Saurosuchus

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Saurosuchus
Temporal range: Late Triassic, Late Carnian to Early Norian 231.4–225  Ma
Saurosuchus.jpg
Mounted skeleton of Saurosuchus galilei in Mori Art Museum Gallery, Japan
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Paracrocodylomorpha
Clade: Loricata
Family:† Prestosuchidae
Genus:† Saurosuchus
Reig, 1959
Species:
†S. galilei
Binomial name
†Saurosuchus galilei
Reig, 1959

Saurosuchus (meaning "lizard crocodile") is an extinct genus of large loricatan pseudosuchian archosaurs that lived in South America during the Late Triassic period. It was a heavy, ground-dwelling, quadrupedal carnivore, likely being the apex predator in the Ischigualasto Formation. [1]

Contents

Discovery and naming

Posterior view of the mount in the Ischigualasto Provincial Park Saurosuchus galilei Ischigualasto.JPG
Posterior view of the mount in the Ischigualasto Provincial Park

The holotype, PVL 206, was discovered by Galileo J. Scaglia and Leocadio Soria in 1957, lying in a greenish sandstone on the Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina. It consists of a nearly complete, but deformed skull. Saurosuchus was formally described and named later in 1959 by Osvaldo. A. Reig. The generic name, Saurosuchus, is derived from the Greek σαῦρος (sauros, meaning lizard) and σοῦχος (souchus, meaning crocodile). The specific name, galilei, is in honour to Galileo J. Scaglia, who unearthed and prepared the holotype. [1]

Referred specimens

Saurosuchus is known from numerous specimens coming from the Ischigualasto Formation. Apart from the holotype, another individual was identified: Specimen PVL 2198, consisting of a partial maxilla, left ilium, right and left ischium, 11 dorsal vertebrae, osteoderms, ribs, and teeth. [1] Sill referred additional specimens, PVL 2557, 2472 and 2267. The specimen PVL 2557 consists of two dorsal vertebrae, right and left sacrals, nine caudal vertebrae, right ilium, ischium and partial pubis, right femur, tibia, fibula, tarsus and pes, ribs, and chevrons. PVL 2472 compromises one cervical vertebra, tibia and astragalus. Lastly, PVL 2267 is composed by a fragmented ilium, femur, tibia, fibula, tarsus, and partial pes. [2] In 2010, during the redescription of the skull of Saurosuchus, Alcober referred and described the immature specimen PVSJ 32, consisting of a complete skull, complete cervical and dorsal vertebral series, four anterior caudal vertebrae, ribs, and two dorsal osteoderm rows. [3] The postcranial remains of this specimen, were properly described by Trotteyn et al. 2011. [4]

Here, more specimens of Saurosuchus were referred: PVSJ 369, 675, and 615. In addition, the previous specimens PVL 2472 and PVL 2267 were excluded, with both of them being not referable to Saurosuchus. [4]

Saurosuchus was also reported from the Chinle Formation of Arizona in 2002 on the basis of isolated teeth and small skull fragments. [5] The diagnostic value of these bones has been questioned in later studies, which considered them to be from an indeterminate species of rauisuchian. [6]

Description

Life restoration of S. galilei Saurosuchus BW.jpg
Life restoration of S. galilei

Saurosuchus was a large rauisuchian, measuring 5.5–7 m (18–23 ft) long and weighing over 590 kg (1,300 lb). [1] [2] [7] [8] Two sub-adult specimens are estimated around 4.07 m (13.4 ft) long and weighing approximately 385 kg (849 lb). [9] This would make it one of the largest "rauisuchians", after the enormous Fasolasuchus . Two rows are on either side of the midline, with each leaf-shaped osteoderm joining tightly with the ones in front of and behind it. [2] [4] 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. The skull roof and maxilla are somewhat pitted. [3]

Pitting is also seen in aquatic phytosaurs and crocodilians, but the ridges and grooves are deeper and much more extensive across the skulls of these forms. The frontal bones, located at the top of the skull, are enlarged to form thick ridges over the eyes. As in more evolved rauisuchians, a small rod projects down from the lacrimal bone in front of the eye, but it does not attach firmly to the jugal bone below it. Ridges along the upper surface of the supraoccipital bone at the back of the skull are attachment points for strong neck ligaments. The cervical vertebrae are shortened and robust, forming a strong neck. [3] [4]

Classification

Saurosuchus was considered a member of the Rauisuchia, although the clade is now considered paraphyletic and Saurosuchus is considered a basal member of Loricata, a clade comprising "rauisuchians" as well as crocodylomorphs. Below is the cladogram of the Loricata conducted by Nesbitt 2011: [10]

Paracrocodylomorpha  

In more recent analyses, Saurosuchus has been found within the loricatan clade Prestosuchidae. The cladogram below follows a simplified version of the strict reduced consensus tree by Desojo et al. (2020): [11]

Archosauria  

Paleobiology

Analysis of Saurosuchus' bite indicated that its jaws were relatively weak, as determined in a study by Bestwick et al., in 2023. Its bite force was estimated to have been around 1,015–1,885 N (104–192 kgf; 228–424 lbf), similar to that of modern gharials in regards to strength, due to its relatively thinner bones compared to those of the theropod dinosaurs that would later supplant it, suggesting that Saurosuchus would feed largely on softer food such as flesh and vital organs from its prey, which it would process with its rear teeth. This avoidance of bone also would have left more meat for scavengers to feed on after Saurosuchus had finished with a meal. [12] [8]

A reconstruction of the cranial endocast revealed large olfactory bulbs, poorly developed flocculus and optic lobes, and an anteroposteriorly short lateral semicircular canal, suggesting that Saurosuchus would have relied on smell instead of eyesight to track prey over long distances or at night, and that it would not have been a particularly agile predator. Furthermore, the lagena is relatively long, suggesting a broad hearing sensitivity, especially in low-frequency sounds. [13] [9] A hypertrophied hypophysis has also been reported for Saurosuchus, which may be correlated with large size and possibly rapid growth rates, as observed in the majority of other "rauisuchians" based on bone microstructure. [9]

Paleoecology

Saurosuchus hunting a group of Hyperodapedon Saurosuchus and hyperodapedon.jpg
Saurosuchus hunting a group of Hyperodapedon

Saurosuchus was unearthed in the Cancha de Bochas Member from the Ischigualasto Formation, being the major predator on its environment. [3] The Ischigualasto Formation was dominated by fluvial and floodplain environments with strongly seasonal rainfalls. Interlayered volcanic ash layers above the base and below the top of the formation provide chronostratigraphic control and have yielded ages of 231.4 ± 0.3 Ma and 227 ± 0.9 Ma respectively. [14]

Contemporaneous fauna

Animals that lived alongside included numerous nondinosaurian tetrapods and basal dinosauromorphs. Notable paleofauna that were contemporaneous with Saurosuchus in the Cancha de Bochas Member include: Hyperodapedon , Exaeretodon , Herrerasaurus , Sillosuchus , Eoraptor , Trialestes , Aetosauroides , and Ischigualastia . Herrerasaurus and Saurosuchus are some of the most common predators in the formation, with numerous specimens and remains. [15] [16]

See also

Related Research Articles

<span class="mw-page-title-main">Rauisuchia</span> Informal group of Triassic archosaurs with pillar-erect posture

"Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians than to birds and other dinosaurs. First named in the 1940s, Rauisuchia was a name exclusive to Triassic archosaurs which were generally large, carnivorous, and quadrupedal with a pillar-erect hip posture, though exceptions exist for all of these traits. Rauisuchians, as a traditional taxonomic group, were considered distinct from other Triassic archosaur groups such as early dinosaurs, phytosaurs, aetosaurs, and crocodylomorphs.

<span class="mw-page-title-main">Aetosaur</span> Extinct order of heavily armoured reptiles

Aetosaurs are heavily armored reptiles belonging to the extinct order Aetosauria. They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs more closely related to crocodilians than to birds and other dinosaurs. All known aetosaurs are restricted to the Late Triassic, and in some strata from this time they are among the most abundant fossil vertebrates. They have small heads, upturned snouts, erect limbs, and a body ornamented with four rows of plate-like osteoderms. Aetosaur fossil remains are known from Europe, North and South America, parts of Africa, and India. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic tetrapod index fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site in which they are found.

<i>Venaticosuchus</i> Extinct genus of reptiles

Venaticosuchus is a genus of pseudosuchian archosaurs from the family Ornithosuchidae. Known from a single species, Venaticosuchus rusconii, this genus is described based on an incomplete skull and jaw collected from the Late Triassic (Carnian) Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina, which was deposited around 230 million years ago. This fossil material has been termed the holotype specimen PVL 2578. Venaticosuchus incorporated a myriad of features present in the other two genera of ornithosuchids, Ornithosuchus and Riojasuchus. However, it also had several unique traits, relating to the lower jaw.

<i>Gracilisuchus</i> Genus of fossil reptiles

Gracilisuchus is an extinct genus of tiny pseudosuchian from the Late Triassic of Argentina. It contains a single species, G. stipanicicorum, which is placed in the clade Suchia, close to the ancestry of crocodylomorphs. Both the genus and the species were first described by Alfred Romer in 1972.

<i>Riojasuchus</i> Extinct genus of reptiles

Riojasuchus is an extinct genus of ornithosuchid archosaur from the Late Triassic (Norian) of Argentina. Ornithosuchidae was a widespread family of facultatively bipedal pseudosuchians with adaptations for scavenging. Riojasuchus is notable as one of the youngest and most complete members of the family. The type and only known species, Riojasuchus tenuisceps, was named and described by José Bonaparte in 1967. It was one of the first of many well-preserved Triassic archosaurs to be discovered in Argentina. The holotype specimen, PVL 3827, was found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.

<span class="mw-page-title-main">Prestosuchidae</span> Extinct family of reptiles

Prestosuchidae is a polyphyletic grouping of carnivorous archosaurs that lived during the Triassic. They were large active terrestrial apex predators, ranging from around 2.5 to 7 metres in length. They succeeded the Erythrosuchidae as the largest archosaurs of their time. While resembling erythrosuchids in size and some features of the skull and skeleton, they were more advanced in their erect posture and crocodile-like ankle, indicating more efficient gait. "Prestosuchids" flourished throughout the whole of the middle, and the early part of the late Triassic, and fossils are so far known from Europe, India, Africa (Tanzania), Argentina, and Paleorrota in Brazil. However, for a long time experts disagree regarding the phylogenetic relationships of the group, what genera should be included, and whether indeed the "Prestosuchidae" constitute a distinct family.

<i>Desmatosuchus</i> Extinct genus of reptiles

Desmatosuchus is an extinct genus of archosaur belonging to the Order Aetosauria. It lived during the Late Triassic.

<i>Prestosuchus</i> Extinct genus of reptiles

Prestosuchus is an extinct genus of pseudosuchian in the group Loricata, which also includes Saurosuchus and Postosuchus. It has historically been referred to as a "rauisuchian", and was the defining member of the family Prestosuchidae, though the validity of both of these groups is questionable: Rauisuchia is now considered paraphyletic and Prestosuchidae is polyphyletic in its widest form.

<i>Aetosauroides</i> Extinct genus of reptiles

Aetosauroides is an extinct genus of aetosaur from the Late Triassic of South America. It is one of four aetosaurs known from South America, the others being Neoaetosauroides, Chilenosuchus and Aetobarbakinoides. Three species have been named: the type species A. scagliai, A. subsulcatus and A. inhamandensis. Fossils have been found in the Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina and the Santa Maria Formation in the Paraná Basin in southeastern Brazil. The strata date to the late Carnian and early Norian stages, making Aetosauroides one of the oldest aetosaurs.

<i>Doswellia</i> Extinct genus of reptiles

Doswellia is an extinct genus of archosauriform from the Late Triassic of North America. It is the most notable member of the family Doswelliidae, related to the proterochampsids. Doswellia was a low and heavily built carnivore which lived during the Carnian stage of the Late Triassic. It possesses many unusual features including a wide, flattened head with narrow jaws and a box-like rib cage surrounded by many rows of bony plates. The type species Doswellia kaltenbachi was named in 1980 from fossils found within the Vinita member of the Doswell Formation in Virginia. The formation, which is found in the Taylorsville Basin, is part of the larger Newark Supergroup. Doswellia is named after Doswell, the town from which much of the taxon's remains have been found. A second species, D. sixmilensis, was described in 2012 from the Bluewater Creek Formation of the Chinle Group in New Mexico; however, this species was subsequently transferred to a separate doswelliid genus, Rugarhynchos. Bonafide Doswellia kaltenbachi fossils are also known from the Chinle Formation of Arizona.

<span class="mw-page-title-main">Santa Maria Formation</span> Geologic formation in Brazil

The Santa Maria Formation is a sedimentary rock formation found in Rio Grande do Sul, Brazil. It is primarily Carnian in age, and is notable for its fossils of cynodonts, "rauisuchian" pseudosuchians, and early dinosaurs and other dinosauromorphs, including the herrerasaurid Staurikosaurus, the basal sauropodomorphs Buriolestes and Saturnalia, and the lagerpetid Ixalerpeton. The formation is named after the city of Santa Maria in the central region of Rio Grande do Sul, where outcrops were first studied.

<span class="mw-page-title-main">Los Colorados Formation</span>

The Los Colorados Formation is a sedimentary rock formation of the Ischigualasto-Villa Unión Basin, found in the provinces of San Juan and La Rioja in Argentina. The formation dates back to the Norian age of the Late Triassic.

<i>Luperosuchus</i> Extinct genus of reptiles

Luperosuchus is an extinct genus of loricatan pseudosuchian reptile which contains only a single species, Luperosuchus fractus. It is known from the Chañares Formation of Argentina, within strata belonging to the latest Ladinian stage of the late Middle Triassic, or the earliest Carnian of the Late Triassic. Luperosuchus was one of the largest carnivores of the Chañares Formation, although its remains are fragmentary and primarily represented by a skull with similarities to Prestosuchus and Saurosuchus.

<i>Sillosuchus</i> Extinct genus of reptiles

Sillosuchus is a genus of shuvosaurid poposauroid archosaur that lived in South America during the Late Triassic period. Shuvosaurids were an unusual family of reptiles belonging to the group Poposauroidea; although their closest modern relatives are crocodilians, they were bipedal and lightly armored, with dinosaur-like hip and skull structures. Based on skull remains from members of the family such as Effigia, they were also toothless and likely beaked herbivores.

<i>Fasolasuchus</i> Extinct genus of reptiles

Fasolasuchus is an extinct genus of loricatan. Fossils have been found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina that date back to the Norian stage of the Late Triassic, making it one of the last "rauisuchians" to have existed before the order became extinct at the end of the Triassic.

Stagonosuchus is an extinct genus of loricatan, or possibly a species of Prestosuchus. Fossils have been found from the Late Triassic Manda Formation in Tanzania that are Anisian in age.

<i>Sanjuansaurus</i> Extinct genus of dinosaurs

Sanjuansaurus is a genus of herrerasaurid dinosaur from the Late Triassic (Carnian) Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.

<i>Tarjadia</i> Extinct genus of reptiles

Tarjadia is an extinct genus of erpetosuchid pseudosuchian, distantly related to modern crocodilians. It is known from a single species, T. ruthae, first described in 1998 from the Middle Triassic Chañares Formation in Argentina. Partial remains have been found from deposits that are Anisian-Ladinian in age. Long known mostly from osteoderms, vertebrae, and fragments of the skull, specimens described in 2017 provided much more anatomical details and showed that it was a fairly large predator. Tarjadia predates known species of aetosaurs and phytosaurs, two Late Triassic groups of crurotarsans with heavy plating, making it one of the first heavily armored archosaurs. Prior to 2017, most studies placed it outside Archosauria as a member of Doswelliidae, a family of heavily armored and crocodile-like archosauriforms. The 2017 specimens instead show that it belonged to the Erpetosuchidae.

<span class="mw-page-title-main">Erpetosuchidae</span> Extinct family of reptiles

Erpetosuchidae is an extinct family of pseudosuchian archosaurs. Erpetosuchidae was named by D. M. S. Watson in 1917 to include Erpetosuchus. It includes the type species Erpetosuchus granti from the Late Triassic of Scotland, Erpetosuchus sp. from the Late Triassic of eastern United States and Parringtonia gracilis from the middle Middle Triassic of Tanzania; the group might also include Dyoplax arenaceus from the Late Triassic of Germany, Archeopelta arborensis and Pagosvenator candelariensis from Brazil and Tarjadia ruthae from Argentina.

<i>Incertovenator</i> Extinct genus of probable archosaur

Incertovenator is an extinct genus of archosauriform reptile, likely an archosaur, of uncertain affinities. Its unstable position is a result of possessing a number features found in both the bird-line avemetatarsalian archosaurs and the crocodylian-line pseudosuchians. The type and only known species is I. longicollum, which is known from single specimen discovered in the Late Triassic Ischigualasto Formation of Argentina. Incertovenator is known almost entirely by its vertebral column. This indicates that it had a relatively long neck, leading to its uncertain classification due to the convergent evolution of elongated neck vertebrae in both avemetatarsalian and pseudosuchian archosaurs.

References

  1. 1 2 3 4 Reig, O. A. (1959). "Primeros datos descriptivos sobre nuevos arcosaurios del Triásico de Ischigualasto (San Juan, Argentina)". Revista de la Asociación Geológica Argentina. 13 (4): 257–270.
  2. 1 2 3 Sill, W. D. (1974). "The anatomy of Saurosuchus galilei and the relationships of the rauisuchid thecodonts". Bulletin of the Museum of Comparative Zoology. 146: 317–362.
  3. 1 2 3 4 Alcober, O. (2000). "Redescription of the skull of Saurosuchus galilei (Archosauria: Rauisuchidae)". Journal of Vertebrate Paleontology. 20 (2): 302–316. doi:10.1671/0272-4634(2000)020[0302:ROTSOS]2.0.CO;2. S2CID   85967965.
  4. 1 2 3 4 Trotteyn, M.J.; Desojo, J.; Alcober, O. (2011). "Nuevo material postcraneano de Saurosuchus galilei (Archosauria: Crurotarsi) del Triásico Superior del centro-oeste de Argentina". Ameghiniana. 48 (1): 13–27. doi:10.5710/amgh.v48i1(265). hdl: 11336/98158 . S2CID   129032513.
  5. ↑ Heckert, A.B.; Lucas, S.G.; Krzyzanowski, S.E. (2002). "The rauisuchian archosaur Saurosuchus from the Upper Triassic Chinle Group, Southwestern U.S.A., and its biochronological significance" (PDF). In Heckert, A.B.; Lucas, S.G. (eds.). Upper Triassic Stratigraphy and Paleontology. Vol. 21. New Mexico Museum of Natural History and Science Bulletin. pp. 241–247.
  6. ↑ Irmis, R.B. (2005). "The vertebrate fauna of the Upper Triassic Chinle Formation in Northern Arizona". In Nesbitt, S.J.; Parker, W.G.; Irmis, R.B. (eds.). Guidebook to the Triassic Formations of the Colorado Plateau in northern Arizona: Geology, Paleontology, and History. Vol. 9. Mesa Southwestern Museum.
  7. ↑ Henderson, D.M.; Snively, E. (2004). "Tyrannosaurus en pointe: allometry minimized rotational inertia of large carnivorous dinosaurs". Proceedings of the Royal Society of London B. 271 (Suppl 3): S57–S60. doi:10.1098/rsbl.2003.0097. PMC   1809988 . PMID   15101419.
  8. 1 2 Fawcett, Molly J.; Lautenschlager, Stephan; Bestwick, Jordan; Butler, Richard J. (16 August 2023). "Functional morphology of the Triassic apex predator Saurosuchus galilei (Pseudosuchia: Loricata) and convergence with a post-Triassic theropod dinosaur". The Anatomical Record. 307 (3): 549–565. doi: 10.1002/ar.25299 . ISSN   1932-8486. PMID   37584310. S2CID   260924469.
  9. 1 2 3 von Baczko, M. Belén; Cardillo, Ariel F.; Ulloa-Guaiquin, Karen; Desojo, Julia B.; Paulina-Carabajal, Ariana (22 December 2023). "Paleoneurology and neuroanatomical notes on the South American "rauisuchian" Saurosuchus galilei from the Ischigualasto formation, San Juan, Argentina". The Anatomical Record. 307 (4): 1239–1253. doi:10.1002/ar.25362. ISSN   1932-8486. PMID   38133536.
  10. ↑ Nesbitt, S.J. (2011). "The early evolution of archosaurs: relationships and the origin of major clades". Bulletin of the American Museum of Natural History. 352: 1–292. doi: 10.1206/352.1 . hdl:2246/6112. S2CID   83493714.
  11. ↑ Desojo, Julia Brenda; Baczko, María Belén von; Rauhut, Oliver W. M. (18 February 2020). "Anatomy, taxonomy and phylogenetic relationships of Prestosuchus chiniquensis (Archosauria: Pseudosuchia) from the original collection of von Huene, Middle-Late Triassic of southern Brazil". Palaeontologia Electronica. 23 (1): 1–55. doi: 10.26879/1026 . hdl: 11336/127498 . ISSN   1094-8074.
  12. ↑ "Triassic Apex Predator Had Much Weaker Bite than Previously Thought". Sci.News. 21 August 2023. Retrieved 2 October 2023.
  13. ↑ von Baczko, M. Belen; Cardillo, A.F.; Ulloa-Guaiquin, Karen; Desojo, Julia B; Paulina-Carabajal, Ariana (November 2022). "Novel Cranial Endocast of the South American "Rauisuchian" Saurosuchus Galilei (Pseudosuchia: Loricata) from the Ischigualasto Formation of Argentina". Conference: Reunión de Comunicaciones de la Asociación Paleontológica Argentina.
  14. ↑ Wallace, R. V. S. (May 2018). A new close mammal relative and the origin and evolution of the mammalian central nervous system (PDF) (PhD thesis). The University of Texas at Austin.
  15. ↑ Martínez, R. N.; Apaldetti, C.; Alcober, O. A.; Colombi, C. E.; Sereno, P. C.; Fernández, E.; Malnis, P. S.; Correa, G. A.; Abelin, D. (2013). "Vertebrate succession in the Ischigualasto Formation". Journal of Vertebrate Paleontology . 32: 10–30. Bibcode:2013JVPal..32S..10M. doi:10.1080/02724634.2013.818546. hdl: 11336/7771 . S2CID   37918101.
  16. ↑ Weishampel, D. B.; Dodson, P.; Osmolska, H. (2007). "Dinosaur Distribution". The Dinosauria, Second Edition. University of California Press. p. 528.
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