Evolution of terrestrial anatomy revealed by a derived stem tetrapod

Ahlberg, P. E. Elginerpeton pancheni and the earliest tetrapod clade. Nature 373, 420–425 (1995).Article 
ADS 
CAS 

Google Scholar 
Ahlberg, P. E. Postcranial stem tetrapod remains from the Devonian of Scat Craig, Morayshire, Scotland. Zool. J. Linn. Soc. 122, 99–141 (1998).Article 

Google Scholar 
Coates, M. I., Ruta, M. & Friedman, M. Ever since Owen: changing perspectives on the early evolution of tetrapods. Annu. Rev. Ecol. Evol. Syst. 39, 571–592 (2008).Article 

Google Scholar 
Niedźwiedzki, G., Szrek, P., Narkiewicz, K., Narkiewicz, M. & Ahlberg, P. E. Tetrapod trackways from the early Middle Devonian period of Poland. Nature 463, 43–48 (2010).Article 
ADS 
PubMed 

Google Scholar 
Stössel, I. The discovery of a new Devonian tetrapod trackway in SW Ireland. J. Geol. Soc. 152, 407–413 (1995).Article 
ADS 

Google Scholar 
Pardo, J. D., Szostakiwskyj, M., Ahlberg, P. E. & Anderson, J. S. Hidden morphological diversity among early tetrapods. Nature 546, 642–645 (2017).Article 
ADS 
PubMed 
CAS 

Google Scholar 
Smithson, T. R. & Rolfe, W. D. I. Westlothiana gen. nov.: naming the earliest known reptile. Scott. J. Geol. 26, 137–138 (1990).Article 

Google Scholar 
Smithson, T. R., Carroll, R. L., Panchen, A. L. & Andrews, S. M. Westlothiana lizziae from the Viséan of East Kirkton, West Lothian, Scotland, and the amniote stem. Trans. R. Soc. Edinb. Earth Sci. 84, 383–412 (1993).
Google Scholar 
Pardo, J. D., Lennie, K. & Anderson, J. S. Can we reliably calibrate deep nodes in the tetrapod tree? Case studies in deep tetrapod divergences. Front. Genet. 11, 506749 (2020).Article 
PubMed 
PubMed Central 

Google Scholar 
Garza, H. K., Catlos, E. J., Lapen, T. J., Clarke, J. A. & Brookfield, M. E. New U–Pb constraints and geochemistry of the East Kirkton Quarry, Scotland: implications for early tetrapod evolution in the Carboniferous. PLoS ONE 20, e0321714 (2025).Article 
PubMed 
PubMed Central 
CAS 

Google Scholar 
Long, J. A. et al. Earliest amniote tracks recalibrate the timeline of tetrapod evolution. Nature 641, 1193–1200 (2025).Article 
ADS 
PubMed 
PubMed Central 
CAS 

Google Scholar 
Ruta, M., Coates, M. I. & Quicke, D. L. Early tetrapod relationships revisited. Biol. Rev. 78, 251–345 (2003).Article 
PubMed 

Google Scholar 
Clack, J. A. et al. Phylogenetic and environmental context of a Tournaisian tetrapod fauna. Nat. Ecol. Evol. 1, 1–11 (2017).Article 

Google Scholar 
Marjanović, D. & Laurin, M. Phylogeny of Paleozoic limbed vertebrates reassessed through revision and expansion of the largest published relevant data matrix. PeerJ 6, e5565 (2019).Article 
PubMed 
PubMed Central 

Google Scholar 
Jenkins, X. A. et al. The recumbirostran Hapsidopareion lepton from the Early Permian (Cisuralian: Artinskian) of Oklahoma reassessed using HRμCT, and the placement of Recumbirostra on the amniote stem. Pap. Palaeontol. 11, e1610 (2025).Article 

Google Scholar 
Mann, A., Pardo, J. D. & Maddin, H. C. Infernovenator steenae, a new serpentine recumbirostran from the ‘Mazon Creek’ Lagerstätte further clarifies lysorophian origins. Zool. J. Linn. Soc. 187, 506–517 (2019).Article 

Google Scholar 
Mann, A. & Maddin, H. C. Diabloroter bolti, a short-bodied recumbirostran ‘microsaur’ from the Francis Creek Shale, Mazon Creek, Illinois. Zool. J. Linn. Soc. 187, 494–505 (2019).Article 

Google Scholar 
Gee, B. M., Bevitt, J. J. & Reisz, R. R. Computed tomographic analysis of the cranium of the early Permian recumbirostran ‘microsaur’ Euryodus dalyae reveals new details of the braincase and mandible. Pap. Palaeontol. 7, 721–749 (2021).Article 

Google Scholar 
Mann, A., Calthorpe, A. S. & Maddin, H. C. Joermungandr bolti, an exceptionally preserved ‘microsaur’ from the Mazon Creek Lagerstätte reveals patterns of integumentary evolution in Recumbirostra. R. Soc. Open Sci. 8, 210319 (2021).Article 
ADS 
PubMed 
PubMed Central 

Google Scholar 
Mann, A., Pardo, J. D. & Sues, H.-D. Osteology and phylogenetic position of the diminutive ‘microsaur’ Odonterpeton triangulare from the Pennsylvanian of Linton, Ohio, and major features of recumbirostran phylogeny. Zool. J. Linn. Soc. 197, 641–655 (2022).Article 

Google Scholar 
Pardo, J. D. New information on the neurocranium of Archeria crassidisca and the relationships of the Embolomeri. Zool. J. Linn. Soc. 201, zlad156 (2024).Article 

Google Scholar 
Jenkins, X. A. et al. Evolutionary assembly of crown reptile anatomy clarified by late Paleozoic relatives of Neodiapsida. Peer Community J. 5, e89 (2025).Article 

Google Scholar 
Coates, M. I. & Clack, J. A. Romer’s gap: tetrapod origins and terrestriality. Bull. Mus. Natl Hist. Nat. 17, 373–388 (1995).
Google Scholar 
Pardo, J. D., Holmes, R. & Anderson, J. S. An enigmatic braincase from Five Points, Ohio (Westphalian D) further supports a stem tetrapod position for aïstopods. Earth Environ. Sci. Trans. R. Soc. Edinb. 109, 255–264 (2018).
Google Scholar 
Witzmann, F. Phylogenetic patterns of character evolution in the hyobranchial apparatus of early tetrapods. Earth Environ. Sci. Trans. R. Soc. Edinb. 104, 145–167 (2013).
Google Scholar 
Ruta, M., Jeffery, J. E. & Coates, M. I. A supertree of early tetrapods. Proc. R. Soc. B 270, 2507–2516 (2003).Article 
PubMed 
PubMed Central 

Google Scholar 
Ruta, M. & Coates, M. I. Dates, nodes and character conflict: addressing the lissamphibian origin problem. J. Syst. Palaeontol. 5, 69–122 (2007).Article 

Google Scholar 
Gauthier, J., Kluge, A. G. & Rowe, T. Amniote phylogeny and the importance of fossils. Cladistics 4, 105–209 (1988).Article 
PubMed 

Google Scholar 
Ruta, M. & Clack, J. A. A review of Silvanerpeton miripedes, a stem amniote from the lower carboniferous of East Kirkton, West Lothian, Scotland. Trans. R. Soc. Edinb. Earth Sci. 97, 31–63 (2006).Article 

Google Scholar 
Carroll, R. L. in Amphibian Biology Vol. 4 (ed. Heatwole, H.) 1198–1269 (Surrey Beatty, 2000).Laurin, M. & Reisz, R. R. A new study of Solenodonsaurus janenschi, and a reconsideration of amniote origins and stegocephalian evolution. Can. J. Earth Sci. 36, 1239–1255 (1999).Article 
ADS 

Google Scholar 
Clack, J. A. et al. Acherontiscus caledoniae: the earliest heterodont and durophagous tetrapod. R. Soc. Open Sci. 6, 182087 (2019).Article 
ADS 
PubMed 
PubMed Central 

Google Scholar 
Arbez, T., Atkins, J. B. & Maddin, H. C. Cranial anatomy and systematics of Dendrerpeton cf. helogenes (Tetrapoda, Temnospondyli) from the Pennsylvanian of Joggins, revisited through micro-CT scanning. Pap. Palaeontol. 8, e1421 (2022).Article 

Google Scholar 
Klembara, J., Berman, D. S., Henrici, A. C. & Čerňanský, A. New structures and reconstructions of the skull of the seymouriamorph Seymouria sanjuanensis Vaughn. Ann. Carnegie Mus. 74, 217–225 (2005).Article 

Google Scholar 
Rawson, J. R. G., Porro, L. B., Martin-Silverstone, E. & Rayfield, E. J. Osteology and digital reconstruction of the skull of the early tetrapod Whatcheeria deltae. J. Vertebr. Paleontol. 41, e1927749 (2021).Article 

Google Scholar 
Holmes, R. The skull and axial skeleton of the Lower Permian anthracosauroid amphibian Archeria crassidisca Cope. Palaeontogr. Abt. A 207, 161–206 (1989).
Google Scholar 
Porro, L. B., Rayfield, E. J. & Clack, J. A. Computed tomography and three-dimensional reconstruction of the skull of the stem tetrapod Crassigyrinus scoticus Watson, 1929. J. Vertebr. Paleontol. 42, e2183134 (2022).Article 

Google Scholar 
Berman, D. S., Henrici, A. C., Kissel, R. A., Sumida, S. S. & Martens, T. A new diadectid (Diadectomorpha), Orobates pabsti, from the early Permian of central Germany. Bull. Carnegie Mus. Nat. Hist. 35, 1–36 (2004).Article 

Google Scholar 
Downs, J. P., Daeschler, E. B., Long, A. M. & Shubin, N. H. Eusthenopteron jenkinsi sp. nov. (Sarcopterygii, Tristichopteridae) from the Upper Devonian of Nunavut, Canada, and a review of Eusthenopteron taxonomy. Breviora 562, 1–24 (2018).Article 

Google Scholar 
Panchen, A. L. & Smithson, T. R. Character diagnosis, fossils and the origin of tetrapods. Biol. Rev. 62, 341–436 (1987).Article 

Google Scholar 
Ruta, M., Milner, A. R. & Coates, M. I. The tetrapod Caerorhachis bairdi Holmes and Carroll from the Lower Carboniferous of Scotland. Trans. R. Soc. Edinb. Earth Sci. 92, 229–261 (2001).Article 

Google Scholar 
Bolt, J. R. & Lombard, R. E. The mandible of the primitive tetrapod Greererpeton, and the early evolution of the tetrapod lower jaw. J. Paleontol. 75, 1016–1042 (2001).Article 
ADS 

Google Scholar 
Lebedev, O. A. Morphology of a new osteolepidid fish from Russia. Bull. Mus. Natl Hist. Nat. C 17, 287–341 (1995).
Google Scholar 
Clack, J. A. Pholiderpeton scutigerum Huxley, an amphibian from the Yorkshire coal measures. Phil. Trans. R. Soc. Lond. B 318, 1–107 (1987).Article 
ADS 

Google Scholar 
Smithson, T. R. Eldeceeon rolfei, a new reptiliomorph from the Viséan of East Kirkton, West Lothian, Scotland. Trans. R. Soc. Edinb. Earth Sci. 84, 377–382 (1993).
Google Scholar 
Carroll, R. L. A new family of Carboniferous amphibians. Palaeontology 12, 537–548 (1969).
Google Scholar 
Mann, A., Xiong, Z., Calthorpe, A. S., Sues, H.-D. & Maddin, H. C. Carboniferous recumbirostran elucidates the origins of terrestrial herbivory. Nat. Ecol. Evol. 10, 193–202 (2026).Article 
PubMed 

Google Scholar 
Carroll, R. L., Bybee, P. & Tidwell, W. D. The oldest microsaur (Amphibia). J. Paleontol. 65, 314–322 (1991).Article 
ADS 

Google Scholar 
Paton, R. L., Smithson, T. R. & Clack, J. A. An amniote-like skeleton from the Early Carboniferous of Scotland. Nature 398, 508–513 (1999).Article 
ADS 
CAS 

Google Scholar 
Smithson, T. R., Ruta, M. & Clack, J. A. On Ossirarus kierani, a stem tetrapod from the Tournaisian of Burnmouth, Berwickshire, Scotland, and the phylogeny of early tetrapods. Foss. Rec. 27, 333–352 (2024).Article 

Google Scholar 
Pierce, S. E. et al. Vertebral architecture in the earliest stem tetrapods. Nature 494, 226–229 (2013).Article 
ADS 
PubMed 
CAS 

Google Scholar 
Danto, M., Witzmann, F. & Fröbisch, N. B. Vertebral development in Paleozoic and Mesozoic tetrapods revealed by paleohistological data. PLoS ONE 11, e0152586 (2016).Article 
PubMed 
PubMed Central 

Google Scholar 
Otoo, B. K. A., Bolt, J. R., Lombard, R. E., Angielczyk, K. D. & Coates, M. I. The postcranial anatomy of Whatcheeria deltae and its implications for the family Whatcheeriidae. Zool. J. Linn. Soc. 193, 700–745 (2021).Article 

Google Scholar 
Clack, J. A. Eucritta melanolimnetes from the Early Carboniferous of Scotland, a stem tetrapod showing a mosaic of characteristics. Trans. R. Soc. Edinb. Earth Sci. 92, 75–95 (2001).Article 

Google Scholar 
Clack, J. A., Smithson, T. R. & Ruta, M. A Mississippian (early Carboniferous) tetrapod showing early diversification of the hindlimbs. Commun. Biol. 5, 283 (2022).Article 
PubMed 
PubMed Central 

Google Scholar 
Wood, S. P., Panchen, A. L. & Smithson, T. R. A terrestrial fauna from the Scottish Lower Carboniferous. Nature 314, 355–356 (1985).Article 
ADS 

Google Scholar 
Bever, G. S. & Norell, M. A. A new rhynchocephalian (Reptilia: Lepidosauria) from the Late Jurassic of Solnhofen (Germany) and the origin of the marine Pleurosauridae. R. Soc. Open Sci. 4, 170570 (2017).Article 
ADS 
PubMed 
PubMed Central 

Google Scholar 
Foffa, D., Johnson, M. M., Young, M. T., Steel, L. & Brusatte, S. L. Revision of the Late Jurassic deep-water teleosauroid crocodylomorph Teleosaurus megarhinus Hulke, 1871 and evidence of pelagic adaptations in Teleosauroidea. PeerJ 7, e6646 (2019).Article 
PubMed 
PubMed Central 

Google Scholar 
Camaiti, M. et al. A database of the morphology, ecology and literature of the world’s limb-reduced skinks. J. Biogeogr. 49, 1397–1406 (2022).Article 

Google Scholar 
Carter, A. M., Hsieh, S. T., Dodson, P. & Sallan, L. Early amphibians evolved distinct vertebrae for habitat invasions. PLoS ONE 16, e0251983 (2021).Article 
PubMed 
PubMed Central 
CAS 

Google Scholar 
Mihalitsis, M. & Bellwood, D. Functional implications of dentition-based morphotypes in piscivorous fishes. R. Soc. Open Sci. 6, 190040 (2019).Article 
ADS 
PubMed 
PubMed Central 

Google Scholar 
Porro, L. B., Martin-Silverstone, E. & Rayfield, E. J. Descriptive anatomy and three-dimensional reconstruction of the skull of the tetrapod Eoherpeton watsoni Panchen, 1975 from the Carboniferous of Scotland. Earth Environ. Sci. Trans. R. Soc. Edinb. 115, 164–184 (2024).
Google Scholar 
Watson, D. M. S. The evolution of the tetrapod shoulder girdle and fore-limb. J. Anat. 52, 1–63 (1917).PubMed 
PubMed Central 
CAS 

Google Scholar 
Shubin, N. H., Daeschler, E. B. & Coates, M. I. The early evolution of the tetrapod humerus. Science 304, 90–93 (2004).Article 
ADS 
PubMed 
CAS 

Google Scholar 
Milner, A. R. & Sequeira, S. E. K. The temnospondyl amphibians from the Viséan of East Kirkton, West Lothian, Scotland. Trans. R. Soc. Edinb. Earth Sci. 84, 331–361 (1993).
Google Scholar 
Maddin, H. C., Eckhart, L., Jaeger, K., Russell, A. P. & Ghannadan, M. The anatomy and development of the claws of Xenopus laevis (Lissamphibia: Anura) reveal alternate pathways of structural evolution in the integument of tetrapods. J. Anat. 214, 607–619 (2009).Article 
PubMed 
PubMed Central 

Google Scholar 
Anderson, J. S. A new aïstopod (Tetrapoda: Lepospondyli) from Mazon Creek, Illinois. J. Vertebr. Paleontol. 23, 79–88 (2003).Article 

Google Scholar 
Andrews, S. M. & Carroll, R. L. The order Adelospondyli: Carboniferous lepospondyl amphibians. Trans. R. Soc. Edinb. Earth Sci. 82, 239–275 (1991).Article 

Google Scholar 
Mirone, A., Brun, E., Gouillart, E., Tafforeau, P. & Kieffer, J. The PyHST2 hybrid distributed code for high speed tomographic reconstruction with iterative reconstruction and a priori knowledge capabilities. Nucl. Instrum. Methods Phys. Res. B 324, 41–48 (2014).Article 
ADS 
CAS 

Google Scholar 
Paganin, D., Mayo, S. C., Gureyev, T. E., Miller, P. R. & Wilkins, S. W. Simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object. J. Microsc. 206, 33–40 (2002).Article 
PubMed 
MathSciNet 
CAS 

Google Scholar 
Lyckegaard, A., Johnson, G. & Tafforeau, P. Correction of ring artifacts in X-ray tomographic images. Int. J. Tomogr. Simul. 18, F11 (2011).
Google Scholar 
Benoit, J. et al. The evolution of the maxillary canal in Probainognathia (Cynodontia, Synapsida): reassessment of the homology of the infraorbital foramen in mammalian ancestors. J. Mamm. Evol. 27, 329–348 (2020).Article 

Google Scholar 
Revell, L. J. phytools 2.0: an updated R ecosystem for phylogenetic comparative methods (and other things). PeerJ 12, e16505 (2024).Article 
PubMed 
PubMed Central 

Google Scholar 
Bell, M. A. & Lloyd, G. T. strap: an R package for plotting phylogenies against stratigraphy and assessing their stratigraphic congruence. Palaeontology 58, 379–389 (2015).Article 

Google Scholar