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Description

The first fossil remains that can definitely be assigned to a Tyrannosauroid were discovered by Ferdinand V. Hayden in the Judith River Formation, Nebraska, USA. These were among this earliest theropod dinosaur remains discovered in North America. The remains consisted of a few intact and numerus fragmentary teeth, the largest of which possessed a crown height of 50.8 mm (2 in). This set of teeth was formally described in 1856 by Joseph M. Leidy and given the name, Deinodon horridus (Leidy, 1856), the genus name meaning “terrible tooth”.

The teeth were said by Leidy to closely resemble those of Megalosaurus bucklandii (Buckland, 1824), the only other large theropod dinosaur that was known at the time. Although these teeth were broader from side to side and were noted to be slightly heterodont. At the time however, it was believed that heterodonty in reptiles was extremely improbable and so Leidy proposed that the set of teeth may have actually come from at least four different genera of theropods. Although Leidy himself believed it was more likely that the teeth belong to a single taxon, based on the shared locality of their discovery.

In 1866, Edward D. Cope erected the family, Dinodontidae to house D. horridus along with the newly described Laelaps (Dryptosaurus) aquilungus (Cope, 1866). The family was defined by the characteristics of L. anquilungus, despite D. horridus technically being the type species. Lawrence M. Lambe distinguished D. horridus from the newly descried Gorgosaurus (=Albertosaurus) libratus (Lambe, 1914), claiming the anterior dentition of G. libratus were much longer and slenderer compared to the robust proposed anterior teeth of D. horridus. This interpretation would be amended by later researchers. Dinodontidae itself would later be replaced by the family name, Tyrannosauridae, named after the indisputable species Tyrannosaurus rex (Osborn, 1905).

Oliver P. Hay noticed in 1908 that the teeth of D. horridus were similar to those of Albertosaurus sarcophagus (Osborn, 1905), and Hay questioned whether the two should be considered separate taxa at all. In 1922, William D. Matthew and Barnum Brown also concluded that the teeth of D. horridus were indistinguishable from the teeth of Albertosaurus sarcophagus (Osborn, 1905) as well as from G. libratus (Lambe, 1914) despite Lambe’s earlier claim. However, Matthew and Brown did not synonymize D. horridus with either Tyrannosaurid taxon at this time (Matthew & Brown, 1922).

In 1970, Dale. A Russel again concluded that D. horridus and G. libratus were undisguisable and declared that D. horridus should be considered a nomen vanum (empty name), because the original teeth did not possess any specific diagnostic characteristics that would distinguish them from those of other members of the family Tyrannosauridae. In 1972, Ashok Sahni argued that because D. horridus was named first it should have naming priority over G. libratus. Despite this however, most palaeontologists have favored G. libratus and D. horridus is today either still considered a nomen vanum or at least a nomen dubium (doubtful name).

Regardless of its validity as a genuine taxon, Deinodon remains an important footnote in the history of palaeontology as it was not just the first definitive “tyrant lizard” to be given a scientific name but was also the first large theropod dinosaur described in North America.

References:

Buckland, W. (1824). “Notice on the Megalosaurus or great Fossil Lizard of Stonesfield.” Transactions of the Geological Society of London, 2(1): 390-396.

Cope, E. D. (1866a). “Remarks on the remains of a gigantic extinct dinosaur from the Cretaceous Greensand of New Jersey.” Proceedings of the Academy of Natural Sciences of Philadelphia, 18: 275-279.

Hay, O. P. (1908). “On certain genera and species of carnivorous dinosaurs, with special reference to Ceratosaurus nasicornis Marsh.” Proceedings of the United States National Museum, 35(1648): 351-366.

Lambe, L. M. (1914). “On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of Stephanosaurus marginatus from the same horizon.” Ottawa Naturalist, 28: 13-20.

Leidy, J. M. (1856). “Notice of remains of extinct reptiles and fishes, discovered by Dr. FV Hayden in the Bad Lands of the Judith River, Nebraska Territory.” Proceedings of the Academy of Natural Sciences of Philadelphia, 8(7): 72-73.

Matthew, W. D., & Brown, B. (1922). “The family Deinodontidae, with notice of a new genus from the Cretaceous of Alberta.” Bulletin of the American Museum of Natural History, 46(6): 367-385.

Osborn, H. F. (1905). “Tyrannosaurus and other Cretaceous carnivorous dinosaurs.” Bulletin of the American Museum of Natural History. 21(14): 259-265.

Russell, D. A. (1970). “Tyrannosaurs from the Late Cretaceous of western Canada.” National Museum of Natural Science Publications in Palaeontology, 1: 1-34.

Sahni, A. (1972). “The vertebrate fauna of the Judith River Formation, Montana.” Bulletin of the AMNH, 147(6).

Description

The first fossil remains that can definitely be assigned to a Tyrannosauroid were discovered by Ferdinand V. Hayden in the Judith River Formation, Nebraska, USA. These were among this earliest theropod dinosaur remains discovered in North America. The remains consisted of a few intact and numerus fragmentary teeth, the largest of which possessed a crown height of 50.8 mm (2 in). This set of teeth was formally described in 1856 by Joseph M. Leidy and given the name, Deinodon horridus (Leidy, 1856), the genus name meaning “terrible tooth”.

The teeth were said by Leidy to closely resemble those of Megalosaurus bucklandii (Buckland, 1824), the only other large theropod dinosaur that was known at the time. Although these teeth were broader from side to side and were noted to be slightly heterodont. At the time however, it was believed that heterodonty in reptiles was extremely improbable and so Leidy proposed that the set of teeth may have actually come from at least four different genera of theropods. Although Leidy himself believed it was more likely that the teeth belong to a single taxon, based on the shared locality of their discovery.

In 1866, Edward D. Cope erected the family, Dinodontidae to house D. horridus along with the newly described Laelaps (Dryptosaurus) aquilungus (Cope, 1866). The family was defined by the characteristics of L. anquilungus, despite D. horridus technically being the type species. Lawrence M. Lambe distinguished D. horridus from the newly descried Gorgosaurus (=Albertosaurus) libratus (Lambe, 1914), claiming the anterior dentition of G. libratus were much longer and slenderer compared to the robust proposed anterior teeth of D. horridus. This interpretation would be amended by later researchers. Dinodontidae itself would later be replaced by the family name, Tyrannosauridae, named after the indisputable species Tyrannosaurus rex (Osborn, 1905).

Oliver P. Hay noticed in 1908 that the teeth of D. horridus were similar to those of Albertosaurus sarcophagus (Osborn, 1905), and Hay questioned whether the two should be considered separate taxa at all. In 1922, William D. Matthew and Barnum Brown also concluded that the teeth of D. horridus were indistinguishable from the teeth of Albertosaurus sarcophagus (Osborn, 1905) as well as from G. libratus (Lambe, 1914) despite Lambe’s earlier claim. However, Matthew and Brown did not synonymize D. horridus with either Tyrannosaurid taxon at this time (Matthew & Brown, 1922).

In 1970, Dale. A Russel again concluded that D. horridus and G. libratus were undisguisable and declared that D. horridus should be considered a nomen vanum (empty name), because the original teeth did not possess any specific diagnostic characteristics that would distinguish them from those of other members of the family Tyrannosauridae. In 1972, Ashok Sahni argued that because D. horridus was named first it should have naming priority over G. libratus. Despite this however, most palaeontologists have favored G. libratus and D. horridus is today either still considered a nomen vanum or at least a nomen dubium (doubtful name).

Regardless of its validity as a genuine taxon, Deinodon remains an important footnote in the history of palaeontology as it was not just the first definitive “tyrant lizard” to be given a scientific name but was also the first large theropod dinosaur described in North America.

References:

Buckland, W. (1824). “Notice on the Megalosaurus or great Fossil Lizard of Stonesfield.” Transactions of the Geological Society of London, 2(1): 390-396.

Cope, E. D. (1866a). “Remarks on the remains of a gigantic extinct dinosaur from the Cretaceous Greensand of New Jersey.” Proceedings of the Academy of Natural Sciences of Philadelphia, 18: 275-279.

Hay, O. P. (1908). “On certain genera and species of carnivorous dinosaurs, with special reference to Ceratosaurus nasicornis Marsh.” Proceedings of the United States National Museum, 35(1648): 351-366.

Lambe, L. M. (1914). “On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of Stephanosaurus marginatus from the same horizon.” Ottawa Naturalist, 28: 13-20.

Leidy, J. M. (1856). “Notice of remains of extinct reptiles and fishes, discovered by Dr. FV Hayden in the Bad Lands of the Judith River, Nebraska Territory.” Proceedings of the Academy of Natural Sciences of Philadelphia, 8(7): 72-73.

Matthew, W. D., & Brown, B. (1922). “The family Deinodontidae, with notice of a new genus from the Cretaceous of Alberta.” Bulletin of the American Museum of Natural History, 46(6): 367-385.

Osborn, H. F. (1905). “Tyrannosaurus and other Cretaceous carnivorous dinosaurs.” Bulletin of the American Museum of Natural History. 21(14): 259-265.

Russell, D. A. (1970). “Tyrannosaurs from the Late Cretaceous of western Canada.” National Museum of Natural Science Publications in Palaeontology, 1: 1-34.

Sahni, A. (1972). “The vertebrate fauna of the Judith River Formation, Montana.” Bulletin of the AMNH, 147(6).