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Triassic stem caecilian supports dissorophoid origin of living amphibians Project ID: 000382289 Public
8 Media · 8 Specimens · Creator: Kligman, Ben · Managed by: Ben Kligman

Living amphibians (Lissamphibia) include frogs and salamanders (Batrachia), and the limbless worm-like caecilians (Gymnophiona). The estimated Paleozoic gymnophionan-batrachian molecular divergence suggests a major gap in the record of crown lissamphibians prior to their earliest fossil occurrences in the Triassic Period. Recent studies find a monophyletic Batrachia within dissorophoid temnospondyls, but the absence of pre-Jurassic caecilian fossils has made their relationships to batrachians and affinities to Paleozoic tetrapods controversial. Here we report the geologically-oldest stem caecilian, a crown lissamphibian, from the Late Triassic of Arizona, USA, extending the caecilian record by ~35 Ma. These fossils illuminate the tempo and mode of early caecilian morphological and functional evolution, demonstrating a delayed acquisition of musculoskeletal features associated with fossoriality in living caecilians, including the dual jaw closure mechanism, reduced orbits, and the tentacular organ. The provenance of these fossils suggests a Pangean equatorial origin for caecilians, implying that living caecilian biogeography reflects conserved aspects of caecilian function and physiology in combination with vicariance patterns driven by plate tectonics. These fossils reveal a combination of features unique to caecilians alongside features shared with batrachian and dissorophoid temnospondyls, providing new and compelling evidence supporting a single origin of living amphibians within dissorophoid temnospondyls.

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  ID Part Object Taxonomy Type Date Added Publication Status  
000412395 pseudodentary pefo:43891 Funcusvermis gilmorei Mesh 2022-01-10 Restricted Download  
000412387 Composite Skull Reconstruction pefo:43891, 46284, 46480, PEFO 46481 Funcusvermis gilmorei Mesh 2022-01-10 Restricted Download  
000412381 Femur pefo:43811 Funcusvermis gilmorei Mesh 2022-01-10 Restricted Download  
000412375 Postatlantal Pleurocentrum pefo:45910 Funcusvermis gilmorei Mesh 2022-01-10 Restricted Download  
000412369 pseudodentary pefo:45800 Funcusvermis gilmorei Mesh 2022-01-10 Restricted Download  
000412363 Maxillopalatine pefo:46481 Funcusvermis gilmorei Mesh 2022-01-10 Restricted Download  
000412357 pseudodentary pefo:46284 Funcusvermis gilmorei Mesh 2022-01-10 Restricted Download  
000412255 Pseudoangular pefo:46480 Funcusvermis gilmorei Mesh 2022-01-10 Restricted Download  
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