New discoveries of Isochirotherium herculis (Egerton 1838) and a reassessment of chirotheriid footprints from the Triassic of the Isle of Arran, Scotland

Abstract

SynopsisSeveral in situ trackways and individual chirotheriid footprints have been found at a number of locations along the southern coast of the Isle of Arran. A locality on the coast near Sliddery has five trackways with three of over 17 footprints and one locality west of Kildonan also has a trackway with over 10 footprints. They are all from the Triassic Auchenhew Beds, but may belong to several levels within these beds. The state of preservation of the footprints is variable, but a combination of morphological characters and landmark polygons suggests that they belong to Isochirotherium herculis (Egerton) 1838. Previously described footprints from Arran, originally described as Chirotherium barthii (Clark et al. 2002), are reidentified as I. herculis. IntroductionChirotheriid trackways and footprints from the Triassic of Scotland are rare. Only three localities have been previously identified in the literature. In 1850, Harkness (1850a, b) reported on the existence of Chirotherium from near Annan, Dumfriesshire, however, there was neither a detailed description, nor illustration of these footprints that are now lost. These footprints cannot, therefore, be substantiated, but it is hoped that further examples will eventually be discovered in this area. Other footprints found in the Annan area were identified as Delairichnus by Haubold (1971a) and are not considered to be chirotheriid. The only substantiated claim of the existence of chirotheriid footprints in Scotland was published by Clark et al. (2002) on footprints from two localities on the Isle of Arran. The first footprint was found at Levencorroch Hill and is now in the collections of the Oxford University Museum (OUM G.53) and identified by M. King in 1992 as the left pes of Chirotherium. It was initially tentatively identified as dinosaurian (McKerrow and Atkins 1985). The second was on the coast 2.5km northwest of Blackwaterfoot on the southwest coast of Arran near to Cleiteadh nan Sgarbh (NR 886 301) (Clark et al. 2002).

Middle Triassic chirotherid trackways on earthquake influenced intertidal limulid reproduction flats of the European Germanic Basin coasts

“…1), and have been described from different sized individuals with different types of preservation. There are similar, large isochirotherid-like footprints elsewhere in the Upper Bunter [16,42], but the small number of trackways and their poorly preserved shapes, especially in terrestrial beds, do not allow clear attribution to the Isochirotherium ichnogenus, or even to the same ichnospecies or trackmaker. I. archaeum from France [93], together with I. jenense, I. hessbergense, and I. soergeli from Germany [19], and I. marshalli or I. coltoni from the Moenkopi Formation/Group of Northern America [43], all appear to represent trackways of younger individuals or different types of track preservation.…”

“…[36,92,98,99], England and Scotland e.g. [12,30,42,100], and Poland [33,38,101]. They are also known from North America [22,102], The 'oldest tridactyl tracks from Poland' [103] are nothing else than badly and incompletely printed preserved chirotherid tracks in redbed sand facies.…”

Presentation1.pdf

“…However, the digitized pes in this case had a much smaller length (0.13 m) than the smallest reported value in their Table 1 (0.21 m). Based on the trackway photo (Figure 6 in Clark et al, 2002), the pes was the sixth print of SLID_1 in their Table 1, and the caudal portion of the print may have been cropped out of the photo in Figure 6C of Clark and Corrance (2009). To correct this, we extended the caudal point by the length of pes 6 reported in their Table 1 (0.28 cm).…”

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“…The set from their Figure 7B was associated with trackway BWF_5 data in Table 1 of the study by Clark et al (2002), where the trackway was at first assigned to Chirotherium. The trackway set from Figure 6C of Clark and Corrance (2009) was associated with trackway SLID_1 data in their Table 1. However, the digitized pes in this case had a much smaller length (0.13 m) than the smallest reported value in their Table 1 (0.21 m).…”

“…However, the digitized pes in this case had a much smaller length (0.13 m) than the smallest reported value in their Table 1 (0.21 m). Based on the trackway photo (Figure 6 in Clark et al, 2002), the pes was the sixth print of SLID_1 in their Table 1, and the caudal portion of the print may have been cropped out of the photo in Figure 6C of Clark and Corrance (2009). To correct this, we extended the caudal point by the length of pes 6 reported in their Table 1 (0.28 cm).…”