Lewisuchus – new reconstruction

Be wary of the scale bars, but the new data on Lewisuchus by Bittencourt et al. (2014) brings a fresh look to old Romer (1972) data. Here (Fig. 1) the scale of the posterior skull and tibia are pure guesswork until I hear back from the authors on my query.

Figure 1. Lewisuchus from Romer 1972. Tibia and skull do no match published scale bars. Pelvis and femur are hypothetical. Skull above left per Romer. Below left per Bittencourt et al.

Figure 1. Lewisuchus from Romer 1972. Tibia and skull do no match published scale bars. Pelvis and femur are hypothetical. Skull above left per Romer. Below left per Bittencourt et al.

Unfortunately the authors did not include basal archosaurs (Decuriasuchus and Pseudhesperosuchus) in their analysis, but restricted their taxon list to dinos and pre-dinos. Not surprisingly, Lewisuchus nested with Marasuchus. The large reptile tree nests Lewisuchus with Pseudhesperosuchus.

Lewisuchus is the reason why basal crocs and dinos were bipeds. It nests at the base of all archosaurs. The palate is a close match to that of the basal bipedal croc Scleromochlus.

References
Bittencourt JS, Arcucci AB, Maricano CA and Langer MC 2014. Osteology of the Middle Triassic archosaur Lewisuchus admixtus Romer (Chañares Formation, Argentina) its inclusivity, and relationships amongst early dinosauromorphs. Journal of Systematic Palaeontology. Published online: 31 Mar 201. DOI:10.1080/14772019.2013.878758
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna; XIV, Lewisuchusadmixtus, gen. et sp. nov., a further thecodont from the Chañares beds. Breviora 390:1-13

wiki/Lewisuchus

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