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Acherontiscus at the base of the caecilian clade

Saturday, February 18, 2017 11:20
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(Before It's News)

Acherontiscus caledoniae (Carroll 1969; Namurian, Carboniferous; 1967/12/1 Royal Scottish Museum; Fig. 1) is a tiny slender aquatic amphibian with vestigial limbs and a large pectoral girdle.

FIgure 1. Atcherontiscus, a basal adelogyrinid, close to the origin of caecilians, derived from a sister to Microbrachis. ” data-medium-file=”https://pterosaurheresies.files.wordpress.com/2017/02/atcherontiscus_5881.jpg?w=584&h=696?w=252″ data-large-file=”https://pterosaurheresies.files.wordpress.com/2017/02/atcherontiscus_5881.jpg?w=584&h=696?w=584″ class=”size-full wp-image-26108″ src=”https://pterosaurheresies.files.wordpress.com/2017/02/atcherontiscus_5881.jpg?w=584&h=696″ alt=”FIgure 1. Atcherontiscus, a basal adelogyrinid, close to the origin of caecilians, derived from a sister to Microbrachis.” width=”584″ height=”696″ srcset=”https://pterosaurheresies.files.wordpress.com/2017/02/atcherontiscus_5881.jpg?w=584&h=696 584w, https://pterosaurheresies.files.wordpress.com/2017/02/atcherontiscus_5881.jpg?w=126&h=150 126w, https://pterosaurheresies.files.wordpress.com/2017/02/atcherontiscus_5881.jpg?w=252&h=300 252w, https://pterosaurheresies.files.wordpress.com/2017/02/atcherontiscus_5881.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

FIgure 1. Acherontiscus, a basal adelogyrinid, close to the origin of caecilians, derived from a sister to Microbrachis.

Carroll wrote: Acherontiscus combiines cranial characteristics typical of lepospondyls with a vertebral structure resembling that of embolomeres” (like Proterogyrinus). “This form cannot be placed in any recognized amphibian orders but presumably represents an isolated lineage which originated prior to the establishment of the definitive characteristics which differentiate all known lepospondyls and labyrinthodonts.” 

As a lepospondyl
“This genus provides the first conclusive evidence of the presence of multiple central element in the trunk region.”

Here,
in the large reptile tree (LRT) Acherontiscus nests between the microsaur, Microbrachis, and Adelogyrinus + Adelospondylus. Carroll recognized “The pattern of the skull roof of Acherontiscus resembles most closely that of the microsaur Microbrachis” a taxon presently known only from later Late Carboniferous strata (305 mya).

Diagnosis:
“Small stegocephalian amphibia with both pleurocentra and intercenta well-developed cylinders. Skull with lateral line canals, orbits far forward, no otic notch, teeth without labyrinthine infolding of enamel. Demoral pectoral gidle well developed. Long trunk region.”

References
Carroll RL 1969, A new family of Carboniferous amphibians. Palaeontology 12(4):53–548.



Source: https://pterosaurheresies.wordpress.com/2017/02/19/acherontiscus-at-the-base-of-the-caecilian-clade/

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