This page deals with the stem group of the crocodylians (order Crocodylia, class Reptilia), which is a clade that comprises the alligators, caimans, crocodiles and gharials (Brochu et al, 2009). It consists of all modern crocodylians and all the extinct relatives that descended from the last common ancestor of all living crocodylian species. Note that the term Crocodylia is generally restricted to the crown group (Brochu, 2003).

The most complete recent phylogenetic tree is that by Godoy et al (2019), summarized in the following phylogenetic time tree (divided into two panels):
Figure 1a. Time tree of the stem-Crocodylia (Part1)
Figure 1b. Time tree of the stem-Crocodylia (Part2)
The earliest-known fossils in the crocodylian stem line are Xilousuchus sapingensis and Ctenosauriscus koeneni. They are both of Early Triassic (Olenekian) age, but given the lack of illustrations of the former species only Ctenosauriscus will be considered here. It is a member of the clade Poposauroidea from the Early Triassic (latest Olenekian) Solling Formation at Bremketal, near Göttingen, Lower Saxony, Germany (Butler et al, 2011; Benton et al, 2015). Note that the Poposauridae are by no means the most basal pseudosuchians in the above tree, even though Ctenosauriscus koeneni is the oldest pseudosuchian known. This fossil is illustrated below, together with other members of the stem-group. However, owing to the large number of images, we will consider them in groups that are progressively higher (more crownward) in the tree.  (Click on any image to see a larger version.)

Pseudosuchia basal to Loricata
Figure 2a. Images of stem-Crocodylia (​Pseudosuchia basal to Loricata)
​The most basal clade comprises the phytosaurs, which are superficially like crocodiles, but they do actually have several features that distinguish them from all other reptiles (Stocker et al, 2017). The next more crownward clade is the Ornithosuchidae, which appear more similar to modern crocodiles, but had a reversed ankle joint relative to crocodiles and might have been capable of walking on their hind legs (Von Baczko and Ezcurra, 2013). The sister clade to the Ornithosuchidae consists of the Aetosauria and the Erpetosuchidae. The aetosaurs (represented by Stagonolepis robertsoni and Revueltosaurus callenderi above) were heavily armored, while the Erpetosuchidae (represented by Parringtonia gracilis and Erpetosuchus granti above) were also heavily armored but more slender than modern crocodiles.

The next most crownward clade is the Gracilisuchidae (illustrated above by Turfanosuchus dabanensis, Yonghesuchus sangbiensis and Gracilisuchus stipanicicorum). These appear to be rather similar to erpetosuchids but lack their heavy armor. In between the Gracilisuchidae and the Poposauroidea there are several species, of which images are shown above of Ticinosuchus ferox. The latter appears similar in shape to the Gracilisuchidae, but is much larger (up to 3 meters in length). Lastly, we show above some examples of the Poposauroidea clade (Qianosuchus mixtus, Lotosaurus adentus, Ctenosauriscus koeneni and Arizonasaurus babbitti). Some members of the clade (not shown above) were bipedal while others had a “sail” on their back formed by spines extending from the vertebrae. Qianosuchus mixtus appears to have been aquatic (Li et al, 2006).

Finally, some examples of the most crownward species basal to the Loricata (Youngosuchus sinensis, Batrachotomus kupferzellensis and Luperosuchus fractus) are shown above. These represent a return to a more crocodile-like form, but they had longer hind legs relative to the forelegs compared to modern crocodiles.

Loricata basal to Neosuchia
Figure 2b. Images of stem-Crocodylia (​Loricata basal to Neosuchia)
​The above images represent the Loricata that are more basal than the Neosuchia clade. The images are, as usual on this website, placed in order from most basal to most crownward. The species basal to the clade Crocodyliformes (from Prestosuchus chiniquensis to Hallopus victor) show a trend from large, thick-set animals to smaller species with longer legs.

The next most crownward species are those that are basal to the Notosuchia. These species (illustrated above by Protosuchus richardsoni,  Gobiosuchus kielanae, Sichuanosuchus huidongensis and Hsisosuchus chungkingensis) appear to be similar to modern crocodiles, but have a blunter snout and are generally quite small.

The remainder of the images shown above belong to the Notosuchia, which are generally small (less than a meter in length) and pug-nosed. Apart from one of the most basal representatives, Simosuchus clarki, they appear fairly similar to modern crocodiles, although they occupied predominantly terrestrial habitats (Wilberg et al, 2019). 

Neosuchia
Names in   red indicate   that the fossil is younger  than the oldest known crown-group fossil.
Figure 2c. Images of stem-Crocodylia (​Neosuchia)
The images shown above belong to the Neosuchia clade basal to the crown-Crocodylia. The first five images depict examples of the Thalattosuchia, which are seen to be slender animals that are believed to have occupied an aquatic environment (Pierce et al, 2017). The next four images shown above represent the Tethysuchia, the sister clade of the Thalattosuchia. Resembling modern gharials, the Tethysuchia occupied mainly freshwater environments (Wilberg et al, 2019). The remaining images shown above, from Theriosuchus pusillus to Agaresuchus subjuniperus, represent the most crownward members of the stem-Crocodylia. They appear similar to modern alligators.

Note that a few of the species shown above (represented by names in red) post-date the appearance of the crown group; these represent branches of the stem line that continued to evolve after the crown-group had appeared.

The oldest known member of the crown-Crocodylia is Brachychampsa montana, a stem-Alligatoridae first described from the Late Cretaceous “Hell Creek Beds” of the Lance Formation at a location 25 miles southeast of Lismas, Dawson County, Montana (Gilmore, 1911) but later also described in more detail from the Late Cretaceous (Late Campanian) De-na-zin Member of the Kirtland Formation at Willow Wash in the Juan Basin, New Mexico (Sullivan and Lucas, 2003; Norell et al, 1994). A skeleton of the genus and a life restoration of the species are shown below:
Figure 3. Images of the oldest  known member of the crown -Crocodylia
​The above time tree (Figure 1) indicates that the crocodylian stem group developed from Early Triassic to Late Cretaceous time, representing a long stem-to-crown transition of between 169 and 179 million years.

References

Benton, M. J. (2015). Vertebrate Palaeontology - Fourth edition. John Wiley & Sons, 468 pages.

Benton, M. J., Donoghue, P. C., Asher, R. J., Friedman, M., Near, T. J., & Vinther, J. (2015). Constraints on the timescale of animal evolutionary history. Palaeontologia Electronica, 18(1), 1-106.

Brochu, C. A. (2003). Phylogenetic approaches toward crocodylian history. Annual Review of Earth and Planetary Sciences, 31(1), 357-397.

Brochu, C. A., Wagner, J. R., Jouve, S., Sumrall, C. D., & Densmore, L. D. (2009). A correction corrected: consensus over the meaning of Crocodylia and why it matters. Systematic Biology, 58(5), 537-543.

Butler, R. J., Brusatte, S. L., Reich, M., Nesbitt, S. J., Schoch, R. R., & Hornung, J. J. (2011). The sail-backed reptile Ctenosauriscus from the latest Early Triassic of Germany and the timing and biogeography of the early archosaur radiation. PLoS One, 6(10), e25693.

Gilmore, C. W. (1911). A new fossil alligator from the Hell Creek beds of Montana. Proceedings of the United States National Museum.

Godoy, P. L., Benson, R. B., Bronzati, M., & Butler, R. J. (2019). The multi-peak adaptive landscape of crocodylomorph body size evolution. BMC evolutionary biology, 19(1), 1-29.

Li, C., Wu, X. C., Cheng, Y. N., Sato, T., & Wang, L. (2006). An unusual archosaurian from the marine Triassic of China. Naturwissenschaften, 93(4), 200-206.

Norell, M., Clark, J. M., & Hutchison, J. H. (1994). The Late Cretaceous alligatoroid Brachychampsa montana (Crocodylia): new material and putative relationships. American Museum novitates; no. 3116.

Pierce, S. E., Williams, M., & Benson, R. B. (2017). Virtual reconstruction of the endocranial anatomy of the early Jurassic marine crocodylomorph Pelagosaurus typus (Thalattosuchia). PeerJ, 5, e3225.

Stocker, M. R., Zhao, L. J., Nesbitt, S. J., Wu, X. C., & Li, C. (2017). A short-snouted, Middle Triassic phytosaur and its implications for the morphological evolution and biogeography of Phytosauria. Nature Scientific Reports, 7(1), 1-9.

Sullivan, R. M., & Lucas, S. G. (2003). Brachychampsa montana Gilmore (Crocodylia, Alligatoroidea) from the Kirtland Formation (Upper Campanian), San Juan Basin, New Mexico. Journal of Vertebrate Paleontology, 23(4), 832-841.

Von Baczko, M. B., & Ezcurra, M. D. (2013). Ornithosuchidae: a group of Triassic archosaurs with a unique ankle joint. Geological Society, London, Special Publications, 379(1), 187-202.

Wilberg, E. W., Turner, A. H., & Brochu, C. A. (2019). Evolutionary structure and timing of major habitat shifts in Crocodylomorpha. Nature Scientific Reports, 9(1), 1-10.
Image credits - stem-Crocodylia
  • Header (American Alligator, Alligator mississippiensis): TimVickers, Public domain, via Wikimedia Commons
  • Figure 2a (Diandongosuchus fuyuanensis, fossil): Michelle R. Stocker, Li-Jun Zhao, Sterling J. Nesbitt, Xiao-Chun Wu & Chun Li, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
  • Figure 2a (Diandongosuchus fuyuanensis, life restoration): Smokeybjb, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2a (Parasuchus hislopi, fossil): Martin D. Ezcurra, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
  • Figure 2a (Parasuchus hislopi, life restoration): Nobu Tamura under Creative Commons Attribution- ShareAlike (CC BY-SA)  license
  • Figure 2a (Ebrachosuchus neukami): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2a (Nundasuchus songeaensis): Aquakeeper14, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2a (Ornithosuchus woodwardi): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2a (Riojasuchus tenuisceps, fossil): Maria Belen von Baczko, Julia Brenda Desojo, CC BY 2.5 <https://creativecommons.org/licenses/by/2.5>, via Wikimedia Commons
  • Figure 2a (Riojasuchus tenuisceps, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license 
  • Figure 2a (Dynamosuchus collisensis): Rodrigo T. Müller, M. Belén Von Baczko, Julia B. Desojo, and Sterling J. Nesbitt, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
  • Figure 2a (Stagonolepis robertsoni, skeleton): Jeffrey Martz, CC0, via Wikimedia Commons
  • Figure 2a (Stagonolepis robertsoni, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2a (Revueltosaurus callenderi, fossil): National Park Service, Public domain, via Wikimedia Commons
  • Figure 2a (Revueltosaurus callenderi, life restoration): National Park Service/Jeff Martz, Public domain, via Wikimedia Commons
  • Figure 2a (Parringtonia gracilis): Zissoudisctrucker, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2a (Erpetosuchus granti): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2a (Turfanosuchus dabanensis, fossil): Captmondo, Copyrighted free use, via Wikimedia Commons
  • Figure 2a (Turfanosuchus dabanensis, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2a (Yonghesuchus sangbiensis): Richard J. Butler, Corwin Sullivan, Martín D. Ezcurra, Jun Liu, Agustina Lecuona and Roland B. Sookias, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
  • Figure 2a (Gracilisuchus stipanicicorum, fossil): Richard J. Butler, Corwin Sullivan, Martín D. Ezcurra, Jun Liu, Agustina Lecuona and Roland B. Sookias, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
  • Figure 2a (Gracilisuchus stipanicicorum, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2a (Ticinosuchus ferox, fossil): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2a (Ticinosuchus ferox, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2a (Qianosuchus mixtus, fossil): Calamacow75, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2a (Qianosuchus mixtus, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2a (Lotosaurus adentus, fossil): Jonathan Chen, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2a (Lotosaurus adentus, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2a (Ctenosauriscus koeneni, fossil): Richard J. Butler, Stephen L. Brusatte, Mike Reich, Sterling J. Nesbitt, Rainer R. Schoch, and Jahn J. Hornung, CC BY 2.5 <https://creativecommons.org/licenses/by/2.5>, via Wikimedia Commons
  • Figure 2a (Ctenosauriscus koeneni, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2a (Arizonasaurus babbitti): Nobu Tamura under Creative Commons Attribution- ShareAlike (CC BY-SA) license
  • Figure 2a (Youngosuchus sinensis): Jonathan Chen, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2a (Batrachotomus kupferzellensis, fossil): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2a (Batrachotomus kupferzellensis, life restoration): Dmitry Bogdanov, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2a (Luperosuchus fractus, fossil): Fanboyphilosopher (Neil Pezzoni), CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
  • Figure 2a (Luperosuchus fractus, life restoration): Dmitry Bogdanov, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
  • Figure 2b (Prestosuchus chiniquensis, fossil): Photographed by Bob James (owner of website) at American Museum of Natural History, New York, May 2024
  • Figure 2b (Prestosuchus chiniquensis, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2b (Rauisuchus tiradentes): Paleocolour, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2b (Carnufex carolinensis): Susan M. Drymala, Lindsay E. Zanno, CC BY 2.5 <https://creativecommons.org/licenses/by/2.5>, via Wikimedia Commons
  • Figure 2b (Postosuchus sp.): Dallas Krentzel, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
  • Figure 2b (Postosuchus kirkpatricki): Nobu Tamura under Creative Commons Attribution- ShareAlike (CC BY-SA) license
  • Figure 2b (Trialestes romeri): Ghedoghedo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2b (Pseudhesperosuchus jachaleri): Tiouraren, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2b (Saltoposuchus connectens): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2b (Terrestrisuchus gracilis, skeleton): Jaime A. Headden (User:Qilong), CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
  • Figure 2b (Terrestrisuchus gracilis, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2b (Sphenosuchus acutus): Ghedoghedo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2b (Litargosuchus leptorhynchus): Smokeybjb, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2b (Hesperosuchus agilis): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2b (Dibothrosuchus elaphros): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2b (Junggarsuchus sloani): Smokeybjb, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2b (Macelognathus vagans): Jaime A. Headden (User:Qilong), CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
  • Figure 2b (Hallopus victor, skeleton): Jaime A. Headden (User:Qilong), CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
  • Figure 2b (Hallopus victor, life restoraton): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Protosuchus richardsoni, fossil): Photographed by Bob James (owner of website) at American Museum of Natural History, New York, May 2024
  • Figure 2c (Protosuchus richardsoni, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Gobiosuchus kielanae, fossil): Halszka Osmólska, Stephane Hua, and Eric Buffetaut, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
  • Figure 2c (Gobiosuchus kielanae, life restoration): Halszka Osmólska, Stephane Hua & Eric Buffetaut, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
  • Figure 2c (Sichuanosuchus huidongensis, fossil): Zhangzhugang, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2c (Sichuanosuchus huidongensis, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Hsisosuchus chungkingensis): Zhangzhugang, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
  • Figure 2c (Simosuchus clarki, fossil): D. Gordon E. Robertson, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Simosuchus clarki, life restoration): Smokeybjb, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Libycosuchus brevirostris): Ghedo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2c (Hamadasuchus rebouli): CaptMondo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Barreirosuchus franciscoi): BianoPaleontologo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2c (Araripesuchus wegeneri, fossil): Sereno PC, Larsson HCE, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
  • Figure 2c (Araripesuchus wegeneri, life restoration): Todd Marshall, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
  • Figure 2c (Araripesuchus buitreraensis): Museo Provincial Carlos Ameghino, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2c (Anatosuchus minor, fossil): Sereno PC, Larsson HCE, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
  • Figure 2c (Anatosuchus minor, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Teleidosaurus calvadosii, fossil): Société linnéenne de Normandie, No restrictions, via Wikimedia Commons
  • Figure 2c (Teleidosaurus calvadosii, life restoration): ArthurWeasley, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons
  • Figure 2c (Steneosaurus bollensis): Nobu Tamura under Creative Commons Attribution- ShareAlike (CC BY-SA) license
  • Figure 2c (Pelagosaurus typus, fossil): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Pelagosaurus typus, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Pholidosaurus purbeckensis): The Trustees of the Natural History Museum, London, under http://creativecommons.org/licenses/by/4.0/
  • Figure 2c (Pholidosaurus meyeri): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Terminonaris robusta): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Chenanisuchus lateroculi): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Theriosuchus pusillus, fossil): C. L. Griesbach, Public domain, via Wikimedia Commons
  • Figure 2c (Theriosuchus pusillus, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Knoetschkesuchus langenbergensis, fossil): Daniela Schwarz, Maik Raddatz, Oliver Wings, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
  • Figure 2c (Knoetschkesuchus langenbergensis, life restoration): Hyrotrioskjan, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2c (Alligatorium meyeri): Ghedoghedo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2c (Atoposaurus oberndorferi): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Alligatorellus beaumonti, fossil): Ghedoghedo, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2c (Alligatorellus beaumonti, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Nannosuchus gracilidens): The Trustees of the Natural History Museum, London, under http://creativecommons.org/licenses/by/4.0/
  • Figure 2c (Bernissartia fagesii, fossil): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Bernissartia fagesii, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Wannchampsus kirpachi): Wkirpach, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2c (Susisuchus anatoceps): Leite, K. J., & Fortier, D. C. (2018). The palate and choanae structure of the Susisuchus anatoceps (Crocodyliformes, Eusuchia): phylogenetic implications. PeerJ, 6, e5372.
  • Figure 2c (Isisfordia duncani, fossil): Queensland Government, under a Creative Commons Attribution 4.0 International licence (CC BY 4.0).
  • Figure 2c (Isisfordia duncani, life restoration): Smokeybjb, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Shamosuchus djadochtaensis): Alan H. Turner, CC BY 2.5 <https://creativecommons.org/licenses/by/2.5>, via Wikimedia Commons
  • Figure 2c (Batrachomimus pastosbonensis): Smokeybjb, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Acynodon iberoccitanus): Ghedoghedo, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
  • Figure 2c (Lohuecosuchus megadontos): PePeEfe, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
  • Figure 2c (Arenysuchus gascabadiolorum): Eduardo Puértolas, José I. Canudo, Penélope Cruzado-Caballero, CC BY 2.5 <https://creativecommons.org/licenses/by/2.5>, via Wikimedia Commons
  • Figure 2c (Allodaposuchus precedens, fossil): Zoltan Csiki-Sava, Eric Buffetaut, Attila Ősi, Xabier Pereda-Suberbiola, Stephen L. Brusatte, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
  • Figure 2c (Allodaposuchus precedens, life restoration): Nobu Tamura under a Creative Commons 3.0 Unported (CC BY-NC-ND 3.0) license
  • Figure 2c (Agaresuchus subjuniperus): Zoltan Csiki-Sava, Eric Buffetaut, Attila Ősi, Xabier Pereda-Suberbiola, Stephen L. Brusatte, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
  • Figure 3 (Brachychampsa sp.): Daderot, CC0, via Wikimedia Commons
  • Figure 3 (Brachychampsa montana):  Nobu Tamura under Creative Commons Attribution- ShareAlike (CC BY-SA) license