Saurornitholestes
Encyclopedia
Saurornitholestes is a genus
of carnivorous dromaeosaurid theropod dinosaur
from the late Cretaceous
of Alberta
, Montana
and New Mexico
.
Two species have been named: Saurornitholestes langstoni in 1978 and Saurornitholestes robustus in 2006. Saurornithlestes was a small bipedal meat-eating dinosaur, equipped with a sickle-claw on the foot.
. In 1978 Sues named and described the specimen as the type species Saurornitholestes langstoni. The generic name is in reference to the Saurornithoididae, due to the resemblance with this group that is today seen as part of the Troodontidae
, and combines their name with a Greek lestes, "thief". The specific name honours Wann Langston, Jr.
The holotype
specimen, RTMP 74.10.5, was uncovered in a layer of the Dinosaur Park Formation
dating to the late Campanian
. It consists of a very fragmentary skeleton including teeth, skull elements, two vertebrae, ribs, tail elements and a hand. Also three paratype
s were assigned: CMN 12343, CMN 12354, and UA 5283, all frontals.
Two more complete and larger partial skeletons (RTMP 88.121.39 and MOR 660), dozens of isolated bones, and scores of teeth are today known from the badlands of Dinosaur Provincial Park
in Alberta; most of these are housed at the Royal Tyrrell Museum of Palaeontology
, in Drumheller, Alberta
and remain undescribed. The Alberta and Montana remains are usually attributed to the single species Saurornitholestes langstoni, though they come from a variety of rock formations indicating a wide span of time; for example, the Oldman Formation
(dated to about 77 million years ago) and the upper Two Medicine Formation
(about 72 million years ago). Similar teeth are found in younger deposits, but whether they represent S. langstoni or a different, related species is unknown. Neonate-sized Saurornitholestes fossils have been reported in the scientific literature
.
In 2006 Robert Sullivan
named and described a second species, Saurornitholestes robustus, based on holotype SMP VP-1955, a left frontal. The specific name refers to the great thickness of this bone, the only trait in which the species is known to differ from S. langstoni. The holotype and additional remains referred to S. robustus, were found in the Willow Wash fauna of the Kirtland Formation
in New Mexico, dated to about 73 million years ago.
and Dromaeosaurus
. It resembles Velociraptor in having large, fanglike teeth in the front of the jaws. Saurornitholestes most closely resembles Velociraptor, although the precise relationships of the Dromaeosauridae are still relatively poorly understood.
Saurornitholestes was about 1.8 meters (6 feet) long and weighed approximately 10 kilograms (30 pounds). At the hip it stood 0.6 meters (2 feet), or around as tall as the length of a terrier.
. Later studies most often found it a member of the dromaeosaurid Velociraptorinae
, but a cladistic analysis by Philip Currie
in 2009 recovered a position in a more basal dromaeosaurid clade
that was named the Saurornitholestinae
.
Saurornitholestes appears to have been the most common small theropod in Dinosaur Provincial Park, and teeth and bones are much more common than those of its more massive contemporary, Dromaeosaurus. Little is known about what it ate and how it lived, but a tooth of Saurornitholestes has been found embedded in the wing bone of a large pterosaur
, probably a juvenile Quetzalcoatlus
. Because the pterosaur was so much larger than Saurornitholestes, Currie and Jacobsen suggest that the theropod was probably scavenging the remains of an already dead animal.
, small theropods are rare due to the tendency of their thin-walled bones to be broken or poorly preserved, this increases the scientific value of the discovery of a small theropod dinosaur with preserved tooth marks. The dentary is about 12 cm long and preserves fifteen tooth positions, ten of these have teeth, with five of those teeth fully erupted and intact, two broken but functional as evidenced by the presence of wearfacets, three are only partially erupted. Three toothmarks were visible on the lingual
surface of the dentary. Two of the three marks are series of grooves made by the serrations on the maker's teeth.
The first consists of 6-7 parallel grooves within a 4 x 1.3 mm area beneath the alveolus of the third tooth and angled at forty-five degrees to the dentary's longitudinal axis. The striations are between .37 mm and .40 mm thick with cuboidal cross-sections.
The second tooth mark lies between the fifth and sixth alveoli and consists of two smaller grooves separated 1.8 and 1.6 mm respectively from a larger central groove, with a V-shaped groove beneath it at an angle of sixty degrees to the longitudinal axis of the jaw.
The third mark consists of four parallel grooves in a 2 x 2 mm area on the seventh tooth oriented at ninety degrees to the longitudinal axis of the tooth.
The shape of the preserved serrations are too different from those of Saurornitholestes for the marks to be the result of injuries incurred during intraspecific
face biting behaviors. Although the right shape for Dromaeosaurus
tooth serrations, the preserved marks are too coarse to have been left by that genus. Although a specific identification cannot be made, the most likely perpetrator would be a juvenile individual of one of the Dinosaur Park Formation
's tyrannosaurids, like Gorgosaurus
, or Daspletosaurus
. All of the marks on the jawbone seem to have been left by the same animal because the serration marks all share the same morphology.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of carnivorous dromaeosaurid theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
of Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
, Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
and New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
.
Two species have been named: Saurornitholestes langstoni in 1978 and Saurornitholestes robustus in 2006. Saurornithlestes was a small bipedal meat-eating dinosaur, equipped with a sickle-claw on the foot.
Discovery and naming
In 1974 Canadian amateur paleontologist Irene Vanderloh discovered the skeleton of a small theropod near Steveville in Alberta . She showed it to John Storer of the Provincial Museum of Alberta, who brought it to the attention of Hans-Dieter SuesHans-Dieter Sues
Hans-Dieter Sues is a German-born paleontologist who is Senior Scientist and Curator of Vertebrate Paleontology at the National Museum of Natural History of the Smithsonian Institution in Washington, DC. He received his education at Johannes Gutenberg-Universität Mainz , University of Alberta, and...
. In 1978 Sues named and described the specimen as the type species Saurornitholestes langstoni. The generic name is in reference to the Saurornithoididae, due to the resemblance with this group that is today seen as part of the Troodontidae
Troodontidae
Troodontidae is a family of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and scrappy and they have therefore been allied, at various times, with many dinosaurian lineages...
, and combines their name with a Greek lestes, "thief". The specific name honours Wann Langston, Jr.
The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen, RTMP 74.10.5, was uncovered in a layer of the Dinosaur Park Formation
Dinosaur Park Formation
The Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped...
dating to the late Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
. It consists of a very fragmentary skeleton including teeth, skull elements, two vertebrae, ribs, tail elements and a hand. Also three paratype
Paratype
Paratype is a technical term used in the scientific naming of species and other taxa of organisms. The exact meaning of the term paratype when it is used in zoology is not the same as the meaning when it is used in botany...
s were assigned: CMN 12343, CMN 12354, and UA 5283, all frontals.
Two more complete and larger partial skeletons (RTMP 88.121.39 and MOR 660), dozens of isolated bones, and scores of teeth are today known from the badlands of Dinosaur Provincial Park
Dinosaur Provincial Park
Dinosaur Provincial Park is a UNESCO World Heritage Site located about two and a half hours drive southeast of Calgary, Alberta, Canada or , about a half hour drive, northeast of Brooks....
in Alberta; most of these are housed at the Royal Tyrrell Museum of Palaeontology
Royal Tyrrell Museum of Palaeontology
The Royal Tyrrell Museum is a popular Canadian tourist attraction and a leading centre of palaeontological research noted for its collection of more than 130,000 fossils....
, in Drumheller, Alberta
Drumheller, Alberta
Drumheller is a town within the Red Deer River valley in the badlands of east-central Alberta, Canada. It is located northeast of Calgary...
and remain undescribed. The Alberta and Montana remains are usually attributed to the single species Saurornitholestes langstoni, though they come from a variety of rock formations indicating a wide span of time; for example, the Oldman Formation
Oldman Formation
The Oldman Formation is the middle member of the Judith River Group, a major geologic unit in southern Alberta. The formation is widely recognized as bearing a great number of well preserved dinosaur skeletons, as well as other fossils.-Age:...
(dated to about 77 million years ago) and the upper Two Medicine Formation
Two Medicine Formation
The Two Medicine Formation is a geologic formation, or rock body, that was deposited between 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma , during Campanian time, and is located in northwestern Montana...
(about 72 million years ago). Similar teeth are found in younger deposits, but whether they represent S. langstoni or a different, related species is unknown. Neonate-sized Saurornitholestes fossils have been reported in the scientific literature
Scientific literature
Scientific literature comprises scientific publications that report original empirical and theoretical work in the natural and social sciences, and within a scientific field is often abbreviated as the literature. Academic publishing is the process of placing the results of one's research into the...
.
In 2006 Robert Sullivan
Robert Sullivan
Robert Sullivan may refer to:*Robert Sullivan *Robert Baldwin Sullivan, Canadian lawyer, judge, and the second Mayor of Toronto*Robert J. Sullivan, Jr. , American politician...
named and described a second species, Saurornitholestes robustus, based on holotype SMP VP-1955, a left frontal. The specific name refers to the great thickness of this bone, the only trait in which the species is known to differ from S. langstoni. The holotype and additional remains referred to S. robustus, were found in the Willow Wash fauna of the Kirtland Formation
Kirtland Formation
The Kirtland Formation is a sedimentary geological formation. It is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation...
in New Mexico, dated to about 73 million years ago.
Description
Like other theropods in the Dromaeosauridae, Saurornitholestes had a long, curving, blade-like claw on the second toe. Saurornitholestes was more long-legged and lightly built than other dromaeosaurids such as VelociraptorVelociraptor
Velociraptor is a genus of dromaeosaurid theropod dinosaur that existed approximately 75 to 71 million years ago during the later part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils...
and Dromaeosaurus
Dromaeosaurus
Dromaeosaurus was a genus of theropod dinosaur which lived during the Late Cretaceous period , sometime between 76.5 and 74.8 million years ago, in the western United States and Alberta, Canada. The name means 'running lizard'....
. It resembles Velociraptor in having large, fanglike teeth in the front of the jaws. Saurornitholestes most closely resembles Velociraptor, although the precise relationships of the Dromaeosauridae are still relatively poorly understood.
Saurornitholestes was about 1.8 meters (6 feet) long and weighed approximately 10 kilograms (30 pounds). At the hip it stood 0.6 meters (2 feet), or around as tall as the length of a terrier.
Phylogeny
In 1978 Sues assigned Saurornitholestes to the DromaeosauridaeDromaeosauridae
Dromaeosauridae is a family of bird-like theropod dinosaurs. They were small- to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek dromeus meaning 'runner' and sauros meaning 'lizard'...
. Later studies most often found it a member of the dromaeosaurid Velociraptorinae
Velociraptorinae
Velociraptorinae is a subfamily of the theropod group Dromaeosauridae. Velociraptorine remains are found mostly in northern hemisphere. In Late Cretaceous, they are mostly present in Mongolia, Romania and China,and in early, in USA. The earliest velociraptorines are probably Nuthetes from the...
, but a cladistic analysis by Philip Currie
Philip Currie
Philip Henry Wodehouse Currie, 1st Baron Currie GCB , known as Sir Philip Currie between 1885 and 1899, was a British diplomat. He was Ambassador to the Ottoman Empire from 1893 to 1898 and Ambassador to Italy from 1898 to 1902.-Background and education:Currie was the son of Raikes Currie, Member...
in 2009 recovered a position in a more basal dromaeosaurid clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
that was named the Saurornitholestinae
Saurornitholestinae
Saurornitholestinae is a subfamily of Dromaeosauridae.-Species:...
.
Habitat
Alberta, the location of Saurornitholestes langstoni, had a habitat similar to the United States Middle West being plains and floodplain swamps.Saurornitholestes appears to have been the most common small theropod in Dinosaur Provincial Park, and teeth and bones are much more common than those of its more massive contemporary, Dromaeosaurus. Little is known about what it ate and how it lived, but a tooth of Saurornitholestes has been found embedded in the wing bone of a large pterosaur
Pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
, probably a juvenile Quetzalcoatlus
Quetzalcoatlus
Quetzalcoatlus was a pterodactyloid pterosaur known from the Late Cretaceous of North America , and one of the largest known flying animals of all time. It was a member of the Azhdarchidae, a family of advanced toothless pterosaurs with unusually long, stiffened necks...
. Because the pterosaur was so much larger than Saurornitholestes, Currie and Jacobsen suggest that the theropod was probably scavenging the remains of an already dead animal.
Bite marks from tyrannosaur
Aase Roland Jacobsen published a description of a dentary referred to Saurornitholestes with tooth marks in 2001. In the Dinosaur Park FormationDinosaur Park Formation
The Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped...
, small theropods are rare due to the tendency of their thin-walled bones to be broken or poorly preserved, this increases the scientific value of the discovery of a small theropod dinosaur with preserved tooth marks. The dentary is about 12 cm long and preserves fifteen tooth positions, ten of these have teeth, with five of those teeth fully erupted and intact, two broken but functional as evidenced by the presence of wearfacets, three are only partially erupted. Three toothmarks were visible on the lingual
Lingual
Lingual may refer to:* Rap Crew, LINGUAL, an underground widespread hip-hop group from Berlin, Germany. The Group was founded in 2010 with their former member Freddy K. Their music is based on oldschool features with mixtures of Rap, Funk and Jazz and consists of 4 members, Sam-Which, Kurt...
surface of the dentary. Two of the three marks are series of grooves made by the serrations on the maker's teeth.
The first consists of 6-7 parallel grooves within a 4 x 1.3 mm area beneath the alveolus of the third tooth and angled at forty-five degrees to the dentary's longitudinal axis. The striations are between .37 mm and .40 mm thick with cuboidal cross-sections.
The second tooth mark lies between the fifth and sixth alveoli and consists of two smaller grooves separated 1.8 and 1.6 mm respectively from a larger central groove, with a V-shaped groove beneath it at an angle of sixty degrees to the longitudinal axis of the jaw.
The third mark consists of four parallel grooves in a 2 x 2 mm area on the seventh tooth oriented at ninety degrees to the longitudinal axis of the tooth.
The shape of the preserved serrations are too different from those of Saurornitholestes for the marks to be the result of injuries incurred during intraspecific
Intraspecific
Intraspecific is a term used in biology to describe behaviors, biochemical variations and other issues within individuals of a single species, thereby contrasting with interspecific. For example:* Intraspecific antagonism...
face biting behaviors. Although the right shape for Dromaeosaurus
Dromaeosaurus
Dromaeosaurus was a genus of theropod dinosaur which lived during the Late Cretaceous period , sometime between 76.5 and 74.8 million years ago, in the western United States and Alberta, Canada. The name means 'running lizard'....
tooth serrations, the preserved marks are too coarse to have been left by that genus. Although a specific identification cannot be made, the most likely perpetrator would be a juvenile individual of one of the Dinosaur Park Formation
Dinosaur Park Formation
The Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped...
's tyrannosaurids, like Gorgosaurus
Gorgosaurus
Gorgosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 76.5 and 75 million years ago. Fossil remains have been found in the Canadian province of Alberta and possibly the U.S. state of Montana....
, or Daspletosaurus
Daspletosaurus
Daspletosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America between 77 and 74 million years ago, during the Late Cretaceous Period. Fossils of the only named species were found in Alberta, although other possible species from Alberta and Montana await...
. All of the marks on the jawbone seem to have been left by the same animal because the serration marks all share the same morphology.