Scolecophidia

The Scolecophidia, commonly known as blind snakes or thread snakes,[2] are an infraorder[2] of snakes.[3] They range in length from 10 to 100 centimetres (4 to 40 inches). All are fossorial (adapted for burrowing).[4] Five families and 39 genera are recognized.[5] The Scolecophidia infraorder is almost likely paraphyletic.[6]

Scolecophidia Temporal range: 87.8–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N Late Cretaceous - present (but see text)
Brahminy blind snake, Ramphotyphlops braminus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Infraorder:	Scolecophidia Cope, 1864[1]
Families
See text

Systematics

Etymology

The infraorder name Scolecophidia derives from the two Ancient Greek words σκώληξ or σκώληκος (skṓlēx, genitive skṓlēkos), meaning "earthworm", and ὄφις (óphis), meaning "snake".[7][8] It refers to their shape and fossorial lifestyle.

Families

Family[2]	Authority[2]	Genera[5]	Common name[2]	Geographic range[1]
Anomalepididae	Taylor, 1939	4	primitive blind snakes	Southern Central America and South America
Gerrhopilidae	Vidal, Wynn, Donnellan & Hedges, 2010[9]	2	blind snakes	India, Southeast Asia, Indonesia, the Philippines, and New Guinea[10]
Leptotyphlopidae	Stejneger, 1892	13	slender blind snakes or threadsnakes	Africa, western Asia, and the Americas
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	blind snakes	Madagascar

Chronology

Despite only having fossils as early as the Cretaceous, Scolecophidia itself likely originated in the Middle Jurassic, with Anomalepididae, Leptotyphlopidae, and Typhlopoidea diverging from one another during the Late Jurassic. Within Typhlopoidea, Gerrhopilidae likely diverged from the Xenotyphlopidae-Typhlopidae clade during the Early Cretaceous, and Xenotyphlopidae and Typhlopidae likely diverged from one another during the Late Cretaceous.[9]

Fossil record

The extinct fossil species Boipeba tayasuensis from the Late Cretaceous of Brazil was described in 2020, marking the earliest fossil record of Scolecophidia. It was a sister group to Typhlopoidea and was over 1 meter in length, making it much larger than most modern blindsnakes, with only Afrotyphlops schlegelii and Afrotyphlops mucruso rivaling it in size. Prior to this, the earliest scolecophidian fossils were only known from the Paleocene of Morocco and the Eocene of Europe.[11]

Phylogeny

This phylogeny combines the ones recovered by Vidal et al. in 2010 and Fachini et al. in 2020.[9][11]

Scolecophidia	Anomalepididae       Leptotyphlopidae       †Boipeba   Typhlopoidea   Gerrhopilidae       Xenotyphlopidae     Typhlopidae

Biogeographic history

Scolecophidians are believed to have originated on Gondwana, with anomalepidids and leptotyphlopids evolving in west Gondwana (South America and Africa) and typhlopids, gerrhopilids, and xenotyphlopids on east Gondwana, initially on the combined India/Madagascar land mass, during the Mesozoic.[9] Typhlopids then dispersed to Africa and Eurasia. South American typhlopids appear to have evolved from African typhlopids that rafted 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]

Physical description

The common name of Scolecophidia, blind snakes, is based on their shared characteristic of reduced eyes that are located under their head scales.[12] 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.[12] 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 (3.9 to 39.4 in). Their typical body shapes include slender, cylindrical bodies and small, narrow heads.[12] All these families either lack or have a vestigial left lung and lack cranial infrared receptors.[3]

Behavior

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.[13] 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.[13] 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.[13]

See also

• Alethinophidia, all other snakes
• List of snakes, overview of all snake genera

References

1. McDiarmid RW, Campbell JA, Touré TA (1999). Snake Species of the World: A Taxonomic and Geographic Reference, Volume 1. Washington, District of Columbia: Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
2. "Scolecophidia". Integrated Taxonomic Information System. Retrieved 14 August 2007.
3. Vitt, Laurie J.; Caldwell, Janalee P. (2014). Herpetology: An Introductory Biology of Amphibians and Reptiles (Fourth ed.). Academic Press. pp. 597–603. ISBN 978-0-12-386919-7.
4. Scolecophidia at Palaeos. Accessed 21 December 2013.
5. Uetz, Peter. "The Reptile Database". The Reptile Database. Retrieved 31 December 2017.
6. Miralles, Aurélien; Marin, Julie; Markus, Damin; Herrel, Anthony; Hedges, Blair; Vidal, Nicolas (2018). "Molecular evidence for the paraphyly of Scolecophidia and its evolutionary implications". Journal of Evolutionary Biology. 31 (12): 1782–1793. doi:10.1111/jeb.13373. PMID 30193402. S2CID 52174313.
7. Bailly, Anatole (1981-01-01). Abrégé du dictionnaire grec français. Paris: Hachette. ISBN 978-2010035289. OCLC 461974285.
8. Bailly, Anatole. "Greek-french dictionary online". www.tabularium.be. Retrieved January 7, 2019.
9. Vidal, Nicolas; et al. (2010). "Blindsnake evolutionary tree reveals long history on Gondwana". Biology Letters. 6 (4): 558–561, page 560. doi:10.1098/rsbl.2010.0220. PMC 2936224. PMID 20356885.
10. Vitt, Laurie J.; Caldwell, Janalee P. (2013). Herpetology: An Introductory Biology of Amphibians and Reptiles. Academic Press. p. 600. ISBN 9780123869203.
11. Thiago Schineider Fachini; Silvio Onary; Alessandro Palci; Michael S.Y. Lee; Mario Bronzati; Annie Schmaltz Hsiou (2020). "Cretaceous blindsnake from Brazil fills major gap in snake evolution". iScience. in press: Article 101834. doi:10.1016/j.isci.2020.101834.
12. Simões, B. F.; et al. (2015). "Visual system evolution and the nature of the ancestral snake". Journal of Evolutionary Biology. 28 (7): 1309–1320. doi:10.1111/jeb.12663. PMID 26012745. S2CID 24013194.
13. Webb, J. K.; Shine, R.; Branch, W. R.; Harlow, P. S. (2000). "Life‐history strategies in basal snakes: reproduction and dietary habits of the African thread snake Leptotyphlops scutifrons (Serpentes: Leptotyphlopidae)". Journal of Zoology. 250 (3): 321–327. doi:10.1017/s0952836900003058.