ASGP (2021), vol. 91: 113–120

GRAMMEPUS HITCHCOCK, 1858: A SEDIMENTARY VARIANT OF THE FOSSIL INSECT TRACKWAY LITHOGRAPHUS

Patrick R. GETTY (1*), Matthew WARD (2) & Jack SIMON (2)

1) Department of Geology, Collin College, 2800 E. Spring Creek Parkway, Plano TX 75074, USA; e-mail: pgetty@collin.edu
2) Center for Advanced Studies in Mathematics and Natural Sciences, Collin College, 2800 E. Spring Creek Parkway, Plano TX 75074, USA; e-mails: matt.ward@utdallas.edu; JackSimon670@yahoo.com
*) Corresponding author

Getty, P. R., Ward, M. & Simon, J., 2021. Grammepus Hitchcock, 1858: A sedimentary variant of the fossil insect trackway Lithographus. Annales Societatis Geologorum Poloniae, 91: 113–120.

Abstract: The ichnogenus Grammepus, which is inferred to have been made by a winged (pterygote) insect, was differentiated from other ichnotaxa because its largest tracks were nearly continuous, forming two furrows. Otherwise, it strongly resembles the ichnogenus Lithographus. Examination of both ichnogenera indicate that the largest tracks in Lithographus can be very close together, that some specimens of Grammepus lack furrow-like tracks, and that the type specimen of the type species Grammepus erismatus has separate tracks in some places, and furrow-like ones in others. Given the lack of a feature that can consistently differentiate Lithographus and Grammepus, the latter is synonymized with the former. Experiments with the modern cricket Acheta domesticus in sediment of different saturation levels indicate that a single pterygote producer could produce both “Grammepus-” and Lithographus-like morphologies, with the former being formed in wet, soft sediment wherein the legs drag, and the latter being formed in firmer, drier sediment wherein the legs do not drag.

Manuscript received 3 January 2021, accepted 24 April 2021