Gwyneddichnium
From Wikipedia, the free encyclopedia
| Gwyneddichnium Temporal range: Late Triassic | |
|---|---|
Trace fossil classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauromorpha |
| Family: | †Tanystropheidae |
| Ichnogenus: | †Gwyneddichnium Bock, 1952 |
| Type ichnospecies | |
| †Gwyneddichnium major | |
| Ichnospecies | |
| |
Gwyneddichnium is an ichnogenus from the Late Triassic of North America and Europe. It represents a form of reptile footprints and trackways, likely produced by small tanystropheids such as Tanytrachelos. Gwyneddichnium includes a single species, Gwyneddichnium major (also spelled G. majore). Two other proposed species, G. elongatum and G. minore, are indistinguishable from G. major apart from their smaller size and minor taphonomic discrepancies. As a result, they are considered junior synonyms of G. major.[1]
Gwyneddichnium corresponds to footprints from a quadrupedal animal with a small pentadactyl (five-fingered) manus (hand) and a notably larger five-toed pes (foot). The manus and pes are mesaxonic, meaning that the third digit is the longest digit, followed by the subequal second and fourth digits. The innermost digit (digit I) and the outermost digit (digit V) were short and located close to the rest of the foot. Sometimes the small fifth digit is poorly preserved, making the hand or foot appear to be tetradactyl (having only four digits). Overall, the digits are long and narrow, with minimal curvature. There is some variation with how the digits are positioned, with some specimens having digits which evenly radiate away from the sole,[1] and others having digits which separate into two clumps, digits I-III and IV-V.[2]
The skin made pad-like impressions with a characteristic nodular shape, and small, pointed claw impressions are also present. Some specimens preserved irregularly-shaped sole impressions and/or tail drag marks, but these are not always preserved. One purported Gwyneddichnium trackway (CU-MWC 159.10) has been interpreted as swimming traces due to the absence of manus prints. Skin webbing appears to be present between toes I-III,[2] though the webbing has also been interpreted as sediment deformation. Gwyneddichnium trackways in general are widely spaced, with pes prints pointing forwards and manus prints rotated outwards. The positions of the pes and manus prints relative to each other are variable, corresponding to different speeds and gaits.[1]
The overall shape of the footprints are similar to Rhynchosauroides, which sometimes occurs alongside Gwyneddichnium. However, Rhynchosauroides has an exaxonic print (with the fourth digit longer than the third), more curvature in the digits, and a fifth digit more widely separated from the fourth.[1]