Teinolophos
Encyclopedia
Teinolophos trusleri was a prehistoric species
of monotreme
, or egg-laying mammal
. It is known from a lower jawbone found in Flat Rocks, Victoria
, Australia
. It lived during the Aptian
age of the Lower Cretaceous
. It is the earliest known relative of the Platypus
.
The species
name honours the artist Peter Trusler
. The genus
name, Teinolophos, means 'extended ridge', a reference to its tooth structure.
Originally, Teinolophos was thought to be a eupanthothere. Further research revealed similarities to Steropodon
, except in size: the animal was around 10 cm long.
The holotype
is a partial left dentary known as NMV P208231. An age of approximately 123 million years makes this the earliest known monotreme. The lower molar is broadly similar in morphology to the m2 of Steropodon. The trigonid is compressed and the talonid has no basin. The dentary is about one sixth the size of Steropodons, and wear facets indicate an "orthal" occlusion with the upper molars.
The construction of the lower jaw differs from existing monotremes. Among the contrasts are the condyle, which is well above the tooth row (instead of at about the same height); and the ascending ramus
, which is also higher. Also different is that Teinolophos probably had a strong bite. A unique feature for known toothed monotremes is that the trigonid is tall, while the talonid is set much lower. This is more like the general mammalian arrangement. The molar is double-rooted, which is plesiomorphic when compared to ornithorhynchids
, but is a shared characteristic with Steropodon and Kollikodon
. Subsequent monotreme molars are multi-rooted.
The species has been placed in the Steropodontidae
in some classifications.
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...
of monotreme
Monotreme
Monotremes are mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals...
, or egg-laying mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
. It is known from a lower jawbone found in Flat Rocks, Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
, 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...
. It lived during the Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
age of the Lower 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...
. It is the earliest known relative of the Platypus
Platypus
The platypus is a semi-aquatic mammal endemic to eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth to live young...
.
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...
name honours the artist Peter Trusler
Peter Trusler
Peter Trusler is an Australian wildlife artist who illustrates native Australian birds and represents biologically rigorous reconstructions of prehistoric fauna....
. The genus
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...
name, Teinolophos, means 'extended ridge', a reference to its tooth structure.
Originally, Teinolophos was thought to be a eupanthothere. Further research revealed similarities to Steropodon
Steropodon
Steropodon galmani was a prehistoric species of monotreme, or egg-laying mammal, that lived during the middle Albian stage, in the Lower Cretaceous period...
, except in size: the animal was around 10 cm long.
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...
is a partial left dentary known as NMV P208231. An age of approximately 123 million years makes this the earliest known monotreme. The lower molar is broadly similar in morphology to the m2 of Steropodon. The trigonid is compressed and the talonid has no basin. The dentary is about one sixth the size of Steropodons, and wear facets indicate an "orthal" occlusion with the upper molars.
The construction of the lower jaw differs from existing monotremes. Among the contrasts are the condyle, which is well above the tooth row (instead of at about the same height); and the ascending ramus
Ramus
Ramus can refer to:* A branch* A portion of a bone , as in the Ramus of the mandible or Superior pubic ramus* A nerve ramus such as the Dorsal ramus of spinal nerve* Petrus Ramus...
, which is also higher. Also different is that Teinolophos probably had a strong bite. A unique feature for known toothed monotremes is that the trigonid is tall, while the talonid is set much lower. This is more like the general mammalian arrangement. The molar is double-rooted, which is plesiomorphic when compared to ornithorhynchids
Platypus
The platypus is a semi-aquatic mammal endemic to eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth to live young...
, but is a shared characteristic with Steropodon and Kollikodon
Kollikodon
Kollikodon ritchiei is a fossil monotreme species. It is known only from an opalised dentary fragment, with one premolar and two molars in situ...
. Subsequent monotreme molars are multi-rooted.
The species has been placed in the Steropodontidae
Steropodontidae
The Steropodontidae was a family of monotremes that are known from fossils from the Early Cretaceous in Australia.There are two genera placed in this family; Steropodon, and Teinolophos which has been tentatively placed in the family due to the similarity of the lower molars in these two...
in some classifications.
Links and References
- Rich et al. "Early Cretaceous Mammals from Flat Rocks, Victoria, Australia". Records of the Queen Victoria Museum, Launceston (1999).
- Rich, T. H., et al. "Monotreme nature of the Australian Early Cretaceous mammal Teinolophos". Acta Palaeontologica Polonica 46(1). 2001 Pages 113–118.
- Life in the Shadows, Non-reptilian life in Mesozoic Australia
- Mesozoic Mammals: Monotremata, an Internet directory
- "Prehistoric jawbone reveals evolution repeating itself" 10 February 2005