Ischigualasto Provincial Park

Ischigualasto Provincial Park
Parque Provincial Ischigualasto
Valle de la Luna

The Submarine, wind-eroded rock formation

The Submarine, wind-eroded rock formation
Location in Argentina

Location in Argentina

Location San Juan Province, Argentina
Nearest city San José de Jáchal
Coordinates 30°4′0″S 68°0′0″W / 30.06667°S 68.00000°W / -30.06667; -68.00000Coordinates: 30°4′0″S 68°0′0″W / 30.06667°S 68.00000°W / -30.06667; -68.00000
Area 60,370 ha (603.7 km2; 233.1 sq mi)
Established November 3, 1971 (1971-11-03)[1]
Official name
Ischigualasto / Talampaya Natural Parks
Type Natural
Criteria viii
Designated 2000 (24th session)
Reference no. 966[2]
State Party  Argentina
Region Latin America and the Caribbean

Ischigualasto Provincial Park (Spanish: Parque Provincial Ischigualasto), also called Valle de la Luna ("Valley of the Moon" or "Moon Valley"), due to its otherworldly appearance, is a provincial protected area in the north-east of San Juan Province, north-western Argentina, limiting to the north with the Talampaya National Park, in La Rioja Province. Both areas belong to the same geological formation, the Ischigualasto Formation (sometimes Ischigualasto-Talampaya Formation) Established on 3 November 1971,[1] the park has an area of 60,370 ha (603.7 km2; 233.1 sq mi)

In 2000 UNESCO included Ischigualasto and Talampaya National Park among its World Heritage Sites.[2]

History

The most accepted hypothesis gives the name "Ischigualasto" a Quechua origin, meaning "place where the moon sets", although some scholars have proposed Diaguita or Huarpe roots.

The first paleontological description of Ischigualasto dates from 1930. In 1941 the area was studied in more detail, which led to the discovery of 70 species of fossil plants. The region received for the first time the name Valle de la Luna in 1943, in a publication edited by the Automobil Club Argentino. That year, Dr. Ángel Cabrera of University of La Plata described the traversodontid Exaeretodon—the first cynodont found in Ischigualasto—after samples sent by a geologist who was doing prospecting for coal on behalf of an Argentine mining company.[3]

Academic work and geological prospecting proceeded slowly until 1958, when Dr. Alfred Sherwood Romer, a Harvard University expert in ancient mammals, discovered several rich fossil beds which he described as "extraordinary".

Description

Most of the park lies within the Valle Fértil Department, with a minor part in the Jachal Department of San Juan, at an altitude of about 1,300 m (4,300 ft) amsl. The park is part of the western border of the Central Sierras, and it features typical desert vegetation (bushes, cacti and some trees) which covers between 10 and 20% of the area. The climate is very dry, with rainfall mostly during the summer, and temperature extremes (minimum −10 °C (14 °F), maximum 45 °C (113 °F)). There is a constant southern wind with a speed of 20–40 km/h (12–25 mph) after noon and until the evening, sometimes accompanied by the extremely strong Zonda wind.

Paleontology

See also: Choiyoi Group

The Ischigualasto Formation contains Late Triassic (Carnian) deposits (231.4 -225.9 million years before the present[4]), with some of the oldest known dinosaur remains, which are the world's first with regards to quality, number and importance. It is the only place in the world where nearly all of the Triassic is represented in an undisturbed sequence of rock deposits. This allows for the study of the transition between dinosaurs and ancient mammals; research is ongoing.

In the Carnian this area was a volcanically active floodplain dominated by rivers and had a strongly seasonal rainfall. Petrified tree trunks of Protojuniperoxylon ischigualastianus more than 40 m (130 ft) tall attest to a rich vegetation at that time. Fossil ferns and horsetails have also been found.

Rhynchosaurs and cynodonts (especially rhynchosaur Hyperodapedon and cynodont Exaeretodon[4]) are by far the predominant findings among the tetrapod fossils in the park. A study from 1993 found dinosaur specimens to comprise only 6% of the total tetrapod sample;[5] subsequent discoveries increased this number to approximately 11% of all findings.[4] Carnivorous dinosaurs are the most common terrestrial carnivores of the Ischigualasto Formation, with herrerasaurids comprising 72% of all recovered terrestrial carnivores.[4] Dinosaurs of Ischigualasto Formation include early samples of the two major lineages of dinosaurs (ornithischians and saurischians). The carnivorous archosaur Herrerasaurus is the most numerous of these dinosaur fossils. Another important putative dinosaur with primitive characteristics is Eoraptor lunensis, found in Ischigualasto in the early 1990s.

Dinosaurs

The fossils of an undescribed species of theropod are present in San Juan Province.[6]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Dinosaurs of the Ischigualasto Formation
Genus Species Location Stratigraphic position Material Notes Images

Chromogisaurus

C. novasi

San Juan Province[7]

Cancha de Bochas Member[7]

Partial skeleton including limb bones, pelvic bones and caudal vertebrae[7]

A two-meter-long saturnaliine guaibasaurid known from a partial skeleton lacking the skull. It includes elements of the front and hind limbs; the pelvis and two caudal vertebrae.[7]
Eodromaeus
Eoraptor
Herrerasaurus
Panphagia
Pisanosaurus
Sanjuansaurus

Eodromaeus

E. murphi

San Juan Province[4]

Valle de la Luna Member

A nearly complete skeleton and another partial skeleton

A basal theropod with a total length of about 1.2 meters (3.9 feet) from nose to tail, and a weight of about 5 kilograms (11 pounds). The trunk was long and slender. It is unknown how fast Eodromaeus could run, but it has been suggested to about 30 kilometers per hour (19 mph). The forelimbs were much shorter than the hind limbs, ending in hands with 5 digits. Digits IV and V (the ring finger and little finger in humans) were very reduced in size.

Eoraptor[6]

E. lunensis[6]

San Juan Province[6]

Two nearly complete skeletons[8]

An omnivorous, lightly-built, basal eusaurischian, close to the ancestry of theropods[7] and sauropodomorphs.[4] Eoraptor had a slender body that grew to about 1 meter (3.3 feet) in length, with an estimated weight of about 10 kilograms (22 pounds). It has a lightly built skull with a slightly enlarged external naris. Like the coelophysoids which would appear millions of years later, Eoraptor has a kink in its upper jaws, between the maxilla and the premaxilla.

Herrerasaurus[6]

H. ischigualastensis[6]

San Juan Province[6]

"Various partial skeletons, including a complete skull and mandible."[8]

A herrerasaur with a length estimated at 3 to 6 meters (9.8 to 19.7 feet), and its hip height at more than 1.1 meters (3.6 feet). It may have weighed around 210–350 kg (460–770 pounds). In a large specimen, at first thought to belong to a separate (now discredited) genus, Frenguellisaurus, the skull measured 56 cm (22 in) in length. Smaller specimens had skulls about 30 cm (1 foot) long.

Panphagia[9]

P. protos[9]

San Juan Province[6]

A guaibasaurid that is one of the most basal known genera of sauropodomorphs.[7][9][10] Panphagia is currently known from the disarticulated remains of one partially grown individual of about 1.30 meters (4.3 feet) long. Portions of the skull, vertebrae, pectoral girdle, pelvic girdle, and hind limb bones have been recovered. The russet-colored fossils were embedded in a greenish sandstone matrix and took several years to prepare and describe.

Pisanosaurus[6]

P. mertii[6]

La Rioja Province[6]

"Fragmentary skull and skeleton."[11]

A basal ornithischian known from a single partial skeleton. Pisanosaurus was a small, lightly built dinosaur approximately 1 meter (3 feet 3 in) in length. Its weight was between 2.27–9.1 kg (5–20 pounds). These estimates vary due to the incompleteness of the holotype specimen PVL 2577. Some now suggest that Pisanosaurus may have actually been a non-dinosaurian dinosauromorph, but this is debated.

Sanjuansaurus[12]

S. gordilloi

San Juan Province[12]

Cancha de Bochas Member[12]

An incomplete skeleton[12]

A herrerasaur comparable in size to a medium-sized Herrerasaurus, with a thigh bone that was 395 millimeters (15.6 in) long and a tibia that is 260 millimeters (10 in) in length.

An unnamed herrerasaur[7]

Unnamed

Specimen MACN-PV 18649a[7]

A herrerasaur distinct from Herrerasaurus, Staurikosaurus and Sanjuansaurus.[7]

Other archosauromorphs

Non-dinosaurian archosauromorphs of the Ischigualasto Formation[7][13]
Genus Species Location Stratigraphic position Material Notes Images

Aetosauroides

A. scagliai

An aetosaur that is one of four aetosaurs known from South America, the others being Neoaetosauroides, Chilenosuchus and Aetobarbakinoides. It was once proposed to be synonymous with Stagonolepis.
Proterochampsa
Saurosuchus
Venaticosuchus

Hyperodapedon

H. sanjuanensis

San Juan province

A heavily-built, stocky hyperodapedontine hyperodapedont around 1.3 meters (4.3 feet) in length. Apart from its beak, this rhynchosaur had several rows of heavy teeth on each side of the upper jaw, and a single row on each side of the lower jaw, creating a powerful chopping action when it ate. It is believed to have been herbivorous, feeding mainly on seed ferns.

Ignotosaurus[13]

I. fragilis[13]

San Juan Province[13]

Right ilium[13]

A little-known silesaur.[13]

Proterochampsa

P. barrionuevoi

A proterochampsid known from a 44-centimeter skull. It could have grown up to 3.5 m (11 feet).

Pseudochampsa[14]

P. ischigualastensis[14]

San Juan Province[15]

Cancha de Bochas Member[15]

An articulated incomplete skeleton[15]

A proterochampsid originally described a species of Chanaresuchus,[15] subsequently made the type species of a separate genus.[14]

Saurosuchus

S. galilei

A prestosuchid with a length of around 6-9 meters (20-30 feet) in total body length. Dorsal osteoderms run along the back of Saurosuchus. There are two rows to either side of the midline, with each leaf-shaped osteoderm joining tightly with the ones in front of and behind it. It has a deep, laterally compressed skull. The teeth are large, recurved, and serrated. The skull is wide at its back and narrows in front of the eyes.

Sillosuchus

S. longicervix

A shuvosaurid with an estimated length of about 3 m (10 feet). It is the only shuvosaurid currently known from outside North America.

Trialestes

T. romeri

A sphenosuchian once believed to be a primitive dinosaur.

Venaticosuchus[13]

V. rusconii[13]

An medium-sized ornithosuchid, reaching up to 2 m (7 feet) in length. It was once thought to be the ancestor to the carnosaur dinosaurs (which, back then, included Tyrannosaurus); however, now it is known to be more closely related to crocodilians than dinosaurs.

An unnamed lagerpetid[16][13]

Unnamed

San Juan Province[16][13]

Distal end of the left femur[13]

A basal dinosauromorph.

Synapsids

Synapsids of the Ischigualasto Formation[7][13]
Genus Species Location Stratigraphic position Material Notes Images

Chiniquodon

C. sanjuanensis, C. cf. theotonicus[13]

A carnivorous, dog-sized chiniquodontid that was a predatory cynodont being similar in ecological niche as the predatory dinosaurs it coexisted with.
Exaeretodon
Ischigualastia

Diegocanis[17]

D. elegans

San Juan Province

Cancha de Bochas Member

Partial skull, represented by the snout and the orbital region, with partially preserved upper dentition

A little-known ecteniniid.

Ecteninion

E. lunensis

A carnivorous ecteniniid known from a nearly complete skull of about 11 cm in length.

Exaeretodon

E. frenguellii

A gomphodontosuchine traversodont up to 1.8 meters long (5.9 feet), with a specialized grinding action when feeding. Another point of interest is that these cynodonts had deciduous teeth, which is a characteristic of mammals and means that babies could not chew, and required specialized parental care. Only older juveniles had permanent teeth.

Ischigualastia

I.jenseni

A stahleckeriine stahleckeriid that was an enormous dicynodont with a short, high skull, and lacking tusks. It is regarded as larger than its later, more famous relative Placerias.

Jachaleria[13]

J. colorata[13]

A large dicynodont perhaps 3 meters in length and weighed 300 kilograms, making it close in size to Dinodontosaurus.

cf. Probainognathus

Indeterminate

A small probainognathid that had an incipient squamosal-dentary jaw-cranium joint, which is a clearly mammalian anatomical feature. Known from about three dozen specimens, this creature was only about 10 cm long.

An unnamed eucynodont[13]

Unnamed[13]

Specimen PVSJ 882 (a cranium)[13]

Other tetrapods

Other tetrapods of the Ischigualasto Formation[7][13]
Genus Species Location Stratigraphic position Material Notes Images

Pelorocephalus

P. ischigualastensis

A chigutisaurid based on too little material. The largest individuals are estimated to have been over 107 cm in length.

Promastodonsaurus

P. bellmanni

A little-known mastodonsaur.

See also

References

Bibliography

Articles

Books

External links

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