Aistopoda (Greek for "[having] not-visible feet") is an order of highly specialised snake-like stegocephalians known from the Carboniferous and Early Permian of Europe and North America, ranging from tiny forms only 5 centimetres (2 in), to nearly 1 metre (3.3 ft) in length. They first appear in the fossil record in the Mississippian period and continue through to the Early Permian.
The skull is small but very specialised, with large orbits, and large fenestrae. The primitive form Ophiderpeton has a pattern of dermal bones in the skull similar in respects to the temnospondyls. But in the advanced genus Phlegethontia the skull is very light and open, reduced to a series of struts supporting the braincase against the lower jaw, just as in snakes, and it is possible that the aistopods filled the same ecological niches in the Paleozoic that snakes do today.
Fossil of Pseudophlegethontia turnbullorum in the Field Museum of Natural History.
They had an extremely elongated body, with up to 230 vertebrae. The vertebrae were holospondylous, having only a single ossification per segment. They lacked intercentra, even in the tail, and had are no free haemal arches. The neural arch was low and fused to the centrum. All of these features are very similar to those of the Nectridea, both representing the typical lepospondylous condition.
A recent paper described the internal organization of the aistopod head,[2] finding that aïstopods retained many fish-like features of the skull and brain, including a persistent extension of the notochord into the head and an open canal between the pituitary gland and the mouth. Because these features are lost early in tetrapod evolution, this may be evidence that aistopods diverged from other tetrapods soon after the origin of digits.
The ribs were slender, either single or double-headed, with the head shaped like a letter "K". There is no trace of limbs or even limb girdles in any known fossil, and the tail was short and primitive.
^"Fossilworks: Aistopoda". Fossilworks.
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Aistopoda (Greek for "[having] not-visible feet") is an order of highly specialised snake-like stegocephalians known from the Carboniferous and Early...
America. Five major groups of lepospondyls are known: Adelospondyli; Aïstopoda; Lysorophia; Microsauria; and Nectridea. Lepospondyls have a diverse range...
Lethiscus is the earliest known representative of the Aistopoda, a group of very specialised snake-like tetrapodomorphs known from the early Carboniferous...
Swartz in 2012. As recovered by Clack et al. 2016: †Elginerpetontidae †Aistopoda †Whatcheeriidae †Colosteidae †Adelospondyli †Baphetoidea †Embolomeri (a...
Lepospondyli Incertae Sedis Family Acherontiscidae Family Adelogyrinidae Order Aïstopoda Family Ophiderpetontidae Family Phlegethontiidae Order Nectridea Family...
limbs that appear non-functional) and at least three extinct groups (Aïstopoda, Lysorophia, and Adelospondyli). There are no known limbless species of...
preserved. The Leposondyli were generally salamander-like, but one group, the Aïstopoda, was snakelike with flexible, reduced skulls, though whether the families...
Family Branchiosauridae Family Amphibamidae Superorder Lepospondyli Order Aïstopoda Family Phlegethontiidae Order Nectridea Family Diplocaulidae Family Scincosauridae...
(1934) and Carroll (1966), and was eventually recognized as a member of Aistopoda and renamed Andersonerpeton longidentatum by Pardo and Mann (2018) as...
stocki (Tetrapoda: Lepospondyli: Aistopoda) from high-resolution computed tomography and a phylogenetic analysis of Aistopoda" (PDF). Canadian Journal of Earth...
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