Marshosaurus

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Marshosaurus
Temporal range: Late Jurassic, 155–152  Ma
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Marshosaurus bicentissimus skull cast - Natural History Museum of Utah - DSC07218.JPG
Skull cast
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family:† Piatnitzkysauridae
Genus:† Marshosaurus
Madsen, 1976 [1]
Species:
†M. bicentesimus
Binomial name
†Marshosaurus bicentesimus
Madsen, 1976 [1]

Marshosaurus is a genus of medium-sized carnivorous theropod dinosaur, belonging to the family Piatnitzkysauridae, from the Late Jurassic Morrison Formation of Utah and possibly Colorado.

Discovery and naming

Reconstructed skull of Marshosaurus at the Carnegie Museum of Natural History, based on referred material Marshosaurus bicentesimus.jpg
Reconstructed skull of Marshosaurus at the Carnegie Museum of Natural History, based on referred material

During the 1960s, over fourteen thousand fossil bones were uncovered at the Cleveland-Lloyd Quarry in central Utah. The majority of these belonged to Allosaurus but some were of at least two theropods new to science. In 1974 one of these was named by James Henry Madsen Jr. as the genus Stokesosaurus .

In 1976 the second was by Madsen named as the type species Marshosaurus bicentesimus. The generic name honoured the nineteenth century paleontologist Professor Othniel Charles Marsh, who described many dinosaur fossils during the Bone Wars. The specific name was chosen "in honor of the bicentennial of the United States of America". [1]

The holotype, UMNH VP 6373, was found in a layer of the Brushy Basin Member of the Morrison Formation dating from the late Kimmeridgian, approximately 155 - 152 mya. It is a left ilium, or upper pelvis bone. The paratypes consisted of three bones: the ischia UMNH VP 6379 and UMNH VP 380 and the pubic bone UMNH VP 6387. Three ilia and six jaw fragments were provisionally referred. The material represents at least three individuals.

In 1991, Brooks Britt referred tail vertebrae from Colorado, because they resembled non-identified tail vertebrae fragments from the Cleveland-Lloyd Dinosaur Quarry. [2] In 1993 a partial skeleton, CMNH 21704, from the Dinosaur National Monument was referred because its dorsal neural spines resembled non-identified spines from the Cleveland-Lloyd Dinosaur Quarry. [3] This specimen was also the subject of a 1997 SVP abstract. [4]

Description

Restoration with hypothetical feathers. Marshosaurus restoration.jpg
Restoration with hypothetical feathers.

Marshosaurus was medium-sized for a theropod. In 2010, Gregory S. Paul estimated its length at 4.5 meters (15 ft) and its weight at 200 kilograms (440 lb). [5] The holotype ilium has a length of 37.5 centimeters (14.8 in). If the cranial material is correctly referred, the skull was about 60 centimeters (24 in) long.

In 2012, Matthew Carrano established one autapomorphy, a unique derived trait of the holotype: the suture between the pubic peduncle and the pubic bone is convex, curving upwards, at the front and concave at the rear. [6]

Classification

Ischium Marshosaurus bicentesimus ischium.jpg
Ischium

Madsen originally was unsure about the phylogenetic position of Marshosaurus, placing it as Theropoda incertae sedis . Some later analyses showed Marshosaurus to be a member of Avetheropoda, a group of more bird-like theropods including Tyrannosaurus , Velociraptor and Allosaurus . However, Roger Benson (2010) [7] found it to be a megalosauroid in a phylogenetic analysis of Megalosaurus and 40 other theropods.

The position of Marshosaurus in the evolutionary tree, as a possible member of the Piatnitzkysauridae, is shown by the cladogram below. [7]

Megalosauroidea

Paleobiology

Pathology

One right ilium of a Marshosaurus bicentesimus is deformed by "an undescribed pathology" which probably originated as a consequence of injury. Another specimen has a pathological rib. [8] In a 2001 study conducted by Bruce Rothschild and other paleontologists, five foot bones referred to Marshosaurus were examined for signs of stress fracture, but none were found. [9]

Paleoecology

Habitat

The Morrison Formation is a sequence of shallow marine and alluvial sediments which, according to radiometric dating, ranges between 156.3 million years old (Ma) at its base, [10] to 146.8 million years old at the top, [11] which places it in the late Oxfordian, Kimmeridgian, and early Tithonian stages of the Late Jurassic period. This formation is interpreted as a semiarid environment with distinct wet and dry seasons. The Morrison Basin where dinosaurs lived, stretched from New Mexico to Alberta and Saskatchewan, and was formed when the precursors to the Front Range of the Rocky Mountains started pushing up to the west. The deposits from their east-facing drainage basins were carried by streams and rivers and deposited in swampy lowlands, lakes, river channels and floodplains. [12] This formation is similar in age to the Solnhofen Limestone Formation in Germany and the Tendaguru Formation in Tanzania. In 1877 this formation became the center of the Bone Wars, a fossil-collecting rivalry between early paleontologists Othniel Charles Marsh and Edward Drinker Cope.

Paleofauna

The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus , Brachiosaurus , Barosaurus , Diplodocus , and Apatosaurus . Dinosaurs that lived alongside Marshosaurus included the herbivorous ornithischians Camptosaurus , Dryosaurus , Stegosaurus and Othnielosaurus . Predators in this paleoenvironment included the theropods Saurophaganax , Torvosaurus , Ceratosaurus , Stokesosaurus , Ornitholestes and [13] Allosaurus , which accounted for 70 to 75% of theropod specimens and was at the top trophic level of the Morrison food web. [14] Stegosaurus is commonly found at the same sites as Allosaurus, Apatosaurus, Camarasaurus, and Diplodocus. [15] Early mammals were present in this region, such as docodonts, multituberculates, symmetrodonts, and triconodonts. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, cycads, ginkgoes, and several families of conifers. Vegetation varied from river-lining forests of tree ferns, and ferns (gallery forests), to fern savannas with occasional trees such as the Araucaria -like conifer Brachyphyllum . [16]

Related Research Articles

<i>Allosaurus</i> Extinct genus of carnosaurian theropod dinosaur

Allosaurus is an extinct genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period. The name "Allosaurus" means "different lizard", alluding to its unique concave vertebrae. It is derived from the Greek words ἄλλος and σαῦρος. The first fossil remains that could definitively be ascribed to this genus were described in 1877 by famed paleontologist Othniel Charles Marsh. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles.

<i>Camarasaurus</i> Camarasaurid sauropod dinosaur genus from Late Jurassic Period

Camarasaurus was a genus of quadrupedal, herbivorous dinosaurs and is the most common North American sauropod fossil. Its fossil remains have been found in the Morrison Formation, dating to the Late Jurassic epoch, between 155 and 145 million years ago.

<i>Ceratosaurus</i> Genus of theropod dinosaur from the Late Jurassic period

Ceratosaurus was a carnivorous theropod dinosaur that lived in the Late Jurassic period. The genus was first described in 1884 by American paleontologist Othniel Charles Marsh based on a nearly complete skeleton discovered in Garden Park, Colorado, in rocks belonging to the Morrison Formation. The type species is Ceratosaurus nasicornis.

<i>Torvosaurus</i> Megalosaurid theropod dinosaur genus from Late Jurassic Period

Torvosaurus is a genus of large megalosaurine theropod dinosaur that lived approximately 165 to 148 million years ago during the Callovian to Tithonian ages of the late Middle and Late Jurassic period in what is now Colorado, Portugal, Germany, and possibly England, Spain, Tanzania, and Uruguay. It contains two currently recognized species, Torvosaurus tanneri and Torvosaurus gurneyi, plus a third unnamed species from Germany.

<i>Barosaurus</i> Diplodocid sauropod dinosaur genus from Upper Jurassic Period

Barosaurus was a giant, long-tailed, long-necked, plant-eating sauropod dinosaur closely related to the more familiar Diplodocus. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Dakota. It is present in stratigraphic zones 2–5.

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

Dryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont. Fossils have been found in the western United States and were first discovered in the late 19th century. Valdosaurus canaliculatus and Dysalotosaurus lettowvorbecki were both formerly considered to represent species of Dryosaurus.

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

Ornitholestes is a small theropod dinosaur of the late Jurassic of Western Laurasia.

<span class="mw-page-title-main">Como Bluff</span> United States historic place

Como Bluff is a long ridge extending east–west, located between the towns of Rock River and Medicine Bow, Wyoming. The ridge is an anticline, formed as a result of compressional geological folding. Three geological formations, the Sundance, the Morrison, and the Cloverly Formations, containing fossil remains from the Late Jurassic of the Mesozoic Era are exposed.

<span class="mw-page-title-main">Jurassic National Monument</span>

Jurassic National Monument, at the site of the Cleveland-Lloyd Dinosaur Quarry, well known for containing the densest concentration of Jurassic dinosaur fossils ever found, is a paleontological site located near Cleveland, Utah, in the San Rafael Swell, a part of the geological layers known as the Morrison Formation.

Coelurus is a genus of coelurosaurian dinosaur from the Late Jurassic period. The name means "hollow tail", referring to its hollow tail vertebrae. Although its name is linked to one of the main divisions of theropods (Coelurosauria), it has historically been poorly understood, and sometimes confused with its better-known contemporary Ornitholestes. Like many dinosaurs studied in the early years of paleontology, it has had a confusing taxonomic history, with several species being named and later transferred to other genera or abandoned. Only one species is currently recognized as valid: the type species, C. fragilis, described by Othniel Charles Marsh in 1879. It is known from one partial skeleton found in the Morrison Formation of Wyoming, United States. It was a small bipedal carnivore with elongate legs.

<i>Saurophaganax</i> Allosaurid theropod dinosaur genus from Late Jurassic period

Saurophaganax is a genus of large allosaurid dinosaur from the Morrison Formation of Late Jurassic Oklahoma, United States. Some paleontologists consider it to be a junior synonym and species of Allosaurus. Saurophaganax represents a very large Morrison allosaurid characterized by horizontal laminae at the bases of the dorsal neural spines above the transverse processes, and "meat-chopper" chevrons. It was the largest terrestrial carnivore of North America during the Late Jurassic, reaching 10.5 metres (34 ft) in length and 2.7–3.8 metric tons in body mass.

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

Stokesosaurus is a genus of small, carnivorous early tyrannosauroid theropod dinosaurs from the late Jurassic period of Utah, United States.

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

Koparion is a genus of small coelurosaurian theropod dinosaur, from the late Jurassic Period, of Utah. It contains the single named species Koparion douglassi which is known only from a single isolated tooth.

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

Tanycolagreus is a genus of coelurosaurian theropod from the Late Jurassic of North America.

<span class="mw-page-title-main">Dry Mesa Quarry</span>

The Dry Mesa Dinosaur Quarry is situated in southwestern Colorado, United States, near the town of Delta. Its geology forms a part of the Morrison Formation and has famously yielded a great diversity of animal remains from the Jurassic Period, among them Ceratosaurus, Supersaurus, and Torvosaurus. The quarry is found within the Uncompahgre National Forest.

<i>Camarasaurus lentus</i> Species of sauropod

Camarasaurus lentus is an extinct species of sauropod dinosaur that lived during the Jurassic period in what is now the western United States. It is one of the four valid species of the well-known genus Camarasaurus. C. lentus fossils have been found in Wyoming, Colorado, and Utah. It is the species of Camarasaurus found in Dinosaur National Monument and the middle layers of the Morrison Formation. Camarasaurus lentus is among the best-known sauropod species, with many specimens known. A juvenile specimen of C. lentus, CM 11338, is the most complete sauropod fossil ever discovered.

<i>Uteodon</i> Genus of reptiles (fossil)

Uteodon is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the late Jurassic period in what is now Uintah County, Utah. It is known from the middle of the Brushy Basin Member, Morrison Formation. The genus was named by Andrew T. McDonald in 2011 and the type species is U. aphanoecetes.

<span class="mw-page-title-main">Piatnitzkysauridae</span> Extinct family of dinosaurs

Piatnitzkysauridae is an extinct family of megalosauroid or basal allosauroid dinosaurs. It only consists of three to four known dinosaur genera: Condorraptor, Marshosaurus, Piatnitzkysaurus and possibly Xuanhanosaurus. The most complete and well known member of this family is Piatnitzkysaurus, which also gives the family its name.

James "Jim" Henry Madsen Jr. was an American vertebrate paleontologist and geologist and main leader of excavations at the Cleveland-Lloyd Dinosaur Quarry in the 1960s. Madsen primarily worked to describe skeletons of Allosaurus from the quarry, eventually getting the site to become a National Natural Landmark in 1965 and a national monument after his death.

References

  1. 1 2 3 Madsen, James H. (1976). "A second new theropod dinosaur from the Late Jurassic of east central Utah" (PDF). Utah Geology. 3 (1): 51–60. doi:10.34191/UG-3-1_51. S2CID   129534888.
  2. ↑ Britt, Brooks (1991). "Theropods of Dry Mesa Quarry (Morrison Formation, Late Jurassic), Colorado, with emphasis on the osteology of Torvosaurus tanneri" (PDF). Brigham Young University Geology Studies. 37: 1–72.
  3. ↑ Chure, D.; Britt, Brooks; Madsen, James H. (1993). "New data on the theropod Marshosaurus from the Morrison Formation (Upper Jurassic: Kimmeridgian-Tithonian) of Dinosaur NM" (PDF). In Santucci (ed.). National Park Service Paleontology Research Abstract Volume. Technical Report NPS/NRPEFO/NRTR 93/11. p. 23.
  4. ↑ Chure, D.; Britt, Brooks; Madsen, James H. (1997). "A new specimen of Marshosaurus bicentesimus (Theropoda) from the Morrison Formation (Late Jurassic) of Dinosaur National Monument". Journal of Vertebrate Paleontology. 17 (supp 3): 38A. doi:10.1080/02724634.1997.10011028.
  5. ↑ Paul, Gregory S. (2010). The Princeton Field Guide to Dinosaurs . Princeton University Press. p.  91.
  6. ↑ Carrano, Matthew T.; Benson, Roger B. J.; Sampson, Scott D. (2012). "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology . 10 (2): 211–300. doi:10.1080/14772019.2011.630927. S2CID   85354215.
  7. 1 2 Benson, Roger B. J. (2010). "A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods". Zoological Journal of the Linnean Society . 158 (4): 882–935. doi: 10.1111/j.1096-3642.2009.00569.x .
  8. ↑ Molnar, R. E. (2001). "Theropod paleopathology: a literature survey". In Tanke, D. H.; Carpenter, K. (eds.). Mesozoic Vertebrate Life. Indiana University Press. pp. 337–363.
  9. ↑ Rothschild, B.; Tanke, D. H.; Ford, T. L. (2001). "Theropod stress fractures and tendon avulsions as a clue to activity". In Tanke, D. H.; Carpenter, K. (eds.). Mesozoic Vertebrate Life. Indiana University Press. pp. 331–336.
  10. ↑ Trujillo, K. C.; Chamberlain, K. R.; Strickland, A. (2006). "Oxfordian U/Pb ages from SHRIMP analysis for the Upper Jurassic Morrison Formation of southeastern Wyoming with implications for biostratigraphic correlations". Geological Society of America Abstracts with Programs. 38 (6): 7.
  11. ↑ Bilbey, S. A. (1998). "Cleveland-Lloyd Dinosaur Quarry - age, stratigraphy and depositional environments". In Carpenter, K.; Chure, D.; Kirkland, J. I. (eds.). The Morrison Formation: An Interdisciplinary Study. Modern Geology. Vol. 22. Taylor and Francis Group. pp. 87–120. ISSN   0026-7775.
  12. ↑ Russell, Dale A. (1989). An Odyssey in Time: Dinosaurs of North America. Minocqua, Wisconsin: NorthWord Press. pp. 64–70. ISBN   978-1-55971-038-1.
  13. ↑ Foster, J. (2007). "Appendix". Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327–329.
  14. ↑ Foster, John R. (2003). Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. New Mexico Museum of Natural History and Science Bulletin, 23. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. p. 29.
  15. ↑ Dodson, Peter; Behrensmeyer, A. K.; Bakker, Robert T.; McIntosh, John S. (1980). "Taphonomy and paleoecology of the dinosaur beds of the Jurassic Morrison Formation". Paleobiology . 6 (2): 208–232. doi:10.1017/s0094837300025768.
  16. ↑ Carpenter, Kenneth (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus". In Foster, John R.; Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin. Vol. 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 131–138.
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