Gwyneddichnium and Tanytrachelos

It’s rare when body fossils and ichnites are found in the same fossil beds. Gwyneddichnium (Bock 1952, the ichnite, Fig. 1) and Tanytrachelos (Olsen 1979, the body fossil) are exceptions. Found in the Appalachian valleys of Virginia, these relatively small, middle Triassic specimens both help piece together and integrate the trackmaker and the track itself.

Gwyneddichnium

Figure 1. Comparing the ichnotaxon, Gwyneddichnium to the tritosaur Tanytrachelos. Note the longer penultimate phalanges in digits 3 and 4 in YPM 7540.

We’re seeing some variation in Tanytrachelos
Note the length of the penultimate phalanges in digits 3 and 4 and the relative size of m1.1 in the two bone specimens. Note the relative length of manus digits 3 and 4 between Gwyneddichnium and the bone specimen (YPM 7491).

Tanytrachelos

Figure 2. Tanytrachelos. Click for more info.

Comparing Gwyneddichnium to Rotodactylus
Gwyneddichnium demonstrates that pedal digit 5 in Tanytrachelos was oriented alongside digits 1-4 in a plantigrade configuration. By contrast the pes of Cosesaurus was matched to the digitigrade ichnite Rotodactylus (Peters 2000), which inverts digit 5, impressing far behind digits 1-4 without making a heel impression. online story.

Foot bones attributed to Tanytrachelos

Figure 3. Foot bones attributed to Tanytrachelos. Note the great similarity between these phalangeal proportions and those of YPM 7540. Metatarsal 1 was shorter in this specimen.

Adding the Pes of Tanytrachelos to the Large Ptero Tree
A lone pes attributed to Tanytrachelos from the same formation was added to the pterosaur tree. The foot nested with Tanytrachelos.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Bock W 1952. Triassic reptilian tracks and trends of locomotive evolution. Journal of Paleontology 26(3):395-433.
Olsen PE 1979. A new aquatic eosuchian from the Newark Supergroup Late Triassic-Early Jurassic) of North Carolina and Virginia. Postilla 176: 1-14.

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