Herrerasaurus

Herrerasaurus
Skeleton replica of Herrerasaurus in a special exhibition at the Senckenberg Nature Museum in Frankfurt am Main .
Temporal occurrence
Upper Triassic ( Carnian )
235 to 228 million years
Locations
Argentina ( Ischigualasto Formation )
Systematics
Ornithodira Dinosaur (dinosauria) Lizard dinosaur (Saurischia) Herrerasauridae Herrerasaurus
Scientific name
Herrerasaurus
Reig , 1963
Art
Herrerasaurus ischigualastensis

Herrerasaurus was one of the earliest and most basic (primordial) dinosaurs . Fossils of this carnivore come from the early Upper Triassic ( Carnian ) in northwest Argentina . This genus wasscientifically described for the first timein 1963 by Osvaldo Reig with the only known species Herrerasaurus ischigualastensis . Herrerasaurus means something like "Herrera's lizard" and honors Victorino Herrera, a goatherd who found the first fossil of this genus.

The family relationships of Herrerasaurus were unclear for a long time, as initially only very fragmentary remains were known. While some researchers thought it was a basal theropod, other researchers viewed it as a basal representative of the Sauropodomorpha or as a basal Saurischier ; some researchers even suspected that Herrerasaurus wasn't a dinosaur at all.

In 1988 an almost complete skeleton including a skull was discovered. Today Herrerasaurus is considered to be either a basal theropod or a basal Saurischia, although many researchers consider it the most original theropod known to date. Herrerasaurus is the eponymous representative of the Herrerasauridae .

description

Artistic drawing of a Herrerasaurus eating a synapsid carcass

Size comparison between Herrerasaurus and a human.

Herrerasaurus was a relatively small, lightly built carnivore (carnivore). The body length is estimated to be 3 to 6 meters; the hip height was more than 1.1 meters. The weight is estimated at 250 to 350 kilograms. The skull of a very large specimen, which was once attributed to its own genus, Frenguellisaurus , measures 56 centimeters in length. Smaller specimens had skulls about 30 centimeters long.

skull

Herrerasaurus had a long, narrow skull that resembles those of original archosaurs such as Euparkeria , but which lacks almost all of the specializations that are typical of other dinosaurs. It had five cranial windows on each side: between the eye and nasal cavities there was a large antorbital window and a promaxillary window - a small, 1 cm long slit-like hole. There was a large infratemporal window behind the eye socket .

There was a flexible joint in the lower jaw, which made it easier to hold prey. This specialization is exceptional for dinosaurs and has evolved independently ( convergent ) in lizards. The jaws were equipped with large, serrated teeth. The neck was slender and flexible.

limbs

The Herrerasaurus forelimbs were less than half the length of the hind limbs. The upper and lower arm were quite short while the hand was elongated. The first two fingers and the thumb ended in curved, sharp claws. The fourth and fifth fingers were reduced and clawless.

Unlike most reptiles of its time, Herrerasaurus was completely biped (walking on two legs). The rear legs were sturdy and were characterized by a short thigh and a relatively long foot, which indicates a fast runner. The foot had five toes, but only the middle three (toes II, III, and IV) carried the weight. The outer toes (I and V) were small; the first toe had a small claw. The tail was partially stiffened by overlapping vertebral processes to balance the body while walking.

Derived and basal characteristics

Herrerasaurus shows a mosaic of features of various more derived dinosaur groups as well as more basal archosaurs. Although it shares most of the characteristics with dinosaurs, the hip and leg bones in particular have some basic features that are atypical for dinosaurs. The pelvis resembled those of the Saurischia , but had an ossified acetabulum (hip joint socket) that was only partially open. The ilium (iliac bone) was only supported by two sacral vertebrae - a basic property. However, the pubis (pubic bone) points backwards, a derivative trait that Herrerasaurus shares with the Dromaeosauridae and birds . The end of the pubic bone was boot-shaped and thus resembled that of the Avetheropoda . The vertebral bodies were hourglass-shaped, as in Allosaurus .

Systematics

Dinosauria    Ornithischia   Saurischia     Herrerasauridae   Herrerasaurus     Staurikosaurus     Unnamed Herrerasauride   Eusaurischia   Chindesaurus   Theropoda   Eoraptor     Neotheropoda     Sauropodomorpha    Dinosauria    Ornithischia   Saurischia   Sauropodomorpha   Theropoda   Herrerasaurus     Staurikosaurus     Eoraptor     Tawa     Neotheropoda The upper cladogram is from MD Ezcurra from 2010. Herrerasaurus is a primitive Saurischia here, but not a theropod. The lower cladogram is based on studies by S. Nesbitt from 2011. Herrerasaurus is shown here as a basal theropod.

Herrerasaurus is namesake of the Herrerasauridae family , which was common during the Upper Triassic and includes some of the earliest and most basal dinosaurs. Their relationship to other basal dinosaurs is unclear. Most 21st century studies classify them as basal theropods , although they may have been outside the theropods at the base of the Saurischia , or even were not dinosaurs at all. While Sterling Nesbitt and colleagues (2009, 2011) consider the Herrerasauridae to be a group of very basal theropods, other researchers such as Ezcurra (2010) suspect that they belonged neither to the theropods nor to the sauropodomorphs , but as a sister group of the Eusaurischia stood close to the base of the Saurischia.

It is also disputed which other genera of the Herrerasauridae are to be assigned. Possible Herrerasauriden were Sanjuansaurus , which also comes from the Ischigualasto Formation, Staurikosaurus from the Santa Maria Formation of southern Brazil, Chindesaurus from the Petrified Forest of the Chinle Formation of Arizona, and Caseosaurus from the Dockum Formation of Texas . Other possible basal theropods could have been related to the Herrerasauridae - including Alwalkeria from the Maleri formation of India and Teyuwasu , which is known from very fragmentary remains from Brazil. Novas (1992) defined the Herrerasauridae as a node-based definition , which includes the common ancestor of Herrerasaurus and Staurikosaurus and all descendants of this ancestor. Sereno (1998) defines the group meanwhile as a stem-based definition , which includes all taxa that were more closely related to Herrerasaurus ischigualastensis than to the house sparrow ( Passer domesticus ).

Research history

Herrerasaurus was first scientifically described by Osvaldo Reig in 1963 . The name honors Victorino Herrera, a goatherd who found the first fossils of Herrerasaurus near the Argentine city of San Juan in 1959. These sediments, in which fossils of Eoraptor were also found, belong to the Ischigualasto Formation and are dated to the late Ladinian to early Carnian ( Upper Triassic ). Together with Herrerasaurus , Reig described a second dinosaur from the Ischigualasto formation - Ischisaurus cattoi . Today , however, Ischisaurus is considered a juvenile of Herrerasaurus and therefore a younger synonym . Two further partial skeletons with skulls were described by Fernando Novas in 1986 as Frenguellisaurus ischigualastensis , but today they are also assigned to the genus Herrerasaurus .

The family relationships of Herrerasaurus have been discussed controversially since the first description. Reig suspected that Herrerasaurus was an early representative of the Carnosauria . Steel, on the other hand, classified Herrerasaurus as a prosauropod in 1970 . Peter Galton declared the genus as not further classifiable Saurischia . Other authors saw Herrerasaurus along with Staurikosaurus as very basal dinosaurs outside of Saurischia. Several researchers classify Herrerasaurus outside of dinosaurs.

Skeleton of Herrerasaurus along with a smaller Eoraptor skeleton and a Plateosaurus skull on display at the North American Museum of Ancient Life .

It wasn't until 1988 that a research group led by Paul Sereno succeeded in discovering a complete skull. Based on this new discovery, authors such as Thomas R. Holtz and José Bonaparte classified Herrerasaurus at the base of the Saurischia and outside of the Sauropodomorpha and the Theropoda. Sereno, on the other hand, preferred to view Herrerasaurus (and the Herrerasauridae) as basal theropods. The majority of the more recent studies support one of these two hypotheses: Rauhut (2003) and Bittencourt and Kellner (2004) favor the hypothesis of the basal theropod, while Max Langer (2004), Langer and Benton (2006), and Randall Irmis and co-authors ( 2007) support the basal dinosaur hypothesis. If Herrerasaurus actually was a theropod, this would mean that the Theropoda, Sauropodomorpha and Ornithischia formed before the evolution of the Herrerasauridae - possibly before the middle Carnian, and that these large groups of dinosaurs acquired various characteristics typical of dinosaurs independently of one another such as the advanced ankle or the open acetabulum. This hypothesis is supported by large, three-toed footprints that were probably left by theropod dinosaurs: These tracks come from the Ladinian (Middle Triassic) of the Los Rastros Formation of Argentina and are thus 3 to 5 million years older than the Herrerasaurus fossils .

Studies of early dinosaurs like Herrerasaurus form an important basis for defining dinosaurs as a monophyletic group . A study of Herrerasaurus by Sereno (1992) suggests that many common, newly acquired characteristics of early dinosaurs were not jointly derived characteristics ( synapomorphies ) of the dinosaurs, but developed independently of one another ( convergent ) in different dinosaur groups. In addition, based on his study of Herrerasaurus , Sereno suggested various other synapomorphies of the group Dinosauria.

Paleoecology

Artistic plastic model of Herrerasaurus with prey

Herrerasaurus lived about 235 to 228 million years ago during the early Upper Triassic (Carnian), a time when the dinosaurs were not yet the dominant land vertebrates. The vertebrate fauna of the Ischigualasto Formation and the somewhat younger Los Colorados Formation consisted mainly of a large number of archosaurs from the Crurotarsi group and synapsids . In the Ischigualasto Formation, dinosaurs made up only 6% of the fauna. By the end of the Triassic, they became the dominant land animals, while the diversity and numbers of the other archosaurs and synapsids decreased.

The sediments of the Ischigualasto formation were deposited within floodplains . The area was covered with forest and was volcanically active. The climate was warm and humid, but characterized by seasonal fluctuations; there are indications of heavy seasonal rainfall. The vegetation consisted of ferns such as cladophlebis , horsetail and the giant conifer Protojuniperoxylon . These plants formed highland forests along the river plains. Herrerasaurus appears to have been the most common carnivore of the Ischigualasto formation. Other carnivores in this formation included the Eoraptor , another early dinosaur; Saurosuchus , a giant Rauisuchia ; the smaller Venaticosuchus , an Ornithosuchidae ; and the Chiniquodontidae , a family from the Therapsida group . Herbivores were by rhynchosaurs like Hyperodapedon ; Aetosaurs ; Dicynodonts from the Kannemeyeridae family, such as Ischigualastia , and represented by therapsids from the Traversodontidae family , such as Exaeretodon . There were also herbivorous dinosaurs, such as the Ornithischia Pisanosaurus .

Paleobiology and paleopathology

Cast of a skull in the Museo Civico di Storia Naturale di Milan

Herrerasaurus was believed to be an active predator , as indicated by the flexible jaws. It was larger and probably more cumbersome than its smaller relative, the Staurikosaurus . The top predators of the Ischigualasto fauna were probably great Rauisuchians . Herrerasaurus and Rauisuchier may have stalked the herbivorous rhynchosaurs and synapsids .

In the Ischigualasto Formation, coprolites (fossil dung) occur, which contain small bones but no vegetable remains, and possibly come from Herrerasaurus . Mineralogical and chemical analyzes of these coprolites show that Herrerasaurus was able to digest bones if the assignment of the coprolites to Herrerasaurus were correct.

Comparisons between the scleral rings of Herrerasaurus and modern birds and reptiles suggest that this animal may have lived cathemerally, i.e. was active at short intervals both during the day and at night.

One of the famous Herrerasaurus skulls shows three healed stab wounds. These wounds are found in different areas of the skull, each with a different orientation, indicating that they were inflicted independently of one another. The wounds were suffering from an infection, which was indicated by a porous wall surrounding the wounds, which was interpreted as swelling. These wounds may have been caused by the great Rauisuchian Saurosuchus - but it is more likely that they arose during fights with conspecifics, as indicated by the moderate size of the wounds and the fact that they did not lead to the animal's death.

Bruce Rothschild and colleagues (2001) examined 12 hand bones and 20 foot bones of Herrerasaurus for signs of fatigue fractures , but found none.

Individual evidence

1. ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , p. 69, online ( memento of the original from July 13, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . 
2. ↑ ^{a b} Oscar A. Alcober, Ricardo Martinez N.: A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto formation of Northwestern Argentina. In: ZooKeys. Vol. 63, 2010, ISSN  1313-2989 , pp. 55-81, doi : 10.3897 / zookeys.63.550 .
3. ↑ ^{a b c d} Osvaldo A. Reig: La presencia de dinosaurios saurisquios en los "Estratos de Ischigualasto" (Mesotriásico Superior) de las provincias de San Juan y La Rioja (República Argentina). In: Ameghiniana. Vol. 3, No. 1, 1963, ISSN  0002-7014 , pp. 3-20.
4. ^ Paul C. Sereno , Fernando E. Novas , Andrea B. Arcucci, C. Yu: New evidence on dinosaur and mammal origins from the Ischigualasto Formation (Upper Triassic, Argentina). In: Journal of Vertebrate Paleontology. Vol. 8, Supplement 3, 1988, ISSN  0272-4634 , p. 26A.
5. ↑ ^{a b c d e f} Paul C. Sereno, Fernando E. Novas: The complete skull and skeleton of an early dinosaur. In: Science . Vol. 258, No. 5085, 1992, pp. 1137-1140, doi : 10.1126 / science.258.5085.1137 , PMID 17789086 .
6. ↑ Thomas R. Holtz Jr .: Dinosaurs. The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages. Winter 2010 Appendix. 2011. (PDF; 457 kB).
7. ^ ^{A b} Sterling J. Nesbitt, Nathan D. Smith, Randall B. Irmis, Alan H. Turner, Alex Downs, Mark A. Norell : A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs. In: Science. Vol. 326, No. 5959, 2009, pp. 1530-1533, doi : 10.1126 / science.1180350 , PMID 20007898 .
8. ↑ Marc Airhart: New Meat-Eating Dinosaur Age Evolutionary Tree. Jackson School of Geosciences, December 10, 2009, archived from the original on March 10, 2010 ; Retrieved July 13, 2014 . 
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10. ↑ ^{a b c d} Max C. Langer: Basal Saurischia. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 25-46.
11. ↑ ^{a b c d e} Paul C. Sereno, Fernando E. Novas: The skull and neck of the basal theropod Herrerasaurus ischigualastensis. In: Journal of Vertebrate Paleontology. Vol. 13, No. 4, 1994, pp. 451-476, doi : 10.1080 / 02724634.1994.10011525
12. ^ Paul C. Sereno: The phylogenetic relationships of early dinosaurs: a comparative report. In: Historical Biology. Vol. 19, No. 1, 2007, ISSN  0891-2963 , pp. 145-155, doi : 10.1080 / 08912960601167435 .
13. ^ Samuel B. McDowell, Charles M. Bogert: The systematic position of Lanthanotus and the affinities of the anguinomorphan lizards. In: Bulletin of the American Museum of Natural History. Vol. 105, 1954, ISSN  0003-0090 , pp. 1-142, online .
14. ↑ ^{a b c} Fernando E. Novas: New information on the systematics and postcranial skeleton of Herrerasaurus ischigualastensis (Theropoda: Herrerasauridae) from the Ischigualasto Formation (Upper Triassic) of Argentina. In: Journal of Vertebrate Paleontology. Vol. 13, No. 4, 1994, pp. 400-423, doi : 10.1080 / 02724634.1994.10011523 .
15. ↑ Paul C. Sereno: The pectoral girdle and forelimb of the basal theropod Herrerasaurus ischigualastensis. In: Journal of Vertebrate Paleontology. Vol. 13, No. 4, 1994, pp. 425-450, doi : 10.1080 / 02724634.1994.10011524 .
16. ↑ ^{a b} Martin D. Ezcurra: A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny. In: Journal of Systematic Palaeontology. Vol. 8, No. 3, 2010, ISSN  1477-2019 , pp. 371-425, doi : 10.1080 / 14772019.2010.484650 .
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19. ^ Edwin H. Colbert : A saurischian dinosaur from the Triassic of Brazil. In: American Museum Novitates. No. 2405, 1970, ISSN  0003-0082 , pp. 1-39, online (PDF; 4.06 MB) .
20. ^ Robert A. Long, Phillip A. Murry: Part of Late Triassic (Carnian and Norian) Tetrapods from the Southwestern United States (= New Mexico Museum of Natural History and Science. Bulletin. 4, ISSN  1524-4156 ). New Mexico Museum of Natural History, Albuquerque NM 1995, online (PDF; 86.44 MB) .
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25. ^ Paul C. Sereno: A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. In: New Yearbook for Geology and Paleontology. Treatises. Vol. 210, No. 1, 1998, ISSN  0077-7749 , pp. 41-83.
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30. ↑ Peter M. Galton : On the anatomy and relationships of Efraasia diagnostica (Huene) n. Gen., A prosauropod dinosaur (Reptilia: Saurischia) from the Upper Triassic of Germany. In: Paleontological Journal. Vol. 47, No. 3/4, 1973, ISSN  0031-0220 , pp. 229-255, doi : 10.1007 / BF02985709 .
31. ↑ Fernando E. Novas: The tibia and tarsus in Herrerasauridae (Dinosauria, incertae sedis) and the origin and evolution of the dinosaurian tarsus. In: Journal of Paleontology. Vol. 63, No. 5, 1989, ISSN  0022-3360 , pp. 677-690.
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35. ↑ José F. Bonaparte , José A. Pumares: Notas sobre el primer cráneo de Riojasaurus incertus (Dinosauria, Prosauropoda, Melanorosauridae) del Triásico superior de La Rioja, Argentina. In: Ameghiniana. Vol. 32, No. 4, pp. 341-349.
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39. ↑ Randall B. Irmis, Sterling J. Nesbitt, Kevin Padian, Nathan D. Smith, Alan H. Turner, Daniel Woody, Alex Downs: A Late Triassic Dinosauromorph Assemblage from New Mexico and the Rise of Dinosaurs. In: Science. Vol. 317, No. 5836, 2007, pp. 358-361, doi : 10.1126 / science.1143325 , PMID 17641198 .
40. ^ Augustus T. White, M. Alan Kazlev: Theropoda: Basal Theropods: Herrerasauridae. In: Palaeos.com. 2003, accessed July 13, 2014 . 
41. ↑ Catherine A. Forster, Andrea B. Arcucci, Claudia A. Marsicano, Fernando Abdala, Cathleen L. May: New vertebrate material from the Los Rastros Formation (Middle Triassic), La Rioja province, northwestern Argentina. In: Journal of Vertebrate Paleontology. Vol. 15, Supplement 3, 1995, p. 29A.
42. ↑ Andrea B. Arcucci, Catherine A. Forster, Cathleen L. May, Fernando Abdala, Claudia A. Marsicano: Una nueva icnofauna de la Formación Los Rastros, Triásico Medio, en la Quebrada de Ischichuca Chica (Provincia de La Rioja, Argentina) . In: Acta Geológica Lilloana. Vol. 18, 1998, ISSN  0567-7513 , pp. 152-153.
43. ↑ ^{a b} José F. Bonaparte: Faunas y paleobiogeografía de los tetrápodos mesozoicos de América del Sur. In: Ameghiniana. Vol. 16, No. 3/4, 1979, pp. 217-238.
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45. ↑ Michael J. Benton: Origin and early evolution of dinosaurs. In: James O. Farlow, Michael K. Brett-Surman (Eds.): The complete dinosaur. Indiana University Press, Bloomington IN et al. 1997, ISBN 0-253-33349-0 , pp. 204-215, online .
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47. ↑ Maurice E. Tucker, Michael J. Benton: Triassic environments, climates, and reptile evolution ( Memento of the original from January 26, 2009 in the Internet Archive ) Info: The  archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . In: Palaeogeography, Palaeoclimatology, Palaeoecology. Vol. 4, No. 4, 1982, ISSN  0031-0182 , pp. 361-379, doi : 10.1016 / 0031-0182 (82) 90034-7 . Retrieved July 13, 2014.
48. ↑ Carina E. Columbi: Stable isotope analysis of fossil plants from the Upper Triassic Ischigualasto Formation in the northwest of Argentina. The Geological Society of America, Houston TX October 5, 2008. Retrieved July 13, 2014.
49. ^ William D. Sill: The anatomy of Saurosuchus galilei and the relationships of the rauisuchid thecodonts. In: Bulletin of the Museum of Comparative Zoology. Vol. 146, No. 7, 1974, ISSN  0027-4100 , pp. 317-362, digitized .
50. ^ José F. Bonaparte: Annotated list of the South American Triassic tetrapods. In: Second Gondwana Symposium. South Africa, July to August 1970. Proceedings and Papers. Council for Scientific and Industrial Research, Pretoria 1970, pp. 665-682.
51. ↑ ^{a b c} Hans-Dieter Sues: Staurikosaurus and Herrerasauridae. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . University of California Press, Berkeley CA et al. 1990, ISBN 0-520-06726-6 , pp. 143-147.
52. ^ Kurt T. Hollocher, Oscar A. Alcober, Carina E. Colombi, Thomas C. Hollocher: Carnivore Coprolites from the Upper Triassic Ischigualasto Formation, Argentina: Chemistry, Mineralogy, and Evidence for Rapid Initial Mineralization. In: PALAIOS. Vol. 20, No. 1, 2005, pp. 51-63, doi : 10.2110 / palo.2003.p03-98 .
53. ↑ Lars Schmitz, Ryosuke Motani: Nocturnality in Dinosaurs Inferred from Scleral Ring and Orbit Morphology. In: Science. Vol. 332, No. 6030, 2011, pp. 705-708, doi : 10.1126 / science.1200043 , PMID 21493820 .
54. ↑ Ralph E. Molnar: Theropod paleopathology: a literature survey. In: Darren H. Tanke, Kenneth Carpenter (Eds.): Mesozoic Vertebrate Life. New Research inspired by the Paleontology of Philip J. Currie. Indiana University Press et al., Bloomington IN et al. 2001, ISBN 0-253-33907-3 , pp. 337-363.
55. ↑ Bruce Rothschild, Darren H. Tanke, Tracy L. Ford: Theropod stress fractures and tendon avulsions as a clue to activity. In: Darren H. Tanke, Kenneth Carpenter (Eds.): Mesozoic Vertebrate Life. New Research inspired by the Paleontology of Philip J. Currie. Indiana University Press et al., Bloomington IN et al. 2001, ISBN 0-253-33907-3 , pp. 331-336.

Web links

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