Saiphos | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Squamata |
Family: | Scincidae |
Genus: | Saiphos Gray, 1830 |
Species: | S. equalis |
Binomial name | |
Saiphos equalis (Gray, 1825) | |
Distribution of the Yellow-bellied three-toed Skink | |
Synonyms [2] [3] [4] [5] [6] | |
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Saiphos equalis, commonly known as the yellow-bellied three-toed skink or simply three-toed skink, is a species of burrowing skink found in eastern Australia. It is the only species classified under the genus Saiphos.
The lizard has attracted scientific attention due to its dual reproduction habits of producing young via eggs in coastal populations, or via live young in colder mountain regions. [7]
Saiphos equalis grows to a length of 18 cm (7.1 in) including the tail. It has a brown back and an orange belly. The skink is active at night, and feeds on insects. Along the coastal lowlands of Australia, the skink has been observed laying eggs and giving birth to live young for reproduction. Individuals of the species in the lowlands lay eggs (oviparous), while its neighbors to the north in the mountains are almost exclusively giving birth to live young (viviparous). [7] [8]
Saiphos equalis was originally described by the British zoologist John Edward Gray in 1825 as Seps equalis. [9] In 1831, Gray reclassified it under a genus he separately established, Saiphos. [3]
Saiphos equalis is now considered to be the only member of the genus Saiphos. It belongs to the subfamily Lygosominae of the skink family Scincidae. [10] Phylogenetic analysis in 2003 showed that the closest sister taxa of Saiphos equalis are Coeranoscincus reticulatus and members of the genus Ophioscincus . [11] They are part of the Australian Sphenomorphus group, a large monophyletic clade within Lygosominae. [12]
Saiphos equalis are common in New South Wales and Queensland of eastern Australia. [13]
Saiphos equalis includes populations of three main reproductive modes: oviparous with long (15 days) incubation periods, viviparous with no incubation period (0 days), and intermediate populations that are oviparous with short (~5 days) incubation periods. No populations of this skink exhibit normal scincid oviparity behavior with greater-than-30-day incubation periods, which could further indicate this skink is truly making the transition to exclusively viviparity. [14]
In a study, published in 2001, of coastal Saiphos equalis populations, mitochondrial nucleotide sequences (ND2 and cytochrome b) were used to organize the relationships among the various populations. According to Smith et al. the analysis suggests that the long incubation period oviparous lineage is the sister group to the other short-period oviparous and viviparous populations. These clades are consistent and correspond to variation in reproductive modes as well as geographic location according to latitude and altitude. [15]
Lizards from high elevation sites (greater than 1,000 m (3,300 ft)) in north-eastern New South Wales are viviparous, while low-elevation populations from northern and southern in New South Wales exhibit short-period oviparity, an intermediate between viviparity and typical oviparous behaviors. [16] The viviparous populations give birth to fully developed offspring in transparent membranes, while the short-day oviparous populations give birth to partly shelled eggs that contain mostly developed embryos. The embryo continues to develop in the egg prior to hatching. In the northernmost coastal region of New South Wales, the lizards have relatively long incubation periods (approximately 15 days), and the eggshells are thicker. [11]
In April 2019 Saiphos equalis made news when researchers from the University of Sydney reported observing a female laying eggs and giving birth to live young from the same pregnancy, the first reported observation of a vertebrate doing this. [17]
Skinks are lizards belonging to the family Scincidae, a family in the infraorder Scincomorpha. With more than 1,500 described species across 100 different taxonomic genera, the family Scincidae is one of the most diverse families of lizards. Skinks are characterized by their smaller legs in comparison to typical lizards and are found in different habitats except arctic and subarctic regions.
Egernia is a genus of skinks that occurs in Australia. These skinks are ecologically diverse omnivores that inhabit a wide range of habitats. However, in the loose delimitation the genus is not monophyletic but an evolutionary grade, as has long been suspected due to its lack of characteristic apomorphies.
Eulamprus is a genus of lizards, commonly known as water skinks, in the subfamily Sphenomorphinae of the family Scincidae. The genus is native to Australia.
Lygosoma is a genus of lizards, commonly known as supple skinks or writhing skinks, which are members of the family Scincidae. Lygosoma is the type genus of the subfamily Lygosominae. The common name, writhing skinks, refers to the way these stubby-legged animals move, snake-like but more slowly and more awkwardly.
In animals, viviparity is development of the embryo inside the body of the mother, with the maternal circulation providing for the metabolic needs of the embryo's development, until the mother gives birth to a fully or partially developed juvenile that is at least metabolically independent. This is opposed to oviparity, where the embryos develop independently outside the mother in eggs until they are developed enough to break out as hatchlings; and ovoviviparity, where the embryos are developed in eggs that remain carried inside the mother's body until the hatchlings emerge from the mother as juveniles, similar to a live birth.
Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings known as hatchlings with little or no embryonic development within the mother. This is the reproductive method used by most animal species, as opposed to viviparous animals that develop the embryos internally and metabolically dependent on the maternal circulation, until the mother gives birth to live juveniles.
Lygosominae is the largest subfamily of skinks in the family Scincidae. The subfamily can be divided into a number of genus groups. If the rarely used taxonomic rank of infrafamily is employed, the genus groups would be designated as such, but such a move would require a formal description according to the ICZN standards.
Bougainville's skink is a species of skink, a lizard in the family Scincidae. This species is also commonly called the south-eastern slider and Bougainville's lerista.
The eastern three-lined skink, also known commonly as the bold-striped cool-skink, is a species of skink, a lizard in the family Scincidae. The species is endemic to Australia. A. duperreyi has been extensively studied in the context of understanding the evolution of learning, viviparity in lizards, and temperature- and genetic-sex determination. A. duperreyi is classified as a species of "Least Concern" by the IUCN.
Pseudemoia entrecasteauxii, also known commonly as Entrecasteaux's skink, the southern grass skink, the tussock cool-skink, and the tussock skink, is a species of lizard in the family Scincidae. The species is endemic to Australia.
Oligosoma suteri, known commonly as Suter's skink, the black shore skink, the egg-laying skink, and Suter's ground skink, is a species of lizard in the family Scincidae. The species is endemic to New Zealand.
Chioninia is a genus of skinks, lizards in the subfamily Lygosominae. For long, this genus was included in the "wastebin taxon" Mabuya. The genus Chioninia contains the Cape Verde mabuyas.
Lankascincus deignani, commonly known as Deignan's tree skink and the Deignan tree skink, is a species of lizard in the family Scincidae. The species is endemic to the island of Sri Lanka.
Lankascincus dorsicatenatus, also known as the catenated lankaskink, is a species of skink, a lizard in the family Scincidae. The species is endemic to island of Sri Lanka.
Concinnia is a genus of skinks in the subfamily Lygosominae.
Kaestlea is a genus of skinks. These skinks are small, shiny, smooth-scaled species. They are diurnal, terrestrial and insectivorous. They lay eggs to reproduce. These skinks are identified by their distinct blue tail colour. They live in tropical rainforest and montane forest habitats. These secretive skinks silently move through thick leaf-litter on forest floor. They are all endemic to the Western Ghats mountains and in some parts of Eastern Ghats (Shevaroys) of South India.
Egernia stokesii is a gregarious species of lizard of the Scincidae family. This diurnal species is endemic to Australia, and is also known as the Gidgee skink, spiny-tailed skink, Stokes's skink and Stokes's egernia. The species forms stable, long-term social aggregations, much like the social groups seen in mammalian and avian species. This characteristic is rarely found in the Squamata order, but is widespread within the Australian subfamily of Egerniinae skinks. Populations of E. stokesii are widely distributed, but fragmented, and occur in semi-arid environments. There are three recognised subspecies. The conservation status for the species is listed as least concern, however, one subspecies is listed as endangered.
Sphenomorphinae is a large subfamily of skinks, lizards within the family Scincidae. The genera in this subfamily were previously found to belong to the Sphenomorphus group in the large subfamily Lygosominae.
Silvascincus tryoni, the Border Ranges blue-spectacled skink or forest skink, is a species of lizard in the family Scincidae. It is endemic to the McPherson Range bordering New South Wales and Queensland, Australia.
Sphenomorphus derooyae is a species of skink, a lizard in the family Scincidae. The species is native to Oceania.