ground. Mallison concluded that diplodocids were better adapted to rearing than
elephants, which do so occasionally in the wild. He also argues that stress fractures in the wild do not occur from everyday behaviour, for long would have used some half of its energy intake. Further, to move blood to such a height—dismissing posited auxiliary hearts in the neck—would require a heart 15 times as large as of a similar-sized whale. The above have been used to argue that the long neck must instead have been held more or less horizontally, presumed to enable feeding on plants over a wide area with less need to move about, yielding a large energy saving for such a large animal. Reconstructions of the necks of
Diplodocus and
Apatosaurus have therefore often portrayed them in near-horizontal, so-called "neutral, undeflected posture". However, research on living animals demonstrates that almost all extant
tetrapods hold the base of their necks sharply flexed when alert, showing that any inference from bones about habitual "neutral postures" Meanwhile, computer modeling of
ostrich necks has raised doubts over the flexibility needed for stationary grazing.
Trackways and locomotion ,
Italy at
Serras de Aire e Candeeiros Natural Park,
Portugal Sauropod
trackways and other
fossil footprints (known as "ichnites") are known from abundant evidence present on most continents. Ichnites have helped support other biological hypotheses about sauropods, including general fore and hind foot anatomy (see
Limbs and feet above). Generally, prints from the forefeet are much smaller than the hind feet, and often crescent-shaped. Occasionally ichnites preserve traces of the claws, and help confirm which sauropod groups lost claws or even digits on their forefeet. Sauropod tracks from the
Villar del Arzobispo Formation of early
Berriasian age in Spain support the gregarious behaviour of the group. The tracks are possibly more similar to
Sauropodichnus giganteus than any other ichnogenera, although they have been suggested to be from a basal titanosauriform. The tracks are wide-gauge, and the grouping as close to
Sauropodichnus is also supported by the manus-to-pes distance, the morphology of the manus being kidney bean-shaped, and the morphology of the pes being subtriangular. It cannot be identified whether the footprints of the herd were caused by juveniles or adults, because of the lack of previous trackway individual age identification. Generally, sauropod trackways are divided into three categories based on the distance between opposite limbs: narrow gauge, medium gauge, and wide gauge. The gauge of the trackway can help determine how wide-set the limbs of various sauropods were and how this may have impacted the way they walked. Occasionally, only trackways from the forefeet are found. Falkingham
et al. used computer modelling to show that this could be due to the properties of the substrate. These need to be just right to preserve tracks. Differences in hind limb and fore limb surface area, and therefore contact pressure with the substrate, may sometimes lead to only the forefeet trackways being preserved.
Biomechanics and speed ,
Plaza Huincul,
Argentina In a study published in PLoS ONE on October 30, 2013, by
Bill Sellers,
Rodolfo Coria,
Lee Margetts et al.,
Argentinosaurus was digitally reconstructed to test its locomotion for the first time. Before the study, the most common way of estimating speed was through studying bone
histology and
ichnology. Commonly, studies about sauropod bone histology and speed focus on the postcranial skeleton, which holds many unique features, such as an enlarged process on the
ulna, a wide lobe on the
ilia, an inward-slanting top third of the
femur, and an extremely ovoid femur shaft. Those features are useful when attempting to explain trackway patterns of graviportal animals. When studying ichnology to calculate sauropod speed, there are a few problems, such as only providing estimates for certain gaits because of
preservation bias, and being subject to many more accuracy problems. To estimate the gait and speed of
Argentinosaurus, the study performed a musculoskeletal analysis. The only previous musculoskeletal analyses were conducted on
hominoids,
terror birds, and other
dinosaurs. Before they could conduct the analysis, the team had to create a digital skeleton of the animal in question, show where there would be muscle layering, locate the muscles and joints, and finally find the muscle properties before finding the gait and speed. The results of the biomechanics study revealed that
Argentinosaurus was mechanically competent at a top speed of 2 m/s (5 mph) given the great weight of the animal and the strain that its joints were capable of bearing. The results further revealed that much larger terrestrial vertebrates might be possible, but would require significant body remodeling and possible sufficient behavioral change to prevent joint collapse. Two other possible dwarfs are
Rapetosaurus, which existed on the island of
Madagascar, an isolated island in the Cretaceous, and
Ampelosaurus, a titanosaur that lived on the Iberian peninsula of southern Spain and France.
Amanzia from Switzerland might also be a dwarf, but this has yet to be proven.
Paleopathology and paleoparasitology Sauropods are rarely known for preserved injuries or signs of illnesses, but more recent discoveries show they could suffer from such pathologies. A diplodocid specimen from the
Morrison Formation referred to as "Dolly" was described in 2022 with evidence of a severe respiratory infection. Sauropod ribs from
Yunyang County,
Chongqing, in southwest China show evidence of rib breakage by way of traumatic fracture, bone infection, and
osteosclerosis. A sauropod tibia exhibiting initial fracture has been described from the Middle Jurassic of Yunyang County in southwestern China.
Ibirania, a nanoid
titanosaur fossil from
Brazil, suggests that individuals of various genera were susceptible to diseases such as
osteomyelitis and parasite infestations. The specimen hails from the late cretaceous
São José do Rio Preto Formation,
Bauru Basin, and was described in the journal
Cretaceous Research by
Aureliano et al. (2021). Examination of the titanosaur's bones revealed what appear to be parasitic blood worms similar to the prehistoric
Paleoleishmania but are 10-100 times larger, that seemed to have caused the osteomyelitis. The fossil is the first known instance of an aggressive case of osteomyelitis being caused by blood worms in an extinct animal. ==History of discovery==