Massospondylus
Encyclopedia
Massospondylus is a genus
of prosauropod dinosaur
from the early Jurassic
Period (Hettangian
to Pliensbachian
ages
, ca. 200–183 million years ago). It was described by Sir Richard Owen
in 1854 from remains found in South Africa
, and is thus one of the first dinosaurs to have been named. Fossils have since been found at other locations in South Africa, Lesotho
, and Zimbabwe
. Material from Arizona
's Kayenta Formation
, India
, and Argentina
has been assigned to this genus at various times, but the Arizonan and Argentinian material are now assigned to other genera.
The type
species is M. carinatus; seven other species have been named during the past 150 years, but only M. kallae among these is still considered valid. Prosauropod systematics
have undergone numerous revisions during the last several years, and many scientists disagree where exactly Massospondylus lies on the dinosaur evolutionary tree. The family name Massospondylidae
was once coined for the genus, but because knowledge of prosauropod relationships is in a state of flux, it is unclear which other dinosaurs—if any—belong in a natural grouping of massospondylids; several 2007 papers support the family's validity.
Although Massospondylus was long depicted as quadruped
al, a 2007 study found it to be bipedal. It was probably a plant eater (herbivore), although it is speculated that the prosauropods may have been omnivorous
. This animal, 4–6 meters (13–20 feet) long, had a long neck and tail, with a small head and slender body. On each of its forefeet, it bore a sharp thumb claw that was used in defense or feeding. Recent studies indicate Massospondylus grew steadily throughout its lifespan, possessed air sacs similar to those of birds, and may have cared for its young.
al, a 2007 anatomical study of the forelimbs has questioned this, arguing that their range of motion precluded effective habitual quadrupedal gait. The study also ruled out the possibility of "knuckle-walking" and other forms of locomotion that would avoid the issue of the limited ability of Massospondylus to pronate
its hands. Although its mass suggests a quadrupedal nature, it would have been restricted to its hind legs for locomotion.
Massospondylus was a typical prosauropod in most other respects. It possessed a slender body and long neck, with around nine long cervical (neck) vertebrae, 13 dorsal (back) vertebrae, three sacral (hip) vertebrae, and at least 40 caudal (tail) vertebrae. The pubis
faced forward, as with most saurischia
ns. It had a slighter build than that of Plateosaurus
, an otherwise similar prosauropod dinosaur. A recent discovery shows that Massospondylus possessed well-developed clavicle
s, joined in a furcula
-like arrangement, suggesting both that it had immobile shoulder blades
and that clavicles were not rudimentary and nonfunctional in those dinosaurs that did not have true furculae. This discovery also indicates that the furcula of bird
s is derived from clavicles.
Like Plateosaurus, it had five digits on each foot, with a large thumb claw used for feeding or defense against predators. The fourth and fifth digits of the forepaws were tiny, giving the forepaws a lopsided look. The 2007 study indicated that Massospondylus held its manus
(hands) in a semi-supinated ("prayer-like") orientation, with the palmar surfaces facing one another; the wrist was never found rotated in articulated (still-connected) fossil specimens.
The small head of Massospondylus was approximately half the length of the femur
. Numerous openings, or fenestrae
, in the skull reduced its weight and provided space for muscle attachment and sensory organs. These fenestrae were present in pairs, one on each side of the skull. At the front of the skull were two large, elliptical nares
. The orbits
were proportionally larger in Massospondylus than in related genera such as Plateosaurus. The antorbital fenestra
e, smaller than those seen in Plateosaurus, were situated between the eyes and the nose. At the rear of the skull were two more pairs of temporal fenestrae: the lateral temporal fenestra
e immediately behind the eye sockets and the supratemporal fenestrae on top of the skull. Small fenestrae also penetrated each mandible
. The shape of the skull is traditionally restored as wider and shorter than that of Plateosaurus, but this appearance may be due just to differential crushing experienced by the various specimens. Some features of the skull are variable between individuals; for example, the thickness of the upper border of the orbit and the height of the posterior maxilla
. These differences may be due to sexual dimorphism
or individual variation.
As with other prosauropods, it has been proposed that Massospondylus had cheeks. This theory was proposed because there are a few large holes for blood vessels on the surfaces of the jaw bones, unlike the numerous small holes present on the jaws of cheekless reptiles. The cheeks would have prevented food from spilling out when Massospondylus ate. Crompton and Attridge (1986) described skulls of Massospondylus as possessing pronounced overbite
s and suggested the presence of a horny
beak on the tip of the lower jaw to make up the difference in length and account for tooth wear on the teeth at the tip of the snout. However, this was later shown to be a misinterpretation based on crushing in a top–bottom plane. Skulls not crushed in this orientation do not show an overbite. There also seems to be some variation of tooth morphology based on the position of teeth in the jaw. The heterodont
y present in Massospondylus is greater than that present in Plateosaurus
, although unsurprisingly not as pronounced as the specialization of teeth in Heterodontosaurus
. Teeth closer to the front of the snout had round cross-sections and tapered to points, unlike the back teeth, which were spatula
te and had oval cross-sections.
Sir Richard Owen
in 1854, the name having been derived from the Greek
terms masson/μάσσων 'longer' and spondylos/σπόνδυλος 'vertebra'. These fossils were found in 1853 by J. M. Orpen in the Upper Elliot Formation
at Harrismith
, South Africa
. Included among the remains were vertebrae from the neck, back, and tail; a shoulder blade; a humerus
; a partial pelvis; a femur; a tibia
; and bones of the hands and feet. The original holotype
material was part of the Royal College of Surgeons
collection in London and was destroyed in World War II
; only casts remain. Possible Massospondylus remains have been found in the Upper Elliot Formation, the Clarens Formation
, and the Bushveld Sandstone of South Africa and Lesotho
; the Forest Sandstone and the Upper Karroo Sandstone of Zimbabwe
; and the Kayenta Formation
of Arizona
. These remains consist of at least 80 partial skeletons and four skulls, representing both juveniles and adults.
The report of Massospondylus from Arizona's Kayenta Formation is based on a skull described in 1985. The skull of the Kayenta specimen from Arizona is 25% larger than the largest skull from any African specimen. The Kayenta specimen possesses four teeth in the premaxilla
and sixteen in the maxilla
. Uniquely among dinosaurs, it also had tiny, one-millimeter-(0.04 in-) long palatal teeth. Recent restudy of African Massospondylus skulls, however, indicates that the Kayenta specimen does not pertain to Massospondylus. This Kayenta skull and associated postcranial elements, identified collectively as MCZ 8893, has been recently referred to the newly described genus Sarahsaurus
.
Massospondylus had also been reported from Argentina
, but this has been reassessed as a closely related but distinct genus. The fossils included several partial skeletons and at least one skull, found in the Lower Jurassic
Canon del Colorado Formation
of San Juan
, Argentina. This material was named Adeopapposaurus
in 2009.
. Other named species include: M. browni (Seeley
, 1895), M. harriesi (Broom
1911), M. hislopi (Lydekker
, 1890), M. huenei (Cooper, 1981), M. kaalae (Barrett 2009), M. rawesi (Lydekker, 1890), and M. schwarzi (Haughton, 1924).
M. browni, M. harriesi, and M. schwarzi were all found in the Upper Elliot Formation of Cape Province
, South Africa. All three are based on fragmentary material, and were regarded as indeterminate
in the most recent review. M. browni is based on two cervical
, two back, and three caudal
vertebrae and miscellaneous hind limb elements. M. harriesi is known from a forelimb. M. schwarzi is known from an incomplete hind limb and sacrum
. M. hislopi and M. rawesi were named from fossils found in India
. M. hislopi is based on vertebrae from the Upper Triassic
Maleri Formation of Andhra Pradesh
, whereas M. rawesi is based on a tooth from the Upper Cretaceous
Takli Formation of Maharashtra
. M. hislopi was tentatively retained as an indeterminate sauropodomorph in the latest review, but M. rawesi may be a theropod
or nondinosaur. M. huenei is a combination derived by Cooper for Lufengosaurus huenei
, as he considered Lufengosaurus and Massospondylus to be synonyms. This synonymy is no longer accepted.
M. kaalae was described in 2009 on the basis of a partial skull found from the upper Elliot Formation in the Herschel District of South Africa. This species is known from the same time and region as some specimens of M. carinatus. It differs from the type species in the morphology of the braincase, as well as in several other characters of the skull such as the proportions of the premaxilla.
in 1894. According to Broom (1911), "Originally most of the skeleton was in the rock, and it was regarded by the farmers as the skeleton of a Bushman, but it is said to have been destroyed through fear that a Bushman skeleton in the rock might tend to weaken the religious belief of the rising generation." Some partial leg bones were salvaged. The following year, Richard Owen named a few fossil vertebrae Leptospondylus capensis and Pachyspondylus orpenii. These fragmentary fossils were later destroyed in World War II. Aristosaurus erectus was named by E.C.N. van Hoepen in 1920 based on a nearly complete skeleton. Hoepen also named Dromicosaurus gracilis, which consisted of a partial skeleton. Gryponyx taylori was named by Sidney H. Haughton
in 1924. It consists of hip bones. All of the above fossils come from the Hettangian or Sinemurian faunal stages of South Africa, where Massospondylus has been found. Under the rules of zoological nomenclature, these names are junior synonym
s. They were named after Massospondylus was described in a scientific paper; the name Massospondylus thus takes priority.
Ignavusaurus
, known from a young specimen, may also be synonymous with Massospondylus.
Massospondylus is a prosauropod, a grouping of early saurischia
n dinosaurs that lived during the Triassic and Jurassic, but which had died out by the end of the Jurassic. Other members of the group include Plateosaurus
, Yunnanosaurus
, and Riojasaurus
. Basal sauropodomorph systematics continue to undergo revision, and many genera once considered classic prosauropods have recently been removed from the group in phylogenetic nomenclature
, on the grounds that their inclusion would not constitute a clade
(a natural grouping containing all descendants of a single common ancestor). Exactly which animals constitute a monophyletic
(natural grouping) of prosauropods is unclear. Yates and Kitching
(2003) published a clade consisting of Riojasaurus, Plateosaurus, Coloradisaurus
, Massospondylus, and Lufengosaurus
. Galton and Upchurch (2004) included Ammosaurus
, Anchisaurus
, Azendohsaurus
, Camelotia
, Coloradisaurus, Euskelosaurus
, Jingshanosaurus
, Lessemsaurus
, Lufengosaurus, Massospondylus, Melanorosaurus
, Mussaurus
, Plateosaurus, Riojasaurus, Ruehleia
, Saturnalia
, Sellosaurus, Thecodontosaurus
, Yimenosaurus
and Yunnanosaurus in a monophyletic Prosauropoda. Wilson (2005) considered Massospondylus, Jingshanosaurus, Plateosaurus, and Lufengosaurus a natural group, with Blikanasaurus
and Antetonitrus
possible sauropods. Bonnan and Yates (2007) considered Camelotia, Blikanasaurus and Melanorosaurus possible sauropods. Yates (2007) placed Antetonitrus, Melanorosaurus, and Blikanasaurus as basal sauropods and declined to use the term Prosauropoda, as he considered it synonymous with Plateosauridae. However, he did not rule out the possibility that a small group of prosauropods consisting of Plateosaurus, Riojasaurus, Massospondylus and their closest kin were monophyletic.
Massospondylus is the type genus
of the proposed family Massospondylidae
, to which it gives its name. The Massospondylidae family may also include Yunnanosaurus, although Lu et al. (2007) placed Yunnanosaurus in its own family. Yates (2007) considered Massospondylus, Coloradisaurus, and Lufengosaurus massospondylids, with Yunnanosaurus in Anchisauria
. Smith and Pol (2007) also found a Massospondylidae in their phylogenetic analysis, including Massospondylus, Coloradisaurus, and Lufengosaurus, as well as their new genus, Glacialisaurus
. Adeopapposaurus, based on the fossils once thought to belong to a South American form of Massospondylus, was also classified as a massospondylid. Pradhania
was originally regarded as a basal
sauropodomorph
but new cladistic analysis performed by Novas et al., 2011 suggests that Pradhania is a massospondylid
. Pradhania presents two synapomorphies of Masospondylidae recovered in their phylogenetic analysis and its fossils were discovered from the same region and basin in India
as M. hislopi.
s and flora
s of the Early Jurassic were similar worldwide, with conifer
s adapted for hot weather becoming the common plants, and prosauropods and basal
theropod
s the main constituents of a worldwide dinosaur fauna. The environment of early Jurassic southern Africa has been described as a desert. African Massospondylus was a contemporary of early crocodylomorphs
; tritylodontid
and trithelodontid
therapsid
s; morganucodon
tid mammal
s; and dinosaurs including the small theropod Megapnosaurus rhodesiensis
; a species of Melanorosaurus
(M. thabanensis); and several genera of early ornithischia
ns, such as Lesothosaurus
and the heterodontosaurids
Abrictosaurus
, Heterodontosaurus
, and Lycorhinus
.
It is not clear which carnivores may have preyed on Massospondylus. Most of the theropods which have been discovered in rocks of Early Jurassic age in southern Africa, such as Megapnosaurus, were smaller than mid-sized prosauropods like Massospondylus. These smaller predators have been postulated as using fast slashing attacks to wear down prosauropods, which could have defended themselves with their large hand and foot claws. The 6-meter-(20 ft-) long carnivorous theropod Dracovenator
lived during the same period (Hettangian to Sinemurian stages) as Massospondylus and has also been found in the Elliot Formation of South Africa.
As with all dinosaurs, much of the biology of Massospondylus, including its behavior, coloration, and physiology, remains unknown. However, recent studies have allowed for informed speculation on subjects such as growth patterns, diet, posture, reproduction, and respiration.
A 2007 study suggested that Massospondylus may have used its short arms in defense from predators ("defensive swats"), in intraspecies combat, or in feeding, although its arms were too short to reach its mouth. Scientists speculate that Massospondylus could have used its large pollex
(thumb) claw in combat, to strip plant material from trees, digging, or for grooming.
A 2005 study indicated that Massospondylus sister taxon, Plateosaurus, exhibited growth patterns affected by environmental factors. The study indicated that when food was plentiful, or when the climate was favorable, Plateosaurus exhibited accelerated growth. This pattern of growth is called "developmental plasticity". It is unseen in other dinosaurs, including Massospondylus, despite the close relationship between Plateosaurus and Massospondylus. The study indicated that Massospondylus grew along a specific growth trajectory with little variation in the growth rate and ultimate size of an individual. Another study of age determination
indicated that Massospondylus grew at a maximum rate of 34.6 kg (76.3 lb) per year and was still growing at around 15 years of age.
. As recently as the 1980s, paleontologists debated the possibility of carnivory
in prosauropods. However, the hypothesis of carnivorous prosauropods has been discredited, and all recent studies favor a herbivorous or omnivorous lifestyle for these animals. Galton and Upchurch (2004) found that cranial characteristics (such as jaw articulation) of most prosauropods are closer to those of herbivorous reptiles than those of carnivorous ones, and the shape of the tooth crown
is similar to those of modern herbivorous or omnivorous iguana
s. The maximum width of the crown was greater than that of the root, resulting in a cutting edge similar to those of extant herbivorous or omnivorous reptiles. Barrett (2000) proposed that prosauropods supplemented their herbivorous diets with small prey or carrion
. Gastrolith
s (gizzard stones) have been found in association with Massospondylus fossils in South Africa, and with a Massospondylus-like animal from the Late Triassic
of Virginia
. Massospondylus swallowed these stones to aid in digestion; muscular contractions in the creature's gizzard would have pulverized swallowed plant material, compensating for its inability to chew.
In 1977, seven 190-million-year-old Massospondylus eggs were found in Golden Gate Highlands National Park
in South Africa
by James Kitching
, who identified them as most likely belonging to Massospondylus. It was nearly 30 years before extraction was started on the fossils of the 15-centimeter- (6 in-) long embryos. They remain the oldest dinosaur embryos ever found. Notably, the near-hatchlings had no teeth, suggesting they had no way of feeding themselves. Based on the lack of teeth and the animal's body proportions, scientists speculate that postnatal care might have been necessary. The four legs of the near-hatchlings were of equal length, indicating that newly hatched Massospondylus were quadrupedal. The skull and eyes were proportionately oversized when compared to adults, as is common in other very young vertebrates, although the skulls of juveniles were taller and more narrow as well. The quadrupedality of the hatchlings suggests that the quadrupedal posture of later sauropods may have evolved from retention of juvenile characteristics in adult animals, an evolutionary phenomenon known as pedomorphosis.
n dinosaurs possessed vertebrae and ribs that contained hollowed-out cavities (pneumatic foramina
), which reduced the weight of the bones and may have served as a basic 'flow-through ventilation' system similar to that of modern birds. In such a system, the neck vertebrae and ribs are hollowed out by the cervical air sac; the upper back vertebrae, by the lung
; and the lower back and sacral
(hip) vertebrae, by the abdominal air sac. These organs constitute a complex and very efficient method of respiration. Prosauropods are the only major group of saurischians without an extensive system of pneumatic foramina. Although possible pneumatic indentations have been found in Plateosaurus and Thecodontosaurus, the indentations were very small. One study in 2007 concluded that prosauropods like Massospondylus likely had abdominal and cervical air sacs, based on the evidence for them in sister taxa (theropods and sauropods). The study concluded that it was impossible to determine whether prosauropods had a bird-like flow-through lung, but that the air sacs were almost certainly present.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of prosauropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the early Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
Period (Hettangian
Hettangian
The Hettangian is the earliest age or lowest stage of the Jurassic period of the geologic timescale. It spans the time between 199.6 ± 0.6 Ma and 196.5 ± 1 Ma . The Hettangian follows the Rhaetian and is followed by the Sinemurian.In Europe stratigraphy the Hettangian is a part of the time span in...
to Pliensbachian
Pliensbachian
The Pliensbachian is an age of the geologic timescale or stage in the stratigraphic column. It is part of the Early or Lower Jurassic epoch or series and spans the time between 189.6 ± 1.5 Ma and 183 ± 1.5 Ma . The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian.The...
ages
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
, ca. 200–183 million years ago). It was described by Sir Richard Owen
Richard Owen
Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...
in 1854 from remains found in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, and is thus one of the first dinosaurs to have been named. Fossils have since been found at other locations in South Africa, Lesotho
Lesotho
Lesotho , officially the Kingdom of Lesotho, is a landlocked country and enclave, surrounded by the Republic of South Africa. It is just over in size with a population of approximately 2,067,000. Its capital and largest city is Maseru. Lesotho is a member of the Commonwealth of Nations. The name...
, and Zimbabwe
Zimbabwe
Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...
. Material from Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
's Kayenta Formation
Kayenta Formation
The Kayenta Formation is a geologic layer in the Glen Canyon Group that is spread across the Colorado Plateau province of the United States, including northern Arizona, northwest Colorado, Nevada, and Utah. This rock formation is particularly prominent in southeastern Utah, where it is seen in the...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, and Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
has been assigned to this genus at various times, but the Arizonan and Argentinian material are now assigned to other genera.
The type
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
species is M. carinatus; seven other species have been named during the past 150 years, but only M. kallae among these is still considered valid. Prosauropod systematics
Systematics
Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...
have undergone numerous revisions during the last several years, and many scientists disagree where exactly Massospondylus lies on the dinosaur evolutionary tree. The family name Massospondylidae
Massospondylidae
Massospondylidae is a family of massopod sauropodomorphs. Massospondylids are early sauropodomorph dinosaurs which existed in Asia, Africa and South America during the Late Triassic to the Early Jurassic periods...
was once coined for the genus, but because knowledge of prosauropod relationships is in a state of flux, it is unclear which other dinosaurs—if any—belong in a natural grouping of massospondylids; several 2007 papers support the family's validity.
Although Massospondylus was long depicted as quadruped
Quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al, a 2007 study found it to be bipedal. It was probably a plant eater (herbivore), although it is speculated that the prosauropods may have been omnivorous
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
. This animal, 4–6 meters (13–20 feet) long, had a long neck and tail, with a small head and slender body. On each of its forefeet, it bore a sharp thumb claw that was used in defense or feeding. Recent studies indicate Massospondylus grew steadily throughout its lifespan, possessed air sacs similar to those of birds, and may have cared for its young.
Description
Massospondylus was a mid-sized prosauropod that was around 4 meters (13 ft) in length and weighed approximately 135 kilograms (300 lb), although a few sources have estimated its length at up to 6 meters (20 ft). Although long assumed to have been quadrupedQuadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al, a 2007 anatomical study of the forelimbs has questioned this, arguing that their range of motion precluded effective habitual quadrupedal gait. The study also ruled out the possibility of "knuckle-walking" and other forms of locomotion that would avoid the issue of the limited ability of Massospondylus to pronate
Pronation
In anatomy, pronation is a rotational movement of the forearm at the radioulnar joint, or of the foot at the subtalar and talocalcaneonavicular joints. For the forearm, when standing in the anatomical position, pronation will move the palm of the hand from an anterior-facing position to a...
its hands. Although its mass suggests a quadrupedal nature, it would have been restricted to its hind legs for locomotion.
Massospondylus was a typical prosauropod in most other respects. It possessed a slender body and long neck, with around nine long cervical (neck) vertebrae, 13 dorsal (back) vertebrae, three sacral (hip) vertebrae, and at least 40 caudal (tail) vertebrae. The pubis
Pubis (bone)
In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons pubis....
faced forward, as with most saurischia
Saurischia
Saurischia meaning 'lizard' and ischion meaning 'hip joint') is one of the two orders, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure...
ns. It had a slighter build than that of Plateosaurus
Plateosaurus
Plateosaurus is a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 216 to 199 million years ago, in what is now Central and Northern Europe. Plateosaurus is a basal sauropodomorph dinosaur, a so-called "prosauropod"...
, an otherwise similar prosauropod dinosaur. A recent discovery shows that Massospondylus possessed well-developed clavicle
Clavicle
In human anatomy, the clavicle or collar bone is a long bone of short length that serves as a strut between the scapula and the sternum. It is the only long bone in body that lies horizontally...
s, joined in a furcula
Furcula
The ' is a forked bone found in birds, formed by the fusion of the two clavicles. In birds, its function is the strengthening of the thoracic skeleton to withstand the rigors of flight....
-like arrangement, suggesting both that it had immobile shoulder blades
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
and that clavicles were not rudimentary and nonfunctional in those dinosaurs that did not have true furculae. This discovery also indicates that the furcula of bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s is derived from clavicles.
Like Plateosaurus, it had five digits on each foot, with a large thumb claw used for feeding or defense against predators. The fourth and fifth digits of the forepaws were tiny, giving the forepaws a lopsided look. The 2007 study indicated that Massospondylus held its manus
Manus (zoology)
The manus is the zoological term for the distal portion of the fore limb of an animal. In tetrapods, it is the part of the pentadactyl limb that includes the metacarpals and digits . During evolution, it has taken many forms and served a variety of functions...
(hands) in a semi-supinated ("prayer-like") orientation, with the palmar surfaces facing one another; the wrist was never found rotated in articulated (still-connected) fossil specimens.
Cranial anatomy
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
. Numerous openings, or fenestrae
Fenestrae
Fenestræ is a Latin word that means "window".* In histology, fenestræ are small pores in endothelial cells that allow for rapid exchange of molecules between sinusoid blood vessels and surrounding tissue...
, in the skull reduced its weight and provided space for muscle attachment and sensory organs. These fenestrae were present in pairs, one on each side of the skull. At the front of the skull were two large, elliptical nares
Nostril
A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation...
. The orbits
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
were proportionally larger in Massospondylus than in related genera such as Plateosaurus. The antorbital fenestra
Antorbital fenestra
An antorbital fenestra is an opening in the skull, in front of the eye sockets. This skull formation first appeared in archosaurs during the Triassic Period. Living birds today possess antorbital fenestrae, but the feature has been lost in modern crocodilians...
e, smaller than those seen in Plateosaurus, were situated between the eyes and the nose. At the rear of the skull were two more pairs of temporal fenestrae: the lateral temporal fenestra
Infratemporal fenestra
An infratemporal fenestra, also called the lateral temporal fenestra is an opening in the skull behind the orbit in some animals. An opening in front of the eye sockets, conversely, is called an antorbital fenestra. Both of these openings reduced the weight of the skull. Infratemporal fenestrae are...
e immediately behind the eye sockets and the supratemporal fenestrae on top of the skull. Small fenestrae also penetrated each mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
. The shape of the skull is traditionally restored as wider and shorter than that of Plateosaurus, but this appearance may be due just to differential crushing experienced by the various specimens. Some features of the skull are variable between individuals; for example, the thickness of the upper border of the orbit and the height of the posterior maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
. These differences may be due to sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
or individual variation.
As with other prosauropods, it has been proposed that Massospondylus had cheeks. This theory was proposed because there are a few large holes for blood vessels on the surfaces of the jaw bones, unlike the numerous small holes present on the jaws of cheekless reptiles. The cheeks would have prevented food from spilling out when Massospondylus ate. Crompton and Attridge (1986) described skulls of Massospondylus as possessing pronounced overbite
Malocclusion
A malocclusion is a misalignment of teeth or incorrect relation between the teeth of the two dental arches. The term was coined by Edward Angle, the "father of modern orthodontics", as a derivative of occlusion, which refers to the manner in which opposing teeth meet.-Presentation:Most people have...
s and suggested the presence of a horny
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
beak on the tip of the lower jaw to make up the difference in length and account for tooth wear on the teeth at the tip of the snout. However, this was later shown to be a misinterpretation based on crushing in a top–bottom plane. Skulls not crushed in this orientation do not show an overbite. There also seems to be some variation of tooth morphology based on the position of teeth in the jaw. The heterodont
Heterodont
The anatomical term heterodont refers to animals which possess more than a single tooth morphology. For example, members of the Synapsida generally possess incisors, canines , premolars, and molars. The presence of heterodont dentition is evidence of some degree of feeding/hunting specialization...
y present in Massospondylus is greater than that present in Plateosaurus
Plateosaurus
Plateosaurus is a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 216 to 199 million years ago, in what is now Central and Northern Europe. Plateosaurus is a basal sauropodomorph dinosaur, a so-called "prosauropod"...
, although unsurprisingly not as pronounced as the specialization of teeth in Heterodontosaurus
Heterodontosaurus
Heterodontosaurus is a genus of small herbivorous dinosaur with prominent canine teeth which lived in the Early Jurassic of South Africa. It was similar to a hypsilophodont in shape, and ate plants, despite its canines.Heterodontosaurus is currently known from specimens of the SAFM from South...
. Teeth closer to the front of the snout had round cross-sections and tapered to points, unlike the back teeth, which were spatula
Spatula
The term spatula is used to refer to various small implements with a broad, flat, flexible blade used to mix, spread and lift materials including foods, drugs, plaster and paints...
te and had oval cross-sections.
Discovery
The first fossils of Massospondylus were described by paleontologistPaleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
Sir Richard Owen
Richard Owen
Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...
in 1854, the name having been derived from the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
terms masson/μάσσων 'longer' and spondylos/σπόνδυλος 'vertebra'. These fossils were found in 1853 by J. M. Orpen in the Upper Elliot Formation
Upper Elliot Formation
The Upper Elliot Formation is a geological formation dating to roughly between 200 to 190 million years ago and covering the Hettangian to Sinemurian stages. The Upper Elliot Formation is found in South Africa and Lesotho and is a member of the Stormberg Group. It consists mainly of limestone,...
at Harrismith
Harrismith
Harrismith, named after Sir Harry Smith, is a large town in the Free State province of South Africa, situated on the N3 highway approximately midway between Johannesburg, about 300 km north-east, and Durban. The town is at the junction with the N5 highway, which continues west towards the...
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. Included among the remains were vertebrae from the neck, back, and tail; a shoulder blade; a humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
; a partial pelvis; a femur; a tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
; and bones of the hands and feet. The original holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
material was part of the Royal College of Surgeons
Royal College of Surgeons of England
The Royal College of Surgeons of England is an independent professional body and registered charity committed to promoting and advancing the highest standards of surgical care for patients, regulating surgery, including dentistry, in England and Wales...
collection in London and was destroyed in World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
; only casts remain. Possible Massospondylus remains have been found in the Upper Elliot Formation, the Clarens Formation
Clarens Formation
The Clarens Formation is a prominent fossil site in the Tuli Basin, in the KwaZulu-Natal region of South Africa.-Fauna of the Clarens Formation:Unidentified dinosaur eggs have been recovered from the formation.-Bony fish:-Dinosaurs:-Synapsids:...
, and the Bushveld Sandstone of South Africa and Lesotho
Lesotho
Lesotho , officially the Kingdom of Lesotho, is a landlocked country and enclave, surrounded by the Republic of South Africa. It is just over in size with a population of approximately 2,067,000. Its capital and largest city is Maseru. Lesotho is a member of the Commonwealth of Nations. The name...
; the Forest Sandstone and the Upper Karroo Sandstone of Zimbabwe
Zimbabwe
Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...
; and the Kayenta Formation
Kayenta Formation
The Kayenta Formation is a geologic layer in the Glen Canyon Group that is spread across the Colorado Plateau province of the United States, including northern Arizona, northwest Colorado, Nevada, and Utah. This rock formation is particularly prominent in southeastern Utah, where it is seen in the...
of Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
. These remains consist of at least 80 partial skeletons and four skulls, representing both juveniles and adults.
The report of Massospondylus from Arizona's Kayenta Formation is based on a skull described in 1985. The skull of the Kayenta specimen from Arizona is 25% larger than the largest skull from any African specimen. The Kayenta specimen possesses four teeth in the premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
and sixteen in the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
. Uniquely among dinosaurs, it also had tiny, one-millimeter-(0.04 in-) long palatal teeth. Recent restudy of African Massospondylus skulls, however, indicates that the Kayenta specimen does not pertain to Massospondylus. This Kayenta skull and associated postcranial elements, identified collectively as MCZ 8893, has been recently referred to the newly described genus Sarahsaurus
Sarahsaurus
Sarahsaurus is a genus of basal sauropodomorph dinosaur which lived during the lower Jurassic period in what is now northeastern Arizona, USA....
.
Massospondylus had also been reported from Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, but this has been reassessed as a closely related but distinct genus. The fossils included several partial skeletons and at least one skull, found in the Lower Jurassic
Early Jurassic
The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...
Canon del Colorado Formation
Canon del Colorado Formation
The Canon del Colorado Formation is a Mesozoic geologic formation. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.-See also:...
of San Juan
San Juan, Argentina
San Juan is the capital city of the Argentine province of San Juan in the Cuyo region, located in the Tulúm Valley, west of the San Juan River, at above mean sea level, with a population of around 112,000 as per the ....
, Argentina. This material was named Adeopapposaurus
Adeopapposaurus
Adeopapposaurus is a genus of prosauropod dinosaur from the Early Jurassic Cañón del Colorado Formation of San Juan, Argentina. It was similar to Massospondylus. Four partial skeletons with two partial skulls are known.The type specimen, PVSJ568, includes a skull and most of a skeleton to just...
in 2009.
Species
Many species have been named, although most are no longer considered valid. M. carinatus, named by Richard Owen, is the type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
. Other named species include: M. browni (Seeley
Harry Seeley
Harry Govier Seeley was a British paleontologist.-Career:Seeley was born in London, the son of Richard Hovill Seeley, goldsmith, and his second wife Mary Govier. He attended classes at the Royal School of Mines, Kensington before becoming an assistant to Adam Sedgwick at the Woodwardian Museum,...
, 1895), M. harriesi (Broom
Robert Broom
Professor Robert Broom was a Scottish South African doctor and paleontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University of Glasgow...
1911), M. hislopi (Lydekker
Richard Lydekker
Richard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.-Biography:...
, 1890), M. huenei (Cooper, 1981), M. kaalae (Barrett 2009), M. rawesi (Lydekker, 1890), and M. schwarzi (Haughton, 1924).
M. browni, M. harriesi, and M. schwarzi were all found in the Upper Elliot Formation of Cape Province
Cape Province
The Province of the Cape of Good Hope was a province in the Union of South Africa and subsequently the Republic of South Africa...
, South Africa. All three are based on fragmentary material, and were regarded as indeterminate
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
in the most recent review. M. browni is based on two cervical
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...
, two back, and three caudal
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
vertebrae and miscellaneous hind limb elements. M. harriesi is known from a forelimb. M. schwarzi is known from an incomplete hind limb and sacrum
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
. M. hislopi and M. rawesi were named from fossils found in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
. M. hislopi is based on vertebrae from the Upper Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
Maleri Formation of Andhra Pradesh
Andhra Pradesh
Andhra Pradesh , is one of the 28 states of India, situated on the southeastern coast of India. It is India's fourth largest state by area and fifth largest by population. Its capital and largest city by population is Hyderabad.The total GDP of Andhra Pradesh is $100 billion and is ranked third...
, whereas M. rawesi is based on a tooth from the Upper Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
Takli Formation of Maharashtra
Maharashtra
Maharashtra is a state located in India. It is the second most populous after Uttar Pradesh and third largest state by area in India...
. M. hislopi was tentatively retained as an indeterminate sauropodomorph in the latest review, but M. rawesi may be a theropod
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
or nondinosaur. M. huenei is a combination derived by Cooper for Lufengosaurus huenei
Lufengosaurus
Lufengosaurus is a genus of prosauropod dinosaur which lived during the Early Jurassic period in what is now southwestern China.-Discovery and species:...
, as he considered Lufengosaurus and Massospondylus to be synonyms. This synonymy is no longer accepted.
M. kaalae was described in 2009 on the basis of a partial skull found from the upper Elliot Formation in the Herschel District of South Africa. This species is known from the same time and region as some specimens of M. carinatus. It differs from the type species in the morphology of the braincase, as well as in several other characters of the skull such as the proportions of the premaxilla.
Dubious names
Several dinosaurs are often considered synonymous with Massospondylus. These include Aristosaurus, Dromicosaurus, Gryponyx taylori, Hortalotarsus, Leptospondylus, and Pachyspondylus, which are dubious names of little scientific value. Hortalotarsus skirtopodus was named by Harry SeeleyHarry Seeley
Harry Govier Seeley was a British paleontologist.-Career:Seeley was born in London, the son of Richard Hovill Seeley, goldsmith, and his second wife Mary Govier. He attended classes at the Royal School of Mines, Kensington before becoming an assistant to Adam Sedgwick at the Woodwardian Museum,...
in 1894. According to Broom (1911), "Originally most of the skeleton was in the rock, and it was regarded by the farmers as the skeleton of a Bushman, but it is said to have been destroyed through fear that a Bushman skeleton in the rock might tend to weaken the religious belief of the rising generation." Some partial leg bones were salvaged. The following year, Richard Owen named a few fossil vertebrae Leptospondylus capensis and Pachyspondylus orpenii. These fragmentary fossils were later destroyed in World War II. Aristosaurus erectus was named by E.C.N. van Hoepen in 1920 based on a nearly complete skeleton. Hoepen also named Dromicosaurus gracilis, which consisted of a partial skeleton. Gryponyx taylori was named by Sidney H. Haughton
Sidney H. Haughton
Sidney Henry Haughton, , was an English-born South African paleontologist and geologist. The eldest of three children born to Henry Charles Haughton and Alice Aves, he is best-known for his description of the sauropodomorph dinosaur Melanorosaurus in 1924, and his work on the geology of the...
in 1924. It consists of hip bones. All of the above fossils come from the Hettangian or Sinemurian faunal stages of South Africa, where Massospondylus has been found. Under the rules of zoological nomenclature, these names are junior synonym
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
s. They were named after Massospondylus was described in a scientific paper; the name Massospondylus thus takes priority.
Ignavusaurus
Ignavusaurus
Ignavusaurus is a genus of basal sauropodomorph dinosaur that lived during the Early Jurassic in what is now present-day Lesotho. Its fossils were found in the upper Elliot Formation which is probably Hettangian in age. It was described on the basis of a partial, well preserved articulated skeleton...
, known from a young specimen, may also be synonymous with Massospondylus.
Classification
| {clade|style=font-size:75% | label1= Plateosauria Plateosauria Plateosauria is a clade of sauropodomorph dinosaurs which lived during the Late Triassic to the Late Cretaceous. The name Plateosauria was first coined by Gustav Tornier in 1913. The name afterwards fell out of use until the 1980s, when a new generation of paleontologists began using the name... |
1= }} |
Massospondylus is a prosauropod, a grouping of early saurischia
Saurischia
Saurischia meaning 'lizard' and ischion meaning 'hip joint') is one of the two orders, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure...
n dinosaurs that lived during the Triassic and Jurassic, but which had died out by the end of the Jurassic. Other members of the group include Plateosaurus
Plateosaurus
Plateosaurus is a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 216 to 199 million years ago, in what is now Central and Northern Europe. Plateosaurus is a basal sauropodomorph dinosaur, a so-called "prosauropod"...
, Yunnanosaurus
Yunnanosaurus
Yunnanosaurus is a genus of prosauropod dinosaur from the Early to Middle Jurassic Period, a position in time that makes it one of the last prosauropods. It is closely related to Lufengosaurus...
, and Riojasaurus
Riojasaurus
Riojasaurus was a herbivorous prosauropod dinosaur named after La Rioja Province in Argentina where it was found by José Bonaparte. It lived during the Late Triassic and grew to about long. Riojasaurus is the only known riojasaurid to live in South America.-Description:Riojasaurus had a heavy...
. Basal sauropodomorph systematics continue to undergo revision, and many genera once considered classic prosauropods have recently been removed from the group in phylogenetic nomenclature
Phylogenetic nomenclature
Phylogenetic nomenclature or phylogenetic taxonomy is an alternative to rank-based nomenclature, applying definitions from cladistics . Its two defining features are the use of phylogenetic definitions of biological taxon names, and the lack of obligatory ranks...
, on the grounds that their inclusion would not constitute a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
(a natural grouping containing all descendants of a single common ancestor). Exactly which animals constitute a monophyletic
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
(natural grouping) of prosauropods is unclear. Yates and Kitching
James Kitching
James William Kitching was a South African vertebrate palaeontologist and regarded as one of the world’s greatest fossil finders.-Career:...
(2003) published a clade consisting of Riojasaurus, Plateosaurus, Coloradisaurus
Coloradisaurus
Coloradisaurus is a genus of massospondylid sauropodomorph dinosaur. It lived during the Late Triassic period in what is now La Rioja Province, Argentina. It is known from the holotype PVL 5904, nearly complete skull...
, Massospondylus, and Lufengosaurus
Lufengosaurus
Lufengosaurus is a genus of prosauropod dinosaur which lived during the Early Jurassic period in what is now southwestern China.-Discovery and species:...
. Galton and Upchurch (2004) included Ammosaurus
Ammosaurus
Ammosaurus is a genus of sauropodomorph dinosaur from the Early and Middle Jurassic Period of North America. At 4 meters in length, it was small compared to some other members of its suborder, which included the largest animals ever to walk the Earth...
, Anchisaurus
Anchisaurus
Anchisaurus is a genus of basal sauropodomorph, and was an early herbivorous dinosaur. Until recently it was classed as a member of Prosauropoda. The name comes from the Greek αγχι/agkhi...
, Azendohsaurus
Azendohsaurus
Azendohsaurus was a genus of herbivorous archosauromorph from the Late Triassic Period of Morocco. The type species is known only from a partial jaw fragment from Morocco. Azendohsaurus was previously regarded as a dinosaur, as either an ornithischian or a prosauropod...
, Camelotia
Camelotia
Camelotia was a genus of prosauropod or sauropod dinosaur from the Late Triassic of what is now England. Paleontologists are divided on which family it may belong to; in the past, Camelotia has generally been assigned to the prosauropods, but this group of primitive dinosaurs is in constant...
, Coloradisaurus, Euskelosaurus
Euskelosaurus
Euskelosaurus was a semi-bipedal dinosaur from the Late Triassic. It was a prosauropod that lived in the Late Triassic Period, in present-day South Africa, Lesotho, and Zimbabwe. It was first described by Thomas Henry Huxley in 1866 as Euskelesaurus brownii based on holotype BMNH R1625, limb and...
, Jingshanosaurus
Jingshanosaurus
Jingshanosaurus is a genus of prosauropod dinosaurs from the Early Jurassic. Its fossils, a nearly complete skeleton including the skull, were found near the town of Jingshan , Lufeng County, Yunnan Province, China, from which the name derives. First described in 1995, the type species is J....
, Lessemsaurus
Lessemsaurus
Lessemsaurus is an extinct genus of sauropodomorph dinosaur named for the writer of popular science books Don Lessem. The type species, L. sauropoides, was formally described by José Fernando Bonaparte in 1999...
, Lufengosaurus, Massospondylus, Melanorosaurus
Melanorosaurus
Melanorosaurus , is a genus of basal sauropodomorph dinosaur that lived during the Late Triassic period. A herbivore from South Africa, it had a large body and sturdy limbs, suggesting it moved about on all fours...
, Mussaurus
Mussaurus
Mussaurus was a genus of herbivorous prosauropod dinosaur that lived in southern Argentina during the Late Triassic Period, about 215 million years ago...
, Plateosaurus, Riojasaurus, Ruehleia
Ruehleia
Ruehleia is a genus of prosauropod dinosaur from the Late Triassic period of Germany. The type species is R. bedheimensis, described by Galton in 2001, and is named for the German paleontologist Hugo Ruehle von Lilienstern...
, Saturnalia
Saturnalia (dinosaur)
Saturnalia is an extinct genus of basal sauropodomorph dinosaur known from the Triassic of Rio Grande do Sul, southern Brazil.-Discovery:Saturnalia was originally named on the basis of three partial skeletons...
, Sellosaurus, Thecodontosaurus
Thecodontosaurus
Thecodontosaurus is a genus of herbivorous basal sauropodomorph dinosaur which lived during the late Triassic period ....
, Yimenosaurus
Yimenosaurus
Yimenosaurus is a genus of prosauropod dinosaur from the Early Jurassic. Fossils from several individuals were recovered from Yimen, China, and the type species Y. youngi was named by Bai, Yang & Wang in 1990. Reconstructions are based on mostly complete skeletons, missing only parts of the...
and Yunnanosaurus in a monophyletic Prosauropoda. Wilson (2005) considered Massospondylus, Jingshanosaurus, Plateosaurus, and Lufengosaurus a natural group, with Blikanasaurus
Blikanasaurus
Blikanasaurus was a genus of sauropodomorph dinosaur found in Lower Elliot Formation rocks from the Late Triassic in what is now South Africa's Cape Province. Known from a left lower limb only, it has been variously classified as a prosauropod or basal sauropod...
and Antetonitrus
Antetonitrus
Antetonitrus is the oldest known genus of sauropod dinosaur, living during the Late Triassic Period of southern Africa. It was a quadrupedal herbivore, like many of its later relatives, although it was far smaller than some of them...
possible sauropods. Bonnan and Yates (2007) considered Camelotia, Blikanasaurus and Melanorosaurus possible sauropods. Yates (2007) placed Antetonitrus, Melanorosaurus, and Blikanasaurus as basal sauropods and declined to use the term Prosauropoda, as he considered it synonymous with Plateosauridae. However, he did not rule out the possibility that a small group of prosauropods consisting of Plateosaurus, Riojasaurus, Massospondylus and their closest kin were monophyletic.
Massospondylus is the type genus
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
of the proposed family Massospondylidae
Massospondylidae
Massospondylidae is a family of massopod sauropodomorphs. Massospondylids are early sauropodomorph dinosaurs which existed in Asia, Africa and South America during the Late Triassic to the Early Jurassic periods...
, to which it gives its name. The Massospondylidae family may also include Yunnanosaurus, although Lu et al. (2007) placed Yunnanosaurus in its own family. Yates (2007) considered Massospondylus, Coloradisaurus, and Lufengosaurus massospondylids, with Yunnanosaurus in Anchisauria
Anchisauria
The Anchisauria were a clade of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Anchisauria was first used by Galton and Upchurch in the second edition of The Dinosauria...
. Smith and Pol (2007) also found a Massospondylidae in their phylogenetic analysis, including Massospondylus, Coloradisaurus, and Lufengosaurus, as well as their new genus, Glacialisaurus
Glacialisaurus
Glacialisaurus is a genus of massospondylid sauropodomorph dinosaur. It lived during the Early Jurassic period in what is now central Transantarctic Mountains of Antarctica. It is known from the holotype FMNH PR1823, a partial hind limb and from the referred material FMNH PR1822, a left...
. Adeopapposaurus, based on the fossils once thought to belong to a South American form of Massospondylus, was also classified as a massospondylid. Pradhania
Pradhania
Pradhania is a genus of massospondylid sauropodomorph dinosaur from the Sinemurian-age Upper Dharmaram Formation of India. It was first named by T. S. Kutty, Sankar Chatterjee, Peter M. Galton and Paul Upchurch in 2007 and the type species is Pradhania gracilis...
was originally regarded as a basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
sauropodomorph
Sauropodomorpha
Sauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs which includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth. The...
but new cladistic analysis performed by Novas et al., 2011 suggests that Pradhania is a massospondylid
Massospondylidae
Massospondylidae is a family of massopod sauropodomorphs. Massospondylids are early sauropodomorph dinosaurs which existed in Asia, Africa and South America during the Late Triassic to the Early Jurassic periods...
. Pradhania presents two synapomorphies of Masospondylidae recovered in their phylogenetic analysis and its fossils were discovered from the same region and basin in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
as M. hislopi.
Paleoecology
The faunaFauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
s and flora
Flora
Flora is the plant life occurring in a particular region or time, generally the naturally occurring or indigenous—native plant life. The corresponding term for animals is fauna.-Etymology:...
s of the Early Jurassic were similar worldwide, with conifer
Pinophyta
The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being...
s adapted for hot weather becoming the common plants, and prosauropods and basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
theropod
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
s the main constituents of a worldwide dinosaur fauna. The environment of early Jurassic southern Africa has been described as a desert. African Massospondylus was a contemporary of early crocodylomorphs
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
; tritylodontid
Tritylodontidae
Tritylodontids were small to medium-sized, highly specialized and extremely mammal-like cynodonts. They were the last family of the non-mammalian synapsids. One of the last cynodont lines to appear, the Tritylodontidae descended from a Cynognathus-like cynodont...
and trithelodontid
Trithelodontidae
The tritheledontids, also known as ictidosaurs, were small to medium-sized cynodonts. They were extremely mammal-like, highly specialized cynodonts, although they still retained a very few reptilian anatomical traits. Tritheledontids were mainly carnivorous or insectivorous, though some species...
therapsid
Therapsida
Therapsida is a group of the most advanced synapsids, and include the ancestors of mammals. Many of the traits today seen as unique to mammals had their origin within early therapsids, including hair, lactation, and an erect posture. The earliest fossil attributed to Therapsida is believed to be...
s; morganucodon
Morganucodon
Morganucodon is an early mammalian genus which lived during the Late Triassic. It first appeared about 205 million years ago. This has also been identified with Eozostrodon. Unlike many other early mammals, Morganucodon is well represented by abundant and well preserved, though in the vast...
tid mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s; and dinosaurs including the small theropod Megapnosaurus rhodesiensis
Megapnosaurus
Megapnosaurus was a dinosaur of the theropod family Coelophysidae, formerly called Syntarsus , living during the Early Jurassic. It was renamed by American entomologist Dr. Michael Ivie , Polish Australian Dr...
; a species of Melanorosaurus
Melanorosaurus
Melanorosaurus , is a genus of basal sauropodomorph dinosaur that lived during the Late Triassic period. A herbivore from South Africa, it had a large body and sturdy limbs, suggesting it moved about on all fours...
(M. thabanensis); and several genera of early ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
ns, such as Lesothosaurus
Lesothosaurus
Lesothosaurus is an herbivorous ornithischian dinosaur. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from Lesotho". The genus is monotypic, having only one valid species, Lesothosaurus diagnosticus, within the genus....
and the heterodontosaurids
Heterodontosauridae
Heterodontosauridae is a family of early ornithischian dinosaurs that were likely among the most basal members of the group...
Abrictosaurus
Abrictosaurus
Abrictosaurus is a genus of heterodontosaurid dinosaur from the Early Jurassic Period of what is now southern Africa. It was a small bipedal herbivore or omnivore, approximately 1.2 meters long, and weighing less than 45 kilograms .This dinosaur is known from the fossil remains of only...
, Heterodontosaurus
Heterodontosaurus
Heterodontosaurus is a genus of small herbivorous dinosaur with prominent canine teeth which lived in the Early Jurassic of South Africa. It was similar to a hypsilophodont in shape, and ate plants, despite its canines.Heterodontosaurus is currently known from specimens of the SAFM from South...
, and Lycorhinus
Lycorhinus
Lycorhinus is a genus of heterodontosaurid ornithischian dinosaur hailing from the Early Jurassic strata of the Elliot Formation located in the Cape Province, South Africa....
.
It is not clear which carnivores may have preyed on Massospondylus. Most of the theropods which have been discovered in rocks of Early Jurassic age in southern Africa, such as Megapnosaurus, were smaller than mid-sized prosauropods like Massospondylus. These smaller predators have been postulated as using fast slashing attacks to wear down prosauropods, which could have defended themselves with their large hand and foot claws. The 6-meter-(20 ft-) long carnivorous theropod Dracovenator
Dracovenator
Dracovenator is the name of a genus of dinosaur from the Early Jurassic. It was a theropod which lived in what is now South Africa.The type species, Dracovenator regenti, was formally described by A.M. Yates in 2006. The genus name is a contraction of the Latin draco, "dragon", and venator, "hunter"...
lived during the same period (Hettangian to Sinemurian stages) as Massospondylus and has also been found in the Elliot Formation of South Africa.
Paleobiology
A 2007 study suggested that Massospondylus may have used its short arms in defense from predators ("defensive swats"), in intraspecies combat, or in feeding, although its arms were too short to reach its mouth. Scientists speculate that Massospondylus could have used its large pollex
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
(thumb) claw in combat, to strip plant material from trees, digging, or for grooming.
Growth
Age determination of dinosaurs
Age determination in dinosaurs is mainly used to determine the approximate age of a dinosaur when the animal died.-History:Early attempts to estimate the longevity of dinosaurs used allometric scaling principles. Ages were determined by dividing individual mass estimates by rates of growth for...
indicated that Massospondylus grew at a maximum rate of 34.6 kg (76.3 lb) per year and was still growing at around 15 years of age.
Diet
Prosauropods such as Massospondylus may have been herbivorous or omnivorousOmnivore
Omnivores are species that eat both plants and animals as their primary food source...
. As recently as the 1980s, paleontologists debated the possibility of carnivory
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
in prosauropods. However, the hypothesis of carnivorous prosauropods has been discredited, and all recent studies favor a herbivorous or omnivorous lifestyle for these animals. Galton and Upchurch (2004) found that cranial characteristics (such as jaw articulation) of most prosauropods are closer to those of herbivorous reptiles than those of carnivorous ones, and the shape of the tooth crown
Crown (tooth)
In dentistry, crown refers to the anatomical area of teeth, usually covered by enamel. The crown is usually visible in the mouth after developing below the gingiva and then erupting into place.-References:...
is similar to those of modern herbivorous or omnivorous iguana
Iguana
Iguana is a herbivorous genus of lizard native to tropical areas of Central America and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena...
s. The maximum width of the crown was greater than that of the root, resulting in a cutting edge similar to those of extant herbivorous or omnivorous reptiles. Barrett (2000) proposed that prosauropods supplemented their herbivorous diets with small prey or carrion
Carrion
Carrion refers to the carcass of a dead animal. Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters include vultures, hawks, eagles, hyenas, Virginia Opossum, Tasmanian Devils, coyotes, Komodo dragons, and burying beetles...
. Gastrolith
Gastrolith
A gastrolith, also called a stomach stone or gizzard stones, is a rock held inside a gastrointestinal tract. Gastroliths are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. The grain size depends upon the size of the animal and the gastrolith's...
s (gizzard stones) have been found in association with Massospondylus fossils in South Africa, and with a Massospondylus-like animal from the Late Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
of Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
. Massospondylus swallowed these stones to aid in digestion; muscular contractions in the creature's gizzard would have pulverized swallowed plant material, compensating for its inability to chew.
Reproduction
Golden Gate Highlands National Park
Golden Gate Highlands National Park is located in Free State, Republic of South Africa, near the Lesotho border. It covers an area of 340 km² . The park's most notable features are its golden, ochre, and orange-hued deeply eroded sandstone cliffs and outcrops, especially the Brandwag rock...
in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
by James Kitching
James Kitching
James William Kitching was a South African vertebrate palaeontologist and regarded as one of the world’s greatest fossil finders.-Career:...
, who identified them as most likely belonging to Massospondylus. It was nearly 30 years before extraction was started on the fossils of the 15-centimeter- (6 in-) long embryos. They remain the oldest dinosaur embryos ever found. Notably, the near-hatchlings had no teeth, suggesting they had no way of feeding themselves. Based on the lack of teeth and the animal's body proportions, scientists speculate that postnatal care might have been necessary. The four legs of the near-hatchlings were of equal length, indicating that newly hatched Massospondylus were quadrupedal. The skull and eyes were proportionately oversized when compared to adults, as is common in other very young vertebrates, although the skulls of juveniles were taller and more narrow as well. The quadrupedality of the hatchlings suggests that the quadrupedal posture of later sauropods may have evolved from retention of juvenile characteristics in adult animals, an evolutionary phenomenon known as pedomorphosis.
Respiratory system
Many saurischiaSaurischia
Saurischia meaning 'lizard' and ischion meaning 'hip joint') is one of the two orders, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure...
n dinosaurs possessed vertebrae and ribs that contained hollowed-out cavities (pneumatic foramina
Foramina of skull
The human skull has numerous holes through which cranial nerves, arteries, veins and other structures pass.-List of foramina and the structures that pass through them:...
), which reduced the weight of the bones and may have served as a basic 'flow-through ventilation' system similar to that of modern birds. In such a system, the neck vertebrae and ribs are hollowed out by the cervical air sac; the upper back vertebrae, by the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
; and the lower back and sacral
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
(hip) vertebrae, by the abdominal air sac. These organs constitute a complex and very efficient method of respiration. Prosauropods are the only major group of saurischians without an extensive system of pneumatic foramina. Although possible pneumatic indentations have been found in Plateosaurus and Thecodontosaurus, the indentations were very small. One study in 2007 concluded that prosauropods like Massospondylus likely had abdominal and cervical air sacs, based on the evidence for them in sister taxa (theropods and sauropods). The study concluded that it was impossible to determine whether prosauropods had a bird-like flow-through lung, but that the air sacs were almost certainly present.
Further reading
- Hinic, S. (2002). "The cranial anatomy of Massospondylus carinatus Owen, 1854 and its implications for prosauropod phylogeny". Journal of Vertebrate Paleontology. Abstracts of papers. Society of Vertebrate Paleontology, 22, Supplement to number 3, 65A.
- Martínez, R. (1999). "The first South American record of Massospondylus (Dinosauria: Sauropodomorpha)". Journal of Vertebrate Paleontology, Abstracts of papers. Society of Vertebrate Paleontology, 20–23 October, 19, Suppl. 3, 61A.
- Martínez, R.N. (1999). "Massospondylus (Dinosauria: Sauropodomorpha) in northwestern Argentina". Abstracts VII International Symposium on Mesozoic Terrestrial Ecosystems, Buenos Aires, 40.
External links
- Locomotion and Ontogeny of Massospondylus carinatus from the University of Toronto at Missisauga.
- Massospondylidae from Palaeos.com (technical).
- Massospondylus at DinoData.org.
- Massospondylus from PrimeOrigins.co.za (for children).
- "Oldest known dinosaur embryos identified" University of the Witwatersrand. National Geographic.
- Sauropodomorpha on Thescelosaurus!