Saltopus preserves early archosaur skin and scales

Basal Crocodylomorpha

Figure 1. Basal Crocodylomorpha, including Gracilisuchus, Saltopus, Scleromochlus and Terrestrisuchus

The basal archosaur
(crocs + dinos) Saltopus (von Huene 1910; Late Triassic; ~210 mya, ±60 cm long; Figs. 1–3) poorly preserves bones, but also preserves some scaly skin.

Figure 2. Saltopus skin and scales surrounding the right pelvis.

Figure 2. Saltopus skin and scales surrounding the right pelvis. Not all bones nor all scales are traced here. Benton and Walker 2011 reported no evidence for osteoderms. The bones are hard to delineate and segregate from scales because here they are covered with fossilized desiccated skin. Photo from Benton and Walker 2011 who trace the femoral head extending beneath the pelvis. 

Saltopus nests well within
the Crocodylomorpha and, along with Scleromochlus (Fig. 1), present examples of basal archosaur skin and scales. Even more basal, Gracilisuchus (Fig. 1) had dorsal scutes derived from ancestors going back to the Early Triassic Euparkeria.

Figure 2. Saltopus pelvis latex peel from Benton and Walker 2011. They found two large sacrals. Using DGS I found four sacrals, the same length as the dorsals and causals. Sister taxa have four sacrals.

Figure 2. Saltopus pelvis latex peel from Benton and Walker 2011. They found two large sacrals. Using DGS I found four sacrals, the same length as the dorsals and causals. Sister taxa have four sacrals.

Gracilisuchus and basal dinosaurs
had only two sacral vertebrae, but basal bipedal crocs, like Scleromochlus, double that number. Benton and Walker 2011 traced two sacrals in a latex cast of the sacral area, but each sacral was twice as long as proximal dorsals and causals. Here four sacrals are tentatively identified in the latex peel, all about as long as proximal non-sacral vertebrae.

Dinosaur skin
can be scaly, or naked with feathers, or a combination of the two. Dinosaur scales may be different than croc or lizard scales in that at least some dinosaur scales, like those on the metatarsus of theropods appear to be derived from former feathers.

References
Benton MJ and Walker AD 2011. Saltopus, a dinosauriform from the Upper Triassic of Scotland. Earth and Environmental Science Transactions of the Royal Society of Edinburgh: 101 (Special Issue 3-4):285-299. DOI:10.1017/S1755691011020081
von Huene FR 1910. Ein primitiver Dinosaurier aus der mittleren Trias von Elgin. Geol. Pal. Abh. n. s., 8:315-322.

wiki/Saltopus

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