Ricardoestesia
Encyclopedia
Richardoestesia is a medium-sized (~100 kg) genus
of theropod dinosaur
from the late Cretaceous
Period of what is now North America
. It is known from a single pair of lower jaw bones and a large number of isolated teeth.
The jaws were found in 1917 by Charles Hazelius Sternberg
and sons in the Dinosaur Provincial Park
in Alberta
at the Little Sandhill Creek site. In 1924 Charles Whitney Gilmore named Chirostenotes
pergracilis and referred the jaws to this species. In the eighties it became clear that Chirostenotes was a oviraptosaur to which the long jaws could not have belonged. Therefore in 1990 Phillip Currie, John Keith Rigby and Robert Evan Sloan named a separate species: Richardoestesia gilmorei. The genus is named for Richard Estes, to honor his important work on small vertebrates and especially theropod teeth of the Late Cretaceous. The naming authors actually intended to use the spelling Ricardoestesia, Ricardus being the normal latinisation of "Richard". However, except in one overlooked figure caption, the editors of the paper altered the spelling to include the 'h'.http://dml.cmnh.org/1997Nov/msg00416.html Ironically, in 1991 George Olshevsky
in a species list also used the spelling Richardoestesia, and indicated Ricardoestesia to be the misspelling, unaware that the original authors actually intended the name to be spelled this way. As a result, under ICZN
rules, he acted as "first revisor" choosing between the two spelling variants of the original publication and inadvertently made the misspelt name official. Subsequently, the original authors have adopted the spelling Richardoestesia. The specific name honors Gilmore.
The holotype
, NMC 343, consists of the pair of lower jaws found in the Judith River Formation
, dating from the Campanian
. The jaws are slender and rather long, 193 millimeter, but the teeth are small and very finely serrated with five to six denticles per millimeter. The serration density is a distinctive trait of the species. Richardoestesia type teeth are also found in the Late Cretaceous Horseshoe Canyon Formation
, and the Scollard Formation
. Its teeth are extremely common in the Lance Formation
. Paronychodon
teeth may come from Richardoestesia. Similar teeth have been referred to this genus from as early as the Barremian
age (Cedar Mountain Formation
, 125 million years ago). Because of the disparity in location and time of the many referred teeth, Richardoestesia is often seen as a form taxon
, in this case actually functioning as the name of a tooth type.
In 2001, Julia Sankey named a second species: Richardoestesia isosceles, based on a tooth, LSUMGS 489:6238, from the Texan Aguja Formation
, which is of a longer and less recurved type.
It has been suggested that Richardoestesia was a fish eater, like a heron
. Because so little is known of the animal, its relationships are unclear, the original authors classifying it as Theropoda
incertae sedis
. However, the jaws resemble Archaeopteryx
, Troodontidae
and some Dromaeosauridae
, in having a strong groove on the lateral surface.
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 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...
Period of what is now North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. It is known from a single pair of lower jaw bones and a large number of isolated teeth.
The jaws were found in 1917 by Charles Hazelius Sternberg
Charles Hazelius Sternberg
Charles Hazelius Sternberg , was an American fossil collector and amateur paleontologist. His older brother, Dr. George M. Sternberg was a military surgeon assigned to Fort Harker near Ellsworth, Kansas and brought the rest of Sternberg family to Kansas to live on his ranch about 1868...
and sons in the 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
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...
at the Little Sandhill Creek site. In 1924 Charles Whitney Gilmore named Chirostenotes
Chirostenotes
Chirostenotes is a genus of oviraptorosaurian dinosaur from the late Cretaceous of Alberta, Canada. The type species is Chirostenotes pergracilis. Some researchers recognize a second species, C...
pergracilis and referred the jaws to this species. In the eighties it became clear that Chirostenotes was a oviraptosaur to which the long jaws could not have belonged. Therefore in 1990 Phillip Currie, John Keith Rigby and Robert Evan Sloan named a separate species: Richardoestesia gilmorei. The genus is named for Richard Estes, to honor his important work on small vertebrates and especially theropod teeth of the Late Cretaceous. The naming authors actually intended to use the spelling Ricardoestesia, Ricardus being the normal latinisation of "Richard". However, except in one overlooked figure caption, the editors of the paper altered the spelling to include the 'h'.http://dml.cmnh.org/1997Nov/msg00416.html Ironically, in 1991 George Olshevsky
George Olshevsky
George Olshevsky is a freelance editor, writer, publisher, amateur paleontologist, and mathematician living in San Diego, California.Olshevsky maintains the comprehensive online Dinosaur Genera List...
in a species list also used the spelling Richardoestesia, and indicated Ricardoestesia to be the misspelling, unaware that the original authors actually intended the name to be spelled this way. As a result, under ICZN
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
rules, he acted as "first revisor" choosing between the two spelling variants of the original publication and inadvertently made the misspelt name official. Subsequently, the original authors have adopted the spelling Richardoestesia. The specific name honors Gilmore.
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...
, NMC 343, consists of the pair of lower jaws found in the Judith River Formation
Judith River Formation
The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the upper Cretaceous, between 80 and 75 million years ago, corresponding to the "Judithian" land vertebrate age...
, dating from the 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 ...
. The jaws are slender and rather long, 193 millimeter, but the teeth are small and very finely serrated with five to six denticles per millimeter. The serration density is a distinctive trait of the species. Richardoestesia type teeth are also found in the Late Cretaceous Horseshoe Canyon Formation
Horseshoe Canyon Formation
The Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230m in thickness. It is Late Campanian to Early Maastrichtian in age and is composed of mudstone, sandstone, and carbonaceous shales...
, and the Scollard Formation
Scollard Formation
-References:* Ryan, M. J., and Russell, A. P., 2001. Dinosaurs of Alberta : In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 279-297....
. Its teeth are extremely common in the Lance Formation
Lance Formation
The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas...
. Paronychodon
Paronychodon
Paronychodon was a theropod dinosaur genus. It is a tooth taxon, considered dubious because of the fragmentary nature of the fossils, which include "buckets" of teeth but no other remains...
teeth may come from Richardoestesia. Similar teeth have been referred to this genus from as early as the Barremian
Barremian
The Barremian is an age in the geologic timescale between 130.0 ± 1.5 Ma and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch...
age (Cedar Mountain Formation
Cedar Mountain Formation
The Cedar Mountain Formation is the name given to distinctive sedimentary rocks in eastern Utah that occur between the underlying Morrison Formation and overlying Naturita Formation . It is composed of non-marine sediments, that is, sediments deposited in rivers, lakes and on flood plains...
, 125 million years ago). Because of the disparity in location and time of the many referred teeth, Richardoestesia is often seen as a form taxon
Form taxon
Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships...
, in this case actually functioning as the name of a tooth type.
In 2001, Julia Sankey named a second species: Richardoestesia isosceles, based on a tooth, LSUMGS 489:6238, from the Texan Aguja Formation
Aguja Formation
The Aguja Formation is a geological formation in North America, exposed in Texas, whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Ammonites:-Crurotarsans:...
, which is of a longer and less recurved type.
It has been suggested that Richardoestesia was a fish eater, like a heron
Heron
The herons are long-legged freshwater and coastal birds in the family Ardeidae. There are 64 recognised species in this family. Some are called "egrets" or "bitterns" instead of "heron"....
. Because so little is known of the animal, its relationships are unclear, the original authors classifying it as Theropoda
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
. However, the jaws resemble Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
, 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 some Dromaeosauridae
Dromaeosauridae
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'...
, in having a strong groove on the lateral surface.