Torvosaurus: Beast of the Week

Today we are going to look at a huge Jurassic predatory dinosaur, Torvosaurus tanneri! 

Torvosaurus lived about 150 million years ago during the Late Jurassic period. Its bones have been unearthed in Colorado, USA, Portugal, and possibly Germany (Europe and North America weren't separated by an ocean back then, remember).  From head to tail it measured up to 36 feet (about 11m) and would have been among the largest, most formidable meat eaters of its time.  The name, Torvosaurus, translates to "Fierce Reptile".
  

Torvosaurus in watercolors life reconstruction by Christopher DiPiazza.

Torvosaurus is a member of the megalosaurid family, and is most closely related to the more famous, Megalosaurus.  Megalosaurids are mostly known from the middle and late Jurassic period, and are not super well known, since not many of them have ever been found compared to most other dinosaurs.  That being said they tend to have long, low skulls with large robust teeth with serrations for cutting meat.  Their arms were powerful with three fingers, tipped with proportionally large hooked claws.  Their legs also tend to be proportionally shorter.  The more striking and spinosaurs are currently thought to be closely related to the megalosaurids (both are classified within the broader megalosauroid group), and it is likely that the megalosaurids gave rise to the first spinosaurs, although we currently don't have any obvious transition fossils that demonstrate this yet.

Torvosaurus, itself currently contains two distinct species.  Torvosaurus tanneri from North America, and the slightly larger Torvosaurus gurneyi, from Europe.

Torvosaurus Skeletal mount on display at the Mesalands Dinosaur Museum in New Mexico.

Torvosaurus is especially important to paleontology because its one of the few dinosaurs paleontologists have actually found eggs from.  The nest of eggs found in Portugal, appeared to have been methodically buried in life by the parent.  They were close to hatching because the bones of embryos were also found inside, making them the oldest carnivorous dinosaur embryos known.  

When alive Torvosaurus tanneri would have coexisted with many famous dinosaurs, including the long-necked sauropods, Apatosaurus, Brontosaurus, Diplodocus, Barosaurus, Camarasaurus, and Braciosaurus, the armored Stegosaurus and Gargoyleosaurus, and the ornithopod Camptosaurus, all of which it may have hunted.  It also would have coexisted with fellow predators, Allosaurus and Ceratosaurus.  In Europe it lived alongside Allosaurus (different species) and the long-necked stegosaur, Dacentrurus, to name just a few.

References

Araújo, Ricardo; Castanhinha, Rui; Martins, Rui M. S.; Mateus, Octávio; Hendrickx, Christophe; Beckmann, F.; Schell, N.; Alves, L. C. (2013). "Filling the gaps of dinosaur eggshell phylogeny: Late Jurassic Theropod clutch with embryos from Portugal". Scientific Reports. 1924 1924: 8.

Chure, Daniel J.; Litwin, Ron; Hasiotis, Stephen T.; Evanoff, Emmett; and Carpenter, Kenneth (2006). "The fauna and flora of the Morrison Formation: 2006". In Foster, John R.; and Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 233–248.

Mateus, O., Walen, A., and Antunes, M.T. (2006). "The large theropod fauna of the Lourinha Formation (Portugal) and its similarity to that of the Morrison Formation, with a description of a new species of Allosaurus." New Mexico Museum of Natural History and Science Bulletin, 36.

 Mateus, O., & Antunes, M. T. (2000). Torvosaurus sp.(Dinosauria: Theropoda) in the late Jurassic of Portugal. In I Congresso Ibérico de Paleontologia/XVI Jornadas de la Sociedad Española de Paleontología (pp. 115-117).

Ribeiro, Vasco; Mateus, Octávio; Holwerda, Femke; Araújo, Ricardo; Castanhinha, Rui (March 4, 2014). "Two new theropod egg sites from the Late Jurassic Lourinhã Formation, Portugal". Historical Biology. 26 (2): 206–217.

Hesperosuchus: Beast of the Week

This week we will be checking out a relative of modern crocodilians that has tricked scientists multiple times!  Enter Hesperosuchus agilis!

Hesperosuchus was a pseudosuchian (related to crocodilians) that lived in what is now Arizona and New Mexico, USA, during the late Triassic period, about 210 million years ago.  It would have been a meat-eater and from snout to tail the most complete skeleton measures about four feet (1.2m) but other fossils suggest it could have grown larger, up to about six feet (1.8m).  The genus name translates to "Western Crocodile" due to where it was fond and its relation to modern crocodilians, and the species name to "agile" in reference to how it was likely a swift and agile runner in life.

Hesperosuchus stealing an egg from the dinosaur, Coelophysis. Watercolor reconstruction by Christopher DiPiazza.

When Hesperosuchus was first discovered it was initially thought to be a kind of dinosaur.  This is due to the fact that it had hollow bones, a trait that at that time was not known to be in pseudosuchians.  Hesperosuchus is just one of many examples of how the group that includes modern crocodilians was extremely diverse and evolved into many different forms during the Mesozoic, especially the Triassic.  Not only did Hesperosuchus have hollow bones, but it also possessed fully erect upright posture with long slender limbs.  It may have even been able to run on its hind legs.  

Hesperosuchus also possessed a laterally compressed skull (again like most theropod dinosaurs) which is in contrast to modern crocodilians, all of which have skulls that are more flattened top to bottom, an adaptation for spending much of their time in the water.  Aquatic crocodilians had not yet evolved in the Triassic and all of their closest relatives from then, like Hesperosuchus, were actually land animals.  Hesperosuchus possessed pointed teeth that were serrated on both the front and rear edges, implying it at meat when alive, probably focusing on snatching up small animals.  Like modern crocodiles it had a slight notch in its snout where its bottom teeth interlocked with its top jaws.

Hesperosuchus skull image from the 2012 paper by Nesbitt et al., referenced below.

 Like most pseudosuchians, Hesperosuchus also had osteoderms, bony armor that exists in the skin, in the form of two rows of almost square-shaped scutes running down its back.  This was likely for defense against predators, of which there were many Hesperosuchus had to be weary of.  That being said it appears this armor may not have protected Hesperosuchuchus every time since there is a famous skeleton of the dinosaur, Coelophysis, has what appears to be bones from Hesperosuchus (which were initially thought to be from a baby Coelophysis) inside its stomach cavity. 

When alive, Hesperosuchus would have lived alongside other pseudosuchians, like the herbivorous aetosaurs and shuvosaurs, and the large  carnivore, Postosuchus.  It also would have shared its environment with the not-crocodile-but-crocodile-resembling phytosaurs, as well as the carnivorous dinosaur, Coelophysis.  

References

Clark, James M.; Sues, Hans-Dieter; Berman, David S. (19 January 2001). "A new specimen of Hesperosuchus agilis from the Upper Triassic of New Mexico and the interrelationships of basal crocodylomorph archosaurs". Journal of Vertebrate Paleontology. 20 (4): 683–704.

Colbert, E. H. 1952. A pseudosuchian reptile from Arizona. Bulletin of the American Museum of Natural History 99:561–592.

Nesbitt, Sterling J.; Turner, Alan H.; Erickson, Gregory M.; Norell, Mark A. (22 December 2006). "Prey choice and cannibalistic behaviour in the theropod Coelophysis". Proceedings of the Royal Society B. 2 (4): 611–4.

Nesbitt, Sterling J.; Turner, Alan H.; Weinbaum, Jonathan C. (September 2012). "A survey of skeletal elements in the orbit of Pseudosuchia and the origin of the crocodylian palpebral". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 103 (3–4): 365–381.