| Scolecophidia | |
|---|---|
 | |
| Brahminy blind snake, Ramphotyphlops braminus | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Infraorder: | Scolecophidia Cope, 1864[1] |
| Families | |
See text | |
TheScolecophidia, commonly known asblind snakes orthread snakes,[2] are aninfraorder[2] ofsnakes.[3] They range in length from 10 to 100 centimeters (4 to 40 inches). All arefossorial (adapted for burrowing).[4] Fivefamilies and 39genera are recognized.[5] The Scolecophidia infraorder is most-likelyparaphyletic (with the familyAnomalepididae recovered with strong support as sister clade to the'typical snakes').[6]
The infraorder name Scolecophidia derives from the twoAncient Greek wordsσκώληξ or σκώληκος (skṓlēx, genitiveskṓlēkos), meaning "earthworm", andὄφις (óphis), meaning "snake".[7][8] It refers to their shape and fossorial lifestyle.
| Family[2] | Authority[2] | Genera[5] | Common name[2] | Geographic range[1] |
|---|---|---|---|---|
| Anomalepididae | Taylor, 1939 | 4 | primitive blind snakes | SouthernCentral America andSouth America |
| Gerrhopilidae | Vidal,Wynn,Donnellan &Hedges, 2010[9] | 2 | Indo-Malayan blind snakes | India,Southeast Asia,Indonesia, thePhilippines, andNew Guinea[10] |
| Leptotyphlopidae | Stejneger, 1892 | 13 | slender blind snakes or threadsnakes | Africa, westernAsia, and theAmericas |
| Typhlopidae | Merrem, 1820 | 18 | long-tailed blind snakes | Most tropical and many subtropical regions all over the world |
| Xenotyphlopidae | Vidal,Vences,Branch & Hedges, 2010[9] | 1 | Malagasy blind snakes | Madagascar |
Despite only having fossils as early as theCretaceous, Scolecophidia itself likely originated in theMiddle Jurassic, withAnomalepididae,Leptotyphlopidae, andTyphlopoidea diverging from one another during theLate Jurassic. Within Typhlopoidea,Gerrhopilidae likely diverged from the Xenotyphlopidae-Typhlopidaeclade during theEarly Cretaceous, andXenotyphlopidae andTyphlopidae likely diverged from one another during theLate Cretaceous.[9]
Scolecophidians are believed to have originated onGondwana, with anomalepidids and leptotyphlopids evolving in west Gondwana (South America and Africa) and the Typhlopoidea (typhlopids, gerrhopilids, and xenotyphlopids) on east Gondwana, initially on the combinedIndia/Madagascar land mass, during theMesozoic.[9] Typhlopids, initially isolated on Madagascar, then dispersed to Africa and Eurasia. South American typhlopids appear to have evolved from African typhlopids thatrafted across the Atlantic about 60 million years ago; they, in turn, dispersed to the Caribbean about 33 million years ago.[9] Similarly, typhlopids appear to have reached Australia from Southeast Asia or Indonesia about 28 million years ago.[9] Meanwhile, the gerrhopilids, isolated onInsular India, underwent a radiation throughout tropical Asia following thecollision of India with Asia, while the xenotyphlopids remained isolated on Madagascar.[11]
The Malagasy typhlopoids (Madatyphlops in Typhlopidae andXenotyphlops in Xenotyphlopidae) are among the only extant terrestrial vertebrates on Madagascar whose isolation occurred due tovicariance from the Cretaceous breakup of Gondwana. The only other terrestrial vertebrate on Madagascar that shares this evolutionary history is theMadagascan big-headed turtle (Erymnochelys madagascariensis); all other Malagasy land vertebrates dispersed from the mainland to an already-isolated Madagascar from the latest Cretaceous to the present.[11]
The extinct fossil speciesBoipeba tayasuensis from theLate Cretaceous ofBrazil was described in 2020, marking the earliest fossil record of Scolecophidia. It was asister group toTyphlopoidea and was over 1 meter in length, making it much larger than most modern blindsnakes, with onlyAfrotyphlops schlegelii andAfrotyphlops mucruso rivaling it in size. Prior to this, the earliest scolecophidian fossils were only known from thePaleocene ofMorocco and theEocene ofEurope.[12]
Possible Typhopid skin has been identified inDominican amber.[13]
This phylogeny combines the ones recovered by Vidalet al. in 2010 and Fachiniet al. in 2020.[9][12]
| Scolecophidia | |
The common name of Scolecophidia, blind snakes, is based on their shared characteristic of reduced eyes that are located under their head scales.[14] These head scales are found in all snakes and are referred to as spectacles, but within this infraorder, they are opaque, resulting in decreased visual capabilities.[3] Reduced eyes of the Scolecophidia have been attributed to evolutionary origins of snakes, which are hypothesized to have arisen from fossorial ancestors, causing a loss of genes related to eyesight that later evolved again in higher snakes to be similar to other vertebrates due to convergent evolution.[14] Newer research shows that seven of the 12 genes associated with bright-light vision in most snakes and lizards are not present in this infraorder, and the common ancestor of all snakes had better eyesight.[15] Other shared characteristics include an absent left oviduct in four of the five families, aside from the Anomalepididae, which have a well developed yet reduced left oviduct.[3] Aside from this, these snakes range in length from 10 to 100 cm (4 to 39 in). Their typical body shapes include slender, cylindrical bodies and small, narrow heads.[14] All these families either lack or have a vestigial left lung and lack cranial infrared receptors.[3]
The main shared characteristic found across all Scolecophidia is a fossorial nature, either living underground or within logs and leaf litter.[3] Aside from this, thus far the reproduction remains understudied with all Scolecophidia studied thus far being noted to be oviparous,[3] with elongate eggs noted in both leptotyphlopids and typhlopids.[16] Foraging behaviors vary across families, but all feed on invertebrates. Some of their main food sources include ant or termite eggs, which are tracked down by following chemical cues left by these invertebrates to create trails.[16]Tricheilostomata macrolepis has been seen climbing up trees and waving its head side to side vertically to detect chemical cues in the air to locate insect nests.[3] In a study on the Leptotyphlopidae, some species were found to specialize in eating only termites or ants; some rely on binge feeding patterns, while others do not.[3] While these snakes are often difficult to locate due to their burrowing habits, they are more often seen above ground after rain due to flooding that occurs in burrows. The ancestral nature of the Scolecophidia has resulted in the use of these organisms as models for evolutionary studies in Serpentes to better understand evolution of reproduction, morphology, and feeding habits.[16]
