Morphotype 1

Morphotype 1

( Fig. 12 A-C)

MATERIAL. — Five specimens ( MHNT.PAL.2023.9.53 [ Fig. 12C]; MHNT.PAL.2023.9.54 [ Fig.12A]; MHNT.PAL.2023.9.55 , MHNT. PAL.2023.9.57 [ Fig. 12B]; MHNT.PAL.2023.9.58 ) .

DESCRIPTION

The specimens of this morphotype have an ovoid shape that tapers at one end. Size does not exceed 65 mm in length and 20 mm in width. The coprolites are brown to light gray in color, with an irregular, fragmented surface. This fragmentation does not permit the observation of a potential external morphology, such as a spiral pattern. These coprolites contain inclusions of small bone fragments and numerous small scales. These scales belong to Aeduellidae based one their rectangular to rhombic shape, their possible slight serrations on the posterior margin, and their ornamentation composed of light growth lines. Within the coprolites, they are preserved either in relatively dense localized patches in which they are more or less oriented ( Fig. 12A, B), or they are more regularly spread as regular cluster in the whole volume of the coprolites ( Fig. 12 C). These scales are identical to those found isolated or articulated on the La Découverte Member described above. The bone fragments observed on the surface cannot be determined due to their fragmentary and altered condition.

COMPARISONS

Among the coprolite morphotypes described by Hunt & Lucas (2012), Morphotype 1 herein described is close to Morphotypes F2, F3 and F 4 in its ovoid shape (Hunt & Lucas 2012). However, Morphotype 1 cannot be assigned to one of these morphotypes as its preservation does not allow to see whether it is spiraled or not. This is a key feature as amphipolar spirality characterizes Morphoptype F2 while microscopic heteropolar spirality characterizes Morphotype F3 and macroscopic heteropolar spirality characterizes Morphotype F4 (Hunt & Lucas 2012).

According to the nomenclature of Hunt & Lucas (2012), Morphotype F2 includes the ichnogenera Hyronocoprus Hunt, Lucas & Spielmann, 2005a, Kalocoprus Hunt, Lucas, Spielmann, Cantrell & Suazo, 2012 , Elacacoprus Hunt, Lucas, Spielmann, Cantrell, Suazo & Lerner, 2012 and Iuloeidocoprus Hunt, Lucas & Spielmann, 2012a ( Hunt et al. 2005 a, 2012b, c, d), Morphotype F3 includes Heteropolacoprus Hunt, Lucas & Lockley, 1998, Saurocoprus Hunt, Lucas, Spielmann & Lerner, 2007, Strabelocoprus Hunt, Lucas & Spielmann, 2012b , Malericoprus Hunt, Lucas, Spielmann & Lerner, 2007 and Megaheteropolacopros Hunt, Lucas & Spielmann, 2005b ( Hunt et al. 1998, 2005b, 2007, 2012b; Hunt & Lucas 2012), and Morphotype F4 includes Liassocoprus Hunt, Lucas, Spielmann & Lerner, 2007, Crassocoprus Hunt, Lucas, Spielmann, Cantrell, Suazo & Lerner, 2012 and Speiracoprus Hunt, Lucas, Spielmann, Cantrell, Suazo & Lerner, 2012 (Hunt et al. 2007, 2012d). In their review of Carboniferous and Permian coprolites, Hunt & Lucas (2013) mention very few European specimens. However, coprolites corresponding or likely to correspond to Morphotype F4 have been described from the Carboniferous-Permian basins of Autun ( France), Montceau-les-Mines ( France), Puertollano ( Spain) and Krkonoše-Piedmont ( Czech Republic) ( Renault 1900; Poplin 1994; Štamberg et al. 2016; Mercuzot et al. 2022; Soler-Gijón & Ruiz 2023). Some of these coprolites have inclusions of actinopterygian scales and bone fragments (e.g. Poplin 1994; Štamberg et al. 2016). Krzykawski et al. (2014) described a coprolite from the Upper Carboniferous of Poland with inclusions of vertebrate bony elements and whose external structure is too poorly preserved to distinguish potential spirality. This coprolite is very similar to Morphotype 1 and presents the same identification problems. It has been cautiously attributed to a large actinopterygian ( Krzykawski et al. 2014), but it cannot be ruled out that it may also have been produced by a chondrichthyan.

The poor preservation of Morphotype 1 specimens makes identification difficult, but it seems to correspond more to either Morphotype F2, Morphotype F3 or Morphotype F4. Both morphotypes have been identified as having been produced in the vast majority of cases by chondrichthyans (e.g. Hunt & Lucas 2012; Hunt et al. 1998; 2005a, b, 2012b, c, d). Furthermore, coprolites found in the Permo-Carboniferous basins of Europe belong almost exclusively to Morphotype F4. Taken together, these data point to a close relationship between the Morphotype 1 described here and the Morphotype F4 of Hunt & Lucas (2012). Morphotype 1 could therefore potentially have been produced by a large chondrichthyan. Given our current knowledge of the fauna of the Bourran Formation, Orthacanthus seem a likely candidate.