Ahlberg, P. E. Elginerpeton pancheni and the earliest tetrapod clade. Nature 373, 420–425 (1995).
Ahlberg, P. E. Postcranial stem tetrapod remains from the Devonian of Scat Craig, Morayshire, Scotland. Zool. J. Linn. Soc. 122, 99–141 (1998).
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).
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).
Stössel, I. The discovery of a new Devonian tetrapod trackway in SW Ireland. J. Geol. Soc. 152, 407–413 (1995).
Pardo, J. D., Szostakiwskyj, M., Ahlberg, P. E. & Anderson, J. S. Hidden morphological diversity among early tetrapods. Nature 546, 642–645 (2017).
Smithson, T. R. & Rolfe, W. D. I. Westlothiana gen. nov.: naming the earliest known reptile. Scott. J. Geol. 26, 137–138 (1990).
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).
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).
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).
Long, J. A. et al. Earliest amniote tracks recalibrate the timeline of tetrapod evolution. Nature 641, 1193–1200 (2025).
Ruta, M., Coates, M. I. & Quicke, D. L. Early tetrapod relationships revisited. Biol. Rev. 78, 251–345 (2003).
Clack, J. A. et al. Phylogenetic and environmental context of a Tournaisian tetrapod fauna. Nat. Ecol. Evol. 1, 1–11 (2017).
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).
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).
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).
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).
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).
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).
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).
Pardo, J. D. New information on the neurocranium of Archeria crassidisca and the relationships of the Embolomeri. Zool. J. Linn. Soc. 201, zlad156 (2024).
Jenkins, X. A. et al. Evolutionary assembly of crown reptile anatomy clarified by late Paleozoic relatives of Neodiapsida. Peer Community J. 5, e89 (2025).
Coates, M. I. & Clack, J. A. Romer’s gap: tetrapod origins and terrestriality. Bull. Mus. Natl Hist. Nat. 17, 373–388 (1995).
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).
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).
Ruta, M., Jeffery, J. E. & Coates, M. I. A supertree of early tetrapods. Proc. R. Soc. B 270, 2507–2516 (2003).
Ruta, M. & Coates, M. I. Dates, nodes and character conflict: addressing the lissamphibian origin problem. J. Syst. Palaeontol. 5, 69–122 (2007).
Gauthier, J., Kluge, A. G. & Rowe, T. Amniote phylogeny and the importance of fossils. Cladistics 4, 105–209 (1988).
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).
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).
Clack, J. A. et al. Acherontiscus caledoniae: the earliest heterodont and durophagous tetrapod. R. Soc. Open Sci. 6, 182087 (2019).
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).
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).
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).
Holmes, R. The skull and axial skeleton of the Lower Permian anthracosauroid amphibian Archeria crassidisca Cope. Palaeontogr. Abt. A 207, 161–206 (1989).
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).
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).
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).
Panchen, A. L. & Smithson, T. R. Character diagnosis, fossils and the origin of tetrapods. Biol. Rev. 62, 341–436 (1987).
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).
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).
Lebedev, O. A. Morphology of a new osteolepidid fish from Russia. Bull. Mus. Natl Hist. Nat. C 17, 287–341 (1995).
Clack, J. A. Pholiderpeton scutigerum Huxley, an amphibian from the Yorkshire coal measures. Phil. Trans. R. Soc. Lond. B 318, 1–107 (1987).
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).
Carroll, R. L. A new family of Carboniferous amphibians. Palaeontology 12, 537–548 (1969).
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).
Carroll, R. L., Bybee, P. & Tidwell, W. D. The oldest microsaur (Amphibia). J. Paleontol. 65, 314–322 (1991).
Paton, R. L., Smithson, T. R. & Clack, J. A. An amniote-like skeleton from the Early Carboniferous of Scotland. Nature 398, 508–513 (1999).
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).
Pierce, S. E. et al. Vertebral architecture in the earliest stem tetrapods. Nature 494, 226–229 (2013).
Danto, M., Witzmann, F. & Fröbisch, N. B. Vertebral development in Paleozoic and Mesozoic tetrapods revealed by paleohistological data. PLoS ONE 11, e0152586 (2016).
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).
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).
Clack, J. A., Smithson, T. R. & Ruta, M. A Mississippian (early Carboniferous) tetrapod showing early diversification of the hindlimbs. Commun. Biol. 5, 283 (2022).
Wood, S. P., Panchen, A. L. & Smithson, T. R. A terrestrial fauna from the Scottish Lower Carboniferous. Nature 314, 355–356 (1985).
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).
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).
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).
Carter, A. M., Hsieh, S. T., Dodson, P. & Sallan, L. Early amphibians evolved distinct vertebrae for habitat invasions. PLoS ONE 16, e0251983 (2021).
Mihalitsis, M. & Bellwood, D. Functional implications of dentition-based morphotypes in piscivorous fishes. R. Soc. Open Sci. 6, 190040 (2019).
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).
Watson, D. M. S. The evolution of the tetrapod shoulder girdle and fore-limb. J. Anat. 52, 1–63 (1917).
Shubin, N. H., Daeschler, E. B. & Coates, M. I. The early evolution of the tetrapod humerus. Science 304, 90–93 (2004).
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).
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).
Anderson, J. S. A new aïstopod (Tetrapoda: Lepospondyli) from Mazon Creek, Illinois. J. Vertebr. Paleontol. 23, 79–88 (2003).
Andrews, S. M. & Carroll, R. L. The order Adelospondyli: Carboniferous lepospondyl amphibians. Trans. R. Soc. Edinb. Earth Sci. 82, 239–275 (1991).
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).
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).
Lyckegaard, A., Johnson, G. & Tafforeau, P. Correction of ring artifacts in X-ray tomographic images. Int. J. Tomogr. Simul. 18, F11 (2011).
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).
Revell, L. J. phytools 2.0: an updated R ecosystem for phylogenetic comparative methods (and other things). PeerJ 12, e16505 (2024).
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).