Timimus
Encyclopedia
Timimus is a genus
of small coelurosauria
n theropod
dinosaur
, which was originally identified as an ornithomimosaur, from the Early Cretaceous
of Australia
.
(thighbones), one from an adult and one from a juvenile, were found within a metre of each other at the Dinosaur Cove East
site, in the small "Lake Copco" quarry, at the southern tip of Australia
.
The type species
, Timimus hermani, was formally named and shortly described by Dr Thomas Rich and his wife Patricia Vickers-Rich in 1993/1994. The generic name means "Tim's Mimic" and combines the name of both the discoverers' son Timothy Rich and palaeontologist Tim Flannery
with a Latin
mimus, "mimic", a reference to the presumed affinity of the species with the Ornithomimosauria
. The specific name honours volunteer John Herman who many years assisted the Dinosaur Cove project.
The holotype
specimen, NMV P186303, was found in a layer of the Eumeralla Formation
, dating to the Albian
faunal stage
in the early Cretaceous
, some 106 million years ago. It consists of a left femur of an adult individual.
In 1994 Dr Rich commented that while it would have been more ideal to have had the most complete specimen possible as a holotype
, it was highly unlikely that future material of Timimus would be found, due to the limited nature of sites to be explored in the area. Also, the holotype would have had characteristics which both identified it as an ornithomimosaur and a new genus within that group. Thus the name would serve as a reference point for the material within paleontological literature. Rich stated: "By themselves, the names of dinosaurs are like telephone numbers - they are labels that go with specimens and the ideas that flow from the analysis of the material. Confusing labels, like an inaccurate telephone book, lead to an unworkable system, so one must be careful in putting names or labels on things. But the act of doing so is not creating those specimens or the ideas associated with them; it is merely creating a convenient "handle" for purposes of communication".
The second femur, that of a juvenile, was assigned as the paratype
, specimen NMV P186323. Some vertebrae from the site have been referred to the species
, as well as some other South Australian material.
are rare and dubious; Timimus was thus presented as proof that the group was indeed present in the Southern Hemisphere
and would even have originated there. Immediately however, a position within the Ornithomimosauria was doubted by Thomas Holtz. Today it is recognised that Timimus shares no derived traits, synapomorphies, with the Ornithomimosauria and that thus any proof it would belong to this group is lacking. It perhaps belongs to some coelurosaurian group; some workers consider it a nomen dubium
.
of Timimus consisted of polar forests with mild summers but cold and dark winters due to the closer proximity of the area to the South Pole
during the Early Cretaceous. In 1996, Anusuya Chinsamy, an expert on the microstructure of fossil bones, examined bone material from Timimus and Leaellynasaura
and discovered they exhibited different bone histology. The ornithischia
n showed a continuous rate of bone deposition, while the coelurosaur had a cyclical pattern of bone formation, which suggested Timimus may have hibernated in colder months. A possible Timimus hermani or related form from the Strzelecki Group near Inverloch, Victoria
left a fossil of the first phalanx of its third toe with a depressed fracture on the plantar 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 small coelurosauria
Coelurosauria
Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. In the past, it was used to refer to all small theropods, although this classification has been abolished...
n theropod
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...
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...
, which was originally identified as an ornithomimosaur, from the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
Discovery and species
In 1991, two femoraFemur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
(thighbones), one from an adult and one from a juvenile, were found within a metre of each other at the Dinosaur Cove East
Dinosaur Cove
Not to be confused with the children's book series of the same name.Dinosaur Cove in Victoria, Australia is a fossil bearing site in south-east of the continent where the Otway Ranges meet the sea to the west of Cape Otway, adjacent to Great Otway National Park .The inaccessible ocean-front cliffs...
site, in the small "Lake Copco" quarry, at the southern tip of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, Timimus hermani, was formally named and shortly described by Dr Thomas Rich and his wife Patricia Vickers-Rich in 1993/1994. The generic name means "Tim's Mimic" and combines the name of both the discoverers' son Timothy Rich and palaeontologist Tim Flannery
Tim Flannery
Timothy Fridtjof Flannery is an Australian mammalogist, palaeontologist, environmentalist and global warming activist....
with a Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
mimus, "mimic", a reference to the presumed affinity of the species with the Ornithomimosauria
Ornithomimosauria
The Ornithomimosauria, ornithomimosaurs or ostrich dinosaurs were theropod dinosaurs which bore a superficial resemblance to modern ostriches. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia...
. The specific name honours volunteer John Herman who many years assisted the Dinosaur Cove project.
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, NMV P186303, was found in a layer of the Eumeralla Formation
Eumeralla Formation
The Eumeralla Formation is a geological formation in Victoria, Australia whose strata date back to the Early Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Dinosaurs:...
, dating to the Albian
Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...
faunal stage
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
in the early 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...
, some 106 million years ago. It consists of a left femur of an adult individual.
In 1994 Dr Rich commented that while it would have been more ideal to have had the most complete specimen possible as a 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...
, it was highly unlikely that future material of Timimus would be found, due to the limited nature of sites to be explored in the area. Also, the holotype would have had characteristics which both identified it as an ornithomimosaur and a new genus within that group. Thus the name would serve as a reference point for the material within paleontological literature. Rich stated: "By themselves, the names of dinosaurs are like telephone numbers - they are labels that go with specimens and the ideas that flow from the analysis of the material. Confusing labels, like an inaccurate telephone book, lead to an unworkable system, so one must be careful in putting names or labels on things. But the act of doing so is not creating those specimens or the ideas associated with them; it is merely creating a convenient "handle" for purposes of communication".
The second femur, that of a juvenile, was assigned as the 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...
, specimen NMV P186323. Some vertebrae from the site have been referred to the species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, as well as some other South Australian material.
Description
The holotype thighbone is 44 centimetres long. From this a total length of the animal of 2.5 metres has been extrapolated. The slenderness of the bone suggest a lithe animal. The paratype femur is 19.5 centimetres long. The femora show several features that were considered diagnostic. There is no extensor groove between the condyles of the lower joint, which would have been a basal trait for a ornithomimosaur. The femoral head is anteroposteriorally flattened. The anterior trochanter is in a high position and reaches the level of the major trochanter.Phylogeny
In 1994 the describers assigned Timimus to the "Ornithomimosauridae" with which the Ornithomimidae were meant. Ornithomimosaur remains from GondwanaGondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
are rare and dubious; Timimus was thus presented as proof that the group was indeed present in the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
and would even have originated there. Immediately however, a position within the Ornithomimosauria was doubted by Thomas Holtz. Today it is recognised that Timimus shares no derived traits, synapomorphies, with the Ornithomimosauria and that thus any proof it would belong to this group is lacking. It perhaps belongs to some coelurosaurian group; some workers consider it a nomen dubium
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
.
Paleobiology
The habitatHabitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
of Timimus consisted of polar forests with mild summers but cold and dark winters due to the closer proximity of the area to the South Pole
South Pole
The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...
during the Early Cretaceous. In 1996, Anusuya Chinsamy, an expert on the microstructure of fossil bones, examined bone material from Timimus and Leaellynasaura
Leaellynasaura
Leaellynasaura is a genus of small herbivorous ornithischian dinosaur from the Albian stage of the Early Cretaceous, first discovered in Dinosaur Cove, Australia. The type species is Leaellynasaura amicagraphica...
and discovered they exhibited different bone histology. The ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
n showed a continuous rate of bone deposition, while the coelurosaur had a cyclical pattern of bone formation, which suggested Timimus may have hibernated in colder months. A possible Timimus hermani or related form from the Strzelecki Group near Inverloch, Victoria
Inverloch, Victoria
Inverloch is a seaside village in Victoria, Australia. It is located on the Bass Highway 143 kilometres southeast of Melbourne, at the mouth of Anderson Inlet, in the Bass Coast Shire and is located close to Australia’s southernmost stand of mangroves...
left a fossil of the first phalanx of its third toe with a depressed fracture on the plantar surface.