Apatosaurus ‭(‬Deceptive lizard‭)‬

Short Info

Apatosaurus ‭(‬Deceptive lizard‭)‬

Phonetic : A-pat-oh-sore-us.

Named By : Othniel Charles Marsh‭ ‬-‭ ‬1877

Diet : Herbivore

Size : Estimated 20-23 meters long

Type of Dinosaur : Sauropod

Type Species : A.‭ ‬ajax‭ (‬type‭)‬,‭ ‬A.‭ ‬louisae.

Found in : USA,‭ ‬Colorado,‭ ‬Oklahoma,‭ ‬Utah and Wyoming.

When it Lived : Late Jurassic, 154-145 million years ago

Apatosaurus (/@,paet@’so:r@s(also that means “deceptive lizard”) is an herbivore sauropod genus dinosaurs that was found throughout North America during the Late Jurassic period. Othniel Charles Marsh identified and named the first kind, A. ajax, in 1877. A other species A. louisae first discovered in the hands of William H. Holland in 1916. Apatosaurus was alive from 150 to 150 million years ago (mya) in the latter part of Kimmeridgian to the early Tithonian time period, and is currently recognized as fossils from the Morrison Formation of modern-day Colorado, Oklahoma, New Mexico, Wyoming, and Utah in the United States. Apatosaurus was averaging length of 21-22.8 meters (69-75 feet) and an average weight that was 16.4-22.4 tons (16.1-22.0 large tons, 18.1-24.7 shorter tons). A few of the specimens suggest an average length of 11-30% more than the average, and a weight in the range of 32.7-72.6 tonnes (32.2-71.5 tonnes long; 36.0-80.0 short tons).

Tadek Kurpaski from London, Poland, CC BY 2.0, via Wikimedia Commons

Cervical vertebrae from Apatosaurus are not as long and are more robustly constructed than those of Diplodocus diplodocid similar to Apatosaurus while the bones in the leg appear bigger despite being larger which suggests it was Apatosaurus was a stronger animal. The tail was elevated in the air when it was moving. Apatosaurus was equipped with a single claw for each forelimb as well as 3 claws on the hindlimbs. Its skull Apatosaurus skull, which was thought for a long time to be akin to Camarasaurus but is actually more like that of Diplodocus. Apatosaurus had a wide-ranging predator that probably held its head up. In order to lighten the vertebrae of its, Apatosaurus included air sacs which made the bones internal filled with holes. Similar to diplodocids in general, its tail could have been used to whip up loud sounds.

Apatosaurus ajax skull
James St. John, CC BY 2.0, via Wikimedia Commons

The Apatosaurus skull was mistaken for that from Camarasaurus or Brachiosaurus until 1909 in which the holotype of A. louisae discovered as well as a complete skull was found just a few metres away from the neck’s front. Henry Fairfield Osborn disagreed with the aforementioned association and later mounted the skull of Apatosaurus along with the Camarasaurus skull casting. Apatosaurus Skeletons were mounted using skull casts with speculative skulls up to 1970 which was the year that McIntosh discovered that more robust skulls belonging to Diplodocus were more likely to be from Apatosaurus.

Apatosaurus is one of the genera that belongs to the family of Diplodocidae. It is among the most basal genera with just Amphicoelias and perhaps a new unnamed genus that is that is more primitive. While it is true that the family Apatosaurinae was first named in the year 1929, the name wasn’t officially recognized until the extensive study of 2015. The only exception is that Brontosaurus is part of this subfamily with other genera being classified as synonyms or classified as diplodocines. Brontosaurus is for many years thought of as a junior synonym of Apatosaurus and its type species was classified as A. excelsus by 1903. A study from 2015 found that Brontosaurus is an authentic sauropod genus different from Apatosaurus, however not all paleontologists are in agreement with this classification. Since it was present throughout North America during the late Jurassic, Apatosaurus would have been a part of dinosaurs like Allosaurus, Camarasaurus, Diplodocus and Stegosaurus.

Sharp lull brontosaurus
Dinosaurs, by William Diller Matthew, Public domain, via Wikimedia Commons

Apatosaurus was a huge long-necked, quadrupedal creature with a whip-like tail. The forelimbs of the animal were smaller that its hind limbs. The majority of estimates of size are based on CM 3018, which is the one that is the type one from A. Louisae. In 1936, the measurement was found to be 21.8 meters (72 feet) through the spine. It is estimated that the current estimates are similar in that the individual was 21-22.8 meters (69-75 feet) tall and weighed the weight that was 16.4-22.4 tonnes (16.1-22.0 length tons and 18.1-24.7 short tons). A study from 2015 that calculated the volumetric model’s mass of Dreadnoughtus Apatosaurus as well as Giraffatitan estimates CM 3018’s mass at 21.8-38.2 tons (21.5-37.6 tonnes long; 24.0-42.1 shorter tons) Similar in weight to Dreadnoughtus. The estimates from the past have put the beast’s weight at 35.0 tons (34.4 length tons, 38.6 short tons). A few samples of A. Ajax (such such as OMNH 1670) are who are between 11 and 30 percent larger, indicating mass twice the size of CM 3018. The latter is 32.7-72.6 tons (32.2-71.5 lengthy tons and 36.0-80.0 shorter tons) possibly surpassing the biggest titanosaurs.

The skull is small comparison to the dimensions that the creature. The jaws are lined Spatulate (chisel-like) teeth, which are suitable for an herbivore’s diet. Its snout Apatosaurus and related diplodocoids is square in comparison to Nigersaurus having a more square skull. Braincases of Apatosaurus is preserved well in the specimen BYU 17096, and also preserved a large portion of the bones. A phylogenetic study revealed that the braincase exhibited a shape that was similar to other diplodocoids. Certain skulls from Apatosaurus are in an articulation process together with teeth. The teeth with the enamel exposed do not exhibit any marks on the surface. Instead they show a sweet texture with a very little wear.

Field Museum Apatosaurus with original incorrect skull
Gary Todd, CC0, via Wikimedia Commons

Similar to other sauropods, neck vertebrae are deep bifurcated. They also had neural spines that were surrounded by an enormous trough at the middle, resulting in a large deep neck. The vertebral formula used for the Holotype of A. louisae may be 15 cervicals 10 dorsals 5 sacrals with 82 caudals. The number of caudal vertebrae may vary within species. These cervical vertebrae in Apatosaurus as well as Brontosaurus are bigger and more sturdy than the vertebrae from others diplodocids and were discovered to be the most similar in appearance to Camarasaurus in the work of Charles Whitney Gilmore. They also have cervical ribs that are longer to the ground than diplodocines. They also have ribs and vertebrae which are narrower toward the neck’s top which makes the neck almost three-dimensional in its cross-section. In Apatosaurus louisae, the Atlas-axis structure of first cervicals are almost fused. Dorsal ribs, however, aren’t connected or tightly to vertebrae but more loosely articulated. Apatosaurus has 10 dorsal bones on each sides of its body. The neck’s large size was full of a large system of air sacs to help with weight. Apatosaurus as well as its close cousin Supersaurus has high neural spines, which comprise over half of the bones that make up its vertebrae. The tail’s shape is unique for an diplodocid as it’s comparatively thin due to the declining height of the vertebral spines as they move further of the hips. Apatosaurus also had extremely large ribs in comparison to other diplodocids and had an unusually large chest. Similar to other diplodocids the tail changed into a whip-like structure at the final.

AMNH Apatosaurus
ScottRobertAnselmo, CC BY-SA 3.0, via Wikimedia Commons

The bones in the limbs are extremely robust. Within Apatosaurinae the scapula of Apatosaurus louisae is in the morphology, and is in between A. Ajax along with Brontosaurus excelsus. Arm bones are strong so the humerus in Apatosaurus has a similar shape to Camarasaurus and Brontosaurus. However, the humeri from Brontosaurus along with A. Ajax are more alike that they do similar to A. Louisae. In 1936, Charles Gilmore noted that previous reconstructions of Apatosaurus forelimbs had incorrectly suggested that the ulna and radius could cross. In reality, they should have been in a parallel fashion. Apatosaurus had one massive claw that was on every forelimb which is a characteristic that is shared by all sauropods, with more descent than Shunosaurus. The three first toes had claws for each hindlimb. The Phalangeal formula is 2-1-1-1-1 meaning that the innermost finger (phalanx) that is on the forelimb is made up of two bones while the other has only one. The claw bone that is the only manual (ungual) can be found slightly curving and is squarely truncated at the anterior side of the. The pelvic girdle is comprised of the robust iliaas well as it is connected (co-ossified) pubes as well as the ischia. Femora from Apatosaurus are extremely strong and are among the strongest femora of any species of Sauropoda. The fibula and tibia bones are distinct from the slim bones of Diplodocus however, they are remarkably similar from the bones of Camarasaurus. The fibula is more long and thinner that the tibia. Foot of Apatosaurus is equipped with three claws that are located on the outermost number of digits. The formula for digits is 3-4-5-3-2. The first metatarsal happens to be the most slender, which is a characteristic that is common to diplodocids.

Initial Apatosaurus bones were found through Edward Drinker Cope and the term Apatosaurus Ajax was coined 1877 by the rival of Cope’s Othniel Charles Marsh who was Professor of Paleontology from Yale University, based on the skeleton that was nearly complete (holotype, YPM 1858) found within the foothills of eastern in the Rocky Mountains in Gunnison County, Colorado. The composite term Apatosaurus comes from the Greek words apate (apate)/apatelos (apatelos) meaning “deception”/”deceptive”, and sauros (sauros) meaning “lizard”; thus, “deceptive lizard”. Marsh named it in reference to the chevron bones that differ from the bones of other dinosaurs. rather, the chevron bones of Apatosaurus had similarities to the mosasaurs’ bones, which is probably belonging to the most representative species Mosasaurus. In the course of excavation and transport the bones from the holotype skull were mixed with the bones of an Apatosaurus person originally identified as Atlantosaurus immanis. As result, certain parts cannot be assigned to either specimen with certainty. Marsh has distinguished the new Genus Apatosaurus from Atlantosaurus by examining their amount of sacral vertebrae with Apatosaurus being the only one with three vertebrae, as opposed to Atlantosaurus four. A few two years after, Marsh made public the finding of a more complete specimen found at Como Bluff, Wyoming. Marsh gave the specimen a brand new name following the rules of his day and the comparatively slack fossil records available at the time. It was later discovered that the traits he used to differentiate species and genera were more common in sauropods. The new species was named Brontosaurus excelsus. The current collection of specimens considered Apatosaurus were found in the Morrison Formation, the location of the excavations at Marsh Cope and Marsh Cope.

FMNH Apatosaurus Pano
Zissoudisctrucker, CC BY-SA 4.0, via Wikimedia Commons

Another specimen, located in the American Museum of Natural History under specimen number 460 that is sometimes assigned to Apatosaurus and is thought to be nearly complete. Only the head feet, feet and a portion that make up the tail have been removed and it is the first sauropod skeleton to be mounted. The specimen was discovered near Medicine Bow, Wyoming, in 1898, by Walter Granger, and took all of the summer to extract. To complete the display of sauropods, feet found in the same quarry, as well as the tail that was fashioned to look like Marsh believed it should however, it was missing vertebrae were added. Additionally to a sculpted image of the way the museum believed it was the head of the huge creature would appear like was created. It was not a delicate skull as that of Diplodocus that was later discovered as more precise however it was based upon “the biggest, thickest, strongest skull bones, lower jaws and tooth crowns from three different quarries”. The skulls could be of Camarasaurus The only sauropod for which a good skull material was available in the early days. The construction of the mount was directed by Adam Hermann, who failed to locate Apatosaurus skulls. Hermann required to design an artificial skull using his hands. Osborn wrote in a journal in which the skull had been sculpted that it had been “largely conjectural and based on that of Morosaurus” (now Camarasaurus).

The year 1903 was the time that Elmer Riggs published a study that detailed a well-preserved, preserved diplodocid skeleton from the Grand River Valley near Fruita, Colorado, Field Museum of Natural History specimen P25112. Riggs believed that the fossils were comparable to the ones found at Como Bluff in Wyoming from where Marsh has described Brontosaurus. The majority of the skeleton was discovered, and following a comparison to each of Brontosaurus and Apatosaurus ajax Riggs discovered that the Holotype of A. Ajax was undeveloped and therefore the characteristics distinct between the two genera weren’t valid. Because Apatosaurus was the name used before, Brontosaurus should be considered as a junior synonym for Apatosaurus. Due to this, Riggs changed the name of Brontosaurus excelsus with Apatosaurus excelsus. Based on comparisons to other species believed to be related to the Apatosaurus family, Riggs also concluded that Field Columbian Museum specimen was most likely to be the closest specimen in appearance to A. excelsus.

Despite Riggs book, Henry Fairfield Osborn, who was a fierce opposer of Marsh and the taxa he was a part of classified as the Apatosaurus mounted at the American Museum of Natural History Brontosaurus. Due to this decision, Brontosaurus was named after him. Brontosaurus was frequently used outside of the scientific literature for the species that Riggs thought was Apatosaurus as well as the museum’s fame resulted in Brontosaurus was among the most well-known dinosaurs despite being not valid through the entire 20th and early 21st century.

It wasn’t till 1909 when the first Apatosaurus skull was discovered on the first expedition led by Earl Douglass, to what was later referred to as the Carnegie Quarry at Dinosaur National Monument. The skull was discovered a only a short distance from an bone skeleton (specimen CM 3018) identified as the newly discovered species Apatosaurus louisae. It was named for Louise Carnegie, wife of Andrew Carnegie, who funded field studies to discover complete dinosaur skeletons found in the American West. The skull was identified as CM 1162. It was identical with the skull found in Diplodocus. Another smaller skeleton belonging to A. Louisae was located close to CM 11162 and 3018. The skull was recognized as being part of the Apatosaurus species in the hands of Douglass as well as Carnegie Museum director William H. Holland however, others scientists – including Osborn did not agree with this classification. Holland was able to defend his position in 1914 in a speech in the Paleontological Society of America, however, Holland did not leave his Carnegie Museum mount headless. Some believed Holland was trying to stay out of conflict with Osborn however, some believed Holland had been waiting for an articulated neck and skull was discovered to prove that the skull was linked to and the skeleton. Following the death of Holland in 1934 museum personnel put a mold of the Camarasaurus skull onto the wall.

Although museums were using cast or sculptured Camarasaurus skulls mounted on Apatosaurus mounts however, the Yale Peabody Museum decided to make a skull modelled in the lower jaw of the Camarasaurus and the cranium modelled on the drawing of Marsh’s in 1891 of the skull. The skull also featured nasals that pointed forward – which is a first for any dinosaur, and fenestrae that differed from the drawings and the other skulls.

There was no Apatosaurus skull was ever mentioned in writing until the 1970s, when John Stanton McIntosh and David Berman revised skulls of Diplodocus and Apatosaurus. They discovered that even though Holland never published his thoughts, Holland was almost certainly right, and that Apatosaurus was a skull that resembled Diplodocus. According to them skulls that were thought to be related to Diplodocus could actually be of Apatosaurus. They assigned multiple skulls to Apatosaurus due to the fact that they were associated with and closely related vertebrae. While they were in support of Holland and the other scientists, it was discovered that Apatosaurus could have had the Camarasaurus-like skull. This was in reference to a disarticulated camarasaurus-like tooth discovered at the exact place at which an Apatosaurus skull was found many earlier. On the 20th of October, 1979, following the publication of McIntosh and Berman the first authentic skull found by Apatosaurus was exhibited on a skeleton inside the museum of the Carnegie. In 1998, it was proposed that Felch Quarry skull which Marsh included in his 1896 skeletal reconstruction rather belonged to Brachiosaurus. In 2011, the first example of Apatosaurus with a skull discovered to be articulated by its cervical vertebraes was identified. The example, CMC VP 7180, was found to be different in skull and neck characteristics with A. louisae. However, it shared many of the features of cervical vertebrae and A. Ajax. Another skull that is well preserved can be found in Brigham Young University specimen 17096 which is a well-preserved skull as well as skull, which is also a skeleton with preserved braincase. The specimen was discovered within Cactus Park Quarry in western Colorado.

Most modern paleontologists agree with Riggs that both dinosaurs should be classified as one species. In accordance with guidelines of ICZN (which regulates the scientific names for animals) The name Apatosaurus which was published first, is the one to be used as the official name. Brontosaurus was thought to be a minor synonym, and therefore removed from official use. However, at the very the very least, one paleontologist – Robert T. Bakker – was of the opinion in the 1990s A. Ajax in addition to A. excelsus are actually sufficiently different to warrant an independent species.

The year 2015 was the first time Emanuel Tschopp, Octavio Mateus as well as Roger Benson released a paper on diplodocoid systematics. The authors suggested that genera could be distinguished by 13 distinct characters and that species could be classified by six. The minimal number needed for generic distinction was chosen on the reality that A. Ajax as well as A. louisae are different in 12 characters, and Diplodocus carnegiei as well as D. hallorum differ in eleven characters. Therefore, 13 characters were chosen to verify the differentiation of genera. The six distinct features that are used to define a specific distinction were selected by calculating the number of different characteristics in different specimens that are generally accepted to be a single species. There is only one distinct character between D. carnegiei and A. louisae. However, there are five distinct characteristics in B. excelsus. Therefore, Tschopp et al. claimed the argument that Apatosaurus excelsus, which was originally identified in the genus Brontosaurus excelsus, had sufficient distinct morphological characteristics in comparison to other species belonging to Apatosaurus that it was a good candidate to be classified as a distinct Genus. The decision was based on a study of 477 morphological traits among 81 different dinosaurs. One of the most notable differences is the larger and, presumably, stronger necks of Apatosaurus species as compared the neck of B. excelsus. Other species that were previously classified as Apatosaurus like Elosaurus parvus, and Eobrontosaurus yahnahpin , were also reclassified as Brontosaurus. The features that were proposed to distinguish Brontosaurus from Apatosaurus are: the posterior dorsal vertebrae , with the central region being larger than the width; scapula extending towards the acromial edge, and the distal blade being slit and the acromial edge that is the distal edge of the scapular blade having an expanded rounded shape as well as the proportion of the proximodistal width to the transverse breadth of the astragalus 0.55 or greater. Sauropod specialist Michael Daniel D’Emic pointed out that the criteria selected were in a large degree arbitrarily chosen and would need to be changed Brontosaurus to be re-examined if subsequent analyses yielded different results. The mammal paleontologist Donald Prothero criticized the mass media’s reaction to this study as being rushed and superficial and said the name should remain “Brontosaurus” in quotes and do not regard the name as an actual Genus.

Source: Wikipedia