Tanytrachelos ahynis (Olsen 1979) Latest Triassic, 200 mya, was derived from Macrocnemus and was a sister to Langobardisaurus and Tanystropheus.

Distinct from Langobardisaurus, Tanytrachelos has twelve cervicals, but none were gracile. The posterior cervical ribs had large heads that kept the rods far from each centrum. Heterotopic bones were present. These appear to be elongated chevrons.

The elliptical sternum was wider and longer. The humerus was slightly bowed anteriorly. Metacarpal I aligned with the others.

The ilium had no anterior process. Metatarsal III was the longest. Digit III was the longest as in Langobardisaurus tonelloi.

Gwyneddichnium is an ichnotaxon (footprint) described by Bock (1952) that appears to be the correct size and proportions to match Tanytrachelos, which is found nearby.

Comparing Gwyneddichnium ichnites with the bones of Tanytrachelos. Note the subtle differences in the two bone specimens and the trackmaker. Even so this is a good match. This demonstrates that digit 5 was oriented alongside digits 1-4 in a plantigrade configuration, in contrast to the pes of Cosesaurus, matched to the digitigrade ichnite Rotodactylus, which inverts digit 5, which impresses far behind digits 1-4 without a heel impression. online story