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Snake-like limb loss in a Carboniferous amniote


Among living tetrapods, many lineages have converged on a snake-like body plan, where extreme axial elongation is accompanied by reduction or loss of paired limbs. However, when and how this adaptive body plan first evolved in amniotes remains poorly understood. Here, we provide insights into this question by reporting on a new taxon of molgophid recumbirostran, Nagini mazonense gen. et sp. nov., from the Francis Creek Shale (309–307 million years ago) of Illinois, United States, that exhibits extreme axial elongation and corresponding limb reduction. The molgophid lacks entirely the forelimb and pectoral girdle, thus representing the earliest occurrence of complete loss of a limb in a taxon recovered phylogenetically within amniotes. This forelimb-first limb reduction is consistent with the pattern of limb reduction that is seen in modern snakes and contrasts with the hindlimb-first reduction process found in many other tetrapod groups. Our findings suggest that a snake-like limb-reduction mechanism may be operating more broadly across the amniote tree.

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Fig. 1: Photographs of N. mazonense gen. et sp. nov.
Fig. 2: Interpretive illustrations of N. mazonense gen. et sp. nov.
Fig. 3: Interpretive illustrations of N. mazonense gen. et sp. nov.
Fig. 4: Cranial reconstructions of known molgophids.
Fig. 5: Evolution of body elongation and limb reduction in Recumbirostra.

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Data availability

All fossils contained in this manuscript, including MPM VP359229.2 and FMNH PR 1031, have been properly accessioned into a public repository in this case the Milwaukee Public Museum and Field Museum of Natural History, respectively. The data matrix used in the phylogenetic parsimony analysis is available in Supplementary Information 3. This published work and the nomenclatural acts it contains have been registered in ZooBank, the proposed online registration system for the International Code of Zoological Nomenclature (ICZN). The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix The LSIDs for this publication are: (article); (genus); and (species).


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We would like to thank P. Coorough Burke, D. Scott, R. R. Reisz, D. S. Berman, A. C. Henrici and R. W. Hook for access to comparative material and specimens. We further thank R. W. Hook, B. M. Gee and A. S. Calthorpe for stimulating discussions. Finally, we thank A. S. Calthorpe for her tireless assistance with assembling figures. A. Prieditis is thanked for his aid in taking photographs of the counterparts of MPM VP359229.2. Funding was in part provided by an Ontario Graduate Scholarship awarded to A.M.

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Authors and Affiliations



A.M. analysed the fossil data, performed phylogenetic analyses, constructed the figures and wrote the paper. J.D.P. analysed the fossil data, aided in figure edits and wrote the paper. H.C.M. provided edits to both the manuscript and final figures.

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Correspondence to Arjan Mann.

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Nature Ecology & Evolution thanks David Ford, Marco Camaiti, Hussam Zaher and Timothy Smithson for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 Scanning Electron Micrographs (SEMs) of FMNH PR 1031.

A–D, showing incomplete ossification of the cranium. A–D, respectively show progressively smaller images including close up images of framboidal pyrite D, which likely is replacing cartilage and other soft tissues.

Extended Data Fig. 2 Images of FMNH PR 1031.

Photographs of the part A, and counterpart B, of the referred specimen (FMNH PR 1031) of Nagini mazonense.

Extended Data Fig. 3 Anatomy of the hindlimb and pelvic region of Nagini mazonense.

Close up Images of the well-developed pelvic girdle and hindlimb preserved on FMNH PR 1031. Anatomical Abbreviations: as=astragalus; dt=distal tarsal; ca=calcaneum; fe=femur; fib=fibula; il=Ilium; ph=phalanx; tib=tibia.

Extended Data Fig. 4 Results of the Phylogenetic analysis.

Strict consensus results of the phylogenetic parsimony analysis showing the position of Nagini mazonense as a molgophid in a polytomy with the taxa to Infernovenator and Brachydectes. Bootstrap values are located on top of nodes (only those over 50 reported).

Supplementary information

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Supplementary Sections 1–3, Fig. 1 and references.

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Mann, A., Pardo, J.D. & Maddin, H.C. Snake-like limb loss in a Carboniferous amniote. Nat Ecol Evol 6, 614–621 (2022).

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