Baryonyx

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Saurischia

Family: Spinosauridae

Genus: Baryonyx

Species: Baryonyx walkeri

Introduction

Baryonyx was a large predatory dinosaur that lived on the floodplains and swamps of Early Cretaceous Europe. Relatives of the species have been found in Africa, South America, and Asia and seem to have specialized in living in semi-aquatic habitats.

In the Triassic period, the continents of the world were united into a single land mass known as Pangaea. Dinosaurs first appeared in the Late Triassic (about 230 million years ago) and spread across Pangaea, evolving into a variety of species. In the Jurassic and Cretaceous, Pangaea split under the influence of tectonic movement, resulting in two supercontinents, Gondwana in the south and Laurasia in the north.

Relatives of Baryonyx first begin to appear in the fossil record in the Late Jurassic. Paleontologists believe that an ancestor species evolved and spread in the Jurassic when Gondwana and Laurasia were connected by a land bridge. As the continents split, this ancestor gave rise to several distinct species on both supercontinents.

Classification

Scientists utilize two primary methods to classify organisms into groups. Linnaean taxonomy, or “systematics,” groups organisms according to overall physical similarity, while “cladistics” attempts to organize organisms into groups, called “clades,” that reflect the evolutionary relationships between species.

Taxonomic analysis places Baryonyx into the order Saurischia, or the “lizard-hipped” dinosaurs, based on the reptile-like orientation of its pelvic bones. From there, the species is placed in the suborder Theropoda, which were bipedal, carnivorous dinosaurs. The family Spinosauridae contains theropods with elongated, “spoon-shaped” jaws and skulls similar in morphology to crocodilians.

Cladistic analysis also places Baryonyx in the clade Theropoda based on features of the skull and the presence of a furcula, a forked bone in the animal's chest. The clade Spinosauridae is defined by the presence of conical teeth and elongated, crocodile-like jaws. Baryonyx is further placed into the clade Baryonychinae, along with the closely related genus Suchomimus, based on features of the skull, limb bones, and dentition (development and arrangement of teeth).

Anatomy

Baryonyx was a large carnivore, reaching between 8 and 13 meters (26–42.6 ft) in length and standing nearly 2.5 meters (8.2 ft) at the hip. Paleontologists estimate that the animal may have weighed as much as 1,700 kilograms (3,748 lbs). In addition, paleontologists believe that specimens discovered so far are sub-adult animals and that the full adult size of the species has yet to be determined.

Baryonyx was bipedal, walking on its hind legs and using its front legs for defense and for subduing prey. The animal had four-toed feet with blunt claws and muscular front legs with four clawed fingers. The animal's fourth finger, corresponding to the thumb in humans, had an elongated, hooked claw that could grow as long as 30–35 centimeters (11.8–13.7 in).

The skull of Baryonyx was long and thin compared to those of most theropods. The jaws were lined with at least 96 conical teeth that were somewhat “spoon-shaped.” The end of the snout was curved downward, giving the jaws a hook, possibly for holding prey. Paleontologists have not found skin impressions for Baryonyx and are therefore uncertain about the species’ integument, or the covering of an organism's outer surface, including scales, fur, feathers, and skin. The animal may have had pebbled, mosaic scales similar to most dinosaur species.

Intelligence

No direct EQ measurements have been conducted for Baryonyx, but it is likely that the creature has similar intelligence to modern crocodiles or other large reptiles. Generally speaking, predatory dinosaurs, like most predatory animals, had larger EQ ratings than herbivores, an adaptation that allows predators to “outthink” their prey.

Reproduction and Population

Paleontologists have not found any eggs from Baryonyx or other spinosaurs, but they believe that the species were oviparous, or egg-laying, and probably maintained nests of multiple eggs. There is also insufficient evidence to determine whether males and females of the species were similar in appearance and whether they gathered into groups or displayed any form of parental care.

Few spinosaur specimens have been found, indicating that most species may have been relatively uncommon in their environments. Evidence suggests that members of the subfamily Baryonychinae may have been specialized predators, living only in semi-aquatic habitats and therefore not as common as more generalized species.

Diet

Analyses of the species’ jaw structure and dentition suggests that Baryonyx would not have been able to prey on large species because its jaws could not withstand extreme forces. The presence of small, conical teeth indicates that Baryonyx preyed on smaller animals and may have additionally fed on carrion, or the carcasses of dead animals.

Paleontologists discovered the presence of fish scales in the stomach region of Baryonyx, indicating that that the species may have been a fish eater. Examinations of closely-related spinosaurs in Africa, South America, and Europe indicate that they also consumed small reptiles and dinosaurs. At the same time, they also found Iguanodon bones in the stomach region. The baryonchinae appear to have jaws and teeth close to those of the gharial (also known as the Indian gavial), a modern crocodilian that preys primarily on fish.

Paleontologists have suggested that the claws of Baryonyx may have been used to swipe fish from the surface of lakes and rivers, similar to behavior observed in bears. The hooked end of the animal's snout likewise may have aided in preventing struggling fish from escaping the animal's jaws.

Behavior

In 2010, researchers examined the bones of Baryonyx and other spinosaurs and found that the oxygen isotopic composition of the animals’ bones was similar to modern reptiles that live semi-aquatic lifestyles. Paleontologists now believe that Baryonyx and most other spinosaurs preferred flood plains and river deltas. The species may have avoided competition with other large predatory theropods by specializing in these habitats.

Paleontologists have suggested that the spinosaurs may represent convergent evolution, leading towards specialized features common in crocodilians. Spinosaurs may have displayed other crocodilian behaviors, such as providing limited parental care and utilizing an ambush strategy to capture prey.

Habitat and Other Life Forms

The primary types of vegetation in the Early Cretaceous were gymnosperms, like cycads and conifers, and pteridophytes, a plant group that includes ferns, tree ferns, and other spore-bearing plants. Angiosperms, or flowering plants, evolved in this period and were beginning to spread. In addition to dinosaurs, there were a variety of reptiles, amphibians, small mammals, and fish living in the same environments. Baryonyx also shared its territory with a variety of crocodilians.

There were several species of large theropod predators in Early Cretaceous Europe, including the carcharodontosaurids, large predators related to Tyrannosaurus. Large carcharodontosaurids like Megalosaurus hunted in Laurasia. There were also smaller theropods similar to Compsognathus in the area, many living alongside streams, ponds, and rivers where Baryonyx would have hunted.

Iguanodon was one of the most common herbivores of the period, and many iguanodontid specimens have been uncovered in areas that were once covered in flood plains. Other herbivores included the early ankylosaurid Hylaeosaurus and several sauropod species including Macrurosaurus and Pelorosaurus.

Research

The first Baryonyx specimen was discovered in 1983 by amateur fossil hunter William Walker from a site in England that was part of a prehistoric freshwater system called Wealden Lake. The lake was surrounded by alluvial habitat and broad floodplains. Paleontologists Alan Charig and Angela Milner described and named the species. Partial skeletons were then discovered in Portugal and Spain.

Related species were later discovered in Africa, giving paleontologists new information from which to determine how the group evolved and spread. With newly discovered spinosaurids expanding research on the group, paleontologists soon began to evaluate the hypothesis that spinosaurs were “crocodile mimic” dinosaurs. This theory was further supported by 2010 research showing that spinosaurs lived semi-aquatic lifestyles. In 2014, paleontologists who had pieced together a new partial skeleton of the related Spinosaurus argued that it provided evidence that the dinosaur was built to swim and spent a portion of its life in the water. Before this discovery, Baryonyx specimens had been heavily relied upon to learn more about how such spinosaurs might have lived, particularly the Spinosaurus, as its original fossils had been destroyed when Munich, Germany, was bombed during World War II.

Bibliography

Amiot, Romain, et al. “Oxygen Isotope Evidence for Semi-Aquatic Habits Among Spinosaurid Therapods.” Geology, vol. 38, 2010, pp. 139–42.

"Baryonyx." Natural History Museum, www.nhm.ac.uk/discover/dino-directory/baryonyx.html. Accessed 27 Apr. 2020.

Briggs, Derek E. G., and Peter R. Crowther. Paleobiology II. Wiley-Blackwell, 2001.

Buffetaut, Eric, “The Spinosaurid Dinosaur Baryonyx (Saurischia, Theropoda) in the Early Cretaceous of Portugal.” Geological Magazine, vol. 144, 2007, pp. 1021–25.

Carpenter, Kenneth. Eggs, Nests and Baby Dinosaurs: A Look at Dinosaur Reproduction. Indiana UP, 1999.

"Carnosauria." University of California Museum of Paleontology, www.ucmp.berkeley.edu/taxa/verts/dinosauria/carnosauria.php. Accessed May 2010.

Chang, Kenneth. "A Lost-and-Found Nomad Helps Solve the Mystery of a Swimming Dinosaur." The New York Times, 11 Sept. 2014, www.nytimes.com/2014/09/12/science/a-nomads-find-helps-solve-the-mystery-of-the-spinosaurus.html. Accessed 27 Apr. 2020.

Chinsamay-Turan, Anusuya. Microstructure of Dinosaur Bone: Deciphering Biology with Fine-Scale Techniques. Johns Hopkins UP, 2005.

Fastovsky, David E., and David B. Weishampel. Dinosaurs: A Concise Natural History. 3rd ed., Cambridge UP, 2016.

Fastovsky, David E., and David B. Weishampel. Evolution and Extinction of the Dinosaurs. 2nd ed., Cambridge UP, 2007.

Holtz, Thomas R. “Spinosaurs as Crocodile Mimics.” Science, vol. 282, 1998, p. 1276.

Horner, Jack, and James Gorman. How to Build a Dinosaur: Extinction Doesn’t Have to Be Forever. Dutton, 2009.

Horner, John R., and Edwin Dobb. Dinosaur Lives: Unearthing an Evolutionary Saga. Mariner Books, 1998.

Lucas, Spencer G. Dinosaurs: The Textbook. 6th ed., Columbia UP, 2016.

Martin, Anthony J. Introduction to the Study of Dinosaurs. 2nd ed., Blackwell, 2006.

Osterloff, Emily. "How Did Baryonyx Change What We Knew about Spinosaurs?" National History Museum, 7 Jan. 2019, www.nhm.ac.uk/discover/how-did-baryonyx-change-what-we-knew-about-spinosaurs.html. Accessed 27 Apr. 2020.

Sereno, Paul C., et al. “A Long-Snouted Predatory Dinosaur from Africa and the Evolution of Spinosaurids.” Science, vol. 282, 1998, p. 1298.

"Spinosauroidea." University of California Museum of Paleontology, www.ucmp.berkeley.edu/taxa/verts/dinosauria/spinosauroidea.php. Accessed May 2010.

Weishampel, David B., et al., editors. The Dinosauria. 2nd ed., U of California P, 2004.