Ichniotherium praesidentis ( Schmidt, 1956 ) Voigt & Ganzelewski, 2010

Voigt, Sebastian & Ganzelewski, Michael, 2010, Toward the origin of amniotes: Diadectomorph and synapsid footprints from the early Late Carboniferous of Germany, Acta Palaeontologica Polonica 55 (1), pp. 57-72 : 58-63

Ichniotherium praesidentis ( Schmidt, 1956) comb. nov.

Figs. 1–4, Appendices 1, 2.

1956 Megapezia praesidentis Schmidt, 1956: 200–204 , figs. 1, 2, pl. 14.

1970 Schmidtopus praesidentis Haubold, 1970: 94–95 , fig. 4D.

1982 Schmidtopus praesidentis ; Fichter 1982: 68–72, figs. 29, 30, 32, tables 1, 7.

1984 Schmidtopus (Megapezia) praesidentis ; Haubold 1984: 64, fig. 43: 1.

Holotype: DBM 060003259001 to DBM 060003259010 , original material, preserved as convex hyporelief, and DBM 060003309001 to DBM 060003309004 , plastic cast, four−part. All segments are part of the same trackway surface, 2 × 4.6 m in size, covered by about 80 monospecific imprints of three trackways ( Fig. 1A–C). Owing to a mistake that occurred when the replica of the slab was reconstructed during the 1950s, the first two imprints of the best preserved trackway are portrayed twice ( Fig. 2 ).

Type locality: Former coal−mine „Präsident“ at Bochum, Ruhr area, western Germany ( Kukuk 1924, 1926).

doi:10.4202/app.2009.0021

Type horizon: Above seam “Plasshofsbank”, lowermost Bochum Formation, Westphalian A2, Langsettian, Late Carboniferous.

Lithology.—Based on the original material, the tracks were made in dark grey silt. Natural casts are preserved in light grey medium−grained sandstone showing mud−crack casts up to 6 mm in width.

Description.—Trackway of a quadrupedal tetrapod with pentadactyl, plantigrade footprints; manus and pes imprints are distinct in size and shape ( Figs. 1, 2 ; Appendix 1). Pes imprints measure up to 15 cm in length and up to 17 cm in width. Digits I to IV of the pes imprint exhibit a serial increase in length, whereas digit V is about as long as III. Due to a significant decrease in relief from digit I to V, the outer digit is either reduced to a faint imprint of the digit tip or missing entirely ( Fig. 1D, F). Digit tips I to IV are bent toward the trackway midline. The sole of the pes imprint is represented by a deep and structure−less impression.

The manus imprints average about 11 cm in length and 12 cm in width. Digits I to III of the manus imprints exhibit serial increase in length. Digit III is of nearly the same length as IV, in some cases shorter, in others slightly longer than IV. Digit V varies in length between digits II and III. Digit imprints I to IV commonly with hemispherical, slightly enlarged tips. The digits of the manus tracks are more evenly deep impressed than those ones of the pes tracks. The sole is a deep impression either showing a convex, straight, or slightly concave proximal margin. Some of the tracks notably possess a clearly distinct oval pad proximal to the first digit ( Fig. 1E).

The trackway pattern is characterised by an alternating arrangement of inversely coupled manus−pes imprints ( Fig. 2 ). Inversion means that associated tracks belong to consecutive couples, with the manus imprint lying closely behind the pes imprint of the succeeding step cycle. Low pace angulation, the relatively short length of stride, and a relatively wide gait are further characteristics of the trackway pattern (Appendix 1). The pes imprints are pointed outwardly about 30° on average, whereas the manus imprints are placed almost parallel to the trackway midline.

Remarks.— Kukuk (1924, 1926) interpreted the anterior track of coupled imprints of this trackway to be the imprint of the manus, judged from the trackway pattern and the apparent tetradactyl tracks. Abel (1935) equivocated about the number of digits present in the questionable imprints, whereas Schmidt (1956) and, later, Haubold (1970, 1971) agreed with Kukuk’s interpretation of a four−toed manus. Fichter (1982) proposed the alternative view that both, manus and pes imprints are pentadactyl and that the larger of the two, though placed in front of two closely spaced footprints, corresponds to the pes. The debate stems from two unusual features of the trackway: (i) the mediolateral decrease in relief of the pes imprints, which prevents a distinct impression of the fifth digit ( Fig. 1D); and (ii) the relatively short length of stride, which causes an alternating arrangement of inversely coupled manus−pes imprints ( Fig. 2 ).

Schmidt (1956) assigned the tracks of the Bochum slab to Megapezia Matthew, 1903 from the Mississippian of Nova Scotia. From his point of view, both track morphs share a tetradactyl manus imprint with a posteriorly extended sole. Haubold (1970) agreed that the “manus imprints” are similar, but stressed the short and wide “pes imprint” of the Bochum tracks as being unique. Therefore, he introduced the new ichnogenus Schmidtopus Haubold, 1970 . Even though setting right the interpretation of the trackway pattern, Fichter (1982) maintained Schmidtopus as a separate ichnotaxon referred to the Bochum tracks.

Based on careful reanalysis of the type material, we assign the Bochum tracks to the well−known Permo−Carboniferous ichnogenus Ichniotherium Pohlig, 1892 . Both track morphs share several main imprint characters ( Fig. 1D–G): (i) pentadactyl manus and pes imprints; (ii) distally rounded digit imprints with enlarged tips (“drumsticks” sensu Korn 1933); (iii) pes imprints with a mediolateral decrease in relief; (iv) manus imprints with evenly distributed relief; and (v) inwardly curved digit tips (I–IV). In addition, Ichniotherium praesidentis exhibits the typical preservation of Ichniotherium undertracks ( Fig. 3 ).

In comparison to the well−established Permian ichnospecies Ichniotherium sphaerodactylum (Pabst, 1895) and I. cottae (Pohlig, 1885) , I. praesidentis differs in its inversely coupled manus−pes sets of the trackway pattern ( Fig. 4A–G ). The Bochum trackway indicates a very slow−moving individual with respect to the low stride, short manus−pes distance, high width of pace, and small pace angulation ( Fig. 4H, I ). The relative length of pace lies within the range of variation obtained for the other Permian ichnospecies ( Fig. 4H ). This is possible because the short stride is accompanied by a relatively high width of pace. Another difference concerns the strongly outward rotation of the pes imprints of I. praesidentis (β in Fig. 4I ). More similar are the imprint and digit proportions ( Fig. 4I–K ) with pes imprints being one third longer than the manus imprints (Appendix 2; Voigt et al. 2007). The digit proportions of I. praesidentis are almost congruent with those of I. sphaerodactylum , but differ significantly from the digit proportions of I. cottae by the relatively longer digit V of the pes imprint ( Fig. 4J ). I. sphaerodactylum has the most extended digit V of all Late Carboniferous to Early Permian tetrapod ichnotaxa (Voigt 2005). The relatively long outer digit of the pes imprint clearly separates the Bochum trackway specimen from similar forms such as Amphisauropus Haubold, 1970 , and provides strong basis for placing the tracks within Ichniotherium .

I. praesidentis differs from all other Ichniotherium ichnospecies in having a distinct pad at the base of the first digit. I. willsi Haubold and Sarjeant, 1973 , from the Westphalian D of Great Britain, has outwardly rotated pes imprints similar to the Bochum trackway. Both ichnospecies, however, differ significantly by the relative length of the fifth digit of the pes imprint.

Nomenclature.—The tracks of the Bochum slab are most similar to Ichniotherium Pohlig, 1892 and are thus assigned to that ichnogenus herein. Schmidtopus , which was introduced for these tracks by Haubold (1971), is considered as a junior synonym of Ichniotherium . Being different from all previously defined Ichniotherium ichnospecies in having a doi:10.4202/app.2009.0021

distinct pad at the base of the first digit and a pes imprint that is outwardly rotated, the Bochum track represents a separate ichnospecies. Using the first available specific epithet, the valid name for the discussed tracks is Ichniotherium praesidentis ( Schmidt, 1956) .

Osteological interpretation.— Kukuk (1924) supposed the trackmaker of the Bochum tracks to be a Late Palaeozoic batrachomorph based on the salamander−like trackway pattern and the apparently tetradactyl nature of what were interpreted as manus imprints. Later, he included early amniotes as potential trackmakers, suggesting that the pointed digit tips of some tracks resulted from the presence of claws or nails ( Kukuk 1926). Abel (1935) agreed that the tracks were made by a clawed animal, before Kukuk (1938) speculated on a pareiasaurian−like reptile as the potential trackmaker. Schmidt (1956) stressed the tetradactyly of the misinterpreted manus imprint as the most crucial character identifying the trackmaker as a large temnospondyl such as an eryopid. Haubold (1970, 1971, 1973, 1984) agreed with this interpretation, as did Fichter (1982), who referred to reconstructions of Palaeozoic temnospondyls showing a pentadactyl autopodium of the fore limb.

For about the past decade, Ichniotherium tracks have been regarded as belonging to diadectids ( Fichter 1998; Haubold and Stapf 1998; Haubold 2000; Voigt and Haubold 2000; Voigt 2001, 2005; Berman and Henrici 2003; Kissel and Reisz 2004a; Voigt et al. 2005, 2007). This interpretation is based on the abundant record of Ichniotherium tracks and diadectid skeletal remains at the Early Permian Bromacker locality in central Germany ( Berman et al. 1998, 2004; Haubold 1998; Voigt and Haubold 2000; Voigt et al. 2007). Diadectids are the most diverse clade of the Late Carboniferous to Early Permian Diadectomorpha , which also includes limnoscelids (Williston 1912; Romer 1946) and the monotypic Tseajaiidae ( Vaughn 1964; Moss 1972). Even though some differences in the appendicular skeleton of limnoscelids, tseajaiids, and diadectids exist ( Romer 1946; Berman and Henrici 2003; Pelletier et al. 2007), discrimination of the three biotaxa by tracks is not possible at the current state of knowledge because of inadequate knowledge of the hind limbs, e.g. for Tseaja campi Vaughn, 1964 (cf. Moss 1972). Without associated skeletal remains, as is the case for the discussed Westphalian footprints, biotaxon assignment of Ichniotherium tracks should be conservatively posited no lower than Diadectomorpha .

doi:10.4202/app.2009.0021

Figures

Fig. 2. Tetrapod footprints of Ichniotherium praesidentis (Schmidt, 1956) from the Late Carboniferous Bochum Formation, Ruhr area, Germany, represented by the longest and best preserved trackway of the holotype. Photograph and drawing are based on the four−part resin replica (DBM 060003309001 to DBM 060003309004). Note: the first two imprints are erroneously replicated twice and therefore not shown in the outline drawing. Dotted zigzag line links the pes imprints, and dotted track outlines indicate the position of imprints, which are reasoned from the step cycle but not preserved on the cast.

Fig. 3. Undertrack preservation in Ichniotherium tetrapod footprints. A. Ichniotherium praesidentis (Schmidt, 1956) from the Late Carboniferous Bochum Formation, Ruhr area, Germany; DBM 060003309003. B–D. Ichniotherium cottae (Pohlig, 1885) from Early Permian strata of the Thuringian Forest area, Germany; MNG 2049 (B), MNG 1871 (C), and MNG 2016 (D). Semicircularly arranged spherical imprints of the digit tips of the digits I–III or I–IV, which are typical in appearance to the undertrack preservation of Ichniotherium. Scale bars 100 mm.

Fig. 4. Graphic comparisons of the trackway pattern and selected parameters of three Ichniotherium ichnospecies. A. Ichniotherium praesidentis from the Bochum Formation, Late Carboniferous, Germany; DBM 060003309001 to DBM 060003309004, part). B–D. Ichniotherium sphaerodactylum from the Tambach Formation, Early Permian, Germany; MB ICV.2 (B), MNG 1351 (C), and GZG 1270 (D). E–G. Ichniotherium cottae from the Tambach Formation, Early Permian, Germany; MNG 10179 (E), UGBL F1 (F), and MNG 1352 (G). H, I. Derived trackway and imprint parameters graphically expressing the mean, minimum, and maximum values. J, K. Relative lengths of the manus and pes imprint digit lengths expressed as a percentage of the length of digit IV. Data source for H–K, see Appendix 2.